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When we learn about evolution in school, it feels old and slow. (Charles Darwin's impressive beard later in life probably doesn't help here.)
But evolution is very much still happening today — and it's happening to us.
Right here, right now.
It's too soon to say what humans will look like a few thousand years from now, but here are some of the most recent quirks — and even superpowers — we've acquired thanks to the power of selection.
Drinking milk is one of the defining traits of mammals, but humans are the only species on Earth to digest it after infancy, though even now, more than 75% of the world's population is still lactose intolerant.
After weaning, all other mammals, and most humans, cease producing lactase, the enzyme necessary to break down lactose, milk sugar.
But a mutation that appeared on the plains of Hungary about 7,500 years ago allowed some humans to digest milk into adulthood. We probably started with cheeses — cheddar and feta contain less lactose than fresh milk and softer cheeses, and Parmesan contains almost no lactose.
This may seem nutritionally inconsequential (though delicious) now, but the ability to digest incredibly calorie-dense dairy products was incredibly useful for humans surviving the cold winters of Europe.
Evolution is about the survival of the fittest — and a big part of evolutionary fitness is not dying from a disease before you've had children. So it makes sense that evolution would be giving us a boost against some common diseases.
The most-studied disease we've been outrunning lately is malaria. If you've taken an introductory biology course lately, you may remember a strange connection withsickle-cell anemia. That's because there's a specific gene that, if you have one copy, will protect your red blood cells from invasion by the malaria parasite — but two copies will distort red blood cells and block their passage through blood vessels.
But that isn't the only trick that's evolved in the face of malaria. There are also more than a hundred slightly different genes that cause a shortage of a protein involved in breaking down red blood cells. That makes it harder for the malaria parasite to sneak into a red blood cell.Another type of mutation that's been spreading lately blocks malaria parasites from hanging out in the placenta.
And it's not just malaria — evolution has helped spread adaptations that protect against leprosy, tuberculosis, and cholera in certain populations as well. Some scientists have suggested that living in cities helps this process along.
3. Blue eyes
Blue eyes are another recent-evolved trait and scientists have determined it came from a mutation in a single ancestor 6,000-10,000 years ago.
The mutation affected the OCA2 gene, which codes the protein necessary for producing melanin, which gives our skin, hair and eyes their color. This essentially "switched off" the ability to have brown eyes by limiting the melanin produced in the iris, and "diluting" the eye color from brown to blue.
Having lighter eyes didn't give anyone a particular survival advantage, but because the gene for blue eyes operates similarly to a recessive trait (though it's a little more complicated), blue-eyed fathers could better guarantee that their children were, in fact, their own.
Tibetans live in one of the least hospitable, and therefore one of the last populated areas on the planet: the Himalayan mountains. And their ability to handle the low-oxygen levels up there is not due to mere hardiness — it's coded into their genes.
One study compared indigenous Tibetans, who live at altitudes above 10,000 feet in the Himalayan highlands, with Han Chinese from Beijing, who are closely related genetically but live right around sea level elevation.
The researchers found that the Tibetans' blood was genetically predisposed to produce more of the oxygen-transporting hemoglobin protein. Still up for debate is when this mutation occurred, but some geneticists have estimated it happening as recently as 3,000 years ago(though unsurprisingly, archaeologists push that date much further back).
It's not just oral surgeons who are removing wisdom teeth (third molars) from human mouths — evolution is playing a part too.
On our evolutionary road to becoming humans, our big brains crowded our skulls and narrowed our jaws, making it difficult for the third row of molars to emerge from the gums.
And after we began cooking our food and developed agriculture thousands of years ago, our diet became softer. This switch to soft grains and starches required less strenuous chewing than our past hunter-gatherer diet. This meant our jaw muscles didn't grow as strong as they used to, keeping the wisdom teeth beneath the gums increasing the risk of painful and deadly infection.
A few thousand years ago, a mutation popped up that prevented wisdom teeth from growing at all. Now one in four people are missing at least one wisdom tooth. The people who are most likely to be missing at least one wisdom tooth are the Inuit of the northernmost regions of Greenland, Canada, and Alaska.
Alcohol flush reaction, also known as the "Asian glow," is not only a real thing, it's also a recently evolved trait that may protect East Asian populations from a deadly cancer.
In about 36% of East Asians (Chinese, Japanese, and Koreans), drinking alcohol causes facial flushing and nausea. This is due to a deficiency in the enzyme known as ALDH2.
While this may cause some social challenges amidst peers of more heavy-drinking ancestries, it's an important indicator of a serious health risk. People with an ALDH2 deficiency are also at greater risk of developing esophageal cancer from drinking alcohol.
Curiously, scientists believe this mutation occurred after the development of agriculture — which made producing alcohol possible.
We think pretty highly of our brains, but it turns out they've actually been shrinking for more than 20,000 years. The total change adds up to a piece the size of a tennis ball in an adult male. But scientists don't think that means we're getting dumber.
One theory is that each of us relies more on the structure of society to help us get by, so we don't need as much brain space as individuals. But as we've domesticated animals like cats and dogs, we've watched their brains shrink too. That means some scientists think smaller brains may actually mark more peaceful animals.
