4. Nuclear DNA: Forays into 3 billion base pairs
4.1 Before Vi-80
The Vindija-80 (Vi-80) specimen is an important find for geneticists: it yielded a minimally contaminated sample and provided those first steps into Neanderthal genomics.
Previously, attempts at retrieving ancient nuclear DNA sequences proved to be a notoriously difficult process, plagued with problems of degradation, contamination and chemical damage (Hofreiter et al., 2001). Researchers also need to contend with quantities of nuclear genome available: for every nuclear genome there are approximately several hundred mtDNAs (Green et al., 2008). The severity of these problems, especially contamination, is magnified through Neanderthal genetic similarity with humans (Green et al., 2006). This is troubling because nuclear DNA presents far less variability than mtDNA (Russell, 2002). As a result, huge stretches of nuclear sequences are required to find a significant number of polymorphisms (ibid). Such implications meant that discovering endogenous DNA sequences requires sifting through a large corpus of “[…] more than 70 Neanderthal bone and tooth samples from different sites in Europe and western Asia” (Green et al., 2006, pg. 331).
Continue reading “What conclusions can we draw from Neanderthal DNA pt.2”
February 12th — keep this date in mind and prepare your browser on automatic refresh because the Neanderthal genome is to be unveiled. And just to make it extra special, the date on which we’ll dip into the three billion base pairs of our extinct relative is the 200th anniversary of Charles Darwin‘s birth. Here’s a little extract from the Nature article just to peak your interest:
Comparisons with the human genome may uncover evidence of interbreeding between Neanderthals and humans, the genomes of which overlap by more than 99%. They certainly had enough time for fraternization — Homo sapiens emerged as a separate species by about 400,000 years ago, and Neanderthals became extinct just 30,000 years ago. Their last common ancestor lived about 660,000 years ago, give or take 140,000 years.
I can’t think why we wouldn’t have interbred with Neanderthals. Language of course is one possible reason, acting as a symbolic marker of group boundaries to such an extent that even cultural differences within humans would minimise gene flow (assuming language, or even a protolanguage, was around then). That said, even contemporary humans are quite willing to fuck goats (and god knows what else). So why not the Neanderthals?
N.B. If you’re not familiar with they dynamics surrounding the possibility of Neanderthals having contributed some genes to modern humans, then I strongly suggest you read John Hawks’ Neanderthal FAQ. Also, check out his sections on adaptive introgression.