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"We found a relationship between men's voice pitch and the number of children born to them, but not in the children's mortality rate," said Coren Apicella, a graduate anthropology student at Harvard University, who spent six months in northern Tanzania last year studying the nomadic, hunter-gatherer Hadza people.
"We found that men with deep voices have more children than their high-pitched counterparts," Apicella told AFP.
"But those children were not necessarily healthier, so it doesn't seem like deep-voiced men are passing on good genes to their offspring, as has been hypothesised in the past, but probably has to do with them having greater access to women."
First test of its kind
The study, which was a collaborative effort between Harvard University in Massachusetts, McMaster University in Canada and Florida State University, was the first to try to determine if there is a link between voice pitch in men and "Darwinian fitness" in humans.
"Darwinian fitness, in lay terms, means the number of children we have," Apicella said.
Apicella visited nine Hadza encampments and had 49 men and 52 women from the nomadic tribe "sit in my Landrover (sport-utility vehicle) and say 'Hujambo,' which means 'hello,' into a microphone," she told AFP.
The recordings were then analyzed for frequency.
Study participants were also asked to report how many children they have, and how many were still alive.
"The man with the lowest-pitch voice in the study fathered 10 children, of whom nine are still living, and the man with the highest-pitch voice fathered three children, of whom one is still living," Apicella told AFP.
Mortality rate not affected
But across the study, the mortality rate of children born to men with high-pitched voices was not significantly greater than that of children born to deep-voiced men.
"Based on these findings, we speculate that the associations reported between reproductive success and voice pitch in men are probably mediated by greater access to fecund women," the study says.
Although earlier studies have shown that men prefer women with higher-pitched voices, voice pitch was not found to be a good predictor of a women's Darwinian fitness in the test led by Apicella.
In Tanzania, Apicella also conducted a separate test with Hadza women, which has not yet been reported in an official study but which she shared with AFP.
Attract more women
The test seems to support the hypothesis that low-pitched men make more babies because they have more success in attracting a mate.
"When I manipulated voice pitch, giving the same man a lower and higher pitched voice, and asked women 'Who do you think is the better hunter?', they chose the men with lower pitched voices," Apicella said.
"Maybe it's because these low-pitched men are better hunters that they get a better selection of mates," she hypothesised.
"Maybe they can bring home more food for their families, so their wives have shorter inter-birth intervals because they are able to resume ovulation more quickly." – (Sapa/AFP)
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