How the seal got his genes

The atlantic grey seal is the commoner of Britain’s two seal species: we have 40% of the world population. Not only is it a wonderful animal, but something of a conservation success story, the population having escalated after protective legislation in 1914 from just 500 to 120,000.

They’ve always been a classic example of a species whose breeding is controlled by dominant males fighting for territories, and harems. Whilst not quite as X-certificate as some larger seal species, fights between large males can be quite serious, and draw blood when attackers go for the neck:

The adaptationist evolutionary explanation for this phenomenenon is also a commonplace of wildlife documentaries, as I’m sure is familiar to all readers. Nature favours strong and hulking seals, and so over millions of years the competitive testosterone-charged males struggling for dominance have ensured that these characteristics prevail in the gene pool. For such species, as for others like deer, this behaviour is a major explanation for the survival of the species. And of course the behaviour itself arose from random genetic variation.

It is a classic case of the “struggle for survival” and secondarily, of course, an instance of what leads to the theological hand-wringing of some theistic evolutionists about nature’s dependance on selfish and cruel processes incompatible with God’s designing will.

I suppose one could alternatively invoke the other classic Darwinian mechanism of sexual selection, placing the onus on female seals having an unexplained weakness for beefcake, with the same genetic results.

But on BBC’s Autumnwatch this week, the excellent Chris Packham mentioned some research showing that seal mating behaviour, and therefore the evolutionary story, is far more complex than that. I guess he means this paper, or one like it. (If you don’t have access to Academia, the reference is Wilmer, J. W., Overall, A. J., pomeroy, P. P., Twiss, S. D., and Amos, W., “Patterns of paternal relatedness in British grey seal colonies,” Molecular Ecology (2000) 9, 283–292.

The paper shows by genetic studies that most seal pups born are not the offspring of the dominant males muscling out their territorial rights in onshore haulouts, to the extent that it is thought that most mating happens at sea, in very much less competitive circumstances:

Instead, it appears that the use of behavioural dominance to enhance fitness is effective only at the heart of the breeding colony and involves only a handful of males, perhaps of the order of 10 individuals in a colony the size of those at NR or IoM. Outside this region, the overwhelming majority of pups are fathered by any of a very much larger number of males with low and approximately equal success rates…

In conclusion, the traditional picture of successful grey seal males fathering the majority of all pups is incorrect. Instead, the vast majority of pups appear to be fathered by any of a large number of males, who have small and approximately equal success rates. Only a handful of males manage to use behavioural dominance to achieve disproportionate numbers of offspring, and these appear to occupy positions mainly, if not exclusively, in the centre of the female aggregations.

Now, those wedded to Darwinian narrative explanations will immediately recognise that such an evolutionary strategy is far better at maintaining genetic diversity, which nature favours. But if that’s the case, nature is far less interested in strong and hulking seals than was assumed. That casts serious doubt on whether nature has expressed any clear adaptive preference at all in seal behaviour, unless we assume a priori that adaptation has shaped whatever we see.

That is not to say that the far more complex behavioural mix we now recognise is disadvantageous to seal survival. Clearly, that mix works just fine for grey seals, and no doubt is supremely matched to their ecological role. But to go on to say that the mix is the result of random variation and adaptive selection is simply to assume the theory in the conclusion.

All we can really say is that some male seals have demagogic and polygynous inclinations, whereas far more prefer life as quiet citizens with small families. The same can be said for human society, where the existence in history of the occasional eastern potentate with scores of wives and hundreds of children can scarcely be attributed to genetic evolution. Nor can it be said to have changed the species, beyond enabling Europeans proverbially to claim descent from the Emperor Charlemagne.

One should even be wary of attributing royal polyandry to biological desires for sex and reproduction, since the predominant motivations are political: fear of instability of the nation state is scarcely a universal evolutionary priority.

We can say, then, that the common seal’s biological world is as complex and interesting as our own, though organised on very different lines, that it appears to be purposive and that it works. Maybe there have been adaptive processes at work, but that would be an assumption, not a conclusion from evidence. To quote Asa Gray slightly out of context, it “leaves the question of design just where it was before.”

I have a feeling that there’s more to be gained from a fuller understanding of the species itself, rather than speculating on how it got that way, but that is to buck the modern zeitgeist that origins explain everything. I question that presumption – origins don’t explain Einstein or Stalin, so why insist they must explain seals?

After all, hitherto Darwinian theory predisposed us to over-emphasize the significance of competing bull-seals, at the expense of the bigger picture.

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About Jon Garvey

Training in medicine (which was my career), social psychology and theology. Interests in most things, but especially the science-faith interface. The rest of my time, though, is spent writing, playing and recording music.
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