Humans got immunity boost from Neanderthals, study finds

Reply Fri 26 Aug, 2011 08:23 am
August 25, 2011
Humans got immunity boost from Neanderthals, study finds
By Eryn Brown | McClatchy-Tribune News Service

LOS ANGELES — As recently as 2008, scientists thought that Neanderthals and modern humans had never mated.

Then, last year, they said that the two species had - but that the few Neanderthal genes that survived in modern human DNA were not functional.

Now researchers believe that key versions of immune system genes in modern humans appear to have been passed down by archaic relatives, including Neanderthals, after all.

Indeed, DNA inherited from Neanderthals and newly discovered hominids dubbed the Denisovans has contributed to key types of immune genes still present today among populations in Europe, Asia and Oceania. And scientists speculate that these gene variants must have been highly beneficial to modern humans, helping them thrive as they migrated throughout the world.

This DNA has had "a very profound functional impact in the immune systems of modern humans," said study first author Laurent Abi-Rached, a postdoctoral researcher in the lab of senior author Peter Parham of the Stanford University School of Medicine.

Neanderthals were stocky hunter-gatherers who populated Europe and parts of Asia until about 30,000 years ago. In 2010, a team of biologists led by Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, sequenced the Neanderthal genome via DNA extracted from ancient bones.

From this, they estimated that between 1 percent and 4 percent of modern Eurasian genomes came from our close hominid relatives.

No one knows what Denisovans looked like: The only confirmed evidence of the group, which is thought to have split from the Neanderthals about 350,000 years ago and migrated east, are a tooth and a pinkie finger bone found in a Siberian cave in 2008.

When Paabo and co-workers sequenced DNA extracted from the pinkie in 2010, they calculated that 4 percent to 6 percent of modern Melanesian genomes came from Denisovans.

In the new study, Abi-Rached and co-authors decided to focus on a small set of genes on chromosome 6 known as the human leukocyte antigen (HLA) class I genes.

HLA genes carry instruction for making HLA proteins, which help the immune system spot evidence of problems in cells - infection or cancer, for instance - so that it can wipe out abnormalities to fight disease. The genes come in many forms that vary in frequency around the world, most likely because our genomes have been tailored by evolution to fight specific disease threats that exist in particular places.

Physicians regularly screen HLA types to find donor matches for transplant patients, providing a rich lode of data for the researchers. Millions of people around the world have had their HLA class I genes typed, giving the team a way to look for ancient Neanderthal and Denisovan HLA variants in present-day people, said co-author Ed Green, a genome scientist at the University of California, Santa Cruz.

The researchers carefully analyzed the region of the archaic genomes where the HLA genes were located. Then they compared them with the HLA regions of modern-day human populations from different parts of the world.

From the analysis, the scientists estimated, for example, that more than half of the genetic variants in one HLA gene in Europeans could be traced back to Neanderthal or Denisovan DNA. For Asians, that proportion was more than 70 percent; in people from Papua New Guinea, it was as much as 95 percent.

"We expected we'd see some, but the extent that these contributed to the modern (genomes) is stunning," Abi-Rached said of the findings, released Thursday by the journal Science.

Though the researchers haven't proved it, the vast reach of these gene variants in people today suggests that they probably gave some early modern humans an advantage over others, he said.

Our ancestors' HLA systems may have been perfectly tailored for Africa but naive to bacteria, viruses and parasites that existed in Europe or Asia, rendering them susceptible to disease.

Mating and mixing their genomes with those of their Neanderthal and Denisovan relatives could have been a speedy way to set up their immune systems to combat new, unencountered threats.

"If there are parasites or whatever in Europe, the way (for humans migrating out of Africa) to adapt to them is to mate with Neanderthals and get their genes," said University of Utah anthropologist Henry Harpending, who was not involved in the research.

Paabo of the Max Planck Institute said that he had some "minor quibbles" with the authors' conclusions but that he was happy to see another group using the ancient genomes his lab had produced to further our knowledge of the evolution of Homo sapiens and its closest relatives.

"This is, of course, exactly why we sequenced the genomes," he said.

Harvard Medical School geneticist David Reich, who worked on the reconstruction of the Denisovan genome, said that the new paper was "exciting, if it turns out to be right," but that he was not yet convinced that the genes really came from Denisovans.

Of most excitement to one outside scientist is what these kinds of studies mean for the future of research into the origins of our species. Seemingly overnight, the endeavor has become a lot more than looking over fossilized bones.

"It's like suddenly you've discovered the New World," said John Hawks, an anthropologist at the University of Wisconsin, "and you're wandering around and seeing what's there."

Read more: http://www.mcclatchydc.com/2011/08/25/122011/humans-got-immunity-boost-from.html#ixzz1W91P1NNb
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Reply Fri 26 Aug, 2011 08:28 am
I've always wondered why the Neanderthals died out. One thing I wondered was their demise was caused by the death of their females in child birth? The Neanderthals had very large heads. I wondered if their babies' heads were so large that their mothers couldn't release them and they died during child birth?

Reply Fri 26 Aug, 2011 08:44 am
The Israelis found an archaeological site at which modern humans and Neanderthals lived side by side, and the Neanderthals arrived after the early modern humans were established. The middens (trash heaps) of the two communities revealed that the early modern humans used far more forage food, and the Neanderthals primarily relied on game. Furthermore, there was evidence of fish remains in the middens of the early modern humans, but none in the Neanderthal middens. Their conclusion is that the Neanderthals died out or moved on as game resources got scare (the Neanderthal sites come to an end long before the sites of the early modern humans). From this they concluded that the Nanderthals lacked a varied diet, and exhausted their food sources while early modern humans were still able to rely on a relatively abundant food supply. The disappearance of the Neanderthals may have been a cultural artifact.
Reply Fri 26 Aug, 2011 08:48 am
Your reasoning makes more sense that mine.

Reply Fri 26 Aug, 2011 08:51 am
Not my reasoning, although it's the most plausible explanation i've yet seen.
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Reply Fri 26 Aug, 2011 09:35 am
I would guess that the Neanderthals that lived where Israel is today did not like to be referred to as Neanderthals, but "Neanderthal people," or "Neanderthalish."

But all kidding aside, I was told once, by a biology teacher, that many Ashkenazi Jews seem to have a strong immune system (they may have a propensity to heart attacks from decades of Jewish aggravation); could many Ashkenazi Jews be hybrids? I've asked myself that question many times in a grunting manner.
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Reply Fri 26 Aug, 2011 11:53 am
There was recently an article in the New Yorker about Paabo and his genome project. Very interesting stuff.

Anyway, in that article the theory was actually that early humans caused the extinction of Neanderthals, just as they've (we've) caused the extinction of countless other species.

Found the article but it's subscriber-only and it won't let me copy and paste, so I'll just hand-copy, please excuse typos:

Over the decades, many theories have been offered to explain what caused the demise of the Neanderthals, ranging from climate change to simple bad luck. In recent years, though, it's become increasingly clear that, as Paabo put it to me, "their bad luck was us." Again and again, the archeological evidence in Europe indicates, once modern humans showed up in a region where Neanderthals were living, the Neanderthals in that region vanished. Perhaps the Neanderthals were actively pursued, or perhaps they were just outcompeted. The Neanderthals' "bad luck" is presumably the same misfortune that the hobbits and the Denisovians [other "archaic humans"] encountered, and similar to the tragedy suffered by the giant marsupials that once browsed Australia, and the varied megafauna that used to inhabit North America, and the moas that lived in New Zealand. And it is precisely the same bad luck that has brought so many species -- including every one of the great apes -- to the edge of oblivion today.

"To me, the mystery is not the extinction of the Neanderthals," Jean-Jacques Hublin, the director of the Institute for Evolutionary Anthropology's department of human evolution, told me. "To me the mystery is what makes modern humans such a successful group that they have been replacing not just the Neanderthals but everything. We don't have much evidence that the Neanderthals or other archaic humans ever led to an extinction of a species of mammal or anything else. For modern humans, there are hundreds of examples, and we do it very well."

(Link is just to the abstract.)
Reply Fri 26 Aug, 2011 11:58 am
I took that at face value when I read it but on re-typing it I wasn't so sure. Kolbert definitely has a bias here, and it's not like species didn't become extinct before humans showed up (dinos just for example). I remember reading that while humans are definitely making things worse, no question, there has been a steady drumbeat of species extinction (and emergence) for a long, long time.
Reply Fri 26 Aug, 2011 12:40 pm
. . . there has been a steady drumbeat of species extinction (and emergence) for a long, long time.

Indeed--i used to think the extinction of the megafauna was anthropogenic, but then one cannot ignore that the environments in which they thrived in the ice ages and the interstitials all disappeared by 15,000 years ago. That certainly didn't help. Competition from non-human species cannot be ignored, either. The short-faced bear may well have disappeared simply because it couldn't compete successfully for resouces with the brown bear and the black bear.

By the evidence the Israelis found, the Neanderthals were their own worst enemies, relying as heavily as they did on game and failing to take full advantage of forage foods. That case is significant, too, because the Neanderthals showed up after the early modern humans were established. The fact that we possess even a little Neanderthal genetic materisl further suggests that they were not so much extinguished as that some of the survivors were absorbed.
Reply Sun 28 Aug, 2011 09:22 am
I just posted this new book. It fits our discussion of how and cause of species extinction. I watched the author's excellent presentation on C-SPAN yesterday.---BBB

Tropic of Chaos: Climate Change and the New Geography of Violence
by Christian Parenti

Book Description

From Africa to Asia and Latin America, the era of climate wars has begun. Extreme weather is breeding banditry, humanitarian crisis, and state failure.

In Tropic of Chaos, investigative journalist Christian Parenti travels along the front lines of this gathering catastrophe--the belt of economically and politically battered postcolonial nations and war zones girding the planet's midlatitudes. Here he finds failed states amid climatic disasters. But he also reveals the unsettling presence of Western military forces and explains how they see an opportunity in the crisis to prepare for open-ended global counterinsurgency.

Parenti argues that this incipient "climate fascism"--a political hardening of wealthy states-- is bound to fail. The struggling states of the developing world cannot be allowed to collapse, as they will take other nations down as well. Instead, we must work to meet the challenge of climate-driven violence with a very different set of sustainable economic and development policies.

About the Author

Christian Parenti is a contributing editor at the Nation. The author of Lockdown America, The Soft Cage, and The Freedom, he has written for Fortune, Mother Jones, Conde Nast Traveler, Playboy, the New York Times, and the London Review of Books, among others. He lives in Brooklyn, New York.
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