the importance of evolution for modern medicine

I’ve just started reading Richard Dawkins’ latest book, The Greatest Show on Earth, & I’m thoroughly enjoying it. (At this point I should confess to a small heresy – in the past I haven’t always enjoyed his books. Not that they’re badly written – the reverse is true! But they just didn’t always gel for me. This one’s very different.) The book’s focus is the evidence in support of evolution, and it makes it clear why evolution underpins all of modern biology. So you will see why I was excited to get my hands on a paper called Making evolutionary biology a basic science for medicine (Nesse et al.2009 – Auckland University’s Sir Peter Gluckman is among the authors).

Nesse & his colleagues comment that "[n]ew applications of evolutionary biology in medicine are being discovered at an accelerating rate, but few physicians have sufficient educational background to use them fully." (And, alarmingly, some physicians deny that evolution has any bearing at all on the practice of modern medicine.) This raises the question: how can we best apply evolutionary biology to issues surrounding human health? The authors argue for a change in the way aspiring doctors are educated.

They kick off by referring to Niko Tinbergen’s ‘four questions’. I first encountered these questions back when I was an undergraduate. They were orignally posed about animal behaviour &  fall into two categories: the ‘proximate’ questions, dealing with mechanisms, & the ‘ultimate’, which look at the behaviour from an evolutionary point of view (studies of origins, or functions, for example). Nesse et al. note that such ultimate, evolutionary questions aren’t restricted to ethology – they have resulted in numerous advances in public health and medicine. Doubtful? Try these for size (the authors list several others):

Why hasn’t natural selection slowed the aging process? (Perhaps because medical advances have themselves done away with many of the selective mechanisms? Or because we are essentially invisible to evolution once we’ve passed on our genes?) Why aren’t sex ratios biased towards females – in fact, why do we reproduce sexually at all, when asexual reproduction is so efficient? (Matt Ridley offers one answer in his book The Red Queen.) Why is cancer so persistent in the population? (In part, because the necessary mechanisms of tissue repair, gone awry, lead to the unrestricted cellular growth that we recognise as cancer.) And how does cancer become resistant to chemotherapy anyway? (The chemotherapy drugs act as powerful agents of natural selection.)

Our ability to answer these questions is enhanced by the increasingly large amounts of genetic data now available to researchers. Those of you who’ve looked at Level 3 NCEA biology papers will be aware that such data allow us to trace relationships – to the point where particular strains of disease-causing organisms can be identified and their origins traced. H1N1 flu, anyone? Or see ERV’s regular comments on endogenous retroviruses – this one, for example – and what they can tell us about evolutionary relationships, & more besides.

Despite all this, Nesse et al. comment that most doctors & medical researchers don’t formally study evolutionary biology, let alone its applications. The doctors are probably not alone, by the way – my department’s evolution paper isn’t compulsory for biology majors & I suspect the same is true for other universities – but with the increasing significance of evolutionary biology to medicine, the authors ague that this poses a problem that needs addressing. As a solution, they recommend that all students entering medical training should take a course that increases their competency in the field of evolutionary biology, along the lines of the following: students should ‘[demonstrate] an understanding of how natural selection and other evolutionary processes account for the istory of life and the relationships among species, how these processes have endowed organisms with traits that promote reproductive success, and why they leave some aspects of the human body vulnerable to disease’ (Nesse et al. 2009: 3). And they argue that another course, during training, should see aspiring doctors able to ‘apply knowledge of evolutionary factors that have shaped the body and its regulatorysystems to the prevention, diagnosis, and management of disease (Nesse et al., 2009: 5).

This must surely have positive spin-offs for doctors their patients. But it does need to start early- and isn’t the wording reminiscent of parts of he biology secton of the new New Zealand science curriculum? In fact, I love it that the authors of this paper state quite clearly that students should be learning about evolutionary biology well before they arrive at med school. Hear hear! And they point out something else dear to my heart – that learning about evolution fosters integrative thinking, seeing the big picture rather than just a part of it (& in the case of medicine, seeing the human body as a product of evolution, with all that this entails) and ‘providing the unifying framework for interpreting biological phenomena that otherwise can often seem unrelated and perhaps unintelligible’ (citing work by Avise & Ayala, presented in the same symposium as this paper). This isn’t going to be something that happens overnight, however. There’s an awful lot of content in med school curricula (as is true for most or all university courses), & so those in charge of the programs will need to be persuaded that learning about evolution will make a difference to the work of health-care professionals. (Perhaps we should be making the same case, equally strongly, for the primacy of evolution in the NZ school curriculum.) One way to approach this, say Nesse & his colleagues, is to point out that evolution explains why the human body is the way that it is, & why some aspects of our evolutionary past leave us vulnerable to a variety of health issues. They go on to propose a range of learning objectives that I rather like the look of myself; I can see that I might well use some of them in my own teaching 🙂

The proposals in this paper, if implemented (& I hope that they will be) would see a significant and valuable shift in medical curricula. And one could say, not before time.

"Evolutionary biology is not just another topic vying for inclusion in the curriculum; it is an essential foundation for a biological understanding of health and disease" (Nesse et al., 2009).

R,M,Nesse, C.T.Bergstrom, P.T.Ellison, J.S.Flier, P.Gluckman, D.R.Govindaraju, D.Niethammer, G.S.Omenn, R.L.Perlman, M.Schwartz, M.G.Thomas, S.C.Stearns & D.Valle (2009) Making evolutionary biology a basic science for medicine. Proceedings of the National Academy of Sciences early edition, p1-8.


Leave a Reply

Your email address will not be published. Required fields are marked *