A common misunderstanding of natural selection

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My attention was drawn today to an article in the Atlantic, entitled ‘Why Do Humans Still Have a Gene That Increases the Risk of Alzheimer’s?’ It noted that there are variants of the apoliprotein gene that are associated with an 8- to 12-fold increased risk of the disease. It continued:

“It doesn’t make sense,” says Ben Trumble, from Arizona State University. “You’d have thought that natural selection would have weeded out ApoE4 a long time ago. The fact that we have it at all is a little bizarre.”

The article goes on to discuss research suggesting there might be some compensating advantage to the Alzheimer risk gene variants in terms of protection from brain parasites.

That is as may be – I haven’t studied the research findings – but I do take issue with the claim that the persistence of the risk variants in humans is ‘a little bizarre’.

The quote indicates a common misunderstanding of how natural selection works. In evolution, what matters is whether an individual leaves surviving offspring. If you don’t have any descendants, then gene variants that are specific to you will inevitably disappear from the population. Alzheimer’s is an unpleasant condition that impairs ability to function independently, but the onset is typically long after  child-bearing years are over. If a disease doesn’t affect the likelihood that you have surviving children, then it is irrelevant as far as natural selection is concerned. As Max Coltheart replied when I tweeted about this: “evolution doesn't care about the cost of living in an aged-care facility”.

My most popular posts of 2016

The end of the year is a good time to look over the blog, to see which posts garnered most attention. Perhaps not surprisingly, among the six most popular were several pieces I wrote related to scientific publishing and the reproducibility crisis: examining the problem and potential solutions. This is a topic I have become increasingly passionate about, as I worry about how the current system encourages us to waste precious time and money pursuing 'exciting' and 'ground-breaking' results, rather than doing thoughtful, careful science. Of course, these are not mutually exclusive, but, sadly, the emphasis on innovation and productivity can lead people to cut corners, and we then end up with findings that are not a solid basis on which to build further research.


Here are the top 6 posts of 2016:

Ten serendipitous findings in psychology

Better control of the publication time-line: A further benefit of Registered Reports

The Amazing Significo: why researchers need to understand poker

There is a reproducibility crisis in psychology and we need to act on it

Cost-benefit analysis of the Teaching Excellence Framework

Editorial integrity: Publishers on the front line

Here are slides from and references from a talk I gave on reproducibility


Here is a link to an advanced course for early career researchers on this topic that I am running with Marcus Munafo and Chris Chambers


Here is a link to a complete catalogue of my blog posts.


Happy New Year!