Tuesday, March 9, 2010

Personalized archaeology

A young archaeologist gave a talk in our department last week about his excavation of rock shelters in the north east United States. He tries to deduce from artifacts such things as how much time people spent in each shelter, whether they hunted nearby and what it was they got, whether they returned to the same site year after year, caching hunting implements such as flaked or bola stones there for future use, changes in use of the site over millennia, and so on.  (Image by Larry D. Moore, used under a Creative Commons ShareAlike License.)

Several things were noteworthy, at least to some of the non-archaeologists in the audience. First, he talked about how differences in the construction of projectile points on the east coast versus those found in other sites in the Americas contribute to the idea that North America may not have been peopled entirely by migrants that crossed the Bering Straits, but that some may have come from what is now France. (Called the 'Solutrean hypothesis', after a French archaeological site called Solutré this idea posits hunter-gatherers traveling along an Arctic ice shelf across the Atlantic, either on foot or by canoe. The archaeological and genetic support for this idea is weak to non-existant.)

And second, he contended that his practice of dividing his study sites into smaller sections than the usual (his are 30cm x 30cm x 5cm) yields information at the level of the individual. That is, he believes that by restricting the size of each plot he excavates, and knowing the average human reach radius and so on, he's able to deduce how individuals spent their time in the shelter, shaving the points they'd use to hunt the next day, or cooking the day's catch and so forth.

That could be interesting -- like reconstructing campfire gossip about who was where when, and what they were doing.

But, really, it's hard to figure how it could be much more than that, something that an archaeologist I spoke with after the talk said as well. As a science, archaeology is about synthesizing observations into generalizations, to test or develop theory about human behavior. Just as any science.  This requires many observations, spanning long time periods and many different sites. (Although, certainly, as in any science, some archaeologists are not so interested in generalizing, and campfire gossip is enough.)

Later that day, I happened to be reading an old critique of the Human Genome Project, and I stumbled across the following paragraph:
[The HGP] is a powerful strategem to answer only certain peculiar questions relevant to its narrow purview. In summary, our critique is based on the following assessment: (i) going to the lowest level of organization does not necessarily yield any insight of interest; (ii) reductionist explanation, even when possible, is not cost-effective in terms of effort expended; (iii) mapping is justified, blind sequencing is not; and (iv) the sheer complexity of a system might make reductionist explanation impossible. (Tauber and Sarkar, The ideology of the human genome project, J R Soc Med. 1993 September; 86(9): 537–540.)
This could just as easily be describing the reductionist approach of our young archaeologist -- or indeed reductionism in general. What does it tell you to know that someone sat exactly here in the rock shelter sharpening a point? Or even that he was eating roast rabbit as he did so. (This is assuming, of course, that all the methodological issues that could prevent drawing such conclusions, such as dogs making away with animal bones, or burrowing rodents disturbing the dating information contained in the layering of the artifacts in the soil, and so on, were taken care of.) It certainly can't answer broader questions such as how the Americas were peopled, or how long ago that was.

In its race to reduce normal traits as well as behavior, disease, or risk of disease down to the level of the gene, modern genetics has turned the usual scientific method on its head in some ways, rather like reconstructing the activities of an individual at the campfire. And the torrents of sequence data that have been pouring out of labs around the world have led to 'hypothesis-free' analysis. Researchers now comb the data looking for interesting patterns, or the 'gene for' a trait, rather than for support for an hypothesis.

In this kind of thinking, we are still prisoners of Mendel, reducing our explanations to single genes, rather than accepting what has been known for at least 100 years, that most traits are polygenic, and have a strong environmental contribution. Indeed, even the seminal text on genetics and 'racial hygiene', which helped fuel the eugenic era of Naziism and the Holocaust, first published in 1921 and followed by numerous revisions, Human Heredity by Baur, Fischer and Lenz, explicitly recognizes the role of the environment.

But the seduction of genetic determinism and reductionism remains strong and powerful, in spite of the evidence. 

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