#2. Pregnant Women Get Morning Sickness to Avoid Parasites
If there's one thing Cracked knows a lot about, it's pregnancy. And the first thing we'll tell you about pregnancy is that it's no walk in the park for people who enjoy digesting their food as God intended. For about 80 percent of pregnant women, however, the first three months of pregnancy are a vomitathon. Just full on all-throw-up, all the time. Some women don't even make it through the pregnancy without getting hospitalized for dehydration. Surely the act of ejecting the nourishment that keeps you and your baby alive is an evolutionary mistake, right?
"It was an unusual case of birth-by-mouth."
It Has to Be That Way Because:
The food available to prehistoric women wasn't going to include a prenatal vitamin, non-caffeinated chai with fresh fruit, yogurt and granola. Our great-to-the-power-of-a-thousand grandmothers got to choose from what was on the ground and in the trees -- berries, eggs, wild fruits and fetid animal carcasses.
Enter morning sickness. It turns out the foods that were most likely to carry parasites in our pre-cooking days are the exact same foods that often trigger morning sickness today: red meat, eggs, poultry and fish. In other words, the human body came up with a kickass adaptation to keep the human race going -- scare pregnant women away from dangerous foods by making them vomit at the smell of them. It's a particularly effective adaptation when you realize that nausea is usually strongest during the first few months of the pregnancy, when the fetus is at its most vulnerable.
"I'm fatally allergic to people pressing their face against my womb and cooing."
Women who live in societies that don't use a lot of animal products tend to not get morning sickness at all. Zero. It's not even a concept in their cultures. We don't have the names of those cultures handy, but we're going to guess they're pretty skinny.
#1. Our Spines Don't Heal Thanks to Our Big Brains
Christopher Reeve falls off a horse, and instantly he's paralyzed forever. When you see an athlete go down with a back injury, everybody in the stands holds their breath while the trainers strap the guy to a board, everyone praying that it's not the spine.
Broken bones? No problem. Punctured lung? It's bad, but it will heal. But not the spine. Once the spine is damaged, it's all over. But why?
It's certainly not like that for all creatures -- newts and baby opossums can rebuild their nervous systems with comparative ease. Hell, our lizard cousins voluntarily sever, then regrow, their spinal cords as part of an amazing screw-you escape mechanism.
And nature's most efficient weight loss method.
It's not like human nerves can't heal -- when nerves in the central nervous system are injured, they actually try to regrow right away. As far as they're concerned, all they need is a little chicken noodle soup and a hug and everything will be fine again. But the central nervous system won't let them. Our own bodies abort the regeneration, leaving us paralyzed.
OK, evolution better have a freaking good reason for this.
It Has to Be That Way Because:
The answer is that Mother Nature miraculously managed to cram 2.5 square feet of brain surface into our skulls without making us all look like Burton-inspired Martians. That structure, and the rest of the central nervous system, is unbelievably complex and unbelievably specific in its design. If your face gets damaged from a broken beer bottle and the skin cells don't grow back quite right, it just means you have a kickass scar. But if your central nervous system doesn't grow quite right, suddenly your limbs don't work. There is no margin for error.
This is not a kickass spine scar. This is the tragic image of a woman who can't lower her arms.
So, rather than risk these nerves going rogue and screwing up the whole system, the body just gives them one set of strict blueprints to follow, and if anything goes wrong with that plan (i.e., you fall off a motorcycle and sever your spine), then that's it. Like most of the parts in your laptop, it's just too complex to fix, and unfortunately we haven't figured out how to just do a warranty replacement.
That was the price to pay for having the kind of brain that lets us invent motorcycles in the first place. And also ways to let paralyzed people control shit with their minds.
"Eat shit, evolution!"
And check out why your body hates you in 5 Ways Your Brain Is Messing With Your Head and 6 Ways Your Body Loves to Screw You (Explained by Science).