A year ago, members of the Neanderthal Genome Project discovered evidence that shocked them: modern day humans, some of us anyway, carry around Neanderthal genes. The scientists had long thought, as had most paleontologists, that there had been no successful interbreeding between Neanderthals and early modern humans.
Map of Neanderthal Archaeological Sites Producing DNA. Image courtesy AAAS/Science magazine
After all, mitochondrial DNA studies published by the same group a couple of years ago said had been no Neanderthal mtDNA input into Early Modern Humans. So, the scientists ran more tests, and eventually studied DNA from four Neanderthal sites and came to the inescapable conclusion that they were right. Modern Europeans, Asians and Melanesians all carry a tiny percentage (between 1-4%) of Neanderthal genes: Africans do not (or at least, so far as know at the moment). The Neanderthal Genome Project believes that's because contact between Neanderthals and Early Modern Humans took place after EMH left Africa and met Neanderthals in Europe, and, they, um, got to know one another. The dispersal to Asia and Melanesia came after that. This hypothesis puts the interbreeding as occurring between about 100,000 and 60,000 years ago, and probably someplace in the Middle East.
The best thing about this story, in my opinion, is that we can all read about it, for free, without need of a login or any other filter, in the Science magazines's Special Feature: The Neanderthal Genome. The feature lets anyone download the original articles and access the public science report including a plain English description of the methods and findings.
There are lots of great resources out there explaining this important story, so I needn't go into more detail: but definitely start with the Science website.
Special Feature: The Neanderthal Genome, from Science.
- Vindija Cave, Croatia
- El Sidron, Spain
- Guide to Neanderthals
Related Articles
Burbano HA, et al. 2010. Targeted Investigation of the Neandertal Genome by Array-Based Sequence Capture. Science 238:723-725. Free download
Green RE, et al. 2010. A Draft Sequence of the Neandertal Genome. Science 328:710-722. Free download
Krause J, et al. 2007. The Derived FOXP2 Variant of Modern Humans Was Shared with Neandertals. Current Biology 17:1-5.
Lalueza-Fox C, et al. 2006. Mitochondrial DNA of an Iberian Neandertal suggests a population affinity with other European Neandertals. Current Biology 16(16):R629-R630.
News Stories
- Signs of Neanderthals Mating With Humans, Nicholas Wade in the New York Times
- Neanderthal genes 'survive in us', Paul Rincon, BBC News
- Hey Good Lookin': Early Humans Dug Neanderthals, Joe Palca, NPR
Comments
Still Skeptical Concerning Hybrids
We should remain skeptical about whether or not Neadertals passed on any of their genes. We should await further evidence for two reasons. First, because the sample tested could have been contaminated with modern DNA.
Second, the person sampled may have had a Neandertal and a modern human parent, but we don’t know if the person had any offspring.
A mule has a donkey and a horse as parents, but no offspring. Ditto for bufallo and cattle: hybrid dysgenesis approaches 100%. If, as some specimens suggest, Neandertals originated 800,000 years ago and moderns less than 200,000 years ago, the chances for reduced fertility between Neanderthals and humans may be high and the possibility of hybrid dysgenesis higher still.
If hybrids had Neandertal mothers more commonly than fathers, hybrid dysgenesis might account for the extinction of Neanderthals. Neanderthals could not afford to raise infertile offspring and if caused to do so would have become extinct.
Ezra Zubrow modelled the demographics of Neanderthals and showed that only a slight change in reproduction and survival rates would lead to extinction in one millennium.
(Zubrow considered only demographic, economic and social factors,not fertility.)
I for one will suspend judgement concerning the significance of finding modern human genes in this Neanderthal person.
Having followed the Neanderthal debate for more than thirty years I have seen an incredible amount of academic energy spent in isolating the Neanderthals from our pure and obviously superior blood (gene) line. Surprise to say we share plenty of genes (or at least similar genes) with mice and even fruitflies. Furthermore, if history (and genetics) tell us anything it is that when human populations encounter one another, whether the encounter be friendly or hostile, there is always some “genetic leakage” in one direction or the other — or in both directions. Neanderthals had larger brains than modern humans — perhaps they were pickier. Nevertheless someone must have been having sex across whatever boundary (if any) existed — it happens — all the time.
It took a hundred years for someone to publish some kind words about the very first Neanderthal to be identified. As it turned out he was very old (by late Pleistocene standards) and had, as I recall, only two teeth and advanced arthritis (leading to the caricature of the stooped brute depictions of Neanderthals). Someone had to care for him or he would have died. Someone chewed his food for him and made sure he was as comfortable as possible or he would have died. But this humane treatment did not seem to make Neanderthals any more human (as I used to say — being humane has no more with being human than being civil has to do with civilization).
I never did make the T-shirt that said “Proud to be a Neanderthal-American” but every Neanderthal trait (making flutes, constructing shrines, burying their dead and even making blade tools) should not be discounted as an oddity. I distinctly remember riding a bus in New York and sitting next to a Neanderthal in a suit. We were going to the American Museum of Natural History.
What a fascinating post!!
I do have to point out to Frank, it doesn’t happen often but there are times when mules have been known to produce viable offspring. “Approaching 100%” is *not* 100%.
A couple of good blog posts:
Neanderthals Live!, John Hawks
Skull Caps and Genomes, Andrew Zimmer at Discover
1 – 4 % is not a “tiny percentage” when you’re talking about genetics. It should be considered a significant contribution because the gene itself is definitely not the whole story when it comes to what it actually does to the body and the mind. We now know from epigenetics that turning genes on or off, manipulating them in all sorts of other ways can have a huge impact.
An individual who is 4% different in terms of genes could probably be many times more different taking epigenetic factors into account, and using a yardstick which accounts for inherited changes other than pure mutations.
It’s time to dump the old and extremely conservative interpretations of genetics and evolution and realize that epigenetic factors are staring us in the face.
The interbreeding seems to have taken place in the
Middle East; the eastern neanderthals were not as
florid in their characteristics as the Europeans. There
is a simple explanation for all this: Homo sapiens and
Homo neanderthalensis may have been “ring species”
with the middle easterners in the middle and occupying
an intermediate position. They are not as extreme in
form as the European neanderthals.