Speech and language skills are unique to modern humans. While this ability evolved over millions of years, it is not possible to trace language in the fossil record because it leaves no direct imprint. Instead, re-examining the ways our nearest living relatives communicate is helping to unravel this mysterious capability.
"The traditional view is that, even though great apes are our closest living relatives, they are not useful for studying how language and speech came about, because their vocal behavior is so different," said climatologist Dr. Adriano Lamar at the University of Warwick, U.K. "It's automatic and reflexive, guided by blind instinct."
During his years spent in jungles studying orangutans in the wild, Lameria discovered that the range and novelty of vocal sounds in wild orangutans varies, and he recently reported that this depends on local population density. Novelty is at a premium when an individual needs to stand out, so that apes living in areas of high population density express their individuality through more distinctive and variable vocal sounds.
Tiger sheets
In Indonesia, Lameira experimented by crawling around the forest floor on all fours, disguised with a tiger-patterned sheet. Recording the responses of the forest apes, he discovered that an orangutan mum holding an infant stay silent when they spot "a tiger," which stayed within sight for two minutes. They suppress alert calls for up to 20 minutes after the tiger has gone.
From there, he reasoned that immediate vocalization could endanger the young orangutan. "A Sumatran tiger can climb 10 meters up a tree in a second," said Lameira. "If you advertise your location, especially if you have an infant, it could be very dangerous."
By vocalizing after the tiger has moved on, the mother alerts the infant to the danger. This helps the juvenile to make the correct association. The remarkable thing about this is that the orangutan was communicating about a past event, rather than something in the here and now. "This was completely outside the box of what we had been thinking," said Lameira.
It opens up the possibility that orangutans communicate about past events, or perhaps even future events. If this ability exists, the possibilities for sharing information are endless. "This could well be a trait that was shared by our last common ancestor—this capacity of communicating about events that are not in the here and now."
It may be that other apes are also able to do this to some degree. "Even if you communicate only about 20 minutes in the past, or future, you can accrue benefits," said Lameira. "Natural selection just needs a bit of something to tinker with and improve upon." Perhaps apes can communicate that a certain tree has such-and-such fruit, though this suggestion remains speculative.
Monkey talk
"The goal of the research is to better understand the way the human brain evolved," said Belie, a neuroscientist at the Marseille University in France. "We study humans and three other types of primates—marmosets, macaques and baboons—to try to better understand differences and similarities, especially in vocal communications."
In one experiment, three macaques were trained to stay still in an MRI machine, which scanned their brains as they listened to dozens of sounds, including vocalizations from other macaques.
Consonant contacts
Orangutans have a rich repertoire of lip-smacking clicks and raspberries, which they combine with grunts and other vowel-like sounds. "They combine voiced calls with voiceless calls, so like vowel-like with consonant-like sounds," said Lameira. "We think there is something quite unique about this marriage between two distinct types of call, so powerful that every language was built on this formula of consonant plus vowel".
He calls on scientists studying gorillas, bonobos and chimpanzees to similarly look for shared traits, such as combinations of some consonant-like and vowel-like sounds, or evidence of communications about recent past events. By investigating our primate relatives, we may uncover vestiges of ancestral humans and the origins of our speech and language of today.
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