Tuesday, November 27, 2007

Deep Voiced Men Father More Children

From Newscientist.com:

In evolutionary terms, Barry White's rich, bass voice may hit all the right notes – a new study among modern-day hunter-gatherers shows that men with the deepest voices produce significantly more children than their more falsetto counterparts. The finding helps explain why men have evolved lower voices than women, say researchers.

Scientists have long known that women perceive men with deep voices as sexy, healthier, and more dominant. Previous studies have even shown that women show the strongest preference for low-pitched voices at the most fertile phase in their menstrual cycle.

This background research hinted that men with the deepest voices had the most luck with the ladies, giving them an evolutionary edge.

However, the use of modern-day contraceptives makes it difficult to link voice range with fertility. So experts lacked hard evidence to back up the notion that men with bass voices had any real reproductive advantage over those talking in tenor tones.

'Huge difference'

Coren Apicella at Harvard University in Cambridge, Massachusetts, US, and her colleagues found a way around this challenge by studying the Hadza, one of the last remaining hunter-gatherer cultures in the world. The Hadza women generally dig for root plants and gather fruits, while men primarily hunt animals and collect honey. The Hadza, who live in Tanzania, have no modern birth control and practice serial monogamy.

Apicella recorded 49 Hadza men saying the Swahili word hujambo, which loosely translates as ‘hello’ in English, and calculated their voice pitch using computer analysis. She also recorded their age and the number of children they had fathered.

On average, the men had 4.8 children and a voice pitch of around 115 Hz. After controlling for possible confounding factors, such as age, researchers discovered that men with the lowest voices had the most children. For example, men who had an average voice pitch around 90 Hz had about two more children on average than those with a super-high voice around 160 Hz.

"That's a huge difference" in terms of reproductive success, says David Puts, an anthropologist at Penn State in University Park, Pennsylvania, US, who studies voice preferences.

Hormone link

Puts explains that men typically have deep voices as a result of high testosterone levels. High levels of this hormone cause the vocal cords to lengthen and thicken, and therefore vibrate at a lower frequency.

"Testosterone is associated with all sorts of things, like high libido and physical competitive ability," Puts notes. He adds that there appears to be a connection between testosterone and sperm quality, which might explain why the Hadza men with low-pitched voices fathered the most children.

Another possible explanation is that women prefer men with deep voices because such men are perceived as holding higher social status, says Puts.

Researchers speculate that evolution favoured men with deeper voices, and that this perhaps explains why men's voices are so much lower than that of women. For example, while Hadza men have an average voice pitch of 115 Hz, the women average around 210 Hz.

However, Apicella notes that some of the children listed by the Hadza men as being their own, might have in fact been fathered by other members of the group. This, she says, allows for an alternate explanation for her findings: "Maybe men with lower pitched voices feel more confident to say the children are theirs."

Journal reference: Biology Letters (DOI: 10.1098/rsbl.2007.0410)