A new paper poses new hypothesis of why some species of male hermit crabs evolved substantially longer penises, it was so they could mate without having to venture too far outside their shells. This would prevent a rival stealing the shell since they did not have to leave the shell to mate.

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A new paper poses new hypothesis of why some species of male hermit crabs evolved substantially longer penises, it was so they could mate without having to venture too far outside their shells. This would prevent a rival stealing the shell since they did not have to leave the shell to mate.