Like the Abrahamic creation myth most of us a familiar with this scientific version of creation has an Adam and an Eve.
Eve lived in Africa about 150,000 years ago. We come to this conclusion by looking at mitochondrial DNA which is passed from mother and child. The mtDNA changes little over time which is why Eve does not really play a part in this detective story.
Adam also lived in Africa but about 90,000 years after Eve. It's Adam's Y chromosome that provides the evidence for tracing man's journey from it's African origin. Reproduction is all about copying DNA. Whenever anything is copied errors occur. Those errors, 18 to 20 of them, are used to trace the migration of the human race from Africa. We can't know what made this Adam so special that he became the father of the modern human race although Wells makes a guess. It would appear there were two separate migrations - one along the shores of the Indian Ocean and a second north through the middle east.
Although this is a wonderful scientific detective story it may be even more important because it makes as look at the concept of race. We know that the first migration around the Indian Ocean shows a darker population but this journey was primarily in the tropics where darker skin would be an advantage. Another thing we can't know is if the population of pre-migration Africa was dark skinned or if that is an adaptation to changing climatic conditions after the migration.
Humanity is by nature tribal. We are constantly looking for ways to define the tribe we belong to. What we can learn from the detective story described in the Journey of Man is that "race" is no more real than religion, political views or country of origin. We are indeed one race - the human race. If the human race is to survive we must recognize we are all part of the same tribe.
The Journey Of Man reads like a good detective novel but it is packed with good science as well. I highly recommend it.