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The Dependency Ratio in Human Evolution

5/15/2015

As far as I know, humans are unique among animals in having an extended period between weaning and being able to subsist on their own. We call this “childhood.” The long period of post-weaning dependence provides our large brains with a lot of time to mature. It also requires a lot of parental investment (in terms of time, energy, calories, etc.) and means that we would have to wait a long time between offspring if each one had to independent before the mother could have another.   We don’t do that, tending to have a shorter interval between subsequent births (the inter-birth interval, or IBI) than other great apes. The long period of childhood dependence and the short IBI mean that, as a species, humans tend to have multiple, dependent offspring of different ages at the same time. Speaking as a parent of multiple, dependent offspring of different ages, I can tell you that this is often no walk in the park. This peculiar human strategy has a lot of costs.

Understanding when, how, and why this distinctly human reproductive strategy developed is a great evolutionary question. Reducing the IBI increases the potential fertility of human populations, but also creates new demands on the energies of parents and families. Human families today often offset those extra energy demands by getting help (evolutionary anthropologists call it “cooperative breeding”). A new paper in the Journal of Human Evolution titled “When Mothers Need Others” by Karen Kramer and Erik Otárola-Castillo tries to further our understanding of where cooperative breeding comes from, using an “exploratory model” to try to understand the selective pressures associated with the evolution of human-like patterns of reproduction and child-rearing. The goal of the paper “is to develop a model to predict those life history transitions where selective pressure would have been strongest for cooperative childrearing” (pg. 5).

Kramer and Otárola-Castillo call their model the “Force of Dependence Model.” Their model is a simple one, calculating “the net cost of offspring as a function of dispersal age, birth intervals and juvenile dependence” as a 3-dimensional surface (Supplementary Online Material from Kramer and Otárola-Castillo 2015). The authors use several different combinations of settings to represent a range of conditions from “ancestral” (juvenile independence at age 10, IBI of 6 years, and a dispersal age of 14) to “most derived” (juvenile independence at age 20, IBI of 3 years, and a dispersal age of 20). Their graphs show that “net costs” within a domestic group (a mother and her offspring) are lower when offspring are spaced further apart and become independent at a younger age. When offspring hang around past the age of juvenile independence, there is a net benefit to the domestic group as their productive capacities can be used to offset the drain of their younger siblings. The authors find that the strain points – where selective pressures for assistance would be greatest – occur in domestic groups with the most derived set of characteristics: late juvenile independence and a low IBI (lots of children who remain dependent for a long time).

As I understand it, the “net cost” in this model more-or-less mirrors the dependency ratio (the ratio of consumers to producers) of a domestic group or family, something anthropologists have been interested in understanding for a long time. The higher the ratio of consumers to producers, the higher the dependency ratio, and the higher the “cost” to each producer supporting the family. The dependency ratio changes through the lifespan of a family in a patterned way: every domestic group that has children goes through a “pinch” period when the dependency ratio is highest, and the pinch period logically corresponds to the time when there are a lot of dependent offspring. As I wrote in my 2013 paper in the Journal of Anthropological Archaeology (“Subsistence Economics, Family Size, and the Emergence of Social Complexity in Hunter-Gatherer Systems in Eastern North America,” available here):

“the duration and amplitude of the ‘pinch’ is affected by the rapidity of the addition of offspring and how quickly those offspring turn from consumers into producers. The rapidity of addition of offspring will depend on factors such as fertility, infant and childhood mortality, and the number of wives. The productive potential of children will be affected by the presence and distribution of resources that can be procured by children and the foraging strategies that are employed to exploit those resources” (White 2013:128).

The main part of that paper used an agent-based model (ABM) to try to understand how the distribution of family size changes when the age at which children become producers (the “age of juvenile independence” in Kramer and Otárola-Castillo’s model) decreases and there is an incentive for polygynous marriage. In addition to the ABM, I used a simple spreadsheet model to show how the dependency ratio changed through the course of the developmental cycle of an individual family in cases where the age at production was low (8 years old) and where it was high (14 years old). In this simple model, I used an IBI of 3, a dispersal age of 16 for females and 20 for males, and a female reproductive period spanning ages 20-35 years (giving a total fertility of 6 offspring).

The figure below compares Kramer and Otárola-Castillo’s graphs from their cases with early and late juvenile independence (holding IBI at 3 and dispersal age at 14) with my data on changes in dependency ratio through the developmental cycle in cases with a single reproducing female and an age at production of 8 (top) and 14 (bottom).   My model data are the same as in my 2013 paper (Figure 5), but I have re-graphed them to make comparison with Kramer and Otárola-Castillo’s figure easier. I have redrawn the graphs from Kramer and Otárola’s Figure 1 (third graphs from the left, top and bottom rows). The dotted lines on the graphs of my results indicate a dependency ratio of 1.75, which is what I have generally used in my modeling efforts as a “typical” dependency ratio among hunter-gatherers (following Binford 2001:230).

My results showed the same pattern as Kramer and Otárola-Castillo’s: the peak of the “pinch” comes earlier and is less severe when children become producers at an earlier age. Even though our models have some differences (and some of the values of the parameters were different), the correspondence in results is notable. Compare, for example, when the amplitude of the “pinch” (peak dependency ratio in my results, greatest net cost in Kramer and Otárola-Castillo’s results; marked by stars) is greatest and the differences in amplitude between the early and late ages of juvenile contributions to subsistence.

The correspondence between my results and Kramer and Otárola-Castillo’s is unsurprising. The idea that the dependency ratio of a domestic group changes through the course of its developmental cycle in a somewhat predictable way is not new (and the idea that the “pinch” comes when you have lots of little kids running around at the same time won’t come as a revelation to anyone who has multiple children). This is a phenomenon that has been studied for decades (e.g., Chayanov 1966; Donham 1999; Fortes 1958; Goody 1958) and recognized as a key aspect of how hunter-gatherers organize themselves (Binford 2001:229).

So where does this kind of work put us in terms of understanding the evolution of human reproduction, society, and family life? I think it primarily puts us in a spot where we’re asking some good questions. Going back to the issue of the origins of monogamous pair-bonding (which I touched on briefly in this post about birth assistance and this post about australopithecine sexual dimorphism), having a two person (male-female) unit forming the core of a domestic group would have a mitigating effect on the strain caused by a decrease in IBI (i.e., you’d be adding another producer into the equation). If the appearance of male-female pair-bonding was associated with a sexual division of labor (which is I think what most of us would hypothesize), males and females would presumably be focused on procuring somewhat different sets of subsistence resources. Offspring could be largely “independent” with regards to some of those resources but not to others – think about the difference between collecting berries and running down large game. A sexual division of labor and an environment where relatively young children could make some contribution to their own subsistence (even if that contribution does not include the full range of resources that are exploited) would go a long way toward easing the “pinch” that comes from having more children spaced closer together.

When does this happen in human evolution? Of course that’s a tough thing to get at directly. I think if you took a poll, the winner would probably be “around the time our genus emerges” or “with Homo erectus.” An increase in total fertility (coincident with a lowering of the IBI) would help explain the population growth that must have been part of the dispersal of our species out of Africa prior to 1.8 million years ago. It would also fit nicely with the evidence for an increased exploitation of animal resources around that same time. Maybe Glynn Isaac was right all along to propose the emergence of human-like central place foraging with home bases and a sexual division of labor at the beginning of the Lower Paleolithic?

But what if monogamous pair-bonding and a sexual division of labor appeared much earlier – with australopithecines or even some pre-australopithecine like Ardipithecus? If those things came along with bipedal locomotion, would a decreased IBI and increased fertility have followed automatically? Maybe not. Perhaps those earlier hominids just didn’t have the wherewithal to exploit their environments like later hominids did – perhaps the diversity of the resource base they could exploit wasn’t great enough to really leverage a sexual division of labor until animal products became readily attainable. That may have required a suite of anatomical adaptations for daytime exhaustion hunting (loss of body hair, skin pigmentation, greater body size, stiffer foot) and cognitive/behavioral adaptations for making and using stone tools to process carcasses. The date of the “earliest” proposed use of stone tools continues to be pushed back (now it’s at 3.3. million years ago), but as far as I know the density of stone tools and butchered animal bones that appears at about 1.8 million years ago is unlike anything that precedes it.

More modeling work will be required to really understand how changes in the dependency ratio might have articulated with changes in reproductive, social, and technological behaviors deep in human prehistory. In order to understand what changes in reproduction might have meant in terms of social interactions, however, we’ll need a different grade of model than that used by Kramer and Otárola-Castillo. Of course I’m going to say that complex systems modeling is the way to go on this: it will let us get past the limitations of deterministic inputs and help us understand how constraints, costs, and interactions would have played out within a society. In order for “others” to help with raising and provisioning multiple dependents, those others had to have existed within these small-scale hominid societies and (again, speaking as someone involved in raising multiple small kids) there wouldn't have been some inexhaustible Plio-Pleistocene babysitting pool of “others” out there just waiting to step in and provide extra calories for a few years. A different kind of modeling effort with broader scope will let us get at the group- and society-level contexts in which family-level changes in child-bearing and child-rearing would have played out. Stay tuned.

References

Binford, Lewis R. 2001. Constructing Frames of Reference: An Analytical Method for Archaeological Theory Building Using Hunter-Gatherer and Environmental Data Sets. University of California Press, Berkeley.

Chayanov, A. V. 1966. A. V. Chayanov on the Theory of Peasant Economy. University of Wisconsin Press, Madison.

Donham, Donald L. 1999. History, power, ideology: Central issues in Marxism and anthropology. University of California Press, Berkeley.

Fortes, Meyer. 1958. Introduction. In The Developmental Cycle in Domestic Groups, edited by Jack Goody, pp. 1-14. Cambridge Papers in Social Anthropology. Cambridge University Press, London.

Goody, Jack. 1958. The Fission of Domestic Groups among the LoDagaba. In The Developmental Cycle in Domestic Groups, edited by Jack Goody, pp. 53-91. Cambridge Papers in Social Anthropology. Cambridge University Press, London.

Kramer, K., & Otárola-Castillo, E. (2015). When mothers need others: The impact of hominin life history evolution on cooperative breeding Journal of Human Evolution DOI: 10.1016/j.jhevol.2015.01.009

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Bigfoot Researchers Still Insist Native American Skull is Not Human

5/10/2015

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An alert reader of this blog emailed me on Friday to point to a discussion of my posts on the Humboldt and Lovelock skulls (both from Nevada) on the Bigfoot Evidence forum. Those posts were about the "double rows of teeth" alleged to be on the Humboldt skull (an error the author has now corrected) and the size of the mandible from one of the Lovelock skulls. I'm not really into Bigfoot, but I found the misinterpretations of the Nevada skulls interesting because of what seems like a pretty high level of "fringe" chatter revolving around what look to me to be normal human skulls of normal size and with normal features. Both claims (double rows of teeth and "giant-size") are nonsense.

Diehard fans of interpreting the Nevada skulls as Bigfoot crania apparently didn't like my analysis, and one accused me of "not being intellectually honest" because I focused on the misinterpretation of the teeth and avoided "everything else regarding the Humbolt [sic] skull's morphology and ratios, which is what I would have expected an honest, impartial anthropologist to do." In that same exchange, Daniel Dover said "Andy White calls himself a scientist but I'm not impressed with the way he goes off on stuff, making bad assumptions/rants." So there you have it . . . making new friends every day through science! I'm sure neither of these Bigfoot enthusiasts would have had any complaints if I had written a piece declaring that Bigfoot was real.

An aside: I'm not sure why writing a blog post about only one aspect of a skull makes me "intellectually dishonest." By pointing out that the Humboldt skull doesn't have double rows of teeth (which it doesn't) and the Lovelock mandible is not giant-sized (which it's not), did I somehow commit to analyzing every other aspect of those skulls in the same posts? No, I didn't. I mentioned in the Humboldt post that I planned on writing more about the Nevada skulls in the future (and a few days later, voila, I did!). And here I am writing more, which was my original plan. For those of you who want to call me "intellectually dishonest" on some Bigfoot forum that I might never see: if you want to do that (or, perhaps, ask a question or make a point or do something that's actually potentially productive), why not do it on my blog where I'll actually see it? You can even use your same anonymous screen name so your identity will remain a mystery and you can keep your day job without being made fun of for believing in Bigfoot. Try having an honest discussion about evidence. You might like it.

Anyway, let's move on. In this post I'm going to address some of Dover's other claims and interpretations about the Humboldt skull. Dover says that the Humboldt skull has a "browridge, sloping forehead, high vault of the cranium, and protruding jawline . . . all typical sasquatch traits." Here is the image of the skull that he shows, with a "modern human skull" for comparison:

Screenshot from Daniel Dover's webpage about the Humboldt skull: http://sasquatchresearchers.org/blogs/bigfootjunction/2014/11/19/sasquatch-skull-found-near-lovelock-nv/

Outlines of the Humboldt skull (blue) and the "modern human" skull (red) that Dover uses for comparison, aligned on the Frankfort horizontal and roughly scaled the same.

I have added lines representing the Frankfort plane to Dover's image. The Frankfort plane is a reference line that is used to consistently orient skulls for comparison. It is a line that passes through the lower margin of the eye orbit and the upper margin of the external auditory meatus (the ear hole) at a point designated porion. Superimposing this line on both the profile skull images lets us orient them the same so we can really compare. I traced an outline around each skull, roughly scaled them the same (lining up the orbits and porion), and superimposed the drawings on each other so they were both in the Frankfort horizontal (figure to the right).

The superimposed outlines show several of the characteristics that Erik Reed noted in his 1967 paper ("An Unusual Human Skull From Near Lovelock Nevada" - I found a copy of it here on M.K. Davis' website): a supraorbital torus (brow ridge), a sloping forehead, and a well-developed nuchal crest. The jaw of the Humboldt skull also appears to project more than the "modern human" skull, as Dover notes.

Outlines of the Humboldt skull (blue) and the skull drawing from Gray's Anatomy (green), aligned on the Frankfort horizontal and roughly scaled the same.

Let's talk about the jaw first. The "modern human" skull that Dover picked for comparison appears to have something atypical going on with the front teeth and mandible. I don't know what the ultimate source of the image was, but I found a higher resolution version here. The individual (who I would bet was a female based on the shape of the forehead and the small mastoid processes - physical anthropologists out there can feel free to offer an opinion), had a pretty strong overbite, and I wonder if that doesn't contribute to the difference in the profiles of the jaws. To check that, I drew the outline of the drawing of a "normal" human skull as depicted in Gray's Anatomy (illustration here). When that outline (in green) is superimposed on the Humboldt skull outline, the "jutting jaw" pretty much disappears. In other words, the jaw of the Humboldt skull does not protrude greatly compared to a normal human skull.

The brow ridge, sloping forehead, and nuchal crest remain, however. Does that mean this is the skull of a Bigfoot and not a Native American? No. That becomes clear if you try to understand what those features actually mean.

There is a lot of variation in human skulls, and there are several overlapping sources of that variation. Some variation can be attributed to sex (male and female skulls have patterned differences). Some variation is geographical (humans in different parts of the world can look different). Some variation is functional (skulls, like other parts of the skeleton, may reflect adaptions for different environments, different degrees of musculature, etc.). Sorting out how much variation there is, what causes that variation, and what that variation might mean (in terms of human evolution, gene flow between populations, movements of populations, patterns of physical activity, etc.) are things that physical anthropologists, paleoanthropologists, and archaeologists wrestle with all the time.

I guarantee you the simplest explanation for the morphology of the Humboldt skull is not that it's not human. The skull is very much human, and the combination of features (brow ridge, sloping forehead, and occipital area with pronounced attachments for the rear neck muscles) that Dover asserts are "unlike what you will ever find on any normal human skull" can be observed on other prehistoric human skulls and in living humans. That doesn't mean the skull is "average" - it is described as a large, strongly constructed skull that falls at the robust end of the modern human spectrum. But it is thoroughly human. Erik Reed (1967) says the following in his description:

"The skull obviously falls--among New World material--in the general category of the archaic type which is most often referred to by Georg Newmann's term 'Otamid variety.' More specifically, it resembles Early period central California material from the lower Sacramento Valley (Newman, 1957) and from Tranquility in the San Joaquin Valley (Angel 1966). Metrical correspondence to the Tranquility crania, as shown in Table 1, is remarkably close. Strong brow ridges, glabellar prominence, and well-developed occipital torus appear in some of the California material.
Finally, the Humboldt Sink skull closely resembles the Ophir calvarium from Virginia City, Nevada (Reichlen and Heizer, 1966)--even sharing the special peculiarity of a genuine os inca."

The Humboldt skull was presumably that of a large male. The brow ridge and sloping forehead are associated mechanically, as the brow ridge serves to reinforce the face against forces generated during mastication when the forehead slopes away rather than being vertical (that's the explanation of the brow ridge that makes the most sense to me, anyway). The biomechanical model of the brow ridge explains why it is so prominent in chimpanzees, gorillas, and many early hominids, and less prominent (to the point of being absent) in many modern humans. The strain placed on the portion of the skull above the eyes increases when the face is more prognathic (i.e., the jaws protrude more), the frontal bone is less vertical, and there is more emphasis on using the front teeth. The brow ridge - the shelf of bone above the eyes - serves to reinforce the face at the point where strain is greatest. Mary Russell wrote extensively about the biomechanics of the brow ridge in primates: here is a paper of hers from 1982; here is a paper of hers in Current Anthropology from 1985 (but most of it is behind a paywall); here is a 1985 commentary on Russell's work by Milford Wolpoff. The take-away point is that the brow ridge likely has a functional (and perhaps even developmental) origin: it's not some random feature that can be used to discern "human" from "nonhuman" skulls. It's easy to find examples of modern humans with brow ridges, especially associated with large, strong males (which the Humbolt skull presumably was). How about Lex Wotton? Nikolai Valuev? Cain Velasquez? Note the brow ridges and sloping foreheads. Last time I checked, none of these guys was a Bigfoot.

There are also biomechanical explanations for the back of the skull. Dover correctly states that the nuchal plane is where the neck muscles attach to the rear of the skull. There is a general relationship between the robusticity of the nuchal crest and the strength of the rear neck muscles - gorillas and chimpanzees have strongly developed nuchal crests because their neck muscles have to hold their heads up while they are moving about as quadrupeds. That doesn't mean that humans can't have big attachments for the nuchal muscles, however, associated with strong muscles at the back of the neck. I wasn't able to find a comprehensive, cross-primate study of the mechanics of the nuchal line/crest while I was writing this post, but that doesn't mean such a study doesn't exist. I would bet there are other examples of human skulls with nuchal crests like those of the Humboldt skull (here is a paper that has a photograph of a Late Pleistocene human from Romania with a moderately well-developed nuchal crest; here is Angel's 1966 paper on the skeletons from Tranquility, CA, that is mentioned by Reed). Dover's statement that "Human skulls have no such markedly protruding nuchal crest" like that of the Humboldt skull is an assertion that I would guess won't stand up to scrutiny. There's no doubt the Humboldt skull has a big nuchal crest, but that doesn't mean there's nothing else like it in the world and that the skull is therefore not human.

Finally, for your enjoyment, I give you two versions of the outline of the Humboldt skull superimposed upon the profile of former UFC Heavyweight Champion Brock Lesnar (source of profile photo). In the top illustration, I have oriented and scaled the outline of the Humboldt skull by placing the two landmarks used to find the Frankfort plane (the external auditory meatus and the lower margin of the orbit) in their approximate locations on Lesnar's head. In this configuration, the vault of the Humboldt skull is slightly higher than Lesnar's, but the face actually projects less than Lesnar's.

In the bottom illustration, I have placed the Humboldt outline so that it corresponds pretty closely to Lesnar's profile. This puts the orbit a little too far forward and the external auditory meatus a little low, but you get the idea: the shape of the Humboldt skull, presumably that of a large, powerful male, is not inconsistent with the shape of the skull of another large, powerful male. I have no idea what Brock Lesnar's occipital area looks like, but it wouldn't surprise me if his skull had a nuchal crest just as pronounced as that of the Humboldt skull. If you think this makes Lesnar a Bigfoot, I'll let you be the one to tell him that.

The Humboldt skull is the the skull of a human, not a Bigfoot. All the features found on the skull are found in humans. The impression that the jaw of the Humboldt skull juts out significantly farther than a jaws of "modern humans" is incorrect, as shown by the comparison (in proper orientation) with an average human skull. The remaining combination of features that Bigfoot enthusiasts seem to be homing in on as "nonhuman" - the brow ridge, the sloping forehead, and the well-developed nuchal area - are characteristics that are most often expressed in humans that are large, powerful males. I would guess that's what the Humboldt skull is - the remains of a large, powerful male.

A Native American male, not a Bigfoot male.

References:

Reed, Erik K.. 1967. An Unusual Human Skull from Near Lovelock, Nevada. Miscellaneous Paper 10, University of Utah Department of Anthropology, Anthropological Papers. Salt Lake City: University of Utah Press.

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Lovelock Cave and the Illusion of "A Jawbone That Slips Over That of a Large Man"

5/8/2015

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The human skeletal remains from Lovelock Cave, Nevada, are like the pretty girl that all the fringe theorists want to take to the prom. Giant enthusiasts, ancient alien theorists, and Bigfoot researchers all covet them. As you might guess if you've been paying attention, there is no empirical support for the idea that the human remains and the archaeological deposits from Lovelock Cave are related to anything other than Native American inhabitants of the region. And as you also might guess, that doesn't stop fringe theorists from making the same inaccurate statements about Lovelock Cave over and over again.

I won't recount the history of investigations in Lovelock Cave here (you can read a basic outline on Wikipedia). If you Google "Lovelock Cave" you'll get a mixture of results, some focusing on the actual archaeology of the cave and many talking about the Si-Te-Cah legend and the "red-haired giants." Apparently the "Paiute legend" of cannibalistic, red-haired giants originated with a story by a Paiute woman named Sarah Winnemucca Hopkins in her 1883 book Life Among the Piutes: Their Wrongs and Claims (see this 2013 post by Brian Dunning). The part relevant to Lovelock is the last paragraph of Chapter IV. If you read it you'll notice there's no mention of giants: the often-repeated statement that Paiute legends include giants in Lovelock cave seems to be a later addition. I guess it makes it easier to find giants if you just make them up. I haven't spent a lot of time checking into the various legends that are cited as evidence for the worldwide occurrence of giants, but I won't be surprised if a lot of them evaporate when you start to look closely. So far, the giantologists are 0-2 in my book (Lovelock Cave and Steve Quayle's Celtic giants).

So the legend part of the giant story from Lovelock Cave is baloney, but what about the physical remains? For this we have, first, David Hatcher Childress, ancient alien theorist and originator of the Smithsonian conspiracy theory, to help us. In this clip from Ancient Aliens, Childress visits the Humboldt Museum in Winnemuca, Nevada, to examine the Lovelock skulls and proclaim them to be those of giants:

"Inside this cabinet here are three skulls from the Lovelock Caves. When you first see these skulls, they pretty much seem to be normal looking skulls. However, it's when we really start to compare the jawbones with this modern dental impression of a normal adult male that we see that these jawbones are unusually large. And these are really the skulls of giant people. Who were perhaps seven, even eight feet tall. One of the odd things with these skulls is that they're not actually put on display here at the museum and they're kept hidden in this cabinet. Now we don't know if that's really just out of respect for Native Americans or whether there's really something unusual about these giant skulls that they don't want them displayed."

The silliness of the comparison between the "modern dental impression" (which includes only the teeth and a small portion of the gum line) and the Lovelock mandible should be evident to anyone who is breathing. It has been pointed out before. The total size of the cast is smaller because it doesn't include all the bone of the mandible. In what we are shown, the comparable parts of the cast the and the mandible (the teeth and the tooth row) do not really appear to be that different in size. Ancient Aliens only shows us the "normal" plaster cast sitting in front of the Lovelock mandible, however, and doesn't actually give us a view that allows a direct comparison.

Fortunately for us, Childress isn't the only one who has made the plaster cast comparison. There are at least two other pictures floating around on the internet that purport to show a mandible from Lovelock compared to the teeth of a "normal-sized" human (not surprisingly, most of the sites reproducing these photos conclude that the Lovelock mandible is "giant"). The top photo in my illustration is usually attributed to someone named Stan Nielsen and accompanied by his description titled "The Cave of the Red Haired Giants." Nielsen is/was apparently a treasure hunter. The text of his description (e.g., here, here, and here) concludes that "The plaster model was much smaller than the jaw from the skull. In fact, the teeth of the jaw from the skull were almost twice the size of those of my plaster model." I do not know the origin of the bottom photo. The similarities in lighting and background make me suspect that it was taken at the same time as the top photo. [Update: In the comments section Gary pointed out to me that these are actually the same photo. The one on the bottom has just been edited by blacking out the interior of the cast, presumably to make it appear smaller? Anyway . . . there you go. Thanks Gary.]

Both the photos are arranged in the same way, with the plaster cast "inside" the Lovelock mandible, creating the illusion that the mandible is much larger than the plaster cast. Superimposing an outline of the tooth row of the plaster casts onto the mandible shows that, while the teeth and tooth row of the mandible are a little larger, it is not "giant" in comparison to the casts (Terje Dahl points out the same thing on his site, but concludes that that must mean the "real" giant skeletons have been replaced with normal-sized ones).

The illusion of a dramatic size difference is created by the parabolic shape of the human mandible: parabolic objects of similar size can be nested inside one another. Nineteenth and early twentieth century newspaper accounts of "giants" often describe the mandible of the skeleton as being so massive that "it will slip over the jaw of a large man." The uselessness of this comparison was noted by Gerard Fowke in his Archaeological History of Ohio (1902:142-143):

"It is a very common newspaper statement that a Mound Builder has been dug up somewhere 'whose jawbone will slip over that of a large man.' Sometimes the man elevates the marvelous into the miraculous by having a growth of 'remarkably heavy whiskers.'
It is not necessary to procure a Mound Builder in order to perform this feat; the phenomenon is equally apparent with any other full grown human jaw. It may be observed, also, in curved or open-angle objects generally, having approximately the same form and thickness; as spoons, saucers, miter-joints, gutter-spouts, or slices of melon rinds. The significance is a great in one case as in the others. The experimenter has failed to perceive a considerable interval between the end, or angle, of the jaw which he held in his hand and the one with which it was being compared. He should invert the former and apply it to the lower part of the latter, when he would find much less difference than he expected."

Gerard Fowke worked for The Smithsonian, so I'm sure some of you out there will take his basic understanding and explanation of geometry to be part of a vast conspiracy to suppress information about giants. If you're skeptical, I suggest you get some slices of melon rind and try it yourself. Paper cups will also work if you don't have melon rinds or human mandibles sitting around.

The mandibles and skulls of Lovelock Cave are not those of giants, and the "legend" of giants attributed to the Paiute appears do not actually contain any mention of giants. The Humboldt skull does not have double rows of teeth (and neither do any of the Lovelock skulls, if you noticed).

Why does this mythology about Lovelock have such staying power? This is one of the relatively few cases where the skeletal remains of supposed giants have been available to look at. Even when it is perfectly obvious that these are normal human remains, wishful thinkers proclaim them to be the remains of giants. David Hatcher Childress, actually holding the normal-sized skull in his hands, says "these are really the skulls of giant people." I just don't get it. At least when people found mastodon bones in the 1700s they were looking at something that was unexplainable given their knowledge of the natural world. But this isn't that. This is the willful maintenance of a fringe myth that can be easily discarded based on what is sitting right there in front of you. The desire for the "smoking gun" is so strong that not even the most obvious evidence to the contrary can dampen it - when you've made yourself immune to the evidence, you've inoculated yourself to the "truth" you claim to be uncovering. So silly.

If you're mad at yourself for some reason, you can watch this video of M. K. Davis spinning tales about why so many of the skulls from Lovelock Cave appear to be missing. He says that an earlier photo of the cabinet that David Hatcher Childress looked in shows that there used to be more skulls. As pointed out by one of the comments to the video, what Davis is actually looking at is an image that is two photos of the same skulls (in a different arrangement) spliced together. Note that the "shelf" disappears into nothingness on the right side, and the skull on the far right on the top is the same as the second skull from the right on the bottom (you can tell by the missing teeth in the upper and lower jaws). Davis' website makes the same mistake.

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UPDATE: "TreasureForce Commander" Is Upset With Me

5/7/2015

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Photograph of the mysterious "TreasureForce Commander" (pending copyright release).

J. Hutton Pulitzer, aka "TreasureForce Commander," didn't like my post from yesterday. His reaction wasn't to argue with the content, however, but to say I was making unfair use of his copyrighted material by quoting him. On his Copper Culture Artifacts, Finds, Discussion and Debate page on Facebook, he said my "quotes are over the 'allowable length' for using in 'other media' without a release" and he requested that I formally ask him for permission.

I'm not going to do that, because I'm not inclined to think I did anything improper. I believe I'm covered under "fair use," which "is based on the belief that the public is entitled to freely use portions of copyrighted materials for purposes of commentary and criticism" (source). My website is not commercial (I'm not selling anything, let alone producing a product that will compete monetarily with whatever it is Pulitzer is doing), and the post was clearly for the purposes of commentary and criticism. I transcribed 184 words (said in a little over a minute) from a 39 minute interview containing who-knows-how many thousands of words. I used the quote to create something new. I attributed the quote. These are all standard things that researchers, scholars, and reporters do. I'm not a lawyer, and Pulitzer isn't either to the best of my knowledge. I told him to have his lawyer contact me if he really thinks I've done something improper. I'm more than happy to fix a mistake if I've made one (it wouldn't be the first time), but I'm not going to take Pulitzer's word for it that I actually have made one. I don't think I have.

The funny thing here is how quickly he reached for the legal card as a defense to criticism. As far as I know, I didn't misquote him - he said what he said and I wrote it down. Assuming he stands by what he said, you would think he would be happy to be quoted. Am I missing something? Isn't getting attention the whole idea? He likes to brag about how many listeners he has, so I would guess that more listeners would be a good thing. I'm sure he didn't like the overall tone of the post, which was critical. But rather than respond to the substance he supposes he can compel me to change my work by refusing to give me permission to quote him. He purports to be leading a discussion of ideas, but doesn't want to be quoted without permission: so much for the "raging debate" we're all supposed to be having! Can you imagine if scientists did that ("I didn't like your critique of my paper, so I'm not giving you permission to quote me"), or politicians ("you don't agree with what I said on the radio, so I'm not giving you permission to quote me")? That's why we have a thing called "fair use."

Another funny thing: if page views and "likes" are any indication, yesterday's "When To Break Off the Engagement" post was one of the most popular things I've written on this blog. In the 30 hours since I first posted it, it has been "liked" 155 times and viewed 625 times. Those aren't big numbers by internet standards, but they're big numbers for my blog. And, I will note, they are good numbers compared to the number of "plays" and "likes" of Pulitzer's interview with Zimmerman, which has been available for 21 days: as of this writing, that interview has been played 488 times and "liked" twice. Half of those likes, incidentally, are by a mysterious figure that goes by the screen name of TreasureForce Commander.

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When To Break Off the Engagement

5/6/2015

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Since I started making a concerted effort to engage with fringe notions about the human past last November, I've learned a lot. I've learned that strategies for successfully communicating ideas on the internet are very different from those with which most academics are familiar. I've learned that there are people out there who are genuinely interested in exploring ideas and are open to considering evidence that may run counter to the most "exciting" or "mysterious" interpretations. And I've learned that there are plenty of people out there who, despite their repeated statements to the contrary, have no interest in actually discovering the "truth." These are the snake oil salesmen and the ideologues, motivated by money, religion, and/or perhaps even pathology. It isn't always obvious where people are coming from, how best to communicate with them, or if constructive dialog is even possible.

Sometimes, though, it becomes pretty clear pretty quickly.

Fritz Zimmerman, author of The Nephilim Chronicles and self-proclaimed "antiquities preservationist," has decided that the professional archaeological community is keeping the world from seeing whatever "truth" he is attempting to uncover. One of his remedies is to publish a book that he markets by saying it reveals the locations of sensitive archaeological sites that professional archaeologists don't want you to know about. (One of his webpages, for example, states "There is one burial mound at the park, but the DNR won't tell you where it is....but I will" next to the ad for his book - sounds like a pretty serious scholar, right?). He has found a sympathetic ear in treasure hunter J. Hutton Pulitzer, author of numerous books that purport to share "SECRETS and TECHNIQUES that make it possible for people to find lost history and treasure." If you don't see the irony here, you've probably already stopped reading.

In a recent exchange I had with Zimmerman on Facebook, he stated that

"It won't be long before the American people discover that university archaeologists are little more than a criminal organization based on outdated theories, deception and lies."

Now, as a professional archaeologist, that hurts my feelings. I've been doing archaeology now for about twenty years, and I don't recall ever sitting down with a cabal of other archaeologists and plotting about how we were going to suppress the truth with our outdated theories, deception, and lies. We discuss our outdated theories all the time, of course, and that discussion sometimes involves beer. In those cases, the lies and deception we perpetrate are aimed at each other rather than the American people at large. Sometimes bailing on the group before the check arrives is involved, but that's about as egregious as the misbehavior gets.

Zimmerman's statement about the criminality of academic archaeology came after I commented on a Facebook post by Pulitzer. Pulitzer had reposted the 2012 story of Jim Vieira's talk being removed from TEDx with the proclamation "SOMETHING HAS TO BE DONE: This is how the academia are suppressing our Hidden History. This is a sad sad sad state of affairs." Pulitzer, fresh off his TV appearances on The Curse of Oak Island, has been trying to drum up enthusiasm for his exploits by doing a series of audio interviews that he says showcase the "raging debate" about prehistory centered around "the Copper Culture" (I wrote about one of those interviews here; I have not listened to most of them). He says he wants to explore "all sides" of whatever this raging debate is supposedly about (I still haven't figured that part out, as he seems to throw everything including the kitchen sink into the "Copper Culture"), but if you pay attention it's pretty obvious that objectivity isn't really part of the equation. When I saw all the capital letters in his post about the suppression of Jim Vieira, I thought maybe World War III had broken out. And you know it's serious when you use "sad" three times in a row. Anyway, I basically told Pulitzer he was being silly and it was no wonder he had a hard time finding professional archaeologists to interview (he had invited me previously but I had declined). That brought out some giant enthusiasts, and we were off and running with the "but there's thousands of accounts" argument (again), and then Zimmerman, apparently also feeling suppressed, piped up with his commentary.

In addition to the obvious practical love affair one might expect between a person who wants to sell site locations and a person who writes books about how to find buried treasure, Zimmerman and Pulitzer share the common bond of not understanding how science works. That emerges clearly in this interview when they discuss their disdain for academic archaeology (about 13:00 in):

Pulitzer: "What they're talking about in peer review is ten guys just like themselves, who have the same exact degrees, who have the same exact theory. You write all your paper out, you present it to your peers to review. Well, if you do anything that is against the system, anything which is against the status quo, anything against what those degrees taught you it was, not only do they edit it, but in most times you have self-identified yourself as a rebel. And what happens is you get run out of town, you don't get your tenure, you're made into a laughing stock. So peer review is not to assure quality, as much as I believe peer review is actually to hide the smoking guns. And if you are so adamant about coming out about hidden history and forbidden truth, you're actually committing professional suicide if you're willing to talk about it. Do you agree, Fritz?"

Zimmerman: "Absolutely. You know, I liken it to the 15th and 16th century Church and it is why we are in the Dark Ages of history in North America."

According to these two (and many others who believe in giants, alien encounters with the ancient world, unicorns, a flat Earth, Bigfoot, etc.), there is some kind of "truth" out there, known but hidden by scientists, waiting to be revealed by someone courageous enough to do it: it's up to those outside of academia to really figure out what's going on and to somehow work around these obstacles that science has erected in their path. To heighten the drama of this particular battle in the war with the academic elites, the description of the interview loudly announces the existence of SECRET ARCHIVES that hold the "historic smoking guns." As best I can tell, those secret archives are the county history section of the Allen County Public Library where Zimmerman did his research (it is clear from the interview that Pulitzer does not really even know what county histories are - here's a description). Apparently there's a Dunkin' Donuts inside the library now, which is new since I lived in Fort Wayne.

Anyway, this conspiracy of academic archaeologists to suppress the truth comes as news to me, as does Pulitzer's revelation about how peer review actually works. Maybe the other scientists are shutting me out because I let my secret society membership dues lapse.

Zimmerman and Pulitzer aren't the only ones frustrated with science. But they're frustrated for the wrong reasons. As a scientist, I can tell you that there is a human component to all scientific work. Science isn't perfectly efficient. Sometimes it takes longer than it should, for example, for an incorrect idea to be discarded because egos, personalities, or institutional inertia get in the way. But incorrect ideas are eventually discarded, not arbitrarily but because they can be shown to be incorrect. The ability to falsify something (to show that it's wrong) is central to how science works: that's what lets us sort the plausible ideas from the implausible ones; that's what makes science cumulative; that's why we know more about the way the world works today than we did several hundred years ago. And despite what Zimmerman says, we know vastly more about prehistory now than we did a century ago. Watching ideas being proven wrong is watching science in action: it's a demonstration that science works, not evidence that it doesn't. In the classes I teach, I tell my students that each of them could probably outscore Aristotle on a basic quiz about the natural world covering physics, biology, chemistry, astronomy . . . That doesn't mean they're smarter than Aristotle, it just means they have the benefit of 500 years of scientific inquiry that he did not have. There has been an amazing increase in our knowledge that didn't come about by scientists conspiring to hide "the truth."

And there's no doubt that today's peer-review process isn't perfect and could use some fixing (here's an article in The Economist discussing that issue; here's another in Slate). But the imperfections in how science is done are not the reasons why Zimmerman's ideas are not accepted (or even entertained) by mainstream science. Speaking for myself, I can give you two better reasons.

A screenshot from one of Zimmerman's websites, were he posts a photo of skeletons from Mohenjo-daro (in India) with a story about "giant skeletons" from Canada (which is not in India).

The first reason is plainly obvious when you look at his work: it doesn't meet even the lowest standards for presentation of evidence. Pointing out all the errors and misrepresentations Zimmerman makes in his written work, his spoken words, and on his various websites would be a full-time occupation. His online material is one of the most tabloid attempts at giantology you can find, and that's saying something. He freely mixes and matches photos of skeletons and snippets of old newspaper accounts with apparently zero regard for what actually belongs together. Apparently it doesn't matter? You just put "Nephilim" into the headline and slap a picture of some skull on there and voila, you've got yourself a "smoking gun." I own a copy of The Nephilim Chronicles but I honestly haven't read much of it - the errors are so frequent that I found it difficult even to get started (I looked at his coverage of "double rows of teeth" back when I started this adventure, but haven't revisited the book since). Who knows - maybe there are actually some good ideas in there somewhere, or at least something testable.

The second reason is more serious than sloppiness. In the audio interview (starting about 16:00 in), Zimmerman and Pulitzer spend time agreeing with one another that the government's attempts to protect information about the locations of earthworks (and other sensitive archaeological sites which contain human remains and artifacts that are prized by looters because of their monetary value) are a bad thing. Gee, imagine that: a treasure hunter and a fringe theorist coming together to support the endangerment of irreplaceable cultural resources and burial grounds for their own immediate monetary gain. Shocking.

Why won't government officials let Fritz Zimmerman into their site files? That's easy: because it is part of their jobs, by law, to manage and protect information about the locations of archaeological sites that may be harmed if their locations were publicly known. While you listen to Zimmerman and Pulitzer's forbidden history conspiracy tantrum, you should familiarize yourself with Section 304 of the National Historic Preservation Act of 1966. That section reads as follows (bold added):

(a) Authority to Withhold from Disclosure.-The head of a Federal agency or other public official receiving grant assistance pursuant to this Act, after consultation with the Secretary, shall withhold from disclosure to the public, information about the location, character, or ownership of a historic resource if the Secretary and the agency determine that disclosure may-

        (1) cause a significant invasion of privacy;

        (2) risk harm to the historic resource; or

        (3) impede the use of a traditional religious site by practitioners.

(b) Access Determination.-When the head of a Federal agency or other public official has determined that information should be withheld from the public pursuant to subsection (a), the Secretary, in consultation with such Federal agency head or official, shall determine who may have access to the information for the purpose of carrying out this Act.

Records of archaeological site locations maintained by state and federal governments are not public records in the same sense as marriage licenses kept at the courthouse. No-one, neither me nor an "antiquities preservationist" such as Fritz Zimmerman, can walk into a State Archaeologist's office and get access to the site files for no good reason. In fact, archaeological site locations are specifically exempt from the Freedom of Information Act under 16 U.S.C. § 470hh.

The rationale in limiting access to archaeological site records is simple and has nothing to do with concealing a "hidden truth:" it lessens the potential that sites will be looted by people illicitly seeking artifacts or other remains for monetary gain (e.g., treasure hunters). Zimmerman knows that the goal of not putting site locations into the public domain is to protect them from looting, but seems more concerned with positioning himself as someone who is pulling the veil from the "hidden history" that those of us in the professional community are trying to suppress. His goal is to sell books and to sell himself as a liberator. As is obvious from some of his material online, he understands that his willingness to disclose site locations is probably the biggest selling point of his books ("the DNR won't tell you where it is....but I will"). Are those books aimed at serious students of prehistory, do you think? Is this a person whose ideas anyone should take seriously? If he's accusing professional archaeologists of conspiring to keep him from facilitating the pillaging of archaeological sites for things to sell on eBay, I'm on board with being part of that conspiracy. Count me in.

I'm constantly evaluating and re-evaluating my best strategies for engaging with all kinds of people and ideas online. It's been a learning experience. As far as the dynamic duo of Zimmerman and Pulitzer . . . I think I've seen enough. As I mentioned above, Pulitzer has invited me to be interviewed (and to repost one of my blog posts on his site) and I have declined. I know that by doing that I'm losing out on an opportunity to communicate to a different audience than those who read my blog. But I also know that my refusal means I'm not participating in creating content that is designed to draw people to a website that promotes treasure hunting under the guise of "truth." Everything I've seen from Pulitzer so far leads me to believe that joining him in the "debate" and "search for truth" would be a game of charades. He is running a bush-league circus of disinformation. So . . . thanks, but I'm going to pass on this one.

PS: To my archaeology friends in the Midwest (especially Indiana and Ohio): please be aware of Zimmerman's activities. I do not believe he is acting responsibly and I do not believe he has the best interests of the resources at heart. I was a bit conflicted about writing this post because I didn't want to bring any additional attention to his books, but after thinking about it I concluded that anyone who is interested in using his books for illicit and/or unethical activities probably already knows about them. Conversely, I'm guessing that many professional archaeologists in the Midwest were not aware of Zimmerman and Pulitzer. So now you are. I hope some good comes of that.

Update (5/7/2015): The "TreasureForce Commander" is upset with me.

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EWHADP Research Assistant Funded for Fall of 2015

5/5/2015

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The GoFundMe campaign I set up to support a research assistant for the Eastern Woodlands Household Archaeology Data Project (EWHADP) has ended successfully! It got three donations early on (from David Cusack, Ken Kosidlo, and Josh Wells) and then a single person (who has requested anonymity) contributed the remaining funds yesterday. That wasn't how I thought this project was going to get funded but it was a very pleasant surprise. I'm really grateful to those that took in interest in the project this time around, and I think you'll be impressed how it moves forward with someone working on it steadily. And think of how happy the lucky South Carolina graduate student I hire will be: he/she will get some good experience working with grey literature, databases, website management, and GIS, and will also be able to purchase some groceries. It's a win-win. Thank you for your support, donors!

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Steve Quayle Says Evil Giants Turned Humans Gay

5/4/2015

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Here's another right-wing Christian explanation for homosexuality that you can add to your list: the giants did it.

I have no formal training in psychology (the last psychology class I took was as a freshman at Indiana University over twenty years ago), but I'm sure there's some work exploring whatever it is in the human mind that compels us to try to integrate what we see in the world into some kind of internally-consistent framework. Doing that isn't by itself "crazy" - I'm guessing we all do it to one extent or another.

There are a few people out there who have homed in on the idea that giants and/or the Nephilim are the key to explaining the world. Steve Quayle is one of those people, identifying giants as crucial to understanding just about every aspect of world prehistory, history, and current events. His website declares him to be "The leading authority on giants," and he apparently makes a living selling books on giants, speaking about giants, "researching" giants, and doing whatever else it is that someone with the responsibility of being the world's self-proclaimed leading authority on giants would do. He recently appeared on The Rundown Live, a Milwaukee radio show hosted by Kristan Harris, filibustering for an hour about all kinds of topics related to giants (to his credit, Harris does manage to insert occasional comments about mermaids and the "Fiberaci Sequence," but the program was 95% "let's listen to what pours out of Steve Quayle's head"). If you have an hour to kill and want to experience the ramblings of one of the principal stirrers of the Nephilim whirlpool, you can find the program here. If you want to save some time, I recommend Jason Colavito's blog post about the program.

One thing that jumped out at me during the program that I don't recall hearing before was the connection that Quayle makes between giants and the origins of homosexuality (about 47:30 into the interview):

"Let me share this with you: there's so much sanitation of the truth, or there's just downright corruption . . . and to corrupt means to literally destroy, you know, and to ultimately take apart or cause to go to pieces, so to speak . . . the thing is, it's just like moral corruption. It's fascinating to me as scientific corruption takes even higher precedent in the headlines that moral corruption comes along like it. And I'll explain something to everybody: Diodorus - look him up - is one of the most interesting ancient historians talking about the Celtic giants declared that, even though they had comely women giants, meaning they were good-looking giant women, that they preferred the sexual accompaniment of each other. So, that's interesting that most people don't understand but that was introduced to humanity. They weren't born with that: that's what the giants taught them."

So there you have it, straight from the world's leading authority: evil giants gave humans the gay.

I did what Quayle advised me to do and looked up Diodorus. Diodorus Siculus was Greek historian writing in the first century BC. He is most famous for his Bibliotheca historica, a lengthy book of world history and geography. As best I can tell, Quayle's claim that Celtic giants introduced homosexuality to humanity is in reference to Book V, where Diodorus describes the inhabitants of Gaul (I found it reproduced here):

    “For stature they are tall, but of a sweaty and pale complexion, red-haired, not only naturally, but they endeavour all they can to make it redder by art. They often wash their hair in a water boiled with lime, and turn it backward from the forehead to the crown of the head, and thence to their very necks, that their faces may be more fully seen, so that they look like satyrs and hobgoblins. . . .
    . . .
    According to their natural cruelty, they are as impious in the worship of their gods; for malefactors, after that they have been kept close prisoners five years together, they impale upon stakes, in honour to the gods, and then, with many other victims, upon a vast pile of wood, they offer them up as a burnt sacrifice to their deities. In like manner they use their captives also, as sacrifices to the gods. Some of them cut the throats, burn, or otherwise destroy both men and beasts that they have taken in time of war: though they have very beautiful women among them, yet they little value their private society, but are transported with raging lust to the filthy act of sodomy; and, lying upon the ground on beast's skins spread under them, they there tumble together, with their catamites lying on both sides of them: and that which is the most abominable is, that without any sense of shame, or regard to their reputation, they will readily prostitute their bodies to others upon every occasion. And they are so far from looking upon it to be any fault, that they judge it a mean and dishonourable thing for any thus caressed to refuse the favour offered them.”

I’ve omitted a dozen paragraphs between where Diodorus describes the Celts as “tall” and the part about about sexual relations. Those paragraphs describe, among other things, how the Celts eat, dress, fight, treat strangers and enemies, and worship. The Romans were already familiar with Celts by this time, having been in conflict with them in the fourth century BC. The Gallic Wars of 58-51 BC would bring the Romans and the Celts into very close, hostile contact. Diodorus’ description of the Celts was probably not meant to be flattering, which makes sense considering the unfriendly nature of the interactions between Rome and the Celts. I'm sure it was not the first (or last) time in history when descriptions of homosexual and pederastic behavior were used to attempt to demean and distinguish "them" from "us."

The alert reader will note that the actual passages from Bibliotheca historica about the Celts aren’t anything like Quayle portrays them. There is nothing about giants (unless you believe that the simple remark that the Celts were “tall” meant that they were actually giant supernatural human-demon hybrids), and there is nothing about humans becoming gay by watching giant men getting it on with each other. I’m not sure where that particular Nephilim fantasy is coming from, but there’s no basis for it in Bibliotheca historica.

My main goal in writing this post is not simply to point out a factual error made by someone hocking ancient giants to sell books (if I had a nickel . . .), it's to highlight how fringe notions about the human past are used to frame the world today and how we regard the people in it. Quayle's desire to attribute everything "corrupt" to the influence of evil giants may seem quaint and silly, but it's important to recognize how that theory of the way the world is connects to Quayle's statements about what ought to be done about it. As I wrote in this post, Quayle has declared that the Nephilim bloodline needs to be exterminated, and the hunt is on among Nephilim enthusiasts for markers of Nephilim ancestry among living humans. How do homosexuals fit into Quayle's recommendations for behaviors to mitigate the coming End of the Age?

Quayle is selling the search for truth, but it's really snake oil. It’s ironic that one of his dramatic lines in the interview is that “Men and women can choose: do they want to believe a lie? or do they want to believe the truth? Unfortunately the majority will believe a lie.” In reality, though, the willingness of people to believe a lie is what sells Quayle’s books. If you're reading this post and you think Quayle may be onto something, I urge you to check out his claims about the past for yourself. Do what he says: look it up. As an archaeologist who deals mostly with prehistory, I'm not very familiar at all with Greek and Roman historical sources. It only took me a few minutes, however, to track down Quayle's reference and see that his interpretation of Diodorus' account of the Celts was way off. Is that just a mistake on Quayle's part, or is it an intentional fabrication to build the basis for stirring one more aspect of modern human society into his Nephilim crockpot? If he's willing to aggressively misinterpret and misrepresent the past in order to sell you his picture of the present and the future, do you really want to trust him? I don't. Go and look for yourself.

Update (5/5/2105): Jason Colavito followed up on this post with some background about the history of Christian conspiracy theorists equating the Nephilim with homosexuality.

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Australopithecine Sexual Dimorphism: What's Love Got to Do With It?

5/2/2015

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Last week I posted a short piece wondering aloud if we are safe in assuming that female australopithecines, rather than males, were the ones giving assistance to other australopithecines during birth. The response of one of my friends on Twitter was that "Sexual selection says they should've been too busy getting busy to care." Like the ambiguity in the student paper that prompted me to ask the male/female birth assistance question in the first place, I'm not exactly sure of the intent of the response. Was it to use the notion of sexual selection to dismiss the idea that males could have played a beneficial role in australopithecine births? Or was it to poke fun at how much weight we give sexual selection?

Sexual selection is selection (differential reproduction) that occurs when some individuals reproduce more than others because they are better at securing mates, rather than because of interaction with the environment (as in natural selection. Charles Darwin coined the term and explained in On the Origin of Species (1859:88). Sexual selection, he wrote,

"depends, not on a struggle for existence, but on a struggle between the males for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring. Sexual selection is, therefore, less rigorous than natural selection. Generally, the most vigorous males, those which are best fitted for their places in nature, will leave most progeny. But in many cases, victory will depend not on general vigour, but on having special weapons, confined to the male sex. . . . The war is, perhaps, severest between the males of polygamous animals, and these seem oftenest provided with special weapons."

How important was sexual selection among australopithecines? We have traditionally looked at two aspects of sexual dimorphism (differences between males and females) to evaluate the degree of male-male competition in primates: canine size and body size. If sexual selection was important among australopithecines (as it is chimpanzees and gorillas, our two closest living relatives) we would expect to see males with significantly larger canines and of significantly greater body size than females. The fossil record isn't as clear on these things as you might think.

Canine Size

The drawing below shows maxillary dentitions from a chimpanzee, an Australopithecus afarensis (ca. 3.9-2.9 MYA), and a modern human. I think the original drawing is from the (1981) book Lucy: The Beginnings of Humankind by Donald Johanson and Maitland Edey. The difference in the relative sizes of the canines (indicated with red arrows) is obvious. Chimpanzees (especially males) have large canines. The space between the canine and the incisors (called a diastema) is there to accommodate the opposing canine when the jaws are closed. The canines of modern humans barely protrude at all, and there is no diastema. The canines of australopithecines are larger than those of modern humans, but smaller than those of chimps. They protrude slightly, and there is a small diastema.

The australopithecine specimen in the drawing is a reconstruction of the palate of Lucy (AL 200-1), traditionally interpreted as the remains of a female (but see below). So that single specimen alone tells us nothing about male canine size and nothing about sexual dimorphism in canine size. Studies looking at samples of australopithecines have come to different conclusions about the degree of sexual dimorphism in the canines. A 1997 paper by J.Michael Plavcana and Carel P. van Schaik concluded that:

"Estimates of canine dimorphism, relative canine size, and body weight dimorphism in australopithecines provide little definitive information about male–male competition or mating systems. Dimorphism of Australopithecus africanus and Australopithecus robustus can be reconciled with a mating system characterized by low-intensity male–male competition. The pattern of dimorphism and relative canine size in Australopithecus afarensis and A. robustus provides contradictory evidence about mating systems and male–male competition."

This 2005 paper by Sang-Hee Lee paper concluded (based on a resampling method that wasn't dependent on sex estimates) that canine sexual dimorphism in Australopithecus afarensis was comparable to that seen in chimpanzees.

The canines of Ardipithecus ramidus (ca. 4.4 MYA) are smaller than those of chimpanzees but larger than those of modern humans. The image below shows a comparison of a modern human (left), Ardipithecus (middle), and chimpanzee (right) (source). The teeth in the image belong to "Ardi," the relatively complete skeleton of Ardipithecus ramidus discovered in 1994 and published in 2009. That skeleton has been interpreted as the remains of a female. An analysis of other Aridipithecus ramidus teeth (Suwa et al. 2009) concluded that male and female canine teeth were of similar size.

If Ardipithecus is a hominid and the dental remains have been interpreted correctly, it suggests that males early in our lineage did not have large canines, presumably indicating that they were not vigorously competing with one another for mates (i.e., sexual selection was relatively unimportant). It would also suggests that the LCA was unlike chimpanzees in many ways (e.g., perhaps an arboreal biped with a flexible back, mobile wrist, and generalized dentition rather than a knuckle-walking quadruped), making the chimpanzee overall a poor model of the LCA and therefore a poor model upon which to base explanations of evolutionary change in our lineage.

The single published skull from Sahelanthropus, a possible hominid from about 7 MYA, has been interpreted as that of a male with a relatively small canine. I don't claim to have read the Sahelanthropus studies in detail, but I'm dubious that you can accurately estimate sex for a single skull from species about which so little else is known. If the skull is that of a male, whether or not it's a hominid, it would be consistent with a low level of sexual selection in late Miocene apes. If it's a female it doesn't tell us much about competition between males.

So the canine picture is a confusing one. The canines of australopithecines sure don't look large to me (compared to chimpanzees), but at least some studies suggest a relatively high degree of dimorphism among some australopithecines. If either Ardipithecus or Sahelanthropus was a hominid with a low degree of sexual dimorphism of the canines (suggesting low male-male competition), greater canine sexual dimorphism among australopithecines would suggest an increase in sexual selection during the Pliocene. If the LCA was more like a chimpanzee, however, sexual selection may have decreased during the Pliocene.

Body Size

The body size picture is also confusing. You can find a paper to support whatever you want, from a high degree of sexual dimorphism in body size (like gorillas) to a low degree of sexual dimorphism (like modern humans). When I talk to my Human Origins class about it, I just tell them what sexual dimorphism is and why we would like to know about it, and then confess that I can't make up my mind what the best answer is at the moment.

A paper published last week came down on the side of low sexual dimorphism in body size. The authors, Philip Reno and Owen Lovejoy, conclude that:

"The relatively stable size patterns observed between Ardipithecus and Australopithecus suggest there was not strong selection for greater male body size that would result from a reproductive strategy arising from increased individual male reproductive success via inter-individual aggression. In fact, the reduction in canine dimorphism with feminization in the male would argue for reduced “agonistic” behaviors (Lovejoy, 2009). This is particularly so given the strong association between canine dimorphism and reproductive behavior in anthropoids (Plavcan, 2012b) and the lack of a dramatic dietary shift associated with canine modification in early hominids (Suwa et al., 2009)."

This is not a new argument from Lovejoy, who has been hypothesizing the presence of monogamous reproductive strategies among early hominids for decades.

What's Love Got to Do With It?

We've got a lot to learn about australopithecine social organization and the lack of clarity about sexual dimorphism does not help. In my post about whether birth assistance was a gendered activity, I reasoned that it would be more likely that males would be involved in birth assistance if males and females were pair-bonded. In that circumstance, paternity would be more-or-less certain, and male behavior that increased the success of reproduction would be selected for. Overall, I like the anatomical evidence for a relatively low level of sexual selection among australopithecines, consistent with low levels of male-male competition. Without being able to accurately determine the sex of australopithecine fossils, however, its hard to have a lot of confidence. If Lovejoy is right about Ardipithecus, male-female pair-bonding was already present in the ancestors of australopithecines (could it even have been typical of many apes in the late Miocene?). If the LCA was more like a chimpanzee, however, sexual selection may have been strong at the time of the divergence of the chimpanzee and human lineages.

Even if australopithecines had a monogamous, pair-bonded mating system, however, that doesn't mean there was anything like culture attached to it. It may have just been part of a hard-wired biological adaptation, one that emerged along with bipedalism because it made evolutionary sense. Along with certainty of paternity would come greater paternal investment in offspring, presumably resulting in a higher survival rate (hence being selected for). The low/moderate amounts of sexual dimorphism in body size could be accounted for by the positive relationship between body size and energy efficiency during bipedal locomotion: males provisioning females and their offspring would have to travel longer distances than females, selecting for larger body sizes among males (but not larger canines) (see Daniel Lieberman's book The Story of the Human Body). In this scenario, "love" would be related to sexual dimorphism not because of male-male competition but because bigger males would be better providers.

Convinced? I'm not (either way). But it's worth thinking about.

Reno PL, & Lovejoy CO (2015). From Lucy to Kadanuumuu: balanced analyses of Australopithecus afarensis assemblages confirm only moderate skeletal dimorphism. PeerJ, 3 PMID: 25945314

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