Sunday, October 18, 2009

Give her a big hand, folks

The Afar Triangle, at the base of the Red Sea in Ethiopia, is today an inhospitable environment -- hot, volcanic, sparsely vegetated. Not exactly the place you or I would chose to live, if we had the choice.

It was apparently a different sort of place 4.4 million years ago, when Ardi and her kind were around. How do we know? Because researchers recovered more than 150,000 plant and animal fossils from the soil horizon that included Ardi's bones, all consistent with open woodlands with patches of forest. Except for Ardi, the fauna are not unlike what you'd find in similar African habitats today -- antelopes, giraffes, and so on. After all, four million years is not such a long stretch of evolutionary time.

Which raises the old question: What sparked the rapid development from Ardi to Homo sapiens? There has been no shortage of suggestions for contributing factors. Language. Tools. Bipedalism. Opposable thumbs. Fire. Diet. Music. Climate change. Ardi's brain was chimp-sized. Did some or all of the above favor larger brains? Or was it the other way around? We have lots more to learn.

One big surprise with Ardi: Her hands are more humanlike than chimplike. Only modest modification of Ardi's digits -- larger thumbs, shorter fingers -- would yield humanlike dexterity.

It is, of course, our brain that defines our humanity. But it's with our hands that we begin our lives. Sucking. Wiggling. Tugging. Stroking. Grooming. Gesturing. Pointing. Holding tools. Hurling weapons. Before we were Homo sapiens we were Homo digitatis. Before we made looms and potter's wheels, we played with sticks. Before we invented geometry and algebra and calculus, we counted on our fingers. Before we made flutes, and tambourines, and harpsichords, we put blades of grass between our thumbs and blew.

If Ardi does indeed take us closer to our common ancestor with chimps -- our closest living relatives -- it may turn out that the big question is not so much how Ardi became us, as how that common ancestor became a chimp.