before numbers start to be unmanageable. Consider:
each human individual receives an equal amount of genetic
information from two parents, who in turn had two parents,
and those as well... We are dealing with 2^x contributors,
depending on the number of generations one wants to go
back. And it is not long before that number is greater than
the human population at the time. (And this, in turn, leads many to
gossip in the worst way about the mating habits of our ancestors:
A great number of human couples might have been second
cousins!!).
But to have fun with it, let's ask a different question. From a
genetics point of view, how far back can we go to find identifiable
differences between individuals. Here, science tells us, we are looking
for SNPs - single nucleotide polymorphisms - of which there are some
10 million in the human genome. As an example, one can predict eye
color at 90% confidence from 6 SNPS. So working with three generations
per 100 yeas, whch is the current estimate, one could expect some
identifiable traits in a child today form someone in the13th Century.
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