Photograph of three male zebra finches (Taeniopygia castanotis). In this study, more than 4,000 human participants from around the world were presented with pairs of animal sounds from 16 different ...
In the animal kingdom, penises can be spiked, split, corkscrewed—even detachable. They're one of the most diverse structures in biology. The human penis is so uniform, it's an anatomical outlier.
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