ShannonCT
Deity
From Steve Olson's Mapping Human History:
Joseph Chang, a statistician at Yale University, has recently shown that all of the people living in various regions of the world more than about 800 years ago can be divided into two categories. Each individual was either the direct ancestor of everyone in that part of the world alive today (about 80% of people fall into this category), or the lineage represented by a person went extinct, making that person an ancestor of no one today.
[...]
Now factor in the consequences of human migrations. [...] all Africans today descend from Chinese traders who visited Africa, and undoubtedly fathered children, early in the 1400s.
[...]
So if 800 years ago our ancestors included even a single European, African, or Asian, then 1,600 years ago our ancestors included most of the adult population of all three continents.
People like to trace their ancestry to famous figures. In Japan, many families trace their lineages to the ninth-century emperor Seiwa. Many French believe they are descended from Charlemagne. Such claims are typically impossible to prove, and many genealogists dismiss them as fantasies. However, these claims are almost certainly true. The exponential growth in the number of our ancestors going back in time connects us tightly to the past. If a historical figure who lived more than 1600 years ago had children who themselves had children, that person is almost certainly among our ancestors. Everyone in the world today is most likely descended from Nefertiti, from Confucius, and from Julius Caesar.