Out of Africa
Book Review of Before the Dawn
Recovering the Lost History of Our Ancestors
Penguin Books, 2007
It is presumed that these branches converge at their trunk to a single language, perhaps the mother tongue of the ancestral human population. If this is the case, it should be possible to draw up a genealogy of the world’s languages that would demonstrate their tree of descent, a tree similar to the descent of the human races. If the tree of language could then be interwoven with the genetic tree of human descent a unified framework would be created for understanding human prehistory.
Within a language are dialects, often changing from village to village, that were likely even more pronounced in the days when people seldom traveled far from home. The English of Chaucer, only 600 years later, sounds foreign to modern English speakers.
That language has evolved to be local isn’t accidental. Given near-constant warfare between early human groups, a different language or dialect could identify strangers the moment they spoke. Dialects are difficult to learn, usually learned at a very young age, and change rather rapidly, which makes it possible to identify an individual not just within a locality but also within a generation.
New Guinea has many languages because it has been stable for a very long time. Each of New Guinea’s 1200 some languages is spoken on average by some 3,000 people living in 10 to 20 villages. Tribal competition as well as deeply forested mountains and valleys is one reason, the other is political fragmentation. Three factors that have shaped the island’s mosaic of languages are competition, the inability of any one language group to dominate the others, and a long period of time for diversification of language to occur.
The same process may have occurred worldwide after the ancestral humans left their homeland. Over the generations, an ancestral language would have broken down into a mosaic of divergent languages, the situation of the present world. It may be that the languages spoken in New Guinea and Australia are remnants of that ancient mosaic.
One of the implications of Darwin’s theory is that humans are the unplanned product of random processes. Compared to our cousins, the chimpanzees, humans look so much more advanced than they do, as though humans were shaped for a higher purpose. The evolutionary path of the chimpanzees required little change whereas the human lineage, seeking a way to survive beyond the trees, developed differently from the chimps because it was constantly forced to innovate.
Although evolution through natural selection depends on random processes, evolution is also shaped by the environment in which each species struggles to survive. For social species, the most important feature of the environment is their own society. The accumulating evidence from the human genome has brought to light the nature of the interactions between culture and evolution, indicating that human evolution is a continuing process during the last 50,000 years. To the extent humans have shaped their social environment, we have determined the conditions of our own evolution.