Monday, 22 June 2015

More Sex With Neanderthals But No Original Sin

Photo credit: AFP/Getty
An early modern human from Romania with a recent Neanderthal ancestor | Nature

This isn't so much new information as adding detail to what we already know.

We've known for several years now that all non-African populations have some Neanderthal DNA, showing without a doubt that humans came up against and interbred with, to a limited degree, the Neanderthal population that had evolved from members of an earlier migration out of Africa.

This was discovered by Svante Pääbo's team at the Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany when they first extracted enough DNA from Neanderthal remains to make analysis possible. The same unit has now managed to extract DNA from a lower jaw found in a cave in Romania and found that it contains a surprisingly large amount of Neanderthal DNA, although it is undoubtedly that of an early modern Homo sapiens. Unlike modern non-African humans which have 3-5% Neanderthal DNA, this individual had 6-9%.

This new find simply ties down where and when one of these instances of interbreeding happened - it was in what is now Romania about 40,000 years ago, tying in with estimates of when early modern humans migrated out of Africa.

Neanderthals are thought to have disappeared in Europe approximately 39,000–41,000 years ago but they have contributed 1–3% of the DNA of present-day people in Eurasia. Here we analyse DNA from a 37,000–42,000-year-old2 modern human from Peştera cu Oase, Romania. Although the specimen contains small amounts of human DNA, we use an enrichment strategy to isolate sites that are informative about its relationship to Neanderthals and present-day humans. We find that on the order of 6–9% of the genome of the Oase individual is derived from Neanderthals, more than any other modern human sequenced to date. Three chromosomal segments of Neanderthal ancestry are over 50 centimorgans in size, indicating that this individual had a Neanderthal ancestor as recently as four to six generations back. However, the Oase individual does not share more alleles with later Europeans than with East Asians, suggesting that the Oase population did not contribute substantially to later humans in Europe.

The reason we can be fairly confident that this jaw bone was from an individual with a Neanderthal in his recent ancestry - maybe as few as six generations (about 200 years) earlier. Evolutionary biologists know this because of the way DNA gets mixed up in chromosomes over time. A baby with one Homo neanderthalensis parent and one H. sapiens would have one Neanderthal and one H. sapiens chromosome in each pair. However, when sperm or eggs are produced, these pairs swap chunks of DNA over, maybe just one or two large chunks for each chromosome. So his or her children would now have large chunks of Neanderthal DNA.

These are likely to get chopped up again at each generation so, as time goes on, the Neanderthal DNA would be in smaller and smaller pieces, as it is in non-African humans today.

This individual from Romania however still had large chunks of Neanderthal DNA and 2-3 times as much of it as we have on average today. So, it's fairly certain that interbreeding happened just a few generations earlier.

All perfectly straightforward for evolutionary biology and fully consistent with the human evolutionary story, but how does this fit in with creationism and religious notions of original sin?

This depends entirely on the notion that not only were humans specially created but that we share a single ancestral couple who committed this original sin. Even allowing for the creativity of those who accept evolution theory but still like to believe they've inherited a sin and need to be 'saved' by a magic friend, the knowledge that we interbreed is a bit of a problem.

Did Neanderthals inherit original sin from way back in our past - which would mean H. erectus and/or H. habilis needing forgiveness and redemption and needing to accept Jesus to be saved. If not, and if there was not a single ancestral couple when did this sin enter modern humans, and did the hybrids between modern humans and Neanderthals (and Denisovans, incidentally) inherit half the sin or all of it? Why should a Neanderthal's descendants need to be forgiven for something another species did, allegedly?

So many questions and so few answers. It's hard to imagine the mental gymnastics scientifically educated believers need to perform to ride two intellectual horses in different directions simultaneously.

'via Blog this'

submit to reddit
Income from ads will be donated to charities such as moderate centre-left groups, humanist, humanitarian and wildlife protection and welfare organisations.

No comments :

Post a Comment

Obscene, threatening or obnoxious messages, preaching, abuse and spam will be removed, as will anything by known Internet trolls and stalkers, by known sock-puppet accounts and anything not connected with the post,

A claim made without evidence can be dismissed without evidence. Remember: your opinion is not an established fact unless corroborated.

Related Posts Plugin for WordPress, Blogger...
Web Analytics