What do James Earl Jones, Benedict Cumberbatch, and Sean Connery all have in common?
These men have deep, booming voices that could make a girl weak in the knees. Ladies love a baritone, which may be one reason why males of many primate species have such low-pitched voices. But it’s not the only reason, according to a recent study.
By analyzing recordings of monkey and ape (including human) voices, researchers found that deeper male voices are linked to polygyny — a mating system in which males have multiple partners. But in monogamous species, male pitch was more similar to that of females.
This pattern makes sense, considering that in polygynous species, a few males often monopolize the limited mating opportunities, leaving the others with little chance to spread their seed. It’s a situation that leads rival males to compete intensely, and sometimes violently, over access to valuable females.
"If you look at what men's traits are designed for, they look much better designed for intimidating other males than for attracting females," lead author David Puts of Pennsylvania State University told ABC News.
Surprisingly, the researcher found that out of all species studied, the difference in pitch between males and females was the greatest in humans.
The human species is often classified as monogamous because it is a feature of many societies. But as Puts points out, humans are effectively moderately polygynous, even in monogamous societies.
"Men are more likely to marry again after divorce, are likely to marry a younger wife and more likely than women to reproduce again with their new spouse," he said.
The researchers wanted to further understand how deep male voices are perceived in humans. 175 male and 258 female volunteers were enlisted to listen to recordings of both men and women reading the same text out loud, and then to rank the voices based on attractiveness and dominance.
The pitch of female voices did not affect ratings of attractiveness, but women rated the men with deeper voices as more attractive and men rated them as more dominant. Notably, pitch was much more tightly linked to dominance than to attractiveness, suggesting that competition was the main driving force behind the evolution of deep male voices.
Men with deeper voices were also found to have lower levels of the stress hormone cortisol and higher levels of testosterone, which together indicate superior immune function. Thus, a low-pitched voice signals that a male is healthy, which is something that females find attractive. At the same time, it sends a clear message that he is in good condition and could easily win a fight, so rival males need not bother competing.
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