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Marriage not age causes testosterone to wither
Research news and discovery
MARIA STENZEL/NATIONAL GEOGRAPHIC IMAGE COLLECTION
In brief– Easy listening
Men’s hormones settle down when they get their girl TESTOSTERONE gradually declines with age, right? Not for the Ariaal – subsistence pastoralists living in northern Kenya. They experience a decline in levels of the male hormone only when they get married. The finding provides a social and evolutionary explanation for the decrease in testosterone, rather than an age-related one. Ariaal men remain single “warriors” until they are around 30, at which time they marry one or more women. Peter Gray of the University of Nevada, Las Vegas, and colleagues measured testosterone in 205 Ariaal men and
found that those with one wife had lower levels of the hormone than unmarried men, and men with more than one wife had the lowest levels of all (Current Anthropology, DOI: 10.1086/522061). “Testosterone levels are lower among married men probably because they are investing less in mating effort,” he says. Or to put it another way, they no longer have to compete for mates. That link between mating effort and testosterone is made clearer by the fact that the Ariaal have an “aloof” marital system: apart from sex, husbands and wives have very little to do with each other, and men are minimally involved in childcare. In a separate study of 203 married Ariaal men, only three participants cited their wife or wives as a source of emotional support.
Why El Niño makes Earth spin slower EL NIÑO has an immense impact on the weather, so great in fact that the ocean warming phenomenon actually makes the planet spin more slowly. Until now, though, no one knew why. It was also a mystery why the effect did not kick in for several weeks after ocean temperatures reached their peak. Now, Jean Dickey and her colleagues at the California Institute of Technology 22 | NewScientist | 20 October 2007
in Pasadena says that the answer is blowing in the wind. El Niño events warm Pacific surface waters in the tropics, resulting in strong westerly thermal winds. The total Earth system spins with a constant speed, but these winds make the atmosphere spin slightly faster. Due to the conservation of angular momentum the body of Earth then slows to compensate,
making the days a little longer. Because the atmosphere dissipates heat slowly, the temperature takes a month or two to reach its peak, explaining the delay in Earth’s deceleration (Geophysical Research Letters, DOI: 10.1029/2007GL030846). The effect is slight, says Dickey. “The overall changes of angular momentum between the Earth and atmosphere during El Niño cause a slowdown at the 1 millisecond [per day] level,” she says.
PEOPLE blinded early in life often develop better hearing than sighted people. Now it seems they do it by selectively taking over the parts of the visual system that are easiest to adapt. In sighted people, an area of the brain called the medial occipital plays a crucial role in registering visual signals, by setting the threshold at which they are noticed by the brain. Now Alexander Stevens at Oregon Health & Science University has found that people blinded early in life co-opt this brain region to help detect sounds. He played a series of sounds to blind subjects, each preceded by a cue. Brain scans showed that as they heard each cue warning them to pay attention, their medial occipital became more active, revealing that their brains use the same region that alerts them to visual signals to prime them to listen out for sounds (The Journal of Neuroscience, DOI: 10.1523/ JNEUROSCI.1669-07.2007).
Mineral holds clue to life on Venus ANCIENT oceans on Venus may have lasted long enough for life to have emerged. To find out if they did, we should look out for a hardy silicate mineral called tremolite. Tremolite, which forms in the presence of water, can be used as a kind of chemical clock, says David Grinspoon of the Denver Museum of Nature and Science in Colorado. Because we know how long it takes to decompose into other minerals in the extreme temperatures on Venus, the mineral’s abundance could reveal how recently water was present there. “For half of its lifetime, Venus could have been a habitable planet with liquid water oceans,” says Grinspoon, who presented his ideas at the Division for Planetary Sciences meeting in Orlando, Florida, last week. www.newscientist.com
MARIA STENZEL/NATIONAL GEOGRAPHIC IMAGE COLLECTION
In brief– Easy listening
Men’s hormones settle down when they get their girl TESTOSTERONE gradually declines with age, right? Not for the Ariaal – subsistence pastoralists living in northern Kenya. They experience a decline in levels of the male hormone only when they get married. The finding provides a social and evolutionary explanation for the decrease in testosterone, rather than an age-related one. Ariaal men remain single “warriors” until they are around 30, at which time they marry one or more women. Peter Gray of the University of Nevada, Las Vegas, and colleagues measured testosterone in 205 Ariaal men and
found that those with one wife had lower levels of the hormone than unmarried men, and men with more than one wife had the lowest levels of all (Current Anthropology, DOI: 10.1086/522061). “Testosterone levels are lower among married men probably because they are investing less in mating effort,” he says. Or to put it another way, they no longer have to compete for mates. That link between mating effort and testosterone is made clearer by the fact that the Ariaal have an “aloof” marital system: apart from sex, husbands and wives have very little to do with each other, and men are minimally involved in childcare. In a separate study of 203 married Ariaal men, only three participants cited their wife or wives as a source of emotional support.
Why El Niño makes Earth spin slower EL NIÑO has an immense impact on the weather, so great in fact that the ocean warming phenomenon actually makes the planet spin more slowly. Until now, though, no one knew why. It was also a mystery why the effect did not kick in for several weeks after ocean temperatures reached their peak. Now, Jean Dickey and her colleagues at the California Institute of Technology 22 | NewScientist | 20 October 2007
in Pasadena says that the answer is blowing in the wind. El Niño events warm Pacific surface waters in the tropics, resulting in strong westerly thermal winds. The total Earth system spins with a constant speed, but these winds make the atmosphere spin slightly faster. Due to the conservation of angular momentum the body of Earth then slows to compensate,
making the days a little longer. Because the atmosphere dissipates heat slowly, the temperature takes a month or two to reach its peak, explaining the delay in Earth’s deceleration (Geophysical Research Letters, DOI: 10.1029/2007GL030846). The effect is slight, says Dickey. “The overall changes of angular momentum between the Earth and atmosphere during El Niño cause a slowdown at the 1 millisecond [per day] level,” she says.
PEOPLE blinded early in life often develop better hearing than sighted people. Now it seems they do it by selectively taking over the parts of the visual system that are easiest to adapt. In sighted people, an area of the brain called the medial occipital plays a crucial role in registering visual signals, by setting the threshold at which they are noticed by the brain. Now Alexander Stevens at Oregon Health & Science University has found that people blinded early in life co-opt this brain region to help detect sounds. He played a series of sounds to blind subjects, each preceded by a cue. Brain scans showed that as they heard each cue warning them to pay attention, their medial occipital became more active, revealing that their brains use the same region that alerts them to visual signals to prime them to listen out for sounds (The Journal of Neuroscience, DOI: 10.1523/ JNEUROSCI.1669-07.2007).
Mineral holds clue to life on Venus ANCIENT oceans on Venus may have lasted long enough for life to have emerged. To find out if they did, we should look out for a hardy silicate mineral called tremolite. Tremolite, which forms in the presence of water, can be used as a kind of chemical clock, says David Grinspoon of the Denver Museum of Nature and Science in Colorado. Because we know how long it takes to decompose into other minerals in the extreme temperatures on Venus, the mineral’s abundance could reveal how recently water was present there. “For half of its lifetime, Venus could have been a habitable planet with liquid water oceans,” says Grinspoon, who presented his ideas at the Division for Planetary Sciences meeting in Orlando, Florida, last week. www.newscientist.com