Top 7 surprising examples of recent human evolution

When we were in school, learning about evolution felt old and slow. But evolution is still happening and it is happening to us.

Right here, right now.

It's too early to tell what humans will look like in a few thousand years, but for now we can assemble some of the most recent quirks - and even superpowers - that have happened to humans thanks to into the power of selection.

1. Adults drink milk

Drinking milk is one of the hallmarks of mammals, but humans are the only species on Earth that can digest milk after preschool age, although today, more than 75% of the world's population still does not tolerate it. lactose loading.

Humans are the only species on Earth that can digest milk after preschool age.

After weaning, all other mammals, and most humans, stop producing lactase, the enzyme needed to break down lactose, the milk sugar.

But a mutation that appeared on the plains of Hungary about 7,500 years ago has allowed some people to digest milk as adults. We may have already started consuming cheese - cheddar and feta contain less lactose than milk and softer cheeses, and Parmesan is virtually lactose-free.

This may seem nutritionally implausible (despite being delicious), but the ability to digest high-calorie dairy products is incredibly useful for humans needing to survive the frigid European winters.

2. Disease resistance

Evolution is about the survival of the fittest - and an important part of evolutionary fitness is not dying of disease before perpetuating the species. It makes sense that evolution would give us a boost against some common diseases.

The most studied disease that we have come across recently is malaria. If you've taken an introductory biology course, you may remember the uncanny connection to sickle cell anemia. That's because having a specific gene, if you have one, protects your red blood cells from being invaded by the malaria parasite - but two copies will distort the red blood cells and block the way. their passage through blood vessels.

But that's not the only trick developed in the face of malaria. There are also more than a hundred different genes that cause a deficiency in a protein involved in breaking down red blood cells. That makes it harder for the malaria parasite to get into the red blood cells. Another recently circulating mutation prevents the malaria parasite from attaching to the placenta.

And it's not just malaria - evolution has helped spread protective adaptations against leprosy, tuberculosis and cholera in certain populations. Some scientists have suggested that living in cities helps with this process.

3. Green eyes

Blue eyes are another recently developed trait, and scientists have identified it as coming from a mutation in a single ancestor 6,000-10,000 years ago.

The mutation affects the OCA2 gene, which encodes a protein needed to produce melanin, which gives our skin, hair, and eyes their color. This essentially "turned off" the ability to have brown eyes by limiting the melanin produced in the iris, and "diluted" the eye color from brown to blue.

Having brighter eyes does not confer a specific survival advantage on anyone, but because the blue-eyed gene functions similarly to the recessive trait (albeit a bit more complicatedly), blue-eyed fathers have can be more assured that their child is in fact their own.

4. Breathe at altitude

Tibetans have a genetic predisposition to make more of the oxygen-carrying protein hemoglobin.

Tibetans live in one of the least hospitable places: the Himalayas. Their ability to handle low oxygen levels up there isn't due to mere hard work - it's coded into their genes.

One study compared indigenous Tibetans, who live above 3,000 meters in the Himalayan highlands, with Han Chinese from Beijing, who are genetically related but live in around sea level.

The researchers found that Tibetan blood has a genetic predisposition to make more of the oxygen-carrying protein hemoglobin. When this mutation occurred is still debated, but some geneticists have estimated it to have happened as recently as 3,000 years ago (although it's not surprising that archaeologists push back that date is much further away).

5. Lost wisdom teeth

It's not just oral surgeons that have removed wisdom teeth (third molars) from the human mouth - evolution also plays a role.

On our evolutionary path to becoming humans, our large brains packed our skulls and narrowed our jaws, making it harder for the third row of molars to emerge from our gums.

And after we started cooking and farming thousands of years ago, our diets became lighter. The switch to soft and starchy grains requires less chewing than the hunter-gatherer diet of the past. This means the jaw muscles aren't as strong as they used to be, keeping wisdom teeth underneath the gums increasing the risk of a painful and deadly infection.

Keeping wisdom teeth below the gums increases the risk of painful and deadly infections

Several thousand years ago, a mutation appeared that prevented wisdom teeth from erupting. Currently, one in four people is missing at least one wisdom tooth. The people most likely to be missing at least one wisdom tooth are the Inuit of the northernmost regions of Greenland, Canada and Alaska.

6. Blushing when drinking alcohol

The rambunctious reaction isn't just a fact, it's also a recently developed trait that could protect East Asians from deadly cancer.

In about 36% of East Asians (China, Japan, and Korea), flushing and nausea occurs when drinking alcohol. This is due to a deficiency in an enzyme known as ALDH2.

While this can pose some social challenges in the context of more heavily alcoholic colleagues, it is an important sign of a serious health risk. People with an ALDH2 deficiency are also at increased risk of developing esophageal cancer from drinking alcohol.

Curiously, scientists believe this mutation occurred after the development of agriculture, and winemaking.

7. Brain shrinks

We overestimate our brains, but it turns out that it has shrunk over the past 20,000 years. The change in adult males is calculated to be the size of a tennis ball. But scientists don't think that means we're any less intelligent.

One theory is that each of us relies more on the structure of society to help us overcome any obstacles in life so we don't need as much brain space as our ancestors did. When we domesticate animals like dogs and cats, their brains also shrink. Some scientists suggest that smaller brains may actually prove more peaceful, gentle animals.