I was watching a nature documentary where a crab produced several dozen babies, and then turned around and started eating them. If she needed the nutrients so badly, why not just have fewer kids? From a thermodynamic standpoint that would preserve more calories.
I’ve also seen footage of birds brooding, laying, and then hatching multiple eggs, only to push half of the chicks out of the nest. That’s such a huge investment of time and energy. Why not just lay fewer eggs?
In other situations it is more understandable: A male lion might kill another male’s offspring to make room for his own. Cuckoos push other baby birds out of the nest so they can be adopted by the parents. But many cases of infanticide in the wild just seem time-consuming and wasteful.
In: Biology
Not if you look at it from the POV of individuals. The goal of any organism with DNA is to spread that DNA as far and wide as possible. This leads to predictable but sometimes counter intuitive actions that would be good for the individuals genes but bad for the species as a whole. We see something similar in humans with people who suffer from Psychopathy, Anti-Social Personality Disorder, and Narcissism where the self is prioritized at the expense of the many.
Like the baby killing example. There is a drive in male members of some species of mammal to reduce breeding competition which leads them to be highly aggressive towards each other and even their own children. When they grow up they are only going to be more competition for food and mates anyway. Best to take them out now while they are weak. It spreads the genes that lead to that behavior preferentially.
Thus the benefit of polygamous relationships in communal groups. This study was specifically from a species of baboon but when a new alpha male emerges ALL of the pregnant females go into a pseudo ovulation and attempt to mate with him because the alpha male baboon does not tolerate offspring that are not his and will murder them. Due to the colossal investment made in producing offspring females do not want to have to miscarry or have their children murdered at birth so mating with the new alpha male while emitting ovulation hormones allows him to think the child might be his and so he doesn’t murder them. This exact activity is witnessed in humans as well.
Interesting Stuff.
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