Sunday, September 11, 2005


Some interesting new DNA research (below) traces changes in human brain evolution to quite recent times. Certain genes that regulate brain size appear to have become common at just about the same time when human social evolution made great advances -- the beginning of civilization for instance. So we now in fact have a genetic explanation for when civilization began. But instead of welcoming such exciting new information, lots of people are playing down the results. Why? One reason is that the genetic pattern that seems to be associated with the rise of civilization is much less common among blacks. I leave it to readers to connect the rest of the dots. Note however that there has long been evidence that larger brains go with higher intelligence and that the assertion that intelligence is not mainly genetic is contradicted by around a century of research on the subject

"The human brain may still be evolving. So suggests new research that tracked changes in two genes thought to help regulate brain growth, changes that appeared well after the rise of modern humans 200,000 years ago. That the defining feature of humans - our large brains - continued to evolve as recently as 5,800 years ago, and may be doing so today, promises to surprise the average person, if not biologists. "We, including scientists, have considered ourselves as sort of the pinnacle of evolution," noted lead researcher Bruce Lahn, a University of Chicago geneticist whose studies appear in Friday's edition of the journal Science. "There's a sense we as humans have kind of peaked," agreed Greg Wray, director of Duke University's Center for Evolutionary Genomics. "A different way to look at is it's almost impossible for evolution not to happen."

Still, the findings also are controversial, because it's far from clear what effect the genetic changes had or if they arose when Lahn's "molecular clock" suggests - at roughly the same time period as some cultural achievements, including written language and the development of cities.

Lahn and colleagues examined two genes, named microcephalin and ASPM, that are connected to brain size. If those genes don't work, babies are born with severely small brains, called microcephaly. Using DNA samples from ethnically diverse populations, they identified a collection of variations in each gene that occurred with unusually high frequency. In fact, the variations were so common they couldn't be accidental mutations but instead were probably due to natural selection, where genetic changes that are favorable to a species quickly gain a foothold and begin to spread, the researchers report.

Lahn offers an analogy: Medieval monks would copy manuscripts and each copy would inevitably contain errors - accidental mutations. Years later, a ruler declares one of those copies the definitive manuscript, and a rush is on to make many copies of that version - so whatever changes from the original are in this presumed important copy become widely disseminated. Scientists attempt to date genetic changes by tracing back to such spread, using a statistical model that assumes genes have a certain mutation rate over time.

For the microcephalin gene, the variation arose about 37,000 years ago, about the time period when art, music and tool-making were emerging, Lahn said. For ASPM, the variation arose about 5,800 years ago, roughly correlating with the development of written language, spread of agriculture and development of cities, he said. "The genetic evolution of humans in the very recent past might in some ways be linked to the cultural evolution," he said.

Other scientists urge great caution in interpreting the research. That the genetic changes have anything to do with brain size or intelligence "is totally unproven and potentially dangerous territory to get into with such sketchy data," stressed Dr. Francis Collins, director of the National Human Genome Research Institute. Aside from not knowing what the gene variants actually do, no one knows how precise the model Lahn used to date them is, Collins added.

Lahn's own calculations acknowledge that the microcephalin variant could have arisen anywhere from 14,000 to 60,000 years ago, and that the uncertainty about the ASPM variant ranged from 500 to 14,000 years ago.

Those criticisms are particularly important, Collins said, because Lahn's testing did find geographic differences in populations harboring the gene variants today. They were less common in sub-Saharan African populations, for example. That does not mean one population is smarter than another, Lahn and other scientists stressed, noting that numerous other genes are key to brain development. "There's just no correlation," said Duke's Wray, calling education and other environmental factors more important for intelligence than DNA anyway."

Source. NOTE: Steve Sailer has a huge roundup on the subject that is much more scholarly than my few comments. His permalinks suck so look for the heading John Hawks on Lahn's genes


When will the food and lifestyle dictators admit that we don't know enough yet to even SUGGEST to people what they should do, let alone dictate to them? The basic truth that a thing can be bad for you in one way but good for you in another way is regularly ignored

Women who suffer high levels of daily stress may be less likely to develop breast cancer, Danish researchers said yesterday. The findings are based on a study conducted by the National Institute of Public Health, Copenhagen, which followed 6,500 women over an 18-year period.

Writing in the British Medical Journal, the researchers said the survey suggested that high stress could reduce the likelihood of breast cancer, but they warned that stress put women at risk of illnesses such as heart disease.

At the start of the study, the women were asked to describe their stress levels which were ranked as either low, medium or high. Stress-related symptoms such as tension, nervousness, anxiety and sleeplessness were taken into account. The study also recorded whether the women had children or had entered the menopause. It did not take family history of the disease into account. By the end, 251 women had been diagnosed with breast cancer and those who reported high stress levels were found to be 40 per cent less likely to develop the disease than women who suffer low stress.

Naja Rod Nielsen, who worked on the study, said that one explanation might be that sustained high stress may affect oestrogen levels, which may influence the development of breast cancer. Mr Nielsen said: "High endogenous concentrations of oestrogen are a known risk factor for breast cancer, and impairment of oestrogen synthesis induced by chronic stress may explain a lower incidence of breast cancer in women with high stress."

Dr Sarah Rawlings, head of policy at Breakthrough Breast Cancer, said that it is always hard to measure the impact of stress on breast cancer risk. She said: "This study doesn't help us to draw further conclusions."



I have recently put up a few more political correctness postings on Tongue-Tied.

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