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On Type O blood and being set in the past

A minor update on my main review of BSG:

After the show concluded, many viewers complained about how all the clues in the show had pointed — some very directly — to the show being set in the future, and little had suggested it would be set in the past.

Kevin Grazier, science adviser to the show, stated in his book The Science of Battlestar Galactica that Hera’s blood type was such a clue.

Hera had no blood antigens — ie. she was of type O. No colonial was of type O, they were all of types A, B and AB. Since we modern humans are quite commonly type O, this was supposed to be a clue that the story was in the past, and we all got this from Hera.

Except blood type genetics don’t work this way. Everybody has two genes (from two parents) for blood type. You can be AA, AO, AB, BB, BO or OO, getting either an A, B or O from each parent. There are only 4 types because people who are AO have type A blood, and people who are BO have type B blood. Only OO folks have type O blood — the O trait is recessive.

The problem is this. Even if Sharon (the mother) is OO, she can’t have a type O baby if she breeds with people who don’t have any type Os. The colonials are all AA, AB or BB. They have no AOs or BOs because if they did, they would have type O children from time to time. Grazier knows about the pairings and describes them in the book, but somehow misses this important element. So this is not a proper clue that the show is set in the past.

Wait — we could play some games, and give Sharon some magic special O genes that are dominant over A and B from humans, allowing a baby with type O blood. You could, but that would be some new magic, not any known science, and thus hardly something that clever viewers would take as a clue. To top it off, we must also now assume that none of the #8s in the fleet or colonial society ever got their blood typed. Perhaps that’s true, but pretty unlikely once the Cylons were identified and subjected to every medical test they could get their hands on. Sharon’s type O blood would have been well known, and Hera’s type would also be no surprise.

Am I being picky? Of course. But this is worthy of attack because Grazier is holding this out as an example both of the careful attention to scientific detail in the show, and as an example of how the clever viewer would have picked up a clue to the ending by paying attention. It is sadly, neither.

Grazier’s book also contains a major error about Mitochondrial Eve. It admits the mistake that MTE is not the “most recent common ancestor,” but it goes on to make a bigger mistake, saying that MTE is the sole ancestor of people alive today. That is about as wrong as you can get. In fact, most people alive at the time of MTE (and in fact most people alive somewhere around 15,000 to 20,000 years ago, at what is termed the Identical ancestors point) is an ancestor of every human alive today. All of us are descended from all of them. It’s not actually all of them because some of them died without children or grandchildren or otherwise had lines that died out quickly. If somebody’s line did not die out quickly — so they got the usual brood of great-grandchildren and beyond — their tree of descendants quickly becomes so huge it can’t die out and can’t be anything but ancestor to all of us. (There are some exceptions when geographically isolated groups got wiped out completely before they had time to send out members to breed with the rest of humanity.)

Note that even though you are descended from everybody alive 20,000 years ago, that doesn’t mean you inherited DNA from all of them. Through the 700 to 1000 generations since those days, the DNA of most of them has been lost. You are actually descended from all of them many trillions of times over — they occupy lots of slots in your family tree, and some of them more than others. But at this distance the genetic contribution of most is diluted to nothing. The odds you would have any DNA (other than mitochondria) from a hypothetical single person who lived 150,000 years ago are quite slim.