The LERN annual debate: The how and why of evolutionary biology

I had the pleasure yesterday evening of taking part in the annual LERN debate. LERN is the London Evolutionary Research Network – a multi-institution society that brings together London-based researchers in evolutionary biology and associated disciplines. Once a year they hold a debate on a big issue in evolutionary biology. Previous debates have been about group selection, epigenetics and the Modern Synthesis, and human uniqueness. This year’s was about the ultimate/proximate distinction, and I was very pleased to be invited to speak against the motion.

The motion on the table was: This house believes that the ultimate/proximate distinction hinders a complete understanding of evolutionary processes. That’s long and, if I may say so, slightly wonk-ish (for comparison, last year’s was ‘Humans are unique. There is a qualitative difference between humans and other animals as well as a quantitative one’), but the idea behind it is relatively straightforward. The ultimate/proximate (U/P) distinction is a distinction between two types of biological explanation, often glossed as the ‘why’ and the ‘how’. Here’s an example, taken from the opening pages of An Introduction to Behavioural Ecology. Male lions that have recently taken over a pride commit infanticide: they kill the offspring of the previous male. An ultimate explanation of this is one concerned with survival value: the males do this because it means that maternal care will be dedicated solely to their own offspring, and not the offspring of other males. A proximate explanation of this is one concerned with immediate physical and material causes: the operation of the male’s physiology and limbic system, its brain mechanisms, and so on. A strict definition of the terms ‘ultimate’ and ‘proximate’ requires a bit more elaboration, but the basic idea should be clear.

In 1961, a very influential evolutionary biologist, Ernst Mayr, wrote a paper in Science that brought attention to the importance of the U/P distinction for understanding cause and effect in biology. Last year, another paper in Science, timed to coincide with the 50th anniversary of Mayr’s paper, argued that the U/P distinction has outlived its utility as a tool for understanding cause and effect in evolution. It is that claim that motivated the motion for last night’s debate.

Speaking for the motion were John Odling-Smee and Tobias Uller – two of the authors of the 2011 Science paper. Tom Dickins and I spoke against it. We each spoke for 15 minutes, and then had 10 minutes each to respond to the others’ presentations. There was then a short question session with the audience, before a final vote. I won’t rehash all the arguments here: even putting aside the fallibility of memory, I would likely not do justice to the arguments for the motion. And LERN recorded the event, so there should soon be video available for those interested in the details: keep an eye on their website.

At the vote, the audience voted “overwhelmingly against the motion”. There were also some abstentions. However, there was no vote before the debate, so we didn’t get to see if anybody actually changed their mind. I suspect few did: had a vote also been taken before the debate, it would, I think, have looked very similar. I speculated in my presentation that the silent majority of evolutionary biologists agree with Tom and me. The result of the debate was certainly consistent with that.

Debates sometimes get bogged down in details, but in this case something like the opposite happened: all four of us touched, in our own different ways, on the fact that any debate about U/P is just one manifestation of a larger debate within evolutionary biology, about the utility of the Modern Synthesis itself. (Very briefly: The Modern Synthesis is the marriage of Darwinian evolution and Mendelian genetics, which were originally thought to be in conflict with one another, but which once synthesised provided the bedrock on which modern evolutionary biology is based. This one sentence summary over-simplifies, of course.) In recent years a vocal minority of researchers have expressed dissatisfaction with various aspects of the Modern Synthesis. This dissatisfaction is played out in several contemporary debates, such as: the role of organismic activity (called ‘niche construction’) in evolution; the role of epigenetic inheritance in evolution; group selection vs. inclusive fitness; the status of cultural evolution vis à vis biological evolution; and, indeed, the utility of the U/P distinction. The 2011 Science paper made a similar observation, as did an essay published just a few days ago by Pete Richerson, one of the protagonists in these debates: “The sharpest divide… is between what I think of as Strict Neo-Darwinians and Expanded Synthesis Evolutionists”.

It seems to me that a lot of the fuel for these debates comes from the use of evolutionary theory to study humans, human behaviour, and human society. Certainly, a significant proportion of yesterday’s audience were researchers from that area. Those that express dissatisfaction with the modern synthesis often point out that previous attempts to use evolutionary theory to study humans were met with hostility by many social scientists and other students of humanity – and this was, they argue, for justifiable reasons: those previous attempts were reductive in an unprofitable way, in that they wanted to dissolve the social sciences to biology. John Odling-Smee made this point in his presentation. We might dispute whether or not this really was the case – but even if we grant it for the sake of argument, I don’t see this as a problem with the Modern Synthesis. It is, to the extent that it is true, a problem with how the Modern Synthesis is used, not with the synthesis itself. It seems to me that the correct reaction to any such state of affairs is not to hastily modify one of (if not the) most successful paradigms in all of science, but rather to use it with less hubris. That should be the agenda of those of us that use, and wish to promote the use of, evolutionary thinking to study and explain human affairs. Last night’s audience would, it seems, agree.

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