New theory on African exit

Jan 30, 2013 by Alex Peel
New theory on African exit

Modern humans left Africa twice as early as previously thought, spreading in a number of climate-driven waves, new research suggests.

The paper, published in Quaternary International, pours fresh doubt on the previously-held consensus that humans spread from Africa in a single cohort.

'The consensus view has been that modern humans left Africa around 60,000 years ago by a coastal route, skirting around some very arid places, and spread to Australia very quickly,' explains Professor Michael Petraglia of the University of Oxford, one of the study's authors.

'We think that's wrong. We think people left Africa multiple times, probably a long time before, and we think it was terrestrial rather than coastal.'

Previous attempts to put a date on the exit of modern humans from Africa have relied heavily on evidence from genetics and .

Petraglia and his team believe that, by adding evidence on climate and environment into the mix, they will be able to unlock new clues as to both how and why humans spread from the continent.

'We know that the climate has shifted a lot of times. We think that has acted like a pump , pushing of people into .'

'When the climate was humid, there would have been rivers and lakes across the . We think modern humans would have used those as routes, but what we don't know is what happened to those populations when it became arid again.'

The idea goes against a well-established and widely-held consensus. But Petraglia sees signs that academics across the spectrum are beginning to change their minds.

'There are lots of people buying into this idea in many different fields; in genetics, in archaeology, in environmental fields. We're seeing major in the consensus view,' he says.

The team will now zoom in to examine some important sites in more detail, as they attempt to add flesh to their theory.

Petraglia believes that the research has important implications for understanding our present, as well as our past.

'It's in the public imagination. People are fascinated by our own species and how we populated the Earth,' he says.

'But we're also trying to understand this climate pump - how the climate affects the movement of populations and the speed at which that happens - and that could clearly have important implications for today.'

Explore further: Greek mound excavators: No tours please, too busy

More information: Bolvin, N., Fuller, D., Dennell, R., Allaby, R., and Petraglia, M. Human Dispersal Across Diverse Environments of Asia during the Upper Pleistocene, Quaternary International, 2013, doi: 10.1016/j.quaint.2013.01.008

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Shootist
2 / 5 (4) Jan 30, 2013
deatopmg
1.4 / 5 (9) Jan 30, 2013
Another "consensus" view challenged.
Modernmystic
4.6 / 5 (5) Jan 30, 2013
Another "consensus" view challenged.


Indeed consensus is a tricky thing. The ancient consensus about the Earth's shape being flat was wrong...the new one is that it's round(ish) is correct.

Observational facts always are the final arbiter of consensus. There's nothing wrong with consensus per se...unless you're using it in place of observational facts which haven't been made totally clear in order to dishonestly bolster your position.

In the case of this article/consensus? I think it's a bit spurious. Climate and environment trumps genetic evidence? Doubtful, but I'd be willing to listen to the evidence assuming they actually give any. I certainly didn't see any in this article.
Torbjorn_Larsson_OM
4 / 5 (2) Jan 30, 2013
Same old, same old.

@deatompg: "Another "consensus" view challenged."

Since it is not a settled field, not surprisingly so. Only areas where you have pervasive testing (say, classical mechanics) or eliminated all possible contenders (say, standard cosmology) can be certain of that consensus will remain unchallenged.

@natello: "neo-lamarckism". Horisontal gene transfer is pure darwinian (neo-darwinian variation) and zero lamarckism (acquired by usage). No biologist calls HGT "lamarckism" and lamarckism has today zero credit, AFAIK.

Not saying that lamarckism is impossible, it just doesn't seem to happen.

"supersymmetric oscillations"??? You don't know what supersymmetry is, do you? [ http://en.wikiped...symmetry ]
Maggnus
4.3 / 5 (6) Jan 30, 2013
'We think that's wrong. We think people left Africa multiple times, probably a long time before, and we think it was terrestrial rather than coastal.'


The article makes it out like it's an 'either or' proposition, which I have trouble with. Terrestrial migration or coastal migration are not mutually exclusive of each other, and the evidence suggests to me that both types of migration likely occurred.

Furthermore, the article mentions that rivers and lakes would have been used as routes. Following a river up from a coast, then getting cut off and having to migrate across land when arid conditions arose seems like a good possiblity to me.
ValeriaT
3.5 / 5 (4) Jan 30, 2013
"neo-lamarckism". Horisontal gene transfer is pure darwinian

Some people don't think so. If you can get a new genes with using of the bacterias in your guts, then it's the evolution by usage.
RealScience
5 / 5 (2) Jan 31, 2013
@natello - Although it did overturn a consensus, horizontal gene transfer is not 'Lamarckian' because it is not the inheritance of a response to a creature's environment.

@Torbjorn: There are quite a few recent papers a on creature's environment inducing epigenetic alterations in gene expression that are passed on to future generations. While all that I know have affected only the accessibility (methylation, acetlylation, histone packing, etc.) of the genes rather than the genetic sequence itself, they are inherited acquired characteristics.
While most seem to revert with a half-life of a few generations, at least one has been shown (in rats) to persist for dozens of generations. Thus in all fairness Lamarck was not entirely wrong.
(And it did overturn a consensus, so Natello was probably thinking of this).
frajo
not rated yet Jan 31, 2013
[1] Zephir (aka natello):
the neo-lamarckism gains some credit again. Actually I do perceive these supersymmetric oscillations


[2] Torbjorn_Larsson_OM:
@natello: ... No biologist calls HGT "lamarckism" and lamarckism has today zero credit, AFAIK.


[3] Zephir (aka ValeriaT):
Some people don't think so.


Just for the record.
Anda
not rated yet Feb 03, 2013
Not so new.

http://www.edge.o...f-africa


Did you read both???? or just the titles?
Anda
not rated yet Feb 03, 2013
[1] Zephir (aka natello):
the neo-lamarckism gains some credit again. Actually I do perceive these supersymmetric oscillations


[2] Torbjorn_Larsson_OM:
@natello: ... No biologist calls HGT "lamarckism" and lamarckism has today zero credit, AFAIK.


[3] Zephir (aka ValeriaT):
Some people don't think so.


Just for the record.


aka "water ripples", "in AWT...", "IMO", "aether brain", so many nicks more, aka "boring"