Re: Study suggests little-known human relative lived widely across Asia but left little DNA legacy

I know it’s a bit fundy of me, (old traditions die hard), but does anyone 
else think - "that explains Cain's family"?

Interesting stuff.  Thanks.

Mike F.



-----Original Message----- 
From: Peter Chattaway
Sent: Thursday, December 23, 2010 4:09 AM
To: Daniel Amos off-topic listserver
Subject: [DADL-OT] Study suggests little-known human relative lived widely 
across Asia but left little DNA legacy

http://www.macleans.ca/article.jsp?content=w5476528

December 22, 2010 - 13:18
Malcolm Ritter, The Associated Press

NEW YORK, N.Y. - Scientists have recovered the DNA code of a human relative 
recently discovered in Siberia, and it delivered a surprise: This relative 
roamed far from the cave that holds its only known remains.

By comparing the DNA to that of modern populations, scientists found 
evidence that these "Denisovans" from more than 30,000 years ago ranged all 
across Asia. They apparently interbred with the ancestors of people now 
living in Melanesia, a group of islands northeast of Australia.

There's no sign that Denisovans mingled with the ancestors of people now 
living in Eurasia, which made the connection between Siberia and distant 
Melanesia quite a shock.

It's the second report in recent months of using a new tool, genomes of 
ancient human relatives, to illuminate the evolutionary history of 
humankind. In May, some of the same scientists reported using the 
Neanderthal genome to show that Neanderthals interbred with ancestors of 
today's non-African populations. That might have happened in the Middle East 
after the ancestors left Africa but before they entered Eurasia, researchers 
said.

As for the Denisovans, the new work is probably just the start of what can 
be learned from their genome, said one expert familiar with the research. 
Eventually, it should provide clues to traits like eye and skin colour, said 
Todd Disotell of New York University.

"We're going to be able to piece these people together in the next few years 
from this genome," he said.

The existence of a new human relative was first revealed just nine months 
ago from a sampling of DNA recovered from a finger bone discovered in the 
Denisova Cave in southern Siberia. Researchers proposed the informal name 
Denisovans for them in Thursday's issue of the journal Nature, where they 
report the new results.

There's not enough evidence to determine whether Denisovans are a distinct 
species, the researchers said.

The genome, recovered from the finger bone, showed that Denisovans are more 
closely related to Neanderthals than to modern humans. That indicates that 
both they and Neanderthals sprang from a common ancestor on a different 
branch of the evolutionary family tree than the one leading to modern 
humans.

Scientists have no idea what Denisovans looked like, said David Reich, a 
Harvard University researcher and an author of the new paper.

Apart from the genome, the researchers reported finding a Denisovan upper 
molar in the cave. Its large size and features differ from teeth of 
Neanderthals or early modern humans, both of which lived in the same area at 
about the same time as the Denisovans.

Neither the finger bone nor the tooth can be dated directly, but tests of 
animal bones found nearby show the Denisovan remains are at least 30,000 
years old, and maybe more than 50,000 years old, Reich said.

Scientists found evidence that in the genomes of people now living in 
Melanesia, about 5 per cent of their DNA can be traced to Denisovans, a sign 
of ancient interbreeding that took researchers by surprise.

"We thought it was a mistake when we first saw it," Reich said. "But it's 
real."

And that suggests Denisovans once ranged widely across Asia, he said. 
Somehow, they or their ancestors had to encounter anatomically modern humans 
who started leaving Africa some 55,000 years ago and reached New Guinea by 
some 45,000 years ago.

It seems implausible that this journey took a detour through southern 
Siberia without leaving a genetic legacy in other Eurasian populations, 
Reich said. It makes more sense that this encounter happened much farther 
south, indicating Denisovans ranged throughout Asia, over thousands of miles 
and different climate zones, he said.

Yet, archaeologists have reported virtually no sign of the Denisovans, no 
tools or other indications of how they lived. Maybe that's because sites in 
Asia haven't been studied as systematically as Neanderthal sites in Europe, 
he said.

Disotell said he and colleagues were "blown away" by the unexpected 
Melanesia finding, with its implication for where Denisovans lived.

"Clearly they had to have been very widespread in Asia," and DNA sampling of 
isolated Asian populations might turn up more of their genetic legacy, he 
said.

Rick Potts, director of the human origins program at the Smithsonian 
Institution, said the new work greatly strengthens the case that Denisovans 
differed from Neanderthals and modern humans.

Still, they may not be a new species, because they might represent a 
creature already known from fossils but which didn't leave any DNA to 
compare, such as a late-surviving Homo heidelbergensis, he said.

Potts also said the Melanesia finding could mean that the Melanesians and 
the Denisovans didn't intermix, but simply happened to retain ancestral DNA 
sequences that had been lost in other populations sampled in the study. But 
he stressed he doesn't know if that's a better explanation than the one 
offered by the authors.

"I am excited about this paper (because) it just throws so much out there 
for contemplation that is testable," Potts said. "And that's good science."

- - -

FWIW, Steve Sailer comments:

- - -

http://isteve.blogspot.com/2010/12/out-of-africa-with-benefits.html

[ snip ]

If the genomes of New Guineans come almost 5% from non-modern humans, then 
the obvious next step is to test the genomes of Australian Aborigines, who 
are last in line in the original Southern route Out of Africa. However, 
there are a lot of regulatory barriers against testing Aborigines, perhaps 
out of fear that scientists will find something this. After all, they look a 
little archaic, so it wouldn't be terribly surprising if their genes turn 
out to be a little archaic.

It was lucky that the first findings of non-modern human ancestry involved 
Europeans, or it would have been hard to get up the political courage to 
publish this.

So, the Out of Africa model of evolution of the current human race turns out 
to be mostly, but not wholly, correct. Greg Cochran calls the new model Out 
of Africa with Benefits: modern humans picked up useful genes from older 
human types, and not all of those inheritances spread equally to the entire 
current human race.

[ snip ]


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