07 May 2010

We Are All Neanderthals Now

Update 9 May: John Hawks provides a good analysis of the findings here and here
Remember when it was an insult to be called a Neandertal? Scientists at Max Planck have learned that most of the people of the world are descended from Neandertals -- at least partially. So who's the Neandertal now? You, that's who!
Researchers sequencing Neandertal DNA have concluded that between 1 and 4 percent of the DNA of people today who live outside Africa came from Neandertals, the result of interbreeding between Neandertals and early modern humans. _SciAm

They are so closely related that some researchers group them and us as a single species. "I would see them as a form of humans that are bit more different than humans are today, but not much," says Svante Pääbo, a palaeogeneticist at the Max Planck Institute in Leipzig, Germany, whose team sequenced the Neanderthal genome.

The common ancestor of humans and Neanderthals lived in Africa around half a million years ago. After that, the ancestors of Neanderthals moved north and eventually made it to Europe and Asia. Our ancestors, meanwhile, stuck around Africa until about 100,000 years ago before eventually conquering the globe. Neanderthals died out around 28,000 years ago. _NewScientist

The scientists used just half a gram of bone powder, collected from the bones of three individual Neanderthals excavated from the Vindija Cave in Croatia. The data they provide tells a story not just of migration but physical evolution, and allows researchers to isolate what makes humans unique. "The Neanderthals are our closest evolutionary relative," says Svante Pääbo, the project's leader and director of genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. He notes that now scientists can begin to ask what genetically differentiates us from our closest living relative--the chimpanzee--and our closest extinct one....

...The group's combined findings required an immense technological effort, one that spanned six years and multiple high-throughput sequencing technology platforms. It involved finding ways to differentiate Neanderthal DNA from modern human DNA contamination, eliminating microbial DNA that had invaded the bones, and determining how the Neanderthal sequences had chemically changed over time. But the ultimate result, says biological anthropologist John Hawks, of the University of Wisconsin, is "5.3 billion pieces of information about Neanderthals." And that, he says, is something worth waiting for. _TechnologyReview

All humans except those who never left the African continent until the modern age, contain at least a small portion of Neandertal genes. But then, Neandertals were said to have evolved in Africa too, and to have migrated to Europe before modern Homo Sapiens.

It should be obvious that anthropologists are largely guessing at the timeline involved, and the exact locations of important evolutionary transitions. If it has taken us this long to learn that Homo Sapiens interbred with Homo Neandertal, then clearly we are not exactly on top of things.

Nevertheless, this is one more piece of the puzzle. Africans typically lack Neandertal genes, which may mean nothing -- or it may point the way toward significant genetic ---> behavioural differences between Africans and non-Africans. It will take time to sort it all out, assuming the PC Police allow it. Not that you could understand any of this, you Neandertal!

The diagram above is somewhat speculative, but it does describe one possible way in which the genomic admixture could have occurred.

A skeptical look from the sometimes credulous science writer carl zimmer

A skeptical look from the Richard Dawkins (also sometimes credulous) site


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Blogger Bruce Hall said...

Not sure I follow the percentages being used. From Wikipedia:

DNA sequencing
Comparison of the DNA sequences allows organisms to be grouped by sequence similarity, and the resulting phylogenetic trees are typically congruent with traditional taxonomy, and are often used to strengthen or correct taxonomic classifications. Sequence comparison is considered a measure robust enough to be used to correct erroneous assumptions in the phylogenetic tree in instances where other evidence is scarce. For example, neutral human DNA sequences are approximately 1.2% divergent (based on substitutions) from those of their nearest genetic relative, the chimpanzee, 1.6% from gorillas, and 6.6% from baboons.[15] Genetic sequence evidence thus allows inference and quantification of genetic relatedness between humans and other apes.[16][17] The sequence of the 16S ribosomal RNA gene, a vital gene encoding a part of the ribosome, was used to find the broad phylogenetic relationships between all extant life. The analysis, originally done by Carl Woese, resulted in the three-domain system, arguing for two major splits in the early evolution of life. The first split led to modern Bacteria and the subsequent split led to modern Archaea and Eukaryote.


Friday, 07 May, 2010  
Blogger al fin said...

It is not nearly so simple as it is sometimes stated -- eg, wikipedia.

How deeply do you wish to look into the genome, for example? Exons only? Exons and Introns? Copy number variants? Degenerative mutations? Epigenetic mechanisms, transcription factors, promoters, non-coding RNAs, etc etc.

I haven't read the Max Planck sapiens-neandertal paper, but to be honest, biologists and anthropologists have barely scratched the surface of genome homologies. And the subject is already too complex to comprehend without very sophisticated software and computing.

Friday, 07 May, 2010  

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