Genetic Mutations and Human Evolution
The Tibetan plateau is above 4,500 meters of sea level, with only 60% of the Oxygen found below. While the Visitors and new settlers struggle with altitude sickness, Indigenous Tibetans sprint on the mountains like it’s a normal playground. This ability to the native Tibetans does not come from training, or practice but from some genetic mutations in their body which makes the most of limited oxygen that happened through years. These differences are obvious from birth. On average, Tibetan children are more likely to be heavier or obese at birth. Oxygen saturation is already high, they are far more likely to survive than other children born in this same environment.
These genetic mutations are estimated to have evolved over the last 3,000 years or so and are ongoing. This might look like a long time but it is one of the fastest human evolution in the human population. Clearly, human evolution is not over. So, what are other recent changes? Will technological and scientific innovation affects human evolution? In the past few thousand years, many populations in different regions have evolved genetic mutations to their local environments.
People in Siberia and the upper Arctic are uniquely adapted to survive extreme cold. They are slower to get frostbite and can continue to use their hands in subzero temperatures much longer than most people. They have undergone selection for a higher metabolic rate that increases heat production in their body.
The Bajau people are Austronesian ethnic groups in Southeast Asia who can dive 70 meters and stay underwater for nearly a quarter-hour. They have been living as nomadic groups in the sea for thousands of years as hunters. They have oxygen storage as a part of their genetic mutation to assist them to stay longer underwater. Their spleens are genetically large. It is just like the transformation of deep-sea seals.
In comparison, it may seem very small but the ability to drink milk is another such modification. All mammals can drink breast milk as babies. After weaning, the gene that enables the digestion of milk is discontinued. But communities in Sub-Saharan Africa, the middle east, and northwest Europe that used cows for milk have seen a rapid increase in DNA variants that prevent the gene from switching off over the last 7 to 8000 years. Regular milk intake has given people a source of Calcium to aid in Vitamin D production as they moved north and sunlight, the usual source of Vitamin D decreased.
Modern medicine and the future of human evolution
Though not always in obvious ways, all of these changes improve people’s chances of surviving to reproductive age, it’s what drives natural selection. the force behind all these evolutionary changes. Modern medicine removes many of these selective pressures by keeping us alive when our genes, sometimes combined with infectious diseases, would have killed us.
Antibiotics, vaccines, clean water, and good sanitation all make differences between our genes less important. Similarly, our ability to cure childhood cancers, surgically extract inflamed appendixes and deliver babies whose mothers have life-threatening pregnancy-specific conditions, all tend to stop selection by allowing more people to survive to reproductive age.
But even if everyone on earth has access to modern medicine, it does not indicate the end of human evolution. That is because there are other aspects of evolution besides natural selection. Modern medicine makes a genetic variation that would have been subject to natural selection, subject to what’s called genetic drift instead. With the genetic drift, genetic differences vary randomly within a population. On a genetic level, modern medicine might actually increase variety, because potentially dangerous mutations were not eliminated because they did not kill people.
This variation does not necessarily translate to observable, or phenotypic, differences among people, however. Researchers have also been investigating whether genetic adaptations to a specific environment could appear very quickly through epigenetic modification: changes not to genes themselves, but to whether and when certain genes are expressed. These changes can happen during a lifetime, and may even be passed to offspring.
But so far researchers are conflicted over whether epigenetic modifications can really persist over many generations and lead to lasting changes in populations. There may also be other contributors to human evolution. Modern medicine and technology are very new, even compared to the quickest, most recent changes by natural selection. So only time can tell how our present will shape our future.
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