By GAUTAM NAIK
Updated April 15, 2011 12:01 a.m. ET
The finding, published Thursday in the journal Science, could help explain how the first spoken language emerged, spread and contributed to the evolutionary success of the human species.
Cave art may have been spurred by the evolution of complex language. Quentin Atkinson, an evolutionary psychologist at the University of Auckland in New Zealand and author of the study, found that the first migrating populations leaving Africa laid the groundwork for all the world’s cultures by taking their single language with them—the mother of all mother tongues.
“It was the catalyst that spurred the human expansion that we all are a product of,” Dr. Atkinson said. About 50,000 years ago—the exact timeline is debated—there was a sudden and marked shift in how modern humans behaved. They began to create cave art and bone artifacts and developed far more sophisticated hunting tools. Many experts argue that this unusual spurt in creative activity was likely caused by a key innovation: complex language, which enabled abstract thought. The work done by Dr. Atkinson supports this notion.
His research is based on phonemes, distinct units of sound such as vowels, consonants and tones, and an idea borrowed from population genetics known as “the founder effect.” That principle holds that when a very small number of individuals break off from a larger population, there is a gradual loss of genetic variation and complexity in the breakaway group.
Dr. Atkinson figured that if a similar founder effect could be discerned in phonemes, it would support the idea that modern verbal communication originated on that continent and only then expanded elsewhere. In an analysis of 504 world languages, Dr. Atkinson found that, on average, dialects with the most phonemes are spoken in Africa, while those with the fewest phonemes are spoken in South America and on tropical islands in the Pacific. The study also found that the pattern of phoneme usage globally mirrors the pattern of human genetic diversity, which also declined as modern humans set up colonies elsewhere. Today, areas such as sub-Saharan Africa that have hosted human life for millennia still use far more phonemes in their languages than more recently colonized regions do.
“It’s a wonderful contribution and another piece of the mosaic” supporting the out-of-Africa hypothesis, said Ekkehard Wolff, professor emeritus of African Languages and Linguistics at the University of Leipzig in Germany, who read the paper.
Dr. Atkinson’s findings are consistent with the prevailing view of the origin of modern humans, known as the “out of Africa” hypothesis. Bolstered by recent genetic evidence, it says that modern humans emerged in Africa alone, about 200,000 years ago. Then, about 50,000 to 70,000 years ago, a small number of them moved out and colonized the rest of the world, becoming the ancestors of all non-African populations on the planet.
The origin of early languages is fuzzier. Truly ancient languages haven’t left empirical evidence that scientists can study. And many linguists believe it is hard to say anything definitive about languages prior to 8,000 years ago, as their relationships would have become jumbled over the millennia. But the latest Science paper “and our own observations suggest that it is possible to detect an arrow of time” underlying proto-human languages spoken more than 8,000 years ago, said Murray Gell-Mann of the Santa Fe Institute in New Mexico, who read the Science paper and supports it. The “arrow of time” is based on the notion that it is possible to use data from modern languages to trace their origins back 10,000 years or even further.
Dr. Gell-Mann, a Nobel Prize-winning physicist with a keen interest in historical linguistics, is co-founder of a project known as Evolution of Human Languages. He concedes that his “arrow of time” view is a minority one.
Only humans have the biological capacity to communicate with a rich language based on symbols and rules, enabling us to pass on cultural ideas to future generations. Without language, culture as we know it wouldn’t exist, so scientists are keen to pin down where it sprang from.
Dr. Atkinson’s approach has its limits. Genes change slowly, over many generations, while the diversity of phonemes amid a population group can change rapidly as language evolves. While distance from Africa can explain as much as 85% of the genetic diversity of populations, a similar distance measurement can explain only 19% of the variation in phonemic diversity. Dr. Atkinson said the measure is still statistically significant.
Another theory of the origin of modern humans, known as the multiregional hypothesis, holds that earlier forms of humans originated in Africa and then slowly developed their anatomically modern form in every area of the Old World. This scenario implies that several variants of modern human language could have emerged somewhat independently in different locations, rather than solely in Africa. Early migrants from Africa probably had to battle significant odds. A founder effect on a breakaway human population tends to reduce its size, genetic complexity and fitness. A similar effect could have limited “the size and cultural complexity of societies at the vanguard of the human expansion” out of Africa, the paper notes.
Write to Gautam Naik at firstname.lastname@example.org