From this view, the regional anatomical differences that we of this model believe that the ultimate common ancestor of all modern people was an early Homo erectus in Africa who lived at least 1.8 million years ago.It is further suggested that since then there was sufficient gene flow between Europe, Africa, and Asia to prevent long-term reproductive isolation and the subsequent evolution of distinct regional species.In 2003, a discovery was made in a Romanian cave named Alan Templeton, also of Washington University, reported that a computer-based analysis of 10 different human DNA sequences indicates that there has been interbreeding between people living in Asia, Europe, and Africa for at least 600,000 years.This is consistent with the hypothesis that humans expanded again and again out of Africa and that these emigrants interbred with existing populations in Asia and Europe.They point to the fact that many Europeans have relatively heavy brow ridgesdating to 200,000 years ago.
There is no reliable evidence of modern humans elsewhere in the Old World until 60,000-40,000 years ago, Artifactual evidence indicates that modern humans were in Europe by at least 40,000 and possibly as early as 46,000 years ago.
It is argued that intermittent contact between people of these distant areas would have kept the human line a single species at any one time.
However, regional varieties, or subspecies, of humans are expected to have existed., which makes the 200,000 year date for "mitochondrial Eve" unreliable.
The rate of inheritable mutations for a species or a population can vary due to a number of factors including generation time, the efficiency of DNA repair within cells, ambient temperature, and varying amounts of natural environmental mutagens.
In addition, some kinds of DNA molecules are known to be more subject to mutation than others, resulting in faster mutation rates.