How to Argue With a Racist: History, Science, Race and Reality

by Adam Rutherford

the process of genetic shuffling that occurs in the formation of sperm and egg guarantees that each one of those two cells is unique and carries a unique half genome (therefore a unique half is lost in subsequent generations, should that sperm or egg be successful). Which means that not the same half gets transferred each generation. Over the generations, descendants begin to shed the DNA of their actual ancestors. The amount that vanishes is cumulatively huge: you carry DNA from only half of your ancestors eleven generations back. Genealogy and genetic genealogy are not perfectly matched, and progressively grow apart as we go back in time. It is therefore possible that you are genetically unrelated to people from whom you are actually descended as recently as the middle of the eighteenth century.