THE GUARDIAN

Tim Radford, science editor
Monday December 20, 2004

Florida scientists believe they know why complex language evolved. Blame it on baby talk. At least 1.6m years ago, some human ancestor mother started saying "goo-goo" and "ba-ba" to her baby as a way of keeping in touch.

And it all began because humans became bipedal. Modern ape babies cling to the maternal fur. Chimpanzee mothers are silent. There could be a link, says Dean Falk, an anthropologist at Florida State University in Tallahassee. She reports in the journal Behavioural and Brain Sciences that "motherese", the universal language of motherhood, is characterised by a high-pitched voice, long drawn out vowels, repetitive phrases and a singsong cadence. These may hold the key to the emergence of language.

"The epiphany for me was that I knew chimp mommies don't make these noises, so I knew something happened during evolution," she said. "The missing puzzle piece was bipedalism. We stood up; we lost hair. It was then that babies could no longer hang on to their mothers. Mothers had to hang on to their babies. That was a eureka moment."

For two centuries, researchers have tried to understand how one mammal evolved from grunting and hunting to growing bonsai trees and reading Homer. The key lies in the relatively large human brain, and the use of complex language. But nobody knows why language evolved, or why humans developed bigger brains.

Language is a mystery: psychologists have claimed babies as young as seven months can work out the simple rules of language, and begin to build up vocabularies at the rate of 70 words a week. Baby talk has a vital role in language learning for human babies. The next question was: did "goo-goo" evolve into "Good golly Miss Molly"?

Modern humans emerged probably only 200,000 years ago. Modern complex language is believed to be less than 100,000 years old. Professor Falk believes it all began 1.6m years ago, when upright human ancestors were roaming the savannah. The evolutionary development of bigger brains meant that early humans began giving birth before their babies' heads became too big to pass through the birth canal.

This shorter gestational period meant humans gave birth to babies that were undeveloped physically. Foraging mothers would have had to put their babies down to search for food. They may have made noises to reassure them. These noises would have served as codes, and eventually evolved into words.

"The behaviour of chimp mommies and babies and human mothers and infants are delightfully identical in many ways but we are dramatically different in other ways," Prof Falk said.

"We vocalise continually in a way that helps babies begin to learn language. I wanted to find out why we are the only animals that talk, and this need to pacify our babies as humans evolved may be the reason."