What cases in nature are the most troublesome for scientists to reconcile with the theory of evolution by natural selection? Are there any at all? Or are they so numerous that a top-10 list would be in order to get started?
It seems to me that the case of ornaments for sexual selection is troublesome, because I found two competing explanations: one is Fisher's runaway explanation, and the other says an ornament advertises fittness and good genes because its owner is able to survive despite being handicaped by it. But maybe scientists do not consider ornaments troublesome, and it is only what scientists find troublesome that I'm asking about.
Thanks,
IGIT
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