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Art thou my father?

by Vagulus Fri Jan 11th, 2008 at 07:50:07 PM EST

A short and somewhat rambling opening diary, with more questions than answers, prompted by a recent article in The Guardian about the need for children to know the identity of their biological parents. Pay no attention to the tabloidesque title - what I wish to highlight is a detail from the text:


Twins separated at birth married each other
(Dr Allan Pacey, secretary of the British Fertility Society and senior lecturer in andrology... at the University of Sheffield) said about 3.5% of children are not their father's children, with the number rising to as much as 20% in socio-economically deprived areas.


For children who turn out not to be the offspring of their putative fathers, percentages as high as 10% are quoted as lab lore by people involved in genetic testing for inherited disorders. I have yet to find a peer-reviewed publication that addresses these statistics specifically (my keyword searches through the databases haven't been sharp enough so far, I'm afraid), but the figures are not insignificant.

Leaving aside the possibility of inadvertent consanguinity as conveyed by the article, this makes me wonder: are we a species where some males unknowingly look after the genes of other (perhaps more sexually assertive) males alongside their own? The answer is obviously yes, but how far in the past does this reproductive pattern go? How widespread is it among different societies? How relevant to the composition and evolution of our gene pool? And what about the role of the female of the species in this reproductive triangle?

In other words, is this an accident, or is it what we do, and why? To be sure, these themes have not gone unexplored. Here's an interesting example of (in my opinion) a relevant study:


Male facial attractiveness: evidence for hormone-mediated adaptive design

V.S. Johnston, R. Hagel, M. Franklin, B. Fink and K. Grammer

Evolution and Human Behavior, vol. 22, pp. 251-267 (2001)

Experimenters examining male facial attractiveness have concluded that the attractive male face is (1) an average male face, (2) a masculinized male face, or (3) a feminized male face. Others have proposed that symmetry, hormone markers, and the menstrual phase of the observer are important variables that influence male attractiveness. This study was designed to resolve these issues by examining the facial preferences of 42 female volunteers at two different phases of their menstrual cycle. Preferences were measured using a 40-s QuickTime movie (1200 frames) that was designed to systematically modify a facial image from an extreme male to an extreme female configuration. The results indicate that females exhibit (1) a preference for a male face on the masculine side of average, (2) a shift toward a more masculine male face preference during the high-risk phase of their menstrual cycle, and (3) no shift in other facial preferences. (...)

(In men, a more masculine face has been linked to higher male hormone levels, and there may be a relation between face symmetry and perceived health.)

Another consequence of non-biological fatherhood is the dubious accuracy of genealogical studies. Here, though, I'd like to quote from a study by Bryan Sykes, who found a significant correspondence between his surname and a cluster (haplotype) of variable genetic markers (microsatellites) on the Y chromosome, which is exclusively transmitted from father to son:


Surnames and the Y Chromosome

B. Sykes and C. Irven

American Journal of Human Genetics, vol. 66, pp. 1417-1419 (2000)

A randomly ascertained sample of males with the surname "Sykes" was typed with four Y-chromosome microsatellites. Almost half the sample shared the same Y-chromosome haplotype, which has not been observed in control samples either from the same geographic region or from the United Kingdom as a whole. This points to a single surname founder for extant Sykes males, even though written sources had predicted multiple origins. The distribution of other Sykes Y-chromosome haplotypes were not significantly different from those in controls and may be accounted for by the historical accumulation of nonpaternity during the past 700 years, in which case the average rate estimate is 1.3%/generation. If this pattern is reproduced with other surnames, it may have important forensic and genealogical applications.

By the way, matrilineal inheritance is traced on the DNA from mitochondria, mtDNA, cellular elements inherited from the mother that possess a small genome distinct from the main (nuclear) genome.

As a matter of curiosity, B. Sykes wrote a book with a catchy title, The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry and founded a startup company that proposes individual Y and mtDNA studies to the public. As of this writing, my curiosity has not overcome my reluctance to spend money, and I ignore which daughter of Eve conceived by her husband or another man to give rise to my maternal lineage.

Display:
I thought it was interesting that the tragic case of the twins who married surfaced after Lord Alton raised it as an issue with regard to pending legislation.

The peer used it to back up a call for children conceived by donor insemination to be told the circumstances of their conception, during a debate on the human fertilisation and embryology bill, currently going through parliament.

 We should note that objections to the bill on the ground that in a lesbian relationship both parents would be able to be mentioned on a birth certificate without any mention of the father have surfaced

He (Alton) said yesterday he was worried that the biological identity of one parent would not appear on the birth certificate and that there was nothing on the certificate to let a child know he or she had been donor-conceived

Now one should remember that, although Alton was a member of the Lib Dems, he is, due to his catholicism, virulently anti-abortion and, presumably, homophobic.

So basically, two blameless people have had their desperate plight dragged through the papers so that some superstitious fuckwit can continue his campaign of vilification against lesbian parents. May his God have mercy on his soul, cos I know I wouldn't.

keep to the Fen Causeway

by Helen (lareinagal at yahoo dot co dot uk) on Sun Jan 13th, 2008 at 12:32:27 PM EST
I can't judge on the merits of Alton's position but I do think consequences seem to be drawn from a very exceptional case. (IMHO, it's not unlike the erosion of civil liberties by government in the name of overstated risks to our security.) There are other (probably better) reasons to advocate disclosing the identity of biological parents.

You're clearly a dangerous pinko commie pragmatist.
by Vagulus on Sun Jan 13th, 2008 at 04:27:05 PM EST
[ Parent ]
Can we get over the notion that human behaviour is predominantly caused by Darwinian struggle for genes to prevail ? I do not claim our minds are absolutely blank slates, but social constructs have a very deep influence on our behaviour.

Indeed, that is shown by the fact that the proportion of kids "biologically not" of their social father apparently varies according to social class, in the UK. Some societies do not consider that father take any part in the biological process of parenting...

Of course, much is told about the proponents of Evolutionary Psychology by the abstracts you quote : the sample size is 42 women, whom I'd bet are mostly from a single town, possibly all students... That's an impressively thorough study of humanity !

Also, the fear of consanguinity is not only a biological necessity, but mostly a social one, that may have very long roots in our primate ancestors.

Un roi sans divertissement est un homme plein de misères

by linca (antonin POINT lucas AROBASE gmail.com) on Sun Jan 13th, 2008 at 01:35:31 PM EST
Linca:

Of course, much is told about the proponents of Evolutionary Psychology by the abstracts you quote : the sample size is 42 women, whom I'd bet are mostly from a single town, possibly all students... That's an impressively thorough study of humanity !

Small sample size is indeed a problem with many, many studies on human subjects. To me this remains an open question, but an interesting one. Controversy is often an indicator of (very) imperfect scientific knowledge.


Also, the fear of consanguinity is not only a biological necessity, but mostly a social one, that may have very long roots in our primate ancestors.

I agree, though the boundaries of incest are culture-dependent: marriage between first cousins can be forbidden (e.g. for catholics, though allowances are made) or, conversely, regarded as a desirable bond, as is often the case in Muslim communities.

And it can be discouraged on medical grounds, though the risks can be overstated.

NHS -  National Library for Health


The population risk for any couple of having a child with a serious or lethal medical condition is around 2% (1 in 50). The excess risk for a couple who are related as first cousins, in the absence of a known genetic disease in the family, is in the order of 3% (1 in 30). This fact often comes as a relief to couples who expect a significantly higher figure.

Emphasis as in the original - indeed, if a hereditary condition or carrier status has been established in the family, probability calculations will be very different. The maths are only part of the story, of course. To me, personally, 1 in 30 is too high in light of the potentially devastating consequences of a severe genetic disease, but I'm deep in bachelorhood, so who am I to talk?

You're clearly a dangerous pinko commie pragmatist.

by Vagulus on Sun Jan 13th, 2008 at 04:14:47 PM EST
[ Parent ]
Small sample size is indeed a problem with many, many studies on human subjects.

The problem with such studies, especially for a highly culturally determined behavior like mate selection, is not only small sample size but also extreme cultural bias. Those "scientists" are projecting onto various species of humanoids that spanned the whole world the behaviour of 21st century, USian young humans. In many societies, mate choice isn't even an individual choice...

As for the added risk, that means an added risk of 1 in a hundred compared to non-consanguineous couples. I'd bet that in smaller populations of ancient times, the "normal" and "consanguineous" couple relative danger would have been closer, due to a smaller genetic pool.

 

Un roi sans divertissement est un homme plein de misères

by linca (antonin POINT lucas AROBASE gmail.com) on Sun Jan 13th, 2008 at 04:57:52 PM EST
[ Parent ]
Linca:

I'd bet that in smaller populations of ancient times, the "normal" and "consanguineous" couple relative danger would have been closer, due to a smaller genetic pool.

I think you mean that the probability would have been higher, for a non-consanguineous couple in those smaller, ancient communities, to actually share disease-causative alleles that are identical by descent. Am I right?

Actually, the risk may have increased over time as new mutations build up. And you can still find populations in relative geographic or religious isolation nowadays. In addition, if memory serves, the loss of genetic diversity caused by population bottlenecks is an established concept in human population genetics.


You're clearly a dangerous pinko commie pragmatist.

by Vagulus on Sun Jan 13th, 2008 at 05:46:24 PM EST
[ Parent ]
Actually, the risk may have increased over time as new mutations build up.

Well, it's not that clear as lethal mutation would also have a greater tendency to disappear...

As for population isolation, I guess nothing can beat the Sentinelese... And population bottlenecks is well known in population genetics in general ; it's a problem for the cheetah species

Un roi sans divertissement est un homme plein de misères

by linca (antonin POINT lucas AROBASE gmail.com) on Sun Jan 13th, 2008 at 06:31:12 PM EST
[ Parent ]

Well, it's not that clear as lethal mutation would also have a greater tendency to disappear...

Not necessarily, as healthy carriers of recessive mutations are able to pass them on to their offspring.

Thanks for the link on the Sentinelese, I'll check it out.

You're clearly a dangerous pinko commie pragmatist.

by Vagulus on Mon Jan 14th, 2008 at 05:16:20 AM EST
[ Parent ]
In smallish populations (100-2000 people), the volatility of allele preponderance is very high ; whereas a mutation present in a one million strong population at a one percent prevalence is going to stay there, in a 1000 population, it represents 10 people, which might coincidentally not have children (which make the gene disappear), or a lot of children, which weakens the viability of the population significantly.

Un roi sans divertissement est un homme plein de misères
by linca (antonin POINT lucas AROBASE gmail.com) on Mon Jan 14th, 2008 at 08:09:42 AM EST
[ Parent ]


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