December 31, 2008
Neanderthals Lost Out From Competition Not Climate Change
The Neanderthals were out-classed by the upstarts and just couldn't compete.
In a recently conducted study, a multidisciplinary French-American research team with expertise in archaeology, past climates, and ecology reported that Neanderthal extinction was principally a result of competition with Cro-Magnon populations, rather than the consequences of climate change.
The study, reported in the online, open-access journal PLoS ONE on December 24, figures in the ongoing debate on the reasons behind the eventual disappearance of Neanderthal populations, which occupied Europe prior to the arrival of human populations like us around 40,000 years ago. Led by Dr William E. Banks, the authors, who belong to the French Centre National de la Recherche Scientifique, l'Ecole Pratique d'Hautes Etudes, and the University of Kansas, reached their conclusion by reconstructing climatic conditions during this period and analyzing the distribution of archaeological sites associated with the last Neanderthals and the first modern human populations with an approach typically used to study the impact of climate change on biodiversity.
This method uses geographic locations of archaeological sites dated by radiocarbon, in conjunction with high-resolution simulations of past climates for specific periods, and employs an algorithm to analyze relationships between the two datasets to reconstruct potential areas occupied by each human population and to determine if and how climatic conditions played a role in shaping these areas. In other words, by integrating archaeological and paleoenvironmental datasets, this predictive method can reconstruct the regions that a past population could potentially have occupied. By repeating the modeling process hundreds of times and evaluating where the errors occur, this machine-learning algorithm is able to provide robust predictions of regions that could have been occupied by specific human cultures.
In a few weeks I'm going to review an exciting new book that, among other claims, argues humans benefited from an introgression (in flow) of Neanderthal genes that helped humans evolve more rapidly. So not only did our ancestors wipe out Neanderthals but humanity even gained genetically from the interaction.
Why didn't Neanderthals instead take some of our genes and out-compete early modern humans? Not sure. I can think of some possibilities. Even if the hybrids possessed some advantages they existed in small numbers. The beneficial genetic alleles humans gained from Neanderthal genes might not have become widespread until well after Neanderthal numbers had greatly dwindled. Humans might have had such large competitive advantages that Neanderthals couldn't absorb beneficial human genes fast enough to be able to compete. Also, maybe the hybrids were more often born in human communities than in Neanderthal communities. Or maybe humans were more accepting of raising hybrids.
Anyone have a clue on this?
The accepted reason for Neanderthal deaths were that they were too dumb to make clothes or shelter when the glacial age started.
Call me cynical but this study smells of global warming religion where they refuse to admit there were other times in human history where the climate did change.
Could the Neanderthals mate with humans? The separation between the two might be as great as it is between us and apes.
Could also be that hybrids could mate with humans but not with Neanderthals.
"Also, maybe the hybrids were more often born in human communities than in Neanderthal communities."
To expand on this idea, if men were killed and women captured as slaves, an initial military advantage for the humans would result in the capture of a large number of neanderthal women to mate with human men, while far fewer cases of the reverse (neanderthals' capturing human women) would occur.
That said, I hold little stock in the value of simulations, high-resolution or otherwise. It takes a lot of convincing to establish that simulations have any validity beyond summarizing the data they are calibrated upon.
There are many possible explanations related to cognitive ability for why the early humans beat out the neanderthals. One is that early humans were better at cooperation in hunting. Another has to do with tools, whether for hunting or other purposes. Better hunting implements that didn't require humans to close with animals to fight in close quarters reduced muscle mass needed (saving calories) while also reducing injury.
I'll be doing a review of a book that addresses this question and many others relating to human evolution. But I won't post it until it gets close to the initial sales date. It is a thoroughly great book btw.
Global warming religion: actually the idea that Neanderthals were wiped out by warming is used to argue why we shouldn't allow warming. "Look, it leads to advanced primate species extinction". So this latest study makes global warming less relevant, not more relevant.
Interesting idea about hybrid fertility. I'll ask someone who might know.
One thing I have heard is that Neanderthal women would have had problems bearing live young because their skulls were actually much larger than humans'. It might end up that human women taken as sex slaves couldn't bear children (i.e. they would die in childbirth), but the reverse would be true, implying the only interbreeding could take place after male Neanderthals were wiped out.
Neanderthal skulls were about the same size as those of the humans who replaved them : both had larger brains than people today. The Neanderthals had lived through _several_ long glacial periods. and several short warm periods: ~90% of the past five hundred thousand years were icy.
A winning group can pick up some genes from those it displaces , but it takes time (thousands of years) for those alleles to become common if the amount of mixing is small. Imaginer that a few Amerindian alleles are advantageous: it might be thousands of years before those alleles became common in the general American population (assuming near-zero immigration, selection pressures stay the same, the robots refrain from taking over, etc).
Last common ancestry of humans Neanderthals was ~ 500,000 year ago: the split with chimpanzees wsas about 5-6 million. Today, species that are that close can almost always have fertile offspring. Chimps and Bonobos, for example.
I thought it had been established that modern humans and neanderthals could not interbreed.
What is your source for this? The chimps and bonobos have been separated for longer than humans and neanderthals and yet the chimps and bonobos can interbreed.
Easy: Neanderthals were much more heavily built than humans. And had far less developed female secondary sexual characteristics To a neanderthal man, a human female is like the hottest supermodel pornstar conceivable. Meanwhile the human female sees the neanderthal male as like the most amazing football hero ever.
Therefore, the prize women will be those that look most human (have mostly human genes), the prize men, those that look most neanderthal.
So the question of which genotype wins out is simply a question of who makes the decisions? Was it a case of a liberated, modern style where the women choose who they want as a mate? Or was it a case of the best hunter and warrior gets the hot girls and she doesn't get a say in the matter.
I know which one I guess was the case.
Multiple things could have happened. I remember reading about an anthropologist who lived in the Congo with a remote group of pigmys. They were dieing out due to presures of lost forestation. It didn't take much for a neighboring culture, that of a taller aboriginal group, to convince the pigmy familys to give up their daughters to wed the men of the other culture. The pigmys lacked resources and the other group had them. The daughters went to a much easier life. The new husbands in the other culture had tough, fantastic wives who never complained and worked far more than the women of their own culture.They were used to such a hard life. One problem, this neighboring group over the countless years had lost their original height. They were only four to five and a half feet. The pigmys were often only 3 and a half feet.
Non the less, it was a successful intermarriage going one way only. The population of the pigmys continued to plummet.
And that is what very well could have happened to the Neanderthal. The hybridization could have gone one way only. The Neaderthal women to the modern humans, having successful children. Giving birth easily to the smaller babies. The babies growing up to continue integrating with less problems in the second generation. However, the neanderthals population might have continued to die off related to inability to compete with resources. Cross marriage with modern women might have been disaterous with inability to give birth to the larger babies. And one is in no position to get women from the other culture anyway, if you are barely surviving.