I meant to write on this immediately after the recent season finale of Downton Abbey but got distracted, so here it is. Although we do not know whether Mr. Matthew Crawley (heir presumptive of Downton) is dead (my guess: he is), what we do know is that Robert Crawley, Earl of Grantham, does have a new heir, the son of his daughter Lady Mary Crawley and her husband Mr. Matthew Crawley, third cousin to the Earl.
In terms of maximizing Darwinian fitness, the real payoff is reproducing with someone of the same race. As Frank Salter calculates in On Genetic Interests, a white parent would be twice as closely related to (share twice as many genes with) a same-race offspring than if he or she reproduced with a black person. Going below the racial level to the ethnic and distant-cousin level, however, there are still payoffs but they become diminishingly smaller.
Nonetheless, in terms of inclusive fitness, the Earl makes out. Not only will his grandson inherit 1/4 of his DNA (or probably even more, depending on genetic proximity of Matthew Crawley), the grandson will also inherit the Earl’s Y-chromosome (through the paternal Crawley line via Matthew) and the surname attached to it. Although HBD Chick might not like it, if I were the Earl of Grantham, I’d be a happy man!
Crawley Family Tree
Robert Crawley, Earl of Grantham
Occam's Razor 
Lady Mary is Jewish; her maiden name is Levinson. He maximized Jewish inclusive fitness intermarrying with degenerate aristocrats is all he did.
@mindweapon – “He maximized Jewish inclusive fitness intermarrying with degenerate aristocrats is all he did.”
otoh, lord grantham might’ve introduced some familial altruism genes into his family (i.e. the kind, perhaps, found to differing degrees in inbred groups like ashkenazi jews) which might benefit the grantham “clan” going forward.
That’s an interesting point.
Mary’s maiden name is Crawley. But, yea, you are right that her (American) maternal grandparents seem to be Ashkenazi. It’s interesting that show presents them as money-obsessed and tawdry, although the show doesn’t go as far in this direction as does an Anthony Trollope novel. Ashkenazis are genetically distinct but have considerable European DNA, so it is not a complete loss for the Earl to reproduce with one, as it would be, say, by reproducing with a (lower IQ) black or Amerindian mestizo (vs a white). But then you have added problem that many of the Ashkenazi aristocracy seem to be anti-English / Anti-European, as Trollope hints at in his novels. Maybe Mary’s maternal grandparents are mostly European, such as Madame Max Goesler in Phineas Finn, perhaps the one Ashkenazi that Trollope praises and describes as European looking. The actress playing Mrs. Levinson, Shirley MacLaine, doesn’t look Ashkenazi, and the wife, Cora, doesn’t look Ashkenazi, regarding the link between casting and story line, so there might not be a big genetic gap. Of course, the Earl would have actually maximized inclusive fitness by marrying English co-ethnic but he was broke.
The actress playing Mary (regarding cast and storyline) is Michelle Suzanne Dockery, I believe, daughter of working class English and Irish stock.
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nice post
@alfred – “Although HBD Chick might not like it….”
heh. (^_^)
first of all, sorry for my tardy comment to this post. the past month has been … busy!
i feel i should clarify my position on inbreeding vs. outbreeding, and that is — i really don’t have one! if the inbreeding/outbreeding theory is at all right, then it seems that practicing either of these over the long-term has both benefits and drawbacks. with inbreeding, you (seem to) get strong familial altruism, and can really maximize your inclusive fitness like you say, but the negative payoff is that it’s difficult to build a modern, western sort-of society based on nifty things like societal-wide trust … if that’s what you want. otoh, with long-term outbreeding, you seem to be able to build large, trusting societies with liberal democracy (fwtw) and little corruption, but family ties are shorter, and you’ll probably be somewhat blind to others (especially from inbred societies) who will take advantage of you and your system (’cause you’re so trusting).
i’m not opposed to cousins marrying. on a large scale, i think it’s a bad idea — but some amount of it is probably a good idea (i.e. i think northwest europeans have probably outbred too much for their own good).
@alfred – “Although we do not know whether Mr. Matthew Crawley (heir presumptive of Downton) is dead (my guess: he is)….”
dead as a doornail, i’m afraid.