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MEN attempting to show off to their rivals in prehistoric times may have led
to the evolution of speech. The human voice box or larynx was thought to be
unique, but now researchers have found two species of deer with 鈥渄ropped
larynxes鈥� similar to those of humans. For the deer at least, it鈥檚 all about the
advantages of having a deep voice.

A newborn baby鈥檚 larynx resembles that of other mammals. It pokes up into the
nasal passage like a snorkel, so babies can drink and breathe at the same time.
But at three months old, the larynx descends, opening up a cavity behind the
tongue. This was a vital step in the evolution of speech because it allows us to
utter a much wider range of sounds. 鈥淸It makes] speech communication more
effective and reliable,鈥� says Philip Lieberman, who researches the origins of
speech.

But Tecumseh Fitch of Harvard University and David Reby of the Large Mammals
Research Institute in Castanet, France, have discovered that red deer
(Cervus elaphus) and fallow deer (Dama dama) have descended
larynxes too. This shows the trait can evolve for reasons other than
language.

Language expert Steven Pinker says the finding doesn鈥檛 undermine the
importance of the larynx drop in the evolution of complex language some 200,000
years ago. 鈥淚t can鈥檛 be a coincidence that humans are the primates that talk and
the primates with a lowered larynx,鈥� he says. But Reby says speech alone can鈥檛
explain it. 鈥淭he permanent descent of the larynx may have occurred independently
of the evolution of spoken language,鈥� he argues.

Fitch and Reby speculate that in deer, the descended larynx evolved to help
individuals intimidate their rivals. Males with a bigger vocal cavity can make
deeper, more fearsome roars, so dropping the voice box might have allowed
smaller deer to lie about their true size.

Reby says a lowered larynx could also have been an advantage for human males
trying to tell their rivals, 鈥淚鈥檓 bigger than you.鈥� He points out that in
adolescent boys the larynx drops a second time when their voice breaks. While
this drop doesn鈥檛 give them any linguistic advantages, it does make the voice
deeper.

Lieberman says that the intimidation theory is a 鈥渧ery plausible idea鈥�.
However, Pinker is not convinced. 鈥淒eer and humans are so different in behaviour
that inferring a similar evolutionary history is a stretch,鈥� he says.