Saturday, April 16, 2011

The Origins of Humanity

by Richard Crews
Two independent investigations have now placed the birthplace of civilization in the heart of Africa several tens-of-thousands of years ago.

The older study, first proposed a couple of decades ago but greatly filled in over the past few years, traces the migration of human DNA. The genes that make us human vary a bit from place to place around the world. Analyzing hundreds of thousands of DNA samples taken from indigenous populations across six continents shows patterns of drift and change, all pointing back to a spot in East Africa some 160,000 years ago. Take a look at the fantastic map journey depicted at This shows the fits and starts of a long series of migrations including, for example, the devastation from the ice age caused by the massive volcanic eruption at Lake Toba in Sumatra some 74,000 years ago.

In addition to the DNA studies, recently a statistical analysis of the sounds used in some 300 languages around the world has provided a second, independent view of the human migrations out of Africa. It seems that as human groups migrated and their languages evolved over many thousands of years, the vocabularies and grammars changed, often becoming more complex, but the range of consonants used in a given language did not. In fact, the sounds (or "phonemes") used in a language became simpler and more limited the farther the language migrated, in time and place, from the birthplace of human civilization (and language) in Africa so many millennial ago.

Another fascinating discovery that emerges from these studies is that at least twice during this immense journey, the surviving population of human beings was reduced to numbers so small that extinction threatened. The statistical analysis of mitochondrial DNA, the small portion of the genetic material that is inherited maternally--it is only passed from mother to daughter--shows that all human beings on Earth are descended, several thousand generations ago, from a single woman, the so-called "Mitochondrial Eve." Evidently--and luckily--she had 18 daughters, or at least there are 18 distinct lines of maternal inheritance that lead back to her, for example, the seven "European Daughters of Eve" whose descendants now populate the European continent.

In addition, genetic studies of the Y-chromosome (which is inherited only through the male line) show that thousands of years ago there was a "Y-Chromosome Adam." Every human being on Earth is descended from one of his ten sons.

Since Mitochondrial Eve lived about 150,000 years ago and Y-Chromosome Adam dates to 60,000 to 90,000 years ago, there were at least these two near extinctions in human evolution. In addition, the eruption at Lake Toba about 74,000 years ago reduced the human population of the globe to about 1,000 individuals, a number that is also disastrously close to extinction.

Another interesting chapter in human evolution relates to the discovery that about four percent of our genetic material is derived from Neanderthals, a species closely related to us--that is, to Homo sapiens--that was driven to extinction in Europe and Asia some 30,000 years ago. Apparently in addition to overcoming the Neanderthals through our superior mental and physical abilities, adaptability, or luck--and in addition to enslaving and eating them (as observation of more recent human nature would suggest), we interbred with them--again, an observation entirely consistent with behavior observed among modern humans.

The origins of humanity as uncovered by scientific studies has been a long, complex, and at times perilous journey. It makes a fascinating, sparkling tale.