DNA-Genealogy question?

Question

Through a DNA genealogy testing, (both individuals) could 2 men from relatively different families compare markers and find they are distant cousins of almost 400 years ago?

Answer 1

NO.

DNA does not give you any times.  It gives you degrees of relatedness.

You could compare two sets of DNA markers and ESTIMATE the degree of relatedness.  We still do not have the full DNA library for humans.  Until we have a mostly complete library of the variations and more importantly the frequency of variations of the DNA, we do a lot of guessing.  Two completely unrelated individuals can have the same gene marker thru they or their ancestors getting the same damaged (mutated) gene and passing it on.  The assumption is that if two have the same "unusual" gene they are related.  Its not this simple since we do try to only use "stable" genes as markers, but again we just haven't been doing this long enough to do more than give people our best GUESS as to the possibility of relatedness.  Two different labs (using different testing markers) will give different results.  Two specialists using the same test may, too.