Evolution did a terrible job there. So many diseases linked to mitochondrial dysfunction nowadays. We have this amazingly complex machinery, and a single point of failure, no redundancy whatsoever.
Evolution did a great job? I highly recommend reading Nick Lane's "Power, Sex, Suicide". Mitochondrial function is a complicated question. It's amazing nature makes it work at all. Two aspects he discusses:
1) Mitochondrial selection is multilayered and aggressive. Mitochondrial population selection goes on during formation of egg cells [1]. Mitonuclear compatibility is heavily selected for during ontogeny [2]. Many miscarriages are are related to mitochondrial dysfunction. Once someone is born they've already passed a high selective bar for mitochondrial health.
2) There is a tradeoff between mitochondrial selectivity and fertility. Birds have much greater energetic requirements than mammals (flying is hard) and therefore have much greater mitochondrial selectivity. This means fewer offspring though. Pigeons and rats have similar size and metabolic rates, but a pair of rats can have 80+ offspring in a year while a pair of pigeons can only manage under 20.
code_biologist|3 years ago
1) Mitochondrial selection is multilayered and aggressive. Mitochondrial population selection goes on during formation of egg cells [1]. Mitonuclear compatibility is heavily selected for during ontogeny [2]. Many miscarriages are are related to mitochondrial dysfunction. Once someone is born they've already passed a high selective bar for mitochondrial health.
2) There is a tradeoff between mitochondrial selectivity and fertility. Birds have much greater energetic requirements than mammals (flying is hard) and therefore have much greater mitochondrial selectivity. This means fewer offspring though. Pigeons and rats have similar size and metabolic rates, but a pair of rats can have 80+ offspring in a year while a pair of pigeons can only manage under 20.
[1] https://www.nature.com/articles/s41586-019-1213-4
[2] https://www.pnas.org/doi/10.1073/pnas.1910141117