HENRY - The human evolution news relay
Entries written in February 2007
Written February 28, 2007 in evolution, genetics, wednesday-wiki
This week, Muller’s Ratchet:
In evolutionary genetics, Muller’s ratchet (named after Hermann Joseph Muller) is the name given to the process by which the genomes of an asexual population accumulate deleterious mutations in an irreversible manner (hence the word ratchet). The genomes of sexual populations can easily reverse this process thanks to recombination. Continued at wikipedia
Norton et al in Mol. Biol. Evol. use data from the International Hapmap project (which we covered earlier) to test 6 human skin pigmentation genes for positive directional selection. They argue that this shows a pattern of convergent evolution towards ligter skin pigmentation in Europeans and East Asians. Abstract here
Morrell and Clegg in today’s P.N.A.S. investigated differences in haplotype frequency in multiple loci over > 60 Barley species. They argue that this demonstrates that Barley (Hordeum vulgare) was domesticated twice. It was first cultivated in the Fertile Crescent, which lead to most of the current European and American cultivars. The second domestication occured 1,500–3,000 [...]
Stefan Lovgren in National Geographic:
The so-called Clovis people, known for their distinctive spearheads, were not the first humans to set foot in the Americas after all, a new study says. The find supports growing archaeological evidence found in recent years that disputes the notion that the Americas were originally populated by a single migration of people from Asia about 13,000 years ago.
He’s reporting on a paper in Science by Michael Waters & Thomas Stafford:
The Clovis complex is considered to be the oldest unequivocal evidence of humans in the Americas, dating between 11,500 and 10,900 radiocarbon years before the present (14C yr B.P.). Adjusted 14C dates and a reevaluation of the existing Clovis date record revise the Clovis time range to 11,050 to 10,800 14C yr B.P. In as few as 200 calendar years, Clovis technology originated and spread throughout North America. The revised age range for Clovis overlaps non-Clovis sites in North and South America. This and other evidence imply that humans already lived in the Americas before Clovis. (Abstract Only)
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Hobolth et al in PLoS Genetics have re-estimated the date of the chimp-human split using a Coalescent Hidden Markov Model, and infer ancient population sizes of the species in question. The author’s summary:
Primate evolution is a central topic in biology and much information can be obtained from DNA sequence data. A key parameter is the [...]
There’s been a few brief reports recently that chimpanzees have been seen hunting bushbabies with spears (primatology.org, LiveScience), and today the paper on this by Preutz and Bertolani can be found in press at Current Biology:
Although tool use is known to occur in species ranging from naked mole rats to owls, chimpanzees are the most [...]
There’s a nice article on stress in ScienceDaily:
Why do humans and their primate cousins get more stress-related diseases than any other member of the animal kingdom? The answer, says Stanford University neuroscientist Robert Sapolsky, is that people, apes and monkeys are highly intelligent, social creatures with far too much spare time on their hands.
Continue Reading [...]
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