It’s the rutting season. Red deer hinds will be gathering, and the stags have but one thing on their minds. A mature male that has netted himself a harem is very dedicated. He practically stops eating, focusing instead on keeping his hinds near and his competitors at bay. If you’re a red deer stag, one of the ways you make sure that your adversaries know you mean business — and that you’re big — is roaring.

While female red deer prefer the deeper roars of larger stags, roaring also appears to be part of how stags size one another up, before deciding whether or not to get engaged in a full-on physical fight. Most confrontations are settled without locking antlers. In male red and fallow deer, the voicebox or larynx is very low in the throat — and gets even lower when they roar.

Straplike muscles that attach to the larynx contract to drag it down toward the breastbone — lengthening the vocal tract and deepening the stag’s roar. Deepening the voice exaggerates body size. Over generations, stags with deeper roars presumably had more reproductive success, so the position of the larynx moved lower and lower in the neck. When a red deer stag roars his larynx is pulled down so far that it contacts the front of his breastbone.

In human evolution, much is made of the low position of the larynx in the neck. So much, in fact, that it has been considered to be a uniquely human trait, and intrinsically linked to that other uniquely human trait: spoken language. But if red and fallow deer also have low larynges, that means, first, that we’re not as unusual as we like to think we are, and second, that there could be other reasons — that are nothing to do with speaking — for having a descended larynx.

The relative position of the larynx tends to be lower in men than in women, and as far as speaking goes, this may actually be a disadvantage. The human female vocal tract is capable of making a larger range of discrete vowel sounds than the male. It’s safe to assume that the comparatively low position of the male voice box hasn’t evolved to improve the production of intelligible speech. But when we listen to someone speaking, we gain far more information than is contained in just the words themselves. Even though we may not always be aware of it, we size people up by their voices. The deep human male voice, exaggerating body size just as it does in stags, could have come about because women found men with low voices more attractive — perhaps we could call this the “Barry White effect.”

This isn’t just idle speculation; a recent study from the University of Aberdeen found that women expressed a preference for deep voices. It also turned out that women tended to remember information better when they’d been told it by a man with a low voice. But it could also be that men, like stags, have evolved low voices in order to deter sexual competitors.

In support of this idea, it’s been found that men modulate the pitch of their voices when they’re in competition with one another, as revealed by a dating game, played in the interests of science, at the University of Pittsburgh. Male students were pitted against an unseen male rival in order to win a date. Each participant had a conversation with the adversary, so they had an opportunity to “size him up.”

The results of those conversations were fascinating: participants who believed themselves to be more physically dominant than their rival lowered their voices. But students who thought they were less dominant raised their voices to a higher pitch. The men were sizing each other up, just like rutting stags. But they were also changing their voices in a way that suggests they were — without being aware of it — managing the confrontation to avoid conflict. A man who thought he was more dominant lowered his voice to emphasize his dominance and intimidate his competitor. A man who thought he was likely to lose the game, just by listening to his adversary, spoke in a higher voice: don’t bother fighting me — you’ve won, mate.

The low voice of men, like stags, is a trait that probably evolved through sexual selection. This isn’t just about being attractive to the opposite sex, it’s also about beating same-sex rivals. A deep voice may prove an advantage in both cases, helping a man to exclude other men, from the mating game, as well as making him more attractive to women. A win-win situation. Unless, of course, you’re a well-built man with a tenor voice, who’s bucked the trend, or a woman who prefers Justin Timberlake or John Lennon to Jim Morrison or Eddie Vedder. This is biology, after all — variability is what makes it so interesting.

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