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The breakthrough of 2007, as announced by AAAS, the nonprofit organization that publishes Science, is human genetic variation. Human genetic variation has been studied for quite sometime and the primary reason to study genetic variation in humans is to discover and describe the linkage of genes to many human diseases. This is an increasingly powerful motivation in light of our growing understanding of the contribution that genes make to the development of diseases such as cancer, heart disease, etc.

In 2007, we saw many publications in very prestigious journals that used genome-wide association studies (GWAS) to identify common genetic factors that influence health and disease, and I think that’s where the AAAS felt motivated to call human genetic variation the breakthrough of the year. May of 2007, Nature ran a paper where the sample size was around 17,000 and in June, Science published a paper with around 13,00 samples!

But the limelight’s not all in medicine. The impact of human genetic variation in anthropology is just as fascinating. For the last 30 or so years, we have gotten a glimpse of what genetic variation has to offer in helping anthropology; and I hope we can all appreciate (ahem, Martin) that we have another tool in our belt to help us understand human migrations and population structures. With some of the first theoretical papers coming out in ’70′s, I’ve appreciated how fast the field has progressed and how much resolution we now have to understand migratory patterns and the genetic composition of ethnic groups.

For example, in the late ’90′s, we read how Y chromosome sequences tend to be more localized geographically than those of mtDNA. This is an important study for anthropology. Why? The difference seen between female and male migration rates, tells us of human behaviors… women move away from their homes and into the male mate’s natal household far more often than the reverse scenario. Genetic data like this documents us many human populations practiced patrilocal residence, which is a term anyone well versed in socio-cultural anthropology would know by heart. There are a few populations that operate(d) with an opposite social system, such as the Chaco Canyon people, the Nair in Kerala, India, and the Mosou in southern China. But these populations aren’t the norm. For the most part human populations have been paternal and this genetic data supplements the ethnographic, archaeological, and historical data.

In 2007, several human genetic studies told us of how the Americas were peopled. One study analyzed single nucleotide polymorphisms (SNPs) from around 46 different populations within the Americas and Asia to tell us that people camped out in Beringia for a while before making it down to North America and then South America. SNPs are a form of genetic variation, in that a SNP is the difference of one base pair in the same location between two or more alleles.

In late 2007, we also saw a boom in personal genome products from the corporate sector. These products, such as kits from 23andMe, deCODEme, Family Tree DNA, dna.ancestry.com, etc. screen for SNPs to tell us our propensity for some heritable diseases but also our ethnic background. If you’re curious, Mark Fletcher of Wingedpig discussed his results from 23andMe, Myles Axton of Nature Genetics shared his deCODEme results at Free Association, and Megan Smolenyak put up a 17 minute screencast discussion of her husband’s deCODEme results.

Not everyone trusts these sorts of studies. For example, Meredith Small said DNA testing is a scam… and like Martin, argues that our genetic composition/variation can not ultimately tell us who we are. They say that personal identity is not found between base pairs of long sequences. Rather, identityis more effectively found in who humans have associated with, what culture(s) humans followed and are following, what humans do in their daily lives. As an someone trained in archaeology, I can see why Martin sees it this way. He even says his primary expertise is in studying material cultural, a product of human society and culture. As a cultural anthropologist, I can also see why Meredith Small is touting up the we are people… social beings. With their foundations in the social and cultural aspect of anthropology I’m not surprised that they are defending identity and ethnicity as social.

But ethnicity is not entirely social, there definitely is a biological component to ethnicity. The biological component of ethnicity can be seen in the similar phenotype of an ethnic group. Without being too offensive, I think we can all agree that the shape of the eyes of people from China or Japan have a characteristic shape that differ from other ethnicities. Furthermore, for anyone with a background in forensic anthropology, shovel shaped incisors indicate native American decent. Honing in on the genetic aspect of race, in 1997, a Nature paper demonstrated that around ~40% of Jewish males who shared an oral tradition of being Cohanim, also shared a unique set of SNP called the Cohen Modal Haplotype which is on the Y chromosome. Tracing this haplotype, we see it is also present in Italian, Lemba, and Kurdish populations which tells us of integration patterns.

There’s plenty of other haplotypes and genetic markers that help identify backgrounds. Large projects such as the HapMap and National Geographic Genographic projects are collecting data and resolving more haplotypes and genetic markers that can be used in a wide variety of applications. In one situation that comes to my mind, we saw how the unique mtDNA composition of a man named Yu Hong matched the normal composition of Europeans. This genetic evidence correlated with the archaeological evidence helped fulfill our understanding of Yu Hong’s identity.

Ultimately, humans can be classified into groups based on our biological traits, both phenotypically and genetically. Just like we can classify groups based on their cultural traits, such as the style of an artifact, the linguistic similarities. It is not wrong to classify people into groups. It is wrong how people interpret these classifications and apply them, and it is just as wrong for people to shun away any discussion of classifying people!

So, I am surprised that Martin said ethnic essentialism is a thing of the past. It is not a thing of the past. Despite the reductionism shown by the American Anthropological Association’s understanding race project, discussions of ethnic essentialism are a very active and modern aspect within anthropology. Recently, we had our own lively and very informative discussion on race. I hope it to always be an active discussion too. I hope it never stops because it is a very important part of practicing science… to be inquisitive and open. We should always be questioning and investigating. And just because there was a popular movement to eradicate the concept of race decades ago, I don’t think we should dust off our hands and call the debate resolved. I hope that he will once recognize his comment reflects a level of ignorance; in their own way Martin and Small are effectively bullying away any re-evaluation of the biological basis for race because they live by the mantra that “it is an outdated way of thinking.”

Hat tip to Razib.

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