Dmanisi and dispersal of Homo from Africa

Discover last April ran a feature article about the finds from Dmanisi. They have made this available online: “The First Humans to Know Winter”. Dmanisi is in some ways a keystone: Earliest site to preserve evidence of fossil humans outside of Africa, earliest site with clear evidence of H. erectus-like cranial and dental morphology, better chronological control than most East African contexts.

The article has an interesting exchange involving quotes from Michael Chazan and Martha Tappan, about the dispersal of early Homo:

Says Chazan: “The problem that keeps you awake, if you think about these things, is that if there was a dispersal event 2 million years ago, before H. erectus, would we see it? If they were using stone tools made of local materials, would we even pick it up? Are we building our models based on things we can’t see?” Dmanisi team member Tappen agrees the site’s fossils are challenging our current understanding of human evolution — but she’s not losing sleep over it.
“As archaeologists, we go with what we have. We make hypotheses and try to test them, and then you dig up something new and go ‘oops.’ And you have to make up a new hypothesis,” says Tappen.
“The Dmanisi individuals are not too different from H. habilis. We should find them dispersing out of Africa 2.5 million years ago,” she explains. “We don’t have that evidence yet, but we have to expect it’s out there.”

That kind of evidence is what some archaeologists claim to have found in Pakistan, with claimed early stone tools from Riwat and the Pabbi Hills; others believe that a pre-erectus habitation of Asia is necessary to explain the morphology of the Homo floresiensis remains from Liang Bua. In light of recent discoveries, I have no reason to think that such a pre-erectus emigration from Africa need have been very much like H. habilis or H. rudolfensis, though.