Book review: Aging is a Group-Selected Adaptation: Theory, Evidence, and Medical Implications, by Joshua Mitteldorf.
This provocative book argues that our genes program us to age because aging provided important benefits.
I’ll refer here to antagonistic pleiotropy (AP) and programmed aging (PA) as the two serious contending hypotheses of aging. (Mutation accumulation used to be a leading hypothesis, but it seems discredited now, due to the number of age-related deaths seen in a typical species, and due to evidence that aging is promoted by some ancient genes).
Here’s a dumbed down version of the debate:
<theorist>: Hamilton proved that all conceivable organisms age due to AP and/or mutation accumulation.
<critic>: But the PA theories better predict how many die from aging, the effects of telomeres, calorie restriction, etc. Also, here’s some organisms with zero or negative aging …
<theorist>: A few anomalies aren’t enough to overturn a well-established theory. The well-known PA theories are obviously wrong because selfish genes would outbreed the PA genes.
<critic>: Here are some new versions which might explain how aging could enhance a species’ fitness …
<theorist>: I’ve read enough bad group-selection theories that I’m not going to waste my time with more of them.
That kind of reaction from theorists might make sense if AP was well established. But AP seems to have been well established only in the Darwinian sense of being firmly entrenched in scientists’ minds. It got entrenched mainly by being the least wrong of a flawed set of theories, combined with some poor communication between theorists and naturalists. Wikipedia has a surprisingly good page on the evolution of aging that says:
Antagonistic pleiotropy is a prevailing theory today, but this is largely by default, and not because the theory has been well verified.