Who’s a Freak?

What to make of our ancestors and distant relatives, separated from us in time and space? Do we emphasize our connections, symbolically tying us to something bigger–and even potentially boundariless, conceptually defying the impossibility of the close contact from which we build our daily relationships with loved ones and friends? Or do we see those only distantly related to us as an unambiguous–and unambiguously negative–counterpoint to our selves and our locations? … As in, “Thank heavens we’re us and not them, here and not there!” Or, “At least we’re not freaks like them.”

Time, Distance, and Scientific Bias

Cultural anthropologists and linguists have long been struck by the way that symbolically interlinked cultural concepts often involve equating time with space. Distance and duration may be mutally metaphorically evocative.

Of course, metaphors are, by definition, never exact and complete equivalences between two terms. Certain similarities are exaggerated, and the surprise or canniness of those arbitrarily emphasized similarities diverts our attention from what might otherwise be accepted as salient differences.

Time and distance are a case in point. Sure, things that are far away are as inaccessible as things lost in the past or unlikely to be reached until well into the future. But distance is distance. In terms of embodied experience, we’re here or we’re there. And if “there” is far enough away, suddenly distance gets entangled with the experience of time. So, better not compare time and distance too intensely, or you’ll realize you’re trying to compare two things that may better be seen as one complex whole.

In general, the metaphors that we culturally inherit are kind of like having our elders getting us to play magic tricks on ourselves without anyone realizing what we’re missing or misapprehending. In that metaphors are tools for getting us to focus on only part of what’s really a larger, interconnected whole.

It's easier said than done to avoid jumping to conclusions. Just ask Tom Smykowski, who had the emotional, aspirational dream of having a mat that "would have different conclusions written on it that you could jump to." This blog doesn't have an opinion about whether the Android app based on Smykowski's idea is as great or better than the concept of having--even paying for--a pet rock, but the screen-capture image above is indeed from Andrew Boeglin's "Jump to Conclusions" Android app.
Just remember Tom Smykowski’s emotional, aspirational dream of having a mat that “would have different conclusions written on it that you could jump to.” This blog doesn’t have an opinion about whether the Android app based on Smykowski’s idea is as great or better than the concept of having–even paying for–a pet rock, but the screen-capture image above is indeed from Andrew Boeglin’s “Jump to Conclusions” Android app.

And one of the most important lessons of anthropology is that such socially constructed self-deception affects all of us, non-literate hunter-gatherers and over- (or mis-) educated scholars, alike. Among the latter, this definitely includes really sharp ones, whether they are trained in natural sciences, interpretive humanities or both. A lot of my more critical colleagues in biological anthropology have tried to make the point that bias is always more subtle and pervasive in scholarship than you might think. But it’s not such a palatable point to digest, humbling as it is. It is also confusing, because–as I agree with my colleagues in the sciences, as well as many in the humanities–scholarly knowledge tends to increase and grow in reliability over time. This is a kind of epistemological stance of: “historical scholarly crowd-sourcing works over the long term.”

As such, this stance involves admitting individual difficulty in achieving certainty–that is, certainty about how to explain and predict what we’re experiencing and what’s going on in the world. But it’s squarely against jumping to the following conclusion (see right, for a helpful perspective on jumping to conclusions):

  • The inevitable individual difficulty in attaining objectivity entails that knowledge simply and entirely depends on each individual’s subjective position and choices.

So my point is this: it’s not so easy to gain awareness of our biases, even though science and scholarship help us to know more … and know better. And when you think you have a case of unrecognized bias–one that is limiting our figuring out how to know better–well, it’s worth getting your argument out there.

Why are we so cognitively and emotionally susceptible to metaphorical misdirection, the evocativeness and seeming innocence of which tends to keep us from recognizing our biases? As I noted in my previous post on logic and emotion, even the most rigorously, formally constructed logical representation systems in math and science–except the most trivially descriptive or tautologically simplest systems–will produce some form of incompleteness or inconsistency.

Even in science, linguistic descriptions and arguments, pictorial representations, mathematical/statistical models cannot unambiguously achieve a 1:1 correspondence with what the scientist wants or intends to represent. As Wittgenstein already implied in his early work, complex symbolic representations remain substantially indexical and iconic; they direct our attention and prime us to perceive certain patterns. In doing so, we might be limiting our conceptual “field of view,” failing to recognize certain features we might otherwise be able to observe, measure, re-observe, and verify.

One of the challenges here is that we simply don’t have an agreed-upon, rigorously applied method for evaluating and minimizing bias. Scientific progress in predicting and understanding how the world works and how it got this way–well, it’s real. But it’s much slower and less intentional than we would like to believe … or simply like, period. Bringing this point full-circle, metaphor is one of those symbolic features of open representation systems that can divert or filter our attention and perception, without our realizing it. For nonscientists and scientists alike.

What Does Biological Distance Mean to Us?

I thought about this the other day when I heard a quite jarring, fantasy-filled, seemingly improvised statement by Stanford University geneticist Montgomery Slatkin on National Public Radio’s All Things Considered on Wednesday. Slatkin is a very successful genetics researcher who has scientifically contributed to how we analyze the differences in little bits of our DNA (alleles, for those of you in the know) in order to reconstruct how we’re related and how we’ve evolved. But he seems to be taken with the metaphor that our ancient ancestors–I mean, those from around the emergence of our genus, Homo, roughly 2-1 million years ago–were really different and distant from us. Here’s what he said to NPR science reporter Christopher Joyce:

“As someone once said,” Slatkin observes, ” ‘If a Neanderthal came and sat next to you on a bus, you’d probably get up and change seats. But if a Homo erectus came and sat next to you on a bus, you’d probably get off the bus.’ “

I’ll talk below about why NPR was covering Slatkin and his colleagues’ current research. But first, a more immediate observation…

His statement reminds me of when–at the end of Spinal Tap–David St. Hubbins and Nigel Tufnel try to explain what they actually say and mean about brotherhood and equality:

David St. Hubbins: We say, “Love your brother.” We don’t say it really, but…

Nigel Tufnel: We don’t literally say it.

David St. Hubbins: No, we don’t say it.

Nigel Tufnel: We don’t really, literally mean it.

David St. Hubbins: No, we don’t believe it either, but…

As for me, I have no idea who might have said what Slatkin says someone once said.

What he’s probably referring to, though, is a quote usually attributed to the physical anthropologist Carleton Coon, also often credited with the illustration of a well-groomed modern-looking Neanderthal, based on an anatomical reconstruction of the famous male skull from the French cave site La Chapelle aux-Saints (see below, left). Here’s one version of the (usually paraphrased) Coon quote:

Indeed, the late anthropologist Carleton Coon once suggested that a Neandertal dressed in a suit and hat riding the New York City subway would go unnoticed. The next time you ride the subway, look for someone with a stocky, muscular body with short forearms and legs; a large head with bony brow ridges; a jutting face with a very big nose; and perhaps reddish hair and fair skin. (Balter 2009:870)

It’s worth pointing out that, in light of Slatkin’s recent comment, the gist of the Coon-attributed quote is, you probably wouldn’t get up and change seats if a Neanderthal sat down next to you on the bus (or subway, or whatever means of public transport). Because–as long as that Neanderthal was clothed, groomed, and otherwise technologically equipped in a way that was within your notions of reasonably culturally appropriate–he or she wouldn’t have been biologically different enough to make an impression on you.

Forensic artist John Gurche's reconstruction of the skull KNM ER-3733, one of the best preserved early Homo erectus specimens (ca. 1.7 million years old) from East Africa. Image is hyperlinked to the source on the Smithsonian Institution's website. Chip Clark, photographer.
Forensic artist John Gurche’s reconstruction of the skull KNM ER-3733, one of the best preserved early Homo erectus specimens (ca. 1.6 million years old) from East Africa. Image is hyperlinked to the source on the Smithsonian Institution’s website. Chip Clark, photographer.

Let’s use this point to take my critical concern about Slatkin’s statement to its logical conclusion. Let’s go further back into our evolutionary past and consider Homo heidelbergensis (the taxonomic name given to a network of evolving human populations occupying large parts of Africa and Eurasia roughly 750-250 thousand years ago, predominantly contributing to the ancestry of Neanderthals and living humans alike). Should we expect there to have existed a particular regional population or time period within the evolution of H. heidelbergensis when common anatomical features would have been so robust or simply so biologically different that no amount of modern grooming and dress would disguise a time-transported individual today? Similarly, was there a particular region or time period within the earlier evolution of Homo erectus (similar taxonomic name usually applied to the ancestral human lineage emerging in subsaharan Africa roughly 2 million years ago, then spreading out into Eurasia) where anatomy was so different or evolutionary primitive that it would inevitably scream at us, “Biological monster!”

Indeed, the image above right offers an opportunity to consider the question, “Would H. erectus seem like a bunch of evolutionary distant freaks to us?” There is a substantial argument to be made that the Kenyan fossil specimen ER-3733–on which John Gurche’s evocative reconstruction is based–is the cranium of a female (Wolpoff 1999). This adult individual certainly had a brain significantly smaller than ours. She might not have been cognitively or anatomically capable of learning English or Mandarin, although she may well have communicated with a grammatically simpler, more limited “proto-language.” And although she would have probably been wiry and somewhat short, albeit with a very robust face and receding chin, many other features would seem quite human. Other H. erectus finds suggest that her torso and limb proportions would have been more similar to ours than those of the more distantly related H. habilis and the australopithecines. The same goes for posture and gait. And with similar digit (finger and toe) proportions to ours, she apparently had the endurance to walk long distances on two legs and the fine manual dexterity to make stone handaxes. I’d guess we’d be more likely to notice her on the bus for expressing quite transparent emotions of fear, anxiety, and confusion–finding herself so incomprehensibly out of place (due to her being completely away from her time)–than because something about her anatomy is so physically intimidating.

Biological Distance (or its Relevance to Us) in Flux

Modernized Neanderthal, based on Prof. J. Howard McGregor's classic reconstruction of "Old Man of la Chapelle's" skull, the bust of which was created for display in the American Museum of Natural History around 1918. Originally published in Carleton Coon's (1939) The Races of Europe. Although often attributed to Coon, it is not clear whether the drawing is by Coon or McGregor.
Modernized Neanderthal, based on Prof. J. Howard McGregor’s classic reconstruction of “Old Man of la Chapelle’s” skull, the bust of which was created for display in the American Museum of Natural History around 1918. Originally published in Carleton Coon’s (1939) The Races of Europe. Although often attributed to Coon, it is not clear whether the drawing is by Coon or McGregor.

Now, the Neanderthal illustration that’s often noted (or republished) when discussing the aforementioned Coon-attributed quote–and again, which is also usually attributed to Coon–was published in The Races of Europe, appearing as Figure 1 on page 24 (Coon 1939). The illustration (posted here via one of the several locations where it is available on the world wide web) shows what a Neanderthal might have looked like riding on the subway back in the day. Here’s what Coon actually presented as a caption to this figure:

Neanderthal Man in Modern Dress. MacGregor’s (sic) restoration of La Chapelle aux Saints, provided with hat, hair, and clothing by the artist. Although we do not know that the reconstruction of the soft parts is accurate, nevertheless the facial features were probably essentially human. This picture serves to illustrate the fact that our impressions of racial differences between groups of mankind are often largely influenced by modes of hair dressing, the presence or absence of a beard and clothing.

It’s not clear whether J. Howard McGregor was the artist who added the hat, hair, and clothing … or whether it was added by the artist tacitly known as Coon. I have not been able to find a clear attribution of the drawing to Coon, however.

Regardless of who drew the now-famous illustration–based on McGregor’s original Neanderthal reconstruction, later made over as a fashionably modern 1930s era American man–Coon was offering an insightful biocultural point. Group-level human differences that we might believe to be biological or genealogical in nature are, in fact, substantially–if not overwhelmingly–technologically and symbolically constructed through social practice.

This adds a new twist to the backstory behind Slatkin’s apparent misquote of what may well be a pseudo-apocryphal statement (in that what’s often paraphrased was only implied by Coon). Coon went beyond simply saying that a Neanderthal would go unnoticed today because his anatomy is not so different from ours. He further implied that we wouldn’t notice him BECAUSE he was dressed and presented himself like we do in public.

Indeed, the one time I know of personally that someone got off a bus because other passengers were threatening was when a Japanese colleague was harrassed by neo-Nazi skinheads while he was attending a conference in Europe. Obviously, what was really threatening here was ideologically motivated, emotionally charged group-level violence, clearly framed by culturally symbolic, dramatic grooming and clothing style.

Here’s where the story starts to get really anthropological. Coon was the last really influential race scientist. And in the early 1960s, Sherwood Washburn and Ashley Montague led a very public, hostile charge to call him out as such (Trinkaus and Shipman 1994). Coon was hanging onto already scientifically discredited ideas. Those ideas included claiming that races of humans were self-evident biological subunits of H. sapiens that had exchanged genes little over the previous several thousands–perhaps even tens of thousands–of years. As Milford Wolpoff and Rachel Caspari have documented in their book Race and Human Evolution (1998), the most dangerous–and entirely unsubstantiated–idea that Coon developed was that those purportedly scientifically objective major races largely evolved independently into modern humans, crossing the “sapiens threshold” at different times in our prehistoric past.

The main reason why modern biological anthropology has abandoned geographic racial subdivisions as a framework for describing human variation is this: there’s simply no agreed-upon place to draw racial boundaries. Human evolution has involved not only random mutation, random genetic drift, and occasional gene flow. Anthropologists and human biologists are still working on reconstructing detailed and highly dynamic, shifting patterns of cultural-political resistance and institutionalized linguistic and political barriers to migration; cultural intergenerational inheritance of reproductive success; and natural selection across spatial environmental gradients. Racial frameworks are too simple and static. They inaccurately and incompletely account for patterns of human biological variation and genetic relatedness (Bamshad et al. 2004).

How could we reasonably expect that 18th Century European observers of human anatomical variation–including Carolus Linnaeus and Johan Blumenbach–would have figured out the how and why of human variation right off the bat? Racial classifications subdividing humans into geographically organized species or subspecies have always been intertwined culturally with symbolically evocative concerns over political control, hierarchy, morality, vigor, sexuality, and identity. The notion that humans may be scientifically validly sorted into major races was historically a terribly biased one.

The idea of human races–and their purported natural inequality–was fed by and continued to feed an ideology of intrinsic difference and inequality between major regions of the world … and at a historical moment when sovereign states, trade companies, and producers of consumer goods, means of transportation and rapid communication were more tightly connecting and rapidly transforming that world.

This is a classic example of a metaphor (that major groups of humans are naturally of different substance and value, just as differnt kinds of animals and plants are) evoking an ideological myth. In turn, the myth of White European biological superiority legitimized the very political order that it masked, by transforming a political claim into a convincing assertion of natural fact. On top of the irrational appeal to scientific authority per se–rather than scientifically valid critical reasoning and independently verified observations and analyses of those observations–the racial claim is a false one that structures notions of social, geographic, and temporal distance, diverting our attention from the similarities that exist across putative racial boundaries (Bamshad et al. 2004), leading us to feel that those on the other side of the boundary are–in some way–freaks.

The existence of races–that is, geographically well-defined, evolutionarily ancient human subspecies–was virtually taken for granted, with very little effective scientific challenge to this idea until anthropologists and biologists reacted to the appalling reality of how race science inspired and aided Nazi biopolicy that began with eugenic segregation and occasionally sterilization and ended with largely racially focused genocidal cleansing (Wolpoff and Caspari 1998).

Now, Coon was clearly a racist in sentiment and by professional theoretical orientation (Jackson 2001). He was perhaps more susceptible to race-as-scientific-ideology than was his mentor Ernest Hooton (Giles 2012). Thus, in his major–and extensively criticized–book The Races of Man (1962), Coon certainly hung onto biases that his post-World War II contemporaries saw as old-fashioned at best … and politically, dangerously irresponsible at worst.

But … credit where credit is due. Coon was an extraordinarily keen observer and thinker. He could synthesize empirical observations and offer subtle, complex explanations about adaptation or population history. Some of these have been or may well come to be vindicated. Such as his suggestion that multiple later Pleistocene populations, including Neanderthals, contributed to the ancestry of modern Europeans (Coon 1939).

Still, at its core, Coon’s (fundamentally incorrect) way of thinking about biology was that there’s a tendency for competition in nature to be structured and play out at the group level–that is among subpopulations within biological species.

However, Coon’s view of racial origins is different from that of much more blatantly racist biologists (including Ernst Haeckel’s theory of racial competition that so strongly influenced Hitler’s views expressed in Mein Kampf [see Proctor 1988; Wolpoff and Caspari 1998]). Coon saw races as emerging prehistorically from admixture. Out of a complicated, murky pattern of kinship and social boundaries came an important level of structure; consequently, it was independent, regional racial evolution and competition shaped modern Homo sapiens, according to Coon (1962). All ideologies get transformed–sometimes tweaked, sometimes thoroughly inverted–in different places and times. Because ideologies are stories … albeit highly influential ones of political order as cosmological or natural order. Coon’s (1939) story of White racial origins and racial difference reads like an optimistic, mid-century American hegemonic ideology: colonization of the New World gave the Caucasian race the natural ecological opportunity it needed to compete and expand.

Speaking of struggles to claim or maintain hegemony, consider how St. Hubbins and Tufnel tried to clarify what they really thought about race:

David St. Hubbins: No, we don’t believe it either, but…

Nigel Tufnel: But we’re not racists.

David St. Hubbins: But that message should be clear, anyway.

Nigel Tufnel: We’re anything but racists.

Carleton Coon, though, was clear in his writing that he was a racist. He probably didn’t think that it was unfair to have such ideas; he thought they were scientifically warranted. This is why it’s is important to remember that the “race-as-natural-order” metaphor overwhelmed his otherwise keen eye for human population variation in anatomy and behavior. He missed or ignored the extensive similarities across purported contemporary racial boundaries and the geographic gradients in phenotypes that make races impossible to consistently define at any scale relevant to biological processes.

Stay Mindful of History

OK. Back to our point of departure… It’s not a problem in itself that, in a recent radio interview, geneticist Montgomery Slatkin thoughtlessly said something scientifically unwarranted and unnecessary about our Ice Age relatives and ancestors. It’s that his thoughtlessness betrays a lack of awareness or concern with how the metaphor of temporal distance as social distance is historically so closely intertwined with the metaphor of geographic separation–that is, separate and unequally evolved races–as social distance. Slatkin may not be thinking even remotely about race. But the history of how racial metaphors so extensively biased scientific thinking about human variation should help us to better understand how bias indeed influences us, sometimes very dangerously.

And although Slatkin’s statement isn’t perniciously legitimizing of any political ideology of inequality and domination–not in the least–I still want us to respect the importance of effective critique and interpretation, so that we scientists can better interpret our results and convey the content and relevance of our findings to a wider public. So, I wanted to present a big, very thorough, seemingly constantly necessary reminder of where biases come from and why we should actually really care about working to recognize and fix them. And indeed, I suggest that the “temporal-distance-as-social-distance” metaphor may bias Slatkin’s interpretations of some very very interesting recent results.

Overall genome-wide similarities–based on fewest numbers of differing genetic transversion mutations–between pairs of living and ancient individuals. This neighbor-joining tree of genetic similarity/difference shows that the newly reported Altai toe bone was from an individual more closely related to Neanderthals than to the (Homo erectus? … generic archaic Asian?) finger bone found from a slightly later layer in Denisova Cave, Siberia.

Basically, Slatkin was interviewed by NPR because the scientific freight train that is ancient human DNA research is rolling along.

Last Wednesday, Svante Pääbo–along with Slatkin and a typically massive collaborative team of geneticists and paleoanthropologists–published a scientific paper, detailing the impressively recovered and reconstructed genome of a human female whose well-preserved but isolated toe bone was found in a roughly 50,000 year-old archaeological layer at the now-famous Denisova Cave site.

Although Pääbo had earlier announced the general gist of the results on his lab’s website, it is nevertheless exciting to geek out over getting access to details–that is, detailed observations and results confirming the preliminary announcement, along with new and quite thought-provoking conclusions.

So the new paper in Nature (Prüfer et al. 2013) confirms that this late Middle Paleolithic person shared her own recent ancestry with Neandertals inhabiting most of western Eurasia around the same time (again, roughly 50,000 years ago). More simply, she (and the presence of DNA from two X chromosomes lets us know it was from a female) was a Neanderthal.

And this is a big deal, because the slightly geological younger finger bone that recently made Denisova Cave famous (Reich et al. 2010) had preserved DNA that was mostly inherited from a very ancient human ancestor: one shared with Upper Pleistocene Neandertals and living humans alike, but with a large number of intact genetic markers that were lost or mutated over the generations in Neandertal and anatomically modern human populations.

The extraordinary reconstruction of ancient genomes from tiny DNA fragments in ancient human bones provides the evidence to do extensive statistical analyses of the genetic similarities and differences between individuals separated in space and time by thousands of kilometers and tens of thousands of years. And what Slatkin, Pääbo, David Reich and other highly innovative geneticists working on ancient DNA have discovered is this: occasionally, over the past two million years, some groups engaged in substantial dispersals from one continent far into another … and then interbred with some of the other hunter-gatherers who had already colonized those regions. Thus, instead of impermeable reproductive barriers between geographically separated groups of early humans, there were definitely episodes of gene flow across what many paleoanthropologists had supposed were biological species boundaries.

I’m not going to quibble over whether this result should lead to a revision of species names within the genus Homo. At least not now. Because anyone who’s tried to keep up with human evolution research or recently taken an introductory course in biological anthropology knows how little consensus we paleoanthropologists enjoy about just how many different species may have existed at one time or another within our own genus’s evolution. The only thing we agree on is that there’s just one living species today, Homo sapiens. With the further finding of recurrent–albeit occasional–prehistoric genetic admixture between what had been geographically separated groups (Meyer et al. 2013; Prüfer et al. 2013), it’s still not clear that the levels of gene flow are greater than those seen across boundaries between closely related biological species that mainly occupy different ecological niches but maintain a hybrid zone. What seems to be different, especially in Eurasia–which was likely ecologically a population sink-zone because it generally contained fewer food resources and had tougher seasonal conditions than in the Subsaharan African core zone of human evolution–is that this interbreeding took place sporadically through distantly related human groups meeting when one group shifted its geographic range via migration or expanded it via a multi-generation process of population growth and dispersal (Templeton 2002).

Thus, the accumulating evidence to which Slatkin has contributed is that episodes of interbreeding between, say, western Asian Neanderthals and Asian Denisovans–or between African Homo erectus and Asian Homo erectus–were indeed recurrent.

Probably then, as now, human groups exhibited a range of emotions and behaviors when confronted with strangers, ranging from violent notions of exclusion, revulsion, or territoriality to acceptance and intimacy.

Then, as now, members of the genus Homo were only as freaky as they and the others around them made themselves out to be.

 

Postscript: When you check out the thoroughly heroic, artistic Janelle Monae in her recent Q.U.E.E.N. video (with able back-up from Erikah Badu), consider how she uses a poetic, performative medium to make a political move and take over wielding the word “freak.”

References

Balter, M. (2009). A Neandertal Primer. Science, 323(5916), 870–870. doi:10.1126/science.323.5916.870

Bamshad, M., Wooding, S., Salisbury, B. A., & Stephens, J. C. (2004). Deconstructing the relationship between genetics and race. Nature Reviews Genetics, 5(8), 598–609. doi:10.1038/nrg1401

Coon, C. S. (1939). The Races of Europe. New York: The MacMillan Company.

Coon, C. S. (1962). The Origin of Races. New York: Alfred A. Knopf, Inc.

Giles, E. (2012). Two faces of earnest A. Hooton. American Journal of Physical Anthropology, 149(S55), 105–113. doi:10.1002/ajpa.22162

Jackson, J. P., Jr. (2001). “In Ways Unacademical”: The Reception of Carleton S. Coon’s The Origin of Races. Journal of the History of Biology, 34(2), 247–285. doi:10.1023/A:1010366015968

Meyer, M., Fu, Q., Aximu-Petri, A., Glocke, I., Nickel, B., Arsuaga, J.-L., … Pääbo, S. (2013). A mitochondrial genome sequence of a hominin from Sima de los Huesos. Nature, advance online publication. doi:10.1038/nature12788

Proctor, R. (1988). Racial Hygiene: Medicine Under the Nazis. Harvard University Press.

Prüfer, K., Racimo, F., Patterson, N., Jay, F., Sankararaman, S., Sawyer, S., … Pääbo, S. (2013). The complete genome sequence of a Neanderthal from the Altai Mountains. Nature, advance online publication. doi:10.1038/nature12886

Reich, D., Green, R. E., Kircher, M., Krause, J., Patterson, N., Durand, E. Y., … Pääbo, S. (2010). Genetic history of an archaic hominin group from Denisova Cave in Siberia. Nature, 468(7327), 1053–1060. doi:10.1038/nature09710

Trinkaus, E., & Shipman, P. (1994). The Neanderthals: Of Skeletons, Scientists, and Scandal. Random House Incorporated.

Wolpoff, M. H. (1999). Paleoanthropology. McGraw-Hill.

Wolpoff, M. H., & Caspari, R. (1998). Race and Human Evolution. Westview Press.