The SBS TV show “Who’s your daddy?” which was part of the series “Tales of the Unexpected” was one of the best science documentaries I’ve seen recently.

If you missed it, you can watch it on the web. Link here

“Who’s Your Daddy? – In 1972, a study was conducted in the U.K that claimed 30 percent non-paternity, which means one in three children were not biologically related to the man they call Dad. Could this really be true? This program conducts the first ever purpose designed paternity poll, asking some truly awkward questions. It compare rates of paternity uncertainty in Australia and the United States, and follows parents and children as they discover the truth behind who’s their father.”

Although an excellent documentary, I think it missed two important bets. One it missed is the influence of contraception on mistaken paternity. The studies that showed enormously high rates of sneaky sex were before reliable contraception was completely accepted. So a 30% rate of non-paternity in 1972 is not necessarily inconsistent with an estimated rate of 1.5% of non-paternity in the 2010s. (To help you set the time frame, the comedy film Alvin Purple was made in 1973, a few years after hippie culture entered the mainstream).

The second bet it missed was that possibility that inheritance of blood type is unreliable. So far as I can tell, all three studies that showed rates of non-paternity above 20% in humans – two from the UK and one from Australia – were done using blood type. Later studies were based on DNA analysis and showed low rates of non-paternity, close to 1.5%. Where then does that leave the studies on non-paternity of blue wrens Malurus cyaneus and black swans (15% of cygnets are from the wrong father)? High rates of sneaky sex among blue wrens were confirmed using “microsatellite genotyping”. Among the black swans it’s also “microsatellite markers”.

Of humans, this subject gets touched on a bit, being sensitive as it is, it tends a bit taboo, in-large-part because a great portion of societal behaviour controls function around such things, sex and faithfulness get the focus.

These same behaviour controls distort the picture.

An avenue into the truth of it might be to consider humans highly social and consequently naturally somewhat polyamorous, but simultaneously somewhat monogamous, and to-date I’ve seen no evidence or arguments that humans can’t be somewhat instinctively both. Mono in response to the complications of being poly, perhaps.

A woman restricting her self to recombining DNA with one man is not optimally adaptive IMO. Men can die, or worse (figure that).

The truth of the matter is probably better seen from the context of the small groups of the Environments of Evolutionary Adaptation, meaningless as that term is to many it is in fact not only a useful tool for thinking about it but also probably provides a clearer insight into the nature of man that prevails today.

I am guessing that some men in the ancestral environment didn’t actually mind their favourite woman doing the deed with another man considered of ‘safe company’ that way, I mean practical and even special attributes were probably nurtured of all given they were in short supply, numbers being small as they often were. Of course the act of sex(penis in vagina) wasn’t probably so tightly associated with pregnancy and babies being born, but certainly that man and woman getting friendly tended this would have been sort of intuited.

I saw a bit of that doco, and the first thing I thought was that the figures would be skewed because the type of people wanting a paternity test would already have suspicions of infidelity so they my not be representative of the general population.

pommiejohn said:

I saw a bit of that doco, and the first thing I thought was that the figures would be skewed because the type of people wanting a paternity test would already have suspicions of infidelity so they my not be representative of the general population.

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pommiejohn said:

I saw a bit of that doco, and the first thing I thought was that the figures would be skewed because the type of people wanting a paternity test would already have suspicions of infidelity so they my not be representative of the general population.

Yes, they dealt with that, and essentially threw out all scientific results based on paternity tests with one exception. That exception was used to place an upper limit on the number of cases of non-paternity. It seems fair to assume that the fraction of non-paternity from paternity tests will not be smaller than the fraction of non-paternity in the general population.

mollwollfumble said:

pommiejohn said:

I saw a bit of that doco, and the first thing I thought was that the figures would be skewed because the type of people wanting a paternity test would already have suspicions of infidelity so they my not be representative of the general population.

Yes, they dealt with that, and essentially threw out all scientific results based on paternity tests with one exception. That exception was used to place an upper limit on the number of cases of non-paternity. It seems fair to assume that the fraction of non-paternity from paternity tests will not be smaller than the fraction of non-paternity in the general population.

Okay, but an upper limit by itself is not very instructive in this case…