Born in Africa_ The Quest for the Origins of Human Life - Martin Meredith [86]
In dire straits, facing the possibility of extinction, surviving groups were forced to innovate. They began to invent new tools, to form more complex social networks and to become more efficient hunter-gatherers. Some anthropologists speak of ‘a great leap forward’ in human evolution at this juncture. Richard Klein of Stanford University has argued that a crucial change occurred in human brain capacity, set in motion by a genetic event—‘a Big Bang’ that heralded the dawn of human culture. Others believe that change accumulated over a more prolonged period, citing the advances made in Africa in fashioning artefacts over a period of 150,000 years. In an article titled ‘The Revolution That Wasn’t’, two of Klein’s critics, Sally McBrearty of the University of Connecticut and Alison Brooks of George Washington University, stressed the long-term nature of change. ‘As a whole the African archaeological record shows that the transition to fully modern behavior was not the result of biological or cultural revolution, but the fitful expansion of a shared body of knowledge, and the application of novel solutions on an “as needed basis”’.
What appears certain is that by 60,000 years ago, African hunter-gatherers had developed a fully articulate language, making small groups more cohesive and facilitating long-range planning and the transmission of local knowledge and learned skills.
According to genetic evidence, all human lineages in the world today can be traced back to this ancestral population in frica. All men alive today carry a Y chromosome which has been passed down from one generation to another and which dates back to this time. Occasional mutations in the Y chromosome down the ages act as genetic markers, enabling researchers to follow the routes taken by modern humans migrating from this ancestral base. Similar information comes from tests of mitochondrial DNA which is passed down the female line without recombining. By using data from both Y chromosomes and mitochondrial DNA, researchers have managed to construct a chain of ancestral clans, or haplogroups—groups of people who share a set of genetic markers and therefore share an ancestor—linking them to past movements.
The most likely location of the homeland of this ancestral population is the northeastern corner of Africa. Population groups found today in Ethiopia—the Oromo and Amhara peoples—retain traces of Y chromosomes that belong to the deepest branch of the Y-chromosome family tree. The same branch of Y chromosomes occurs among San hunter-gatherers who once occupied much of eastern Africa, including Ethiopia. An alternative possibility put forward by Sarah Tishkoff’s team based at the University of Maryland is that San migrated into northeastern Africa from what may have been their original homeland in southwestern Africa.
As well as genetic links, there are linguistic clues. The modern San of southern Africa use a variety of ‘click’ languages involving percussive sounds of considerable complexity. About thirty different click languages are still spoken in southern Africa. The only other place where click languages are spoken is in eastern Africa, among the hunter-gatherers of Tanzania, the Hadzabe and the Sandawe. Recent research led by Stanford’s Alec Knight has shown that the San and the Hadzabe belong to different ancient lineages that diverged long ago and that their click languages have no common features other than the use of clicks. The implication is that the language their ancestors used further back in time included clicks and may have formed the basis of a linguistic family stretching from Ethiopia to southern Africa. Knight’s team consider it possible that about 60,000 years ago, the use of clicks was widespread before it was filtered out by the evolution of newer languages.
The dispersal of African