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Two teams of scientists have made impressive strides in decoding the Neandarthal DNA. The articles, published in Nature and Science, seem to suggest that the Neandarthals and modern humans genetically parted ways some 500,000 years ago. Thus, these two speacies did not interbreed.

Neanderthals are the extinct hominid group most closely related to contemporary humans, so their genome offers a unique opportunity to identify genetic changes specific to anatomically fully modern humans. We have identified a 38,000-year-old Neanderthal fossil that is exceptionally free of contamination from modern human DNA. Direct high-throughput sequencing of a DNA extract from this fossil has thus far yielded over one million base pairs of hominoid nuclear DNA sequences. Comparison with the human and chimpanzee genomes reveals that modern human and Neanderthal DNA sequences diverged on average about 500,000 years ago. Existing technology and fossil resources are now sufficient to initiate a Neanderthal genome-sequencing effort.

Full articles can be found here and here.

Posted by Naboj at 07:47 PM | Permalink | Comments (0) | TrackBacks (0)

A friend of mine, who is a regular jet-setter, was the first person to alert me to the fact that flying west is an easier way of traveling around the globe. This anecdotal evidence seems to be getting some solid scientific backing. A group of scientists has tested it on mice, and it turns out that there was some significant effect on the health of mice who were exposed to the jet-lagged light conditions in the laboratory:

Despite the fact that trans-meridian travel and shift work are commonplace in our 24/7 society, few controlled studies have addressed the health effects of repeated phase shifts of the biological clock. Shift work and chronic jet-lag reduce mental acuity and increase the risk of a number of medical problems, including cancer, peptic ulcers and sleep disorders. Some of these problems become more severe with the number of years on the job, the result either of cumulative damage or the increased age of the subjects [3]. In general, morbidity associated with many organic disorders is increased in the aged; however, the role played by age-associated alterations in the circadian clock is poorly understood. In particular the effect of repeated schedule changes is largely unaddressed. Here we report evidence that chronic jeg-lag increases mortality rates in aged mice.

The full article can be found here (subscription required).

Posted by Naboj at 09:29 PM | Permalink | Comments (0) | TrackBacks (0)

The preference of human males for younger females is almost proverbial. It is assumed that this is a byproduct of human reproductive cycle - because of the menopause, younger human females yield a larger reproductive advantage. This hypothesis has been indirectly tested by studying chimpanzees. These closest human relatives don't undergo menopause, and it turns out that male chimpanzees prefer older females. This research has been reported in the current issue of Current Biology.

Cross-cultural studies indicate that women's sexual attractiveness generally peaks before motherhood and declines with age. Cues of female youth are thought to be attractive because humans maintain long-term pair bonds, making reproductive value (i.e. future reproductive potential) particularly important to males. Menopause is believed to exaggerate this preference for youth by limiting women's future fertility. This theory predicts that in species lacking long-term pair bonds and menopause, males should not exhibit a preference for young mates. We tested this prediction by studying male preferences in our closest living relative, the chimpanzee (Pan troglodytes). We show that despite their promiscuous mating system, chimpanzee males, like humans, prefer some females over others. However, in contrast to humans, chimpanzee males prefer older, not younger, females. These data robustly discriminate patterns of male mate choice between humans and chimpanzees. Given that the human lineage evolved from a chimpanzee-like ancestor, they indicate that male preference for youth is a derived human feature, likely adapted from a tendency to form unusually long term mating bonds.

The full article can be read here (subscription required).

Posted by Naboj at 03:29 PM | Permalink | Comments (0) | TrackBacks (0)

Human genetic makeup and variability are somewhat controversial topic. Now there is evidence that there is more genetic variability between different humans than previously thought.

Geneticists have generally assumed that your string of DNA 'letters' is 99.9% identical to that of your neighbour's, with differences in the odd individual letter. These differences make each person genetically unique — influencing everything from appearance and personality to susceptibility to disease.

But hold on, say the authors of a new study published in Nature. They have identified surprisingly large chunks of the genome that can differ dramatically from one person to the next. "Everyone has a unique pattern," says one of the lead authors, Matthew Hurles at the Wellcome Trust Sanger Institute in Cambridge, UK.

The sumary of the article can be read here. The original article can be read here.

Posted by Naboj at 02:27 PM | Permalink | Comments (0) | TrackBacks (0)

In the latest issue of Science there have been several reports that suggest a continuing evolution of human species, well after the formation of anatomically modern humans some 200,000 years ago. The particular changes in the human genome that have been detected suggest strong evolutionary pressures that acted 37,000 and 5,800 years ago. These changes seem to have affected the size and functionality of brain.

Posted by Naboj at 01:54 PM | Permalink | Comments (0) | TrackBacks (0)