It is quite awful to try to research the mixing arguments, because it seems like a lot of the people arguing about this are really pretty awful, and the ones whose politics are not stomach turning produce ludicrous, false on the face of it statements on a regular basis (and, honestly, their politics are not appreciably better). I do, really, understand that this is part of the cost of doing business in this area and believe me, it makes me wonder several times a day whether I should even proceed.
However, I am, actually, that much of a fool.
So far, I have not found anything about Brian Pears particularly evil. However, he does produce silly statements at a shocking rate.
http://www.bpears.org.uk/Misc/AncestorParadox/ancpdxya.html
"Would someone living in a small hamlet in the 14th century ever have the opportunity to meet anyone from outside their community? Of course they would -people often travelled many miles to attend church or the nearest market, to give only the most obvious examples."
"Often travelled" "many miles"? In the 14th century (in England). _Really_? I do not think so.
"Blood-group studies in New York State and Sweden have shown that more than half of alleged fathers could not be the true fathers." Not True. There are all kinds of crazy theories afloat about NPEs (there are groups with Axes of Significant Size). An interesting summary can be found here:
http://www.childsupportanalysis.co.uk/analysis_and_opinion/choices_and_behaviours/misattributed_paternity.htm
I'm sure they have issues of their own, but at least they've identified the urban myth issues surrounding NPEs.
In an earlier essay:
http://www.bpears.org.uk/Misc/AncestorParadox/ancpdxrv.html
He produced a table he put together to represent likelihood of spouse coming from a given distance. 1/3rd came from 3 km or less. The remainder came from more. The same fraction (5%) came from 60km as came from 0 km! He based his data on an analysis of 530 baptismal records from the 18th century that gave the parents' birthplaces. Because he left out really long distances, he feels this is "conservative" to project backwards into the arbitrary past.
Goddess save me from people who look at the 18th century and think that represents a time frame indistinguishable in mobility from even 200 years earlier, much less 500.