Artist's impression of a Neanderthal hunter. New evidence suggests the Neanderthals and modern humans interbred.
Credit: American Museum of Natural History
SYDNEY: Modern humans contain a little bit of Neanderthal, according to a new theory, because the two interbred and became one species.
The theory is the latest addition to the ongoing debate about what happened to this early species of human.
In a paper published this week in the U.S. journal Proceedings of the National Academy of Sciences, a team of European researchers report a "mosaic of modern human and archaic Neanderthal features" in 30,000 -year-old human fossils from Romania.
Co-author Erik Trinkaus from Washington University explains: "[Some] closely related species of mammals freely interbreed, produce fertile viable offspring, and blend populations." This is what appears to have happened with Neanderthals and modern humans, he says.
Shorter and stouter than modern humans, but with larger brains, Neanderthals lived in Europe, central Asia and the Middle East for about 170,000 years before disappearing between 33,000 to 24,000 years ago.
Their extinction coincided with the migration of modern humans out of Africa and across Europe. Few mysteries in the history of human ancestry have been as hotly debated as what caused the extinction of the Neanderthals.
Some scientific theories have Neanderthals dying out because they were less well-adapted to the climate changes that occurred across Europe at that time. Others cite evidence of a more brutal end, in which Neanderthals were slaughtered by modern humans.
This new study helps to settle the controversy. According to the researchers, the populations probably blended together through sexual reproduction. "Extinction through absorption is a common phenomenon," says Trinkaus.
The human remains were found in Pestera Muierii ('Cave of the Old Woman'), an elaborate cave system in Romania. First uncovered in 1952, the fossils remained poorly dated and largely ignored until recently.
Using carbon dating techniques, Trinkaus and colleagues found that the remains were 30,000 years old. Their analysis of the bones revealed diagnostic skeletal features of modern humans, including smaller eyebrow ridges, very narrow holes where the nostrils join the skull, and a shin bone that is flat on one side and concave on the other.
However the mostly human skeletons also possessed distinct Neanderthal features; features that were not present in ancestral modern humans in Africa. These include a large bulge at the back of the skull, a more prominent projection around the elbow joint, and a narrow socket at the shoulder joint.
Further analysis of one skeleton's shoulder showed that these humans did not have the full set of anatomical adaptations for throwing projectiles, such as spears, during hunting.
According to the researchers, this mixture of human and Neanderthal features suggests that a complicated reproductive scenario existed as humans and Neandertals interbred. The hypothesis that the Neanderthals were simply replaced should therefore be abandoned, they suggest.
Trinkaus says we may carry some of the genetic legacy of the Neanderthals within us. However it would be difficult to determine which of us are more closely related to the Neanderthals: "there has been 30,000 to 35,000 years of human evolution since then," he says.
Humans and neanderthals interbred.
If this is so, would not modern Europeans have a different genome to that of modern Africans, the African population largely being "uncontaminated" by the Neanderthal influence?
Hmmm...
That seems logical, though a lot of migration is possible in the 30,000 years since. Personally I don't support the gentic-mixing theory, I mean, even if the genome shows 99.9% similarities, that means nothing. We share approx. 99% of our DNA with chimpanzees, and we can't interbreed with them. So I still vouch for replacement.
I'd also like to add that we should be wary of counting the fact that they "did not have the full set of anatomical adaptations for throwing projectiles" as a trait exclusive to neanderthals, as it merely represents a type of subsistence, which is not a gentically inherited trait. We could certainly interpret that as homo sapiens being influenced by contact with neanderthal culture, but again we mustn't assume that this form of subsistence could not have formed independently.
From Ming Sun
It may not necessarily be true that we can't interbreed to produce an offspring with chimps. Animals have (on very rare occasions have produced offsprings at about the same genetical difference). ex Blue whales with humpback whales Asian elephants with African elephants.
Er...
Given that Chimps have 24 paired chromosomes and we have 23, the chances of live offspring (forget whether or not it would capable of producing offspring of its own) are slim to nil...
number of chromosomes
An intersting note is that even with chomosome mismatch fertile offspring still occur in different species.
Take the Modern horse (64 chromosomes) and Przewalski's Horse (66 chromosomes); interbreed them and you get a fertile hybrid with 65 chromosomes.
chimp to human is different than neanderthal to human
Saying that H. sapiens, us can't breed with H. neanderthalensis, Neanderthals is way different than Homo sapiens to Pan tricyclodytes. Since the genetic split was 5 million years ago even before the genus Homo. Sahelanthropus tchadensis was the split. H. sapiens and H. neanderthalensis could freely hybridize early in speciation. Chimps and humans have a chromosome mismatch. Neanderthals and humans don't.
anatomical adaptations
"did not have the full set of anatomical adaptations for throwing projectiles"
This is refering to the creatures biological traits, not just a subsistence stategy, and is therfore most certainly inherted. That point in the article is that the body was not well adapted to the throwing of projectiles.
Possible to an extent
The fact remains that even though Neandrethals migrated somewhat Northwards into Europe, there still remains the possiblility that early Homo Sapian may have migrated around to areas in Africa back to earlier Neandrethalis Settlements, and therefore the Genome would be "contaminated" as so to speak.
Humans and neanderthals interbred. Reply
Dude. Our genomes are pretty much the same. And yes Europeans do have a distinctive genome from Africans. Their skulls possess different features that are distinctive and it has been shown that certain characteristics in skin from DNA are shared between Africans and Asians, but not by Europeans.
Neandertal Claims Are Unscientific
The whole proposition of trying to decide the Neandertal controversy--as to whether they interbred with modern humans or became completely extinct--on the basis of subjective, skeletal analyses is improper. This is not science!
In a more objective approach, genetic studies by Paabo Svante have concluded that the Neandertals were not capable of interbreeding with Homo sapiens because they were a different species, Homo neandertalensis. And, currently, other genetic studies are under way to either validate or refute Svante's research.
Considering this, why is Erik Trinkhaus so eager to end the controversy on the basis of some subjective analyses, ruling in favor of interbreeding? Is it borne out of sympathy for the Neandertals? Is it a desperate attempt to undermine the Out-of-Africa theory of modern human origins. Like his co-conspirator, Milford Wolpoff, in this matter, Trinkhaus has no only lost respect and credibility, but he seems to have lost his mind.