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Are we still evolving?


Flickr Creative Commons image.

For most of human history, being able to live long enough to reproduce was somewhat of a hassle. We had natural predators, diseases we could not treat, and hygiene that could have used some more work. The ones who would survive this war against nature would be able to pass down traits that allowed them to live. This is the idea of natural selection, where “nature rewards those who are better adapted to their environment with survival and reproductive success.”

Today we have safety, a much more profound knowledge of illnesses, and antibacterial soap. All of a sudden it’s as if Mother Nature threw her arms up in exasperation and stopped trying to change us. Yet, thanks to recent discoveries made about the human body and genome, it seems like the human species is continuing to evolve.

Every generation seems to think that they are better than the last, better educated, better looking, etc. So our brains must be getting bigger with each generation too, right? Wrong. The brain has actually been shrinking over the past 5,000 years. Based on skull measurements from archeological data from all over the world, brains have shrunk right around ten percent.

Some theories suggest that since we live in huge societies instead of close-knit hunter-gatherer communities, we rely more on other people than our own brains and can specialize more.Or maybe it is because our overall body mass has shrunk, and since a smaller body needs a smaller nervous system, our brains followed suit. Our bodies have become smaller since the Earth has warmed since the last ice age. Bulkier bodies fare better in cold conditions since they are able to conserve heat better. Perhaps thanks to all the books, computers, and memory storing inventions, we simply don’t need all that space anymore. Or are we going down the path of domesticated animals? Once taken out of the wild, their brains also shrink the more domesticated they are.

The pressures of nature to survive and hunt for food are gone, as is the extra brainpower. For example, our sense of smell is no longer selected for. Instead we use our intellect to know where food came from and can no longer tell as well as we could before if a certain food is good for us or not through smell. The only things those group of geneticists believe is being selected for is who is the most immune and most healthy.

Some of these evolutionary changes are a little less depressing, however. Take a look at this girl. There is something about her that is different than you.

Flickr Creative Commons image.
Flickr Creative Commons image.

She holds abilities you and I definitely do not have. This person is Andean, a descendent of colonizers who arrived to the New World 11,000 years ago. Those descendants live in the Andes at approximately 3,500-4,500 meters above sea level.

To show how tough that actually is, at 4,000 meter of elevation every breath you take contains about 60% of the oxygen at sea level. Normal lungs do not easily adapt to that level. Lungs like yours and mine, the lowlanders, would require  up to 20%-30% more oxygen, rather than just adapt to the lower oxygen levels and require less oxygen. Less oxygen in the air means that there is less oxygen in the bloodstream to make energy for our cells. So our heart rate and breathing rates speed up, making us need even more oxygen to supply that extra effort, but we don’t have enough oxygen so we speed up- you get the point. Yet studies have shown that Andeans take in the same amount of oxygen as lowlanders even at higher altitudes. How are their lungs better than ours at adapting to higher altitudes?

She holds abilities you and I definitely do not have. This person is Andean, a descendent of colonizers who arrived to the New World 11,000 years ago.

Turns out Andeans have a more efficient blood stream and more efficient lungs than we do. Andeans have more hemoglobin-containing red blood cells and unlike us, blood vessels in their lungs don’t shrink up when exposed to less oxygen in the atmosphere (hence why we need more oxygen at high altitudes). The reason why our blood vessels shrink up is to direct blood away from temporarily poorly oxygenated parts of the lung to better oxygenated parts.

A recent, incredible finding shows that people may be becoming less susceptible to HIV. In some parts of South Africa, half of women are infected with HIV, but studies have shown that some women with certain genes that deal with combating HIV could clear the HIV faster than those without those genes. Other examples of humans being able to fight against HIV are found in other parts of the world too. Thirteen percent of Europeans carry a variation that protects people almost completely from HIV, but is extremely rare among other populations around the world. People with those genes are able to survive and fight against HIV and pass down those traits to the next generation.

This selective force, HIV, is causing more and more people with those particular genes to appear each generation. Is this the start of humans evolving an immunity towards HIV? Scientists are still trying to figure that question out, but that very well could be early signs of evolution happening right before our eyes.

Flickr Creative Commons image.
Flickr Creative Commons image.

Truth be told, the most intense evolutionary changes the human species will go through will be in terms of immunities against diseases, bacteria, viruses, and parasites. We descend from ancestors that have survived a multitude of diseases more than anything. The Black Death killed up to 200 million people, and the Spanish Flu just 100 years ago killed 50 million. Perhaps in the future, humans will have immunities to diseases that we don’t have today, having been descended from those that survived the plagues or epidemics that haven’t happened yet.


About the Author

Ana Mandujano is an undergraduate student in the School of Public and International Affairs studying International Relations and pre-medicine. When she’s not studying for organic chemistry and strategic intelligence, she’s a Spanish interpreter for Mercy Clinic and ruining movies for everyone by pointing out historical inaccuracies. More from Ana Mandujano.

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