The universe answers

Aaron's first lecture of the day is with Professor Hamilton herself. Aaron ambles into the lecture hall just in time, still reeling from the insanity of the things he's witnessed so far this morning.

"Today we're starting a new topic in the natural selection module of our course and that's 'Freak Mutations'. That's where a trait just suddenly vanishes from a species thanks to a very unlikely mutation in a gene, which proves so extremely beneficial, that within a few centuries, that mutated individual has become the new Most Recent Common Ancestor of the entire species. There are a few examples, but of course none are as self-evident and well-documented as the human intestines, rectum and anus.

"As you should all already know, around the time that homo sapiens first appeared, due to a Freak Mutation, we split off from all other mammals, developing a brand new way to process and excrete waste, and repurposing our backdoors for all the wonderful conveniences we use them for today. From having a handy internal pocket, to secreting a clever fluid that kills harmful pathogens and therefore cleans anything you put in it, it is clear that the anal passage, in combination with our larger brains, is what has allowed us to dominate the animal kingdom and become the Alpha species on this planet."

Aaron is dumbfounded. He's apparently slipped into an alternate dimension where buttholes serve a very different purpose. Is there any way this could just be an extremely impressively well organized practical joke?

In front of him, Rebecca Porter raises her butt off her seat, and with a quiet grunt, squeezes and entire apple out of her asshole, right in plain view of Aaron and several others. Without even turning round to see who saw this, she raises it to her mouth, and starts munching on it.

This is no practical joke.