Proceedings of the National Academy of Sciences, November 17
When is a goat like a reptile? When it’s cold-blooded, slow-moving, and fond of sitting on warm rocks. Researchers have discovered a bizarre dwarf goat species that lived on the Spanish island Majorca, but that went extinct when human hunters arrived on the island about 3,000 years ago. The study says that the goat’s cold-blooded ways allowed it to survive on the resource-scarce island, as it could match its growth and metabolism to the available food supplies, but its sluggish movements made it easy prey for humans. In medical news, a research team investigating the dramatic failure of an HIV vaccine trial, in which vaccinated people seemed to be at higher risk of infection, has proposed a new theory for the failure. The study suggests that the common cold virus, which was used in the vaccine to carry HIV material around the body so the immune system could learn to recognize HIV, may have been at fault. The vaccine didn’t cause infection. But for people who have previously been exposed to this cold virus, its appearance may have triggered a gathering of immune cells called CD4 T-cells which were ready to fight it off. But those are the cells that HIV infects, so if people were then exposed to the HIV virus, the virus would have been presented with a ready availability of targets. Finally, an interesting study captured a snapshot of evolution-in-action on the Galapagos islands. A husband and wife team of evolutionary biologists is documenting what appears to be the emergence of a new species among Galapagos finches, the same birds that inspired Charles Darwin’s theory of evolution.
New England Journal of Medicine, November 19
Who can resist a story about brain-eaters that also has valuable medical and evolutionary lessons? A NEJM study describes a tribe in Papua New Guinea that used to engage in ritualistic cannibalism; when a member of the tribe died, the others ate the person’s brain as a mark of respect. The practice became a problem in the early 20th century, when some people became infected with a disease similar to mad cow disease and its human variant, Creutzfeldt Jakob disease. These fatal diseases are caused by misfolded proteins in the brain, so when the Fore people of Papua New Guinea consumed an affected brain the disease quickly spread. But a new study of living Fore people revealed that many are immune to the disease, which suggests that evolution has been acting quickly: Those people who had no resistance to the disease died off quickly, while people with resistance lived and multiplied. Researchers also hope to study the Fore people for clues on how to treat or prevent such diseases.
Science, November 20
A fascinating study brought new insight into the disappearance of North America’s prehistoric megafauna, via a study of a fungus present in their mega-dung. The fungus releases a spore that is preserved in sediment samples, which researchers can analyze to determine how prevalent the great beasts were throughout history. The new analysis suggests that megafauna like mastodons, mammoths, and sabre-toothed tigers began a slow decline around 15,000 years ago and vanished completely about 1,000 years later. This suggests that their extinction was not a result of an asteroid or comet that is thought to have exploded over North America much later. It also takes the blame off the Clovis people, who were thought to be North America’s first settlers, but who didn’t establish themselves until about 13,300 years ago. Some researchers have suggested that the Clovis people hunted mammoths and the like into extinction. While the new study makes a good argument, it’s unlikely to persuade all proponents of alternate theories–expect rebuttals to follow. Another study revealed the results of a four-year effort to map the genome of corn. The task turned out to be surprisingly complex, as the corn genome has 12,000 more genes than the human genome, but the resulting data has already helped scientists understand how maize was domesticated, and should help agricultural researchers increase the efficiency of corn crops.
Journal of the American Medical Association, November18
Upper-crust ancient Egyptians weren’t so different from modern Americans in one way: a new study that X-rayed 20 Egyptian mummies found signs of clogged arteries and heart disease in 16 of them. Since only the Egyptian elite were mummified, it’s impossible to say if cardiovascular problems were widespread in ancient Egypt. But the researchers note that the elite often dined on rich dishes such as beef, mutton, and cakes with honey and butter, and suggest that this fatty diet may have contributed to heart disease among the nobility.
Nature, November 19
In another warning bell regarding global warming, a study found that the world’s oceans are absorbing less globe-warming carbon dioxide than they used to. Until about the 1980s, researchers say, the absorption rate kept pace with increasing greenhouse gas emissions. But since then the intake rate has slowed, due to a gradual change in the oceans’ chemistry. The increased load of CO2 in the seawater is changing the pH balance of the oceans and making them more acidic, which then limits the amount of CO2 they can sop up. The results are troubling, because they indicate that even more greenhouse gases will remain in the atmosphere.