Sometimes a good idea just keeps getting rediscovered. The eye has evolved many times independently, and parasitism has evolved for no less than 60 times. This is called convergent evolution. And of course, it has its evil twin... divergent evolution.
Consider this picture below, of the complex shapes of closely related species of Bombus (bumblebees). These species are so similar that the main way to distinguish them is by looking at their penises...
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| Source: The Evolution of Primary Sexual Characters in Animals, Figure 4.1 |
