Their size is inversely proportional, and related to the sexual promiscuity of the female. Female monogamy correlates with a large brain for the male, which is the opposite of what the scientists predicted. Is it more interesting that the big-brained bat-male's sexual partner is monogamous or that a bunch of scientists speculated that promiscuity would evolve along with bigger brains? I'm more interested in human behavior, so I tend to focus on the scientists, guys who are probably proud of their big brains, and I can't help speculating that they are attracted the idea that women at their evolutionary level will be promiscuous.
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