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SCIENCE UPDATE: DNA from Neanderthal leg shows distant split
RESEARCHERS have sequenced DNA from the leg bone of a Neanderthal man who died 38,000 years ago and said “it shows the Neanderthals are truly distant relatives of modern humans who interbred rarely, if at all, with our own immediate ancestors”.
They estimate that modern humans and Neanderthals split from a common ancestor at least 370,000 years ago and possibly 500,000 years ago, although we share 99.95 per cent of our DNA. “We see no evidence of mixing 40,000, 30,000 years ago in Europe. We don’t exclude it, but see no evidence,” Edward Rubin of the US Department of Energy Joint Genome Institute in Walnut Creek, California, who led one study, told reporters.
This conflicts with some evidence from other researchers, including a team who said earlier this month that humans may have inherited a brain gene from Neanderthals. Rubin’s team used one method to isolate and sequence part of the Neanderthal’s DNA, while another team, led by Svante Paabo of the Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany, used a separate method to sequence a much larger amount.
Paabo was the first scientist to find and sequence Neanderthal DNA, in 1997, and first suggested that Neanderthals “will serve as a DNA time machine that will tell us about biology and aspects that we will never be able to get from their bones and a limited number of associated artefacts” Rubin said. Neanderthals and modern humans are both descended from Homo erectus, which left Africa and spread around the world about 1.5 million years ago.
Neanderthals lived in Europe and the Middle East until about 30,000 years ago. Cro-Magnon people, the ancestors of modern humans, started a second wave of migration out of Africa about 10,000 years earlier. One huge question is how closely they interacted. Paabo's and Rubin's genetic analysis both suggest there was little sexual contact, at least according to the genes from this one male found at the back of a cave in Croatia. Paabo's team sorted through 70 Neanderthal specimens before they found a bone well-preserved enough to provide DNA. They took the tiniest samples they could to preserve the valuable bones. They know it was a male because the DNA has a Y chromosome. Females have two X chromosomes.
Paabo's team used a gene sequencer made by 454 Life Sciences Corporation, a majority-owned subsidiary of CuraGen Corporation. He said they have refined their methods and hope to have a complete genetic sequence within two years.
— Dawn/Reuters
Happy people, fewer colds
Staying positive through the cold season could be your best defence against getting sick, new study findings suggest in an experiment that exposed healthy volunteers to a cold or flu virus, researchers found that people with a generally sunny disposition were less likely to fall ill. The findings, published in the journal Psychosomatic Medicine, build on evidence that a “positive emotional style” can help ward off the common cold and other illnesses. Researchers believe the reasons may be both objective -— as in happiness boosting immune function — and subjective — as in happy people being less troubled by a scratchy throat or runny nose. “People with a positive emotional style may have different immune responses to the virus,” explained lead study author Dr Sheldon Cohen of Carnegie Mellon University in Pittsburgh, “and when they do get a cold, they may interpret their illness as being less severe.” Cohen and his colleagues had found in a previous study that happier people seemed less susceptible to catch a cold, but some questions remained as to whether the emotional trait itself had the effect.
For the new study, the researchers had 193 healthy adults complete standard measures of personality traits, self-perceived health and emotional “style.” Those who tended to be happy, energetic and easy-going were judged as having a positive emotional style, while those who were often unhappy, tense and hostile had a negative style. Afterward, the researchers gave them nasal drops containing either a cold virus or a particular flu virus that causes cold-like symptoms. Over the next six days, the volunteers reported on any aches, pains, sneezing or congestion they had, while the researchers collected objective data, like daily mucus production. Cohen and his colleagues found this based on an objective measure of nasal woes; happy people were less likely to develop a cold. What's more, when happy folks did develop a cold, their self-rated symptoms were less severe than would be expected based on objective measures.
When the researchers weighed other factors that could explain the relationship — like volunteers' perception of their general health, their self-esteem and tendency to be optimistic — happiness itself still seemed to protect against cold symptoms.
In contrast, people with negative dispositions were not at increased risk of developing a cold based on objective measures -- though they did tend to get down about their symptoms. “We find that it's really positive emotions that have the big effect,” Cohen said, “not negative ones.” —Dawn/The Guardian News Service
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