Seems we all know people who are an asshole. Sometimes it's just the perfect way to describe someone. Today I will attempt to answer that question once and for all- using science, of course.
All animals, from the simple sponge to the worms, fishes, amphibians, reptiles, birds, Dino's, even mammals (and anyone else I forgot) start out as a single cell, formed by the union of an egg and sperm. Some can propagate, that is reproduce without sex cells,but that's a different post.
This single cell then goes through cell division, mitosis. These copied, identical cells stick together and form a hollow ball called a blastula. This is a critical time in development. See, the ball can only get so big before it falls apart. To prevent that, once side of the ball caves in, much like a deflated kickball. See the picture below, namely (H).
That blastophore is key to answering our question.
There are two types of animals: Protostomes and Deuterstomes. If you're an Protostome that blastophore turns into a mouth, a few types of worms do this. Most others, including us, are the latter, Deuterostomes. The blastophore in deuterostomes turns into an anus.
So there it is. All of us are born assholes.
So why is it that some of us have rectified our rectum-itis? Do we learn as children to get along with others? Do we learn to speak our mind without hurting those around us? Do we just grow out of it?
Or are we still assholes? Are we the norm? Are the people out there that we label as assholes just us, magnified times 100?
Are there people who really took the notion of "doing what you do best" just a little too far?
Is there a gene that superduperfies the asshole in all of us? Like is dwarfism- one set and you're a Little Person, two sets and you're fucked.
Maybe we're the mutants. Maybe there's a gene that minimizes our asshole-ed-ness to the point were that trait doesn't show up. Like albinism, perchance.
You have to admit though- there are some REAL ASSHOLES out there.