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Ancient genomes suggest Africa has two elephant species
tony heald/naturepl.com
IN BRIEF Mitochondria’s cancer secret?
Africa may have two elephant species, not one THERE may be grounds for doubling the number of African elephant species, according to DNA evidence comparing the genomes of the living elephant species and extinct relatives. The finding backs arguments for conserving savannah and forest elephants separately, rather than treating them as one species. “The forest elephant is half the size of the savannah elephant and lives in the forest. Their body shape and how they look is quite different,” says David Reich, an evolutionary biologist at Harvard Medical School. Reich and colleagues compared the DNA of 375 genes
for the forest, savannah and Asian elephants, and the extinct woolly mammoth; and also from the extinct mastodon which split from these elephant groups much earlier in their evolutionary history (PLoS Biology, DOI: 10.1371/journal.pbio.1000564). They looked at the differences in the DNA to estimate when each population diverged. “What was really surprising was that the forest elephant and the savannah elephant were as diverged as the Asian elephant and woolly mammoth,” says Reich. The study suggests that the two African elephants split at least 2.5 million years ago, and possibly much earlier, although Pascal Tassy at the National Museum of Natural History in Paris, France, warns that looking at historical genetic divergence does not give the final word on separating species.
A fat tummy shrivels your brain HAVING a larger waistline may shrink your brain. Obesity is linked to an increased risk of type 2 diabetes, which is known to be associated with cognitive impairment. So Antonio Convit at the New York University School of Medicine wanted to see what impact obesity had on the physical structure of the brain. He used magnetic resonance imaging to compare 14 | NewScientist | 8 January 2011
the brains of 44 obese individuals with those of 19 lean people of similar age and background. He found that obese individuals had more water in the amygdala – a part of the brain involved in eating behaviour. He also saw smaller orbitofrontal cortices in obese individuals, important for impulse control and also involved in feeding behaviour (Brain Research, in press). “It could
mean that there are less neurons, or that those neurons are shrunken,” says Convit. Eric Stice at Oregon Research Institute, Eugene, thinks that the findings strengthen the “slippery slope” theory of obesity. “If you overeat, it appears to result in neural changes that increase the risk for future overeating,” he says. Obesity is associated with a constant, low-level inflammation, which Convit thinks explains the change in brain size.
FRESH insight into prostate cancer has come in a study showing that the mitochondrial DNA of human prostate cancer cells is riddled with mutations. The findings could shake up prostate cancer research, providing targets for treatment of one of the most prevalent cancers in the west. Mutations in mitochondrial DNA have been linked to development of the cancer, so Anita Kloss-Brandstätter of Innsbruck Medical University in Austria and colleagues compared the entire mitochondrial genome of cancerous and non-cancerous tissue from 30 men with prostate cancer (The American Journal of Human Genetics, DOI: 10.1016/ j.ajhg.2010.11.001). In total, 41 mutations were found in cancerous cells that were not observed in healthy cells, suggesting they are associated with prostate cancer development, says Kloss-Brandstätter.
Seeing the light in a womb with a view A FETUS might learn to see before it is born. So much light penetrates a pregnant woman’s tummy that her fetus may develop vision in the final two months of pregnancy. We have long known that fetuses can smell, taste and hear. Marco Del Giudice at the University of Turin in Italy wondered if there was enough light present for them to see, too. He measured the amount of light that could penetrate through to a typical woman’s uterus and found that in a naked woman, about 0.1 to 1 per cent of ambient light would get in (Developmental Psychology, DOI: 10.1002/dev.20506). In bright sunlight, a fetus could receive light equivalent to that found in a typically lit house.
IN BRIEF Mitochondria’s cancer secret?
Africa may have two elephant species, not one THERE may be grounds for doubling the number of African elephant species, according to DNA evidence comparing the genomes of the living elephant species and extinct relatives. The finding backs arguments for conserving savannah and forest elephants separately, rather than treating them as one species. “The forest elephant is half the size of the savannah elephant and lives in the forest. Their body shape and how they look is quite different,” says David Reich, an evolutionary biologist at Harvard Medical School. Reich and colleagues compared the DNA of 375 genes
for the forest, savannah and Asian elephants, and the extinct woolly mammoth; and also from the extinct mastodon which split from these elephant groups much earlier in their evolutionary history (PLoS Biology, DOI: 10.1371/journal.pbio.1000564). They looked at the differences in the DNA to estimate when each population diverged. “What was really surprising was that the forest elephant and the savannah elephant were as diverged as the Asian elephant and woolly mammoth,” says Reich. The study suggests that the two African elephants split at least 2.5 million years ago, and possibly much earlier, although Pascal Tassy at the National Museum of Natural History in Paris, France, warns that looking at historical genetic divergence does not give the final word on separating species.
A fat tummy shrivels your brain HAVING a larger waistline may shrink your brain. Obesity is linked to an increased risk of type 2 diabetes, which is known to be associated with cognitive impairment. So Antonio Convit at the New York University School of Medicine wanted to see what impact obesity had on the physical structure of the brain. He used magnetic resonance imaging to compare 14 | NewScientist | 8 January 2011
the brains of 44 obese individuals with those of 19 lean people of similar age and background. He found that obese individuals had more water in the amygdala – a part of the brain involved in eating behaviour. He also saw smaller orbitofrontal cortices in obese individuals, important for impulse control and also involved in feeding behaviour (Brain Research, in press). “It could
mean that there are less neurons, or that those neurons are shrunken,” says Convit. Eric Stice at Oregon Research Institute, Eugene, thinks that the findings strengthen the “slippery slope” theory of obesity. “If you overeat, it appears to result in neural changes that increase the risk for future overeating,” he says. Obesity is associated with a constant, low-level inflammation, which Convit thinks explains the change in brain size.
FRESH insight into prostate cancer has come in a study showing that the mitochondrial DNA of human prostate cancer cells is riddled with mutations. The findings could shake up prostate cancer research, providing targets for treatment of one of the most prevalent cancers in the west. Mutations in mitochondrial DNA have been linked to development of the cancer, so Anita Kloss-Brandstätter of Innsbruck Medical University in Austria and colleagues compared the entire mitochondrial genome of cancerous and non-cancerous tissue from 30 men with prostate cancer (The American Journal of Human Genetics, DOI: 10.1016/ j.ajhg.2010.11.001). In total, 41 mutations were found in cancerous cells that were not observed in healthy cells, suggesting they are associated with prostate cancer development, says Kloss-Brandstätter.
Seeing the light in a womb with a view A FETUS might learn to see before it is born. So much light penetrates a pregnant woman’s tummy that her fetus may develop vision in the final two months of pregnancy. We have long known that fetuses can smell, taste and hear. Marco Del Giudice at the University of Turin in Italy wondered if there was enough light present for them to see, too. He measured the amount of light that could penetrate through to a typical woman’s uterus and found that in a naked woman, about 0.1 to 1 per cent of ambient light would get in (Developmental Psychology, DOI: 10.1002/dev.20506). In bright sunlight, a fetus could receive light equivalent to that found in a typically lit house.