Planet Earth

Humanity isn't, it becomes

Gene ExpressionBy Razib KhanSep 23, 2012 11:55 PM


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John Hawks prompts to reemphasize an aspect of my thinking which has undergone a revolution over the past 10 years. I pointed to it in my post on the Khoe-San. In short, the common anatomically modern human ancestors of Khoe-San and non-Khoe-San may not have been people. Rather, people may have evolved over the past 100-200,000 years ago. Of course the term "people" is not quite as scientific as you might like. In philosophy and law you have debates about "personhood". Granting the utility of these debates I am basically saying that the common ancestor of Khoe-San and non-Khoe-San may not have been persons, as well understand them. Though, as a person myself, I do think they were persons. At this point I am willing to push the class "person" rather far back in time. As I suggested earlier there is an implicit assumption that personhood is a shared derived trait of our species. Or at least it is a consensus today that all extant members of H. sapiens are persons. Since Khoe-San are persons, the common ancestor of Khoe-San and non-Khoe-San must also be persons if personhood is a shared derived trait. But, we also know that there are many aspects of realized personhood on a sociological or cultural scale which seem to diminish the further back in time you go. For example, the Oldowan lithic technology persisted for ~1 million years. A common modern conception of persons is that persons in the aggregate are simply never so static. Persons have culture, and culture is protean. Therefore, one might infer from the nature of Oldowan technological torpor that the producers of that technology were not persons. But there's a large gap between the decline of the Oldowan and the rise of anatomically modern humans. Where to draw the line? Let's take a step back about a decade. Here's an extract from Richard Klein's excellent Dawn of Human Culture:

Our third and final observation is that the relationship between anatomical and behavioral change shifted abruptly about 50,000 years ago. Before this time, anatomy and behavior appear to have evolved more or less in tandem, very slowly, but after this time anatomy remained relatively stable while behavioral (cultural) change accelerated rapidly. What could explain this better than a neural change that promoted the extraordinary modern human ability to innovate? This is not to say that Neanderthals and their non-modern contemporaries possessed ape-like brains or that they were as biologically and behaviorally primitive as yet earlier humans. It is only to suggest that an acknowledged genetic link between anatomy and behavior in yet earlier people persisted until the emergence of fully modern ones, and that that postulated genetic change 50,000 years ago fostered the uniquely modern ability to adapt to a remarkable range of natural and social circumstances with little or no physiological change. Arguably, the last key neural change promoted the modern capacity for rapidly spoken phonemic language, or for what anthropologists Duane Quiatt and Richard Milo have called "a fully vocal language, phenmiized, syntactical, and infinitely open and productive."

The non-moderns were not ape-like, but they were clearly not human-like, if they lacked language as what we understand language to be. Today this view is likely in the minority position, but why? I think the possibility of admixture between these distinct human lineages suggests that the gap between "them" and "us" was not quite as large Klein postulates above. And even then there is a major problem with Klein's thesis: there was mitochondrial and archaeological evidence even then that the divergence of the Khoe-San and non-Africans far pre-dated the 50,000 year time period alluded to above. Since then the evidence has become even stronger that the divergence of the Khoe-San from other humans, and likely Africans from non-Africans, pre-dates the emergence of "behavioral modernity." An implicit assumption that personhood is a shared derived trait from a common human ancestor to me speaks to the same needs and urges which posit a specific ensoulment or creation of humanity from clay. Our minds are not very good at continuities, so we must create distinctive breaks. One moment an animal, and another moment a man! The occasional scientist who speculates that there may be a set of genes which define humanity I think falls into the trap of assuming discontinuity where there is none. There may be no genetic variant necessary or sufficient to being a human. Let me finish by quoting John Hawks, who inspired me to be a bit more explicit in my own line of thinking:

Personally, I think that "cognitive modernity" is a red herring. Today's people learn some kinds of technical and symbolic complexity that were never present in ancient peoples. Some people living today in Western cultures, despite all our educational efforts, fail to attain levels of technical knowledge that are regular outcomes for the majority of people in the same environment. Human performance varies continuously. I assert that it is unreasonable to suppose that Neandertals had a "stupid gene". If so, it should be just as unreasonable to suppose that a "smart gene" could explain the evolution of human cognition during the last 100,000 years. These unrealistic assumptions are widespread, and impede our understanding just as thoroughly as assumptions about the nature of biological species impeded our understanding of Neandertal ancestry of living human populations. Some archaeologists have concluded that Neandertal cognition is an either/or proposition. Some look at Neandertals, find a lack of evidence that they behave identically to later people, and conclude that the Neandertals were therefore unquestionably cognitive inferiors. Others look at Neandertals, find some signs of modern-like behaviors, and conclude that Neandertals were therefore unquestionably our cognitive equals. Cognition in modern humans varies continuously across many axes of variation. No two humans are cognitively identical in outcomes. Nor can we appeal to "cognitive capacity", a meaningless abstraction unless we are discussing a particular structured learning environment in which the outcomes are potentially measurable. Will we someday raise a Neandertal in a human society to see whether and how they attain the skills and abilities we consider essential?

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