Club EvMed: The evolution of imperfection: why do humans have so many medical problems?

Описание: This Club EvMed event occurred on December 2, 2025. Learn more about Club EvMed at https://clubevmed.org.
Put the term “evolution” into google image search and most that comes back is a version of the “March of Progress”, an inference of which is that humans are somehow the peak of evolution, the “paragon of animals” as Shakespeare put it. But accumulating evidence from our genetics suggest the very inverse: our genome is bloated, our mutation rate is the highest recorded (giving ~5% of us a “rare” genetic disease), about half of human embryos have the wrong number of chromosomes and die instantaneously, about a fifth of recognised pregnancies end in early spontaneous miscarriages, 5% of pregnancies end with pre-eclampsia, potentially lethal to mother and child, and childbirth is remarkably dangerous. These apparent imperfections demand explanation. I argue that there are two broad classes of explanation, theory for which developed in parallel with the recent advances in genetic technology. On the one hand the nearly neutral theory points to reduced efficiency of purifying selection in species, like ours, with low effective population size. This appears to explain genomic bloating and our high mutation rate. Second, mammalian pregnancy permits flexibility of resource allocation, which, amongst other features enables reproductive compensation, an increase in allocation to surviving embryos following the death of others. I illustrate the relevance of this showing that with reproductive compensation, chromosomes (especially centromeres) forced towards the polar body in maternal meiosis I can benefit from poisoning the embryo, for example by rendering it triploid, this potentially explaining high mammalian rates of aneuploidy. Our big brains may however partially rescue us as advances in genomic medicine can help alleviate numerous problem, gene therapy being a case in point.