Human Ancestor Older Than Previously Thought; Finding Offers New Insights Into Evolution

[steven johnson]

Well done, old man.

ScienceDaily (June 30, 2011) — Modern humans never co-existed with Homo erectus -- a finding counter to previous hypotheses of human evolution -- new excavations in Indonesia and dating analyses show. The research, reported in the journal PLoS ONE, offers new insights into the nature of human evolution, suggesting a different role for Homo erectus than had been previously thought.

Homo erectus is widely considered a direct human ancestor -- it resembles modern humans in many respects, except for its smaller brain and differently shaped skull -- and was the first of our ancestors to migrate out of Africa, approximately 1.8 million years ago. Homo erectus went extinct in Africa and much of Asia by about 500,000 years ago, but appeared to have survived in Indonesia until about 35,000 to 50,000 years ago at the site of Ngandong on the Solo River. These late members of Homo erectus would have shared the environment with early members of our own species, Homo sapiens, who arrived in Indonesia by about 40,000 years ago.

However, findings by the SoRT Project show that Homo erectus' time in the region ended before modern humans arrived there. The analyses suggest that Homo erectus was gone by at least 143,000 years ago -- and likely by more than 550,000 years ago. This means the demise of Homo erectus occurred long before the arrival of Homo sapiens.

The existence of the two species simultaneously has important implications for models about the origins of modern humans.


Human Ancestor Older Than Previously Thought; Finding Offers New Insights Into Evolution

[OffWithTheirHeads]

1. How can this be if the Earth is only 6,000 years old?

[xchrom]

2. recommend

[starroute]

3. This doesn't really seem to support parallel evolution, though

The article says it casts doubt on the Out of Africa hypothesis and revives the old idea that modern humans might have evolved in several regions simultaneously -- but that doesn't make any sense to me.

The latest findings from a number of places suggest that archaic Homo sapiens arose sometime between a million and 500,000 years ago and displaced Homo erectus. These archaic humans are the people who made the really pretty teardrop-shaped handaxes, and they were socially and culturally advanced in a number of other ways. It's likely that they had the start of language, where Homo erectus did not. (On this last point, see http://english.ivpp.cas.cn/rh/rp/201106/t20110625_71756.html.)

In Europe, these archaic humans evolved into the Neanderthals, in Asia into the recently-discovered Denisovans, and in Africa into our own ancestors. Then when our ancestors left Africa around 100,000 years ago, they interbred with both Neanderthals and Denisovans, picking up a relatively small number of genes, many of them having to do with disease resistance.

So these new studies don't really change the picture that was already emerging. They mainly reinforce the emerging three-stage model of human evolution, with a well-defined archaic phase lasting for over 500,000 years. And they also make it clear that when our ancestors got to eastern Asia, they encountered the archaic Denisovans and not the long-gone erectus.