This post discusses cliff-edged fitness functions by Randolph Nesse (psychiatrist and one of the founders of evolutionary medicine) and the 2024 paper, “The cliff edge model of the evolution of schizophrenia: Mathematical, epidemiological, and genetic evidence,” by Philipp Mitteroecker and Giuseppe Pierpaolo Merola. Let’s say schizophrenia is associated with a 50% loss of reproductive fitness in 1% of the population (and there is no offsetting benefit in the rest of the population), then it would take roughly 180 generations to cut the rate in half and about 560 generations to reduce it to one-tenth of its original value (Mitteroecker & Merola, 2024). Escott-Price et al. interpreted the observed effects as too small to explain the evolutionary persistence of schizophrenia, but Mitteroecker & Merola (2024) argue that their findings are compatible with the cliff edge model of schizophrenia, and the magnitude of a weak positive selection is also aligned with what we’d expect to see.
Author: Awais Aftab
Published at: 2025-06-28 21:22:14
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