this was an interesting analogy about how vultures who are vultures and storks who look like vultures came to look and act so much alike:
What is perhaps most remarkable, however, is not that New and Old World vultures may not be related but that two possibly unrelated groups of birds have come to look so alike. They differ externally only in the longer and functional hind toe of the Old World vultures and the open nostrils (you can see right through from one side to the other) of the New World vultures.
This similarity is the result of a process called convergent evolution. It’s the selective pressures of the lifestyle that shape an animal, not the shape of an animal that dictates the lifestyle — given sufficient time, that is. So when different animal groups share the same ecological niche independently of one another there is a tendency for them to reinvent the wheel, finding the same solutions to the same challenges and ultimately coming to look very much alike.
Could this explain the similarities between narcissists and sociopaths too? Between borderlines and sociopaths? Could it be that sociopaths actually are on the autism spectrum but just look like vultures (personality disorders) because they've developed to react to different things?