Should You Care If Someone of Notoriety Shares Your Family Name?

Do you have a more or less unusual family name: Clutterbuck, for example, or MacQoid, Twelvetrees, or Fernsby? If so, perhaps you pay particular attention to news stories concerning persons with the same name, this on the assumption that you and your namesake must have shared ancestry. Such identification can be a cause for discomfort should your namesake come to public attention for discreditable or criminal conduct. 

In reality, however, such name identities may mean little in terms of heredity. Genetic similarity within families can dissipate rapidly over the generations. We have about 30 trillion cells, In each of which there are two sets of 23 chromosomes, one set from each parent. Each chromosome carries genes for a distinct collection of traits. Gametes (egg cells and sperm cells) are formed by a  special process of cell division known as meiosis. In this process, cells about to divide engage in what is called  crossing over. Crossing over entails an exchange of pieces of each maternally derived chromosome with its homologous paternally derived chromosome. Thus produced are cells each with two sets of chromosomes, but not the original wholly maternal or wholly paternal chromosomes. Rather, they are chromosomes that are, in part, of maternal, and in part, of paternal origin.  It is these pairs of mixed maternal/paternal chromosomes that then separate in a process of cell division that results in the production of gametes. 

As noted, gametes, unlike all the other human cells, have only one set of chromosomes. What this means is that the genes carried by a gamete are a mix, some from the maternal grandparent, some from the paternal grandparent. In turn, this means that the number of genes passed from one generation to the next that are derived from any particular ancestor is halved at each generation. So after ten generations, or say three hundred years, the genes an individual receives from a particular ancestor will total no more than about one in a thousand, or 0.1% of the total gene complement. So even if your remote ancestor was Ghengis Kahn, as is the case for something like 40 million of the World's present population, there's not much reason for folks to worry. The chances are that you inherit few, if any, of Ghengis's genes. As for any such genes that you do inherit, they're more likely to determine the color of your hair than your propensity for global conquest.