Thursday, December 13, 2007

Human evolution: a pillar falls

I wish "paradigm shift" were not so overused, because it's so well suited to the news that human evolution has accelerated since we developed agriculture and dense settled populations.

The idea that human evolution had stopped once we "conquered nature" was firmly accepted, outside of the x-men, throughout my formative years in the late 70s and early 80s. By the 1980s sociobiology, later rebranded as evolutionary psychology, assumed many modern dispositions reflected frozen adaptations to ancient hunter-gatherer life. Even in the 90s, when I did my cognitive science, everyone assumed that that the human species had changed little since "cro-magnon" woman (the term is obsolete).


The change shouldn't come as a surprise to readers of this blog. Of course I didn't invent any of this (except maybe the concept of evolutionary disorders of the mind). I'm a longtime reader of bloggers like John Hawks - who authored one of the papers in the news. Sure, Hawks claims he was keeping quiet about the topic while his paper waited to be released, but he's been dropping hints for years. Anyone reading Hawks, or knowing what it means to have such a massive population, could see this was coming.

That's the way these things happen. Twenty years from now popular books will claim radical papers swept away stodgy beliefs, but in fact the fortress had been falling for some time.

Still, we shouldn't understate the historic transition. Sure, now it seems so obvious that population density and culture would create vast new niches for variation to fill, but we used to think evolution operated over vast time scales. We didn't understand how fast a species can change.

So, in what ways are we different from the humans of 50,000 years ago? I'd recommend reading John Hawks and following his suggested links. In my reading thus far I've seen mention of far greater variation in skin and eye color, dietary adaptations, changes in teeth, smaller size (for a time, but now bigger), smaller brain (!) for a time, but now ?.

I've not read much yet about how different our brains are from those of pre-industrial humans, but I've posted previously about papers suggesting adaptations enabling reading and other language skills.

We'll be digesting the implications of this for a while. Yes, race as a clinically or biologically significant idea has returned ...

... the new work indicates that variations tend to differ between races, and that these became more, not less, pronounced.

“Human races are evolving away from each other,” said Henry Harpending, Professor of Anthropology at the University of Utah, who led the study.

“Genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin. We are getting less alike, not merging into a single, mixed humanity.

“Our study denies the widely held assumption that modern humans appeared 40,000 years ago, have not changed since and that we are all pretty much the same. We aren’t the same as people even 1,000 or 2,000 years ago.”

The research is published in the journal Proceedings of the National Academy of Sciences. If the trend towards increasing genetic diversity were to continue, it could lead ultimately to the development of different species. Most scientists, however, think this is now highly unlikely.

"Most scientists" ... A few years ago it would have been every scientist. Still, classic speciation is unlikely ...
... The research identified evolutionary currents only in past times. In the modern era, greater movement and gene flow between the continents has probably slowed or even reversed patterns of increasing genetic difference, making the evolution of separate human species virtually impossible.
On the other hand these days geek neo-Liberals feel like a different species from theocratic social conservatives. There may be more than one way for a sentient animal to speciate.

Well, I'm off to catch up on the Hawks links. It's a big day for science, though I imagine it must be a bit rough on the fundies.

Update 12/16/07: Hawks quote (via Marginal Revolution):
We are more different genetically from people living 5,000 years ago than they were different from Neanderthals...

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