Human evolution behaves like our bio-rhythm, sometimes slower, sometimes faster. Where influences play an important role. For example, using smartphones slows down the brain's learning process because less logical thinking is needed.
|Is human evolution speeding up or slowing down.|
At 4,500 meters above sea level, the Tibetan plateau contains only 60% of the flat land's oxygen.
While tourists and new settlers suffer from altitude sickness, Tibetans can climb the mountains with ease.
This is not due to training and practice, but to genetic differences that allow them to make the most of their limited oxygen.
These changes begin at birth. Children of local ancestry live longer, on average, and have higher oxygen saturation levels and are more likely to survive than other locally born children.
These genetic changes are estimated to have begun 3,000 years ago and are still evolving today.
Three thousand years may sound like a long time, but it is the fastest time for human adaptation.
Human evolution is unstoppable - so what are the recent changes? Does technological development affect the process of human evolution? Over the last few thousand years, many human groups have evolved genes adapted to their local environment.
Siberians and Arctic people, for example, can live in extreme cold.
They are less prone to frostbite than ordinary people and can work with their hands for long periods in sub-zero temperatures.
They have a higher metabolic rate and produce more heat to survive natural selection.
Down south, the Bajou people of Southeast Asia can dive to a depth of 70 meters and stay underwater for 15 minutes.
As "nomadic" people who have lived in the sea for thousands of years, the Baju was born with a large spleen that stores oxygen, allowing them to stay underwater longer, much like the genetic adaptation of seals.
Another adaptation, though more mundane than the one just mentioned, is to drink milk.
They have turned off their genes to digest milk.
In sub-Saharan Africa, the Middle East, and northwestern Europe, there has been an explosion of mutations in the DNA of milk-drinking cows, and for the last 7,000 or 8,000 years, the genes that digest milk have been switched off.
In Europe, people have to drink milk to absorb calcium, but they have less sunlight to provide vitamin D as they move northward.
These changes have improved survival rates to childbearing age, although not always in an obvious way.
Modern medicine has solved many of these selection pressures, for example, by protecting our genes from deadly infections.
Thanks to antibiotics, vaccines, clean water, and adequate sanitation, our genetic differences have become less critical.
Under the same circumstances, curing childhood cancers, performing appendectomies, and giving birth to babies when their lives are in danger are all prevented by natural selection by keeping people alive and healthy until they reach childbearing age.
Even if modern medicine were to be available to everyone on the planet, that would not be the end of human evolution.
This is because there are other factors in evolution besides natural selection.
Modern medicine has changed genetic variation from being the subject of natural selection to being the subject of genetic drift.
Genetic drift allows genetic differences within a population to vary randomly.
Genetically speaking, modern medicine increases genetic diversity because harmful mutations are no longer lethal and persist.
These mutations do not necessarily result in observable phenotypic differences.
Researchers are studying if rapid genetic adaptations in a given environment are associated with epigenetic changes. These changes depend on when and how genes are expressed.
Changes in genetic adaptations can last a lifetime and may be passed onto future generations.
So far, researchers have debated whether changes due to epigenetic modifications can be passed down through multiple generations and have long-lasting effects on populations.
Other factors may have influenced human evolution.
Even though modern medical technology is relatively short-lived compared to the latest and fastest changes brought about by natural selection, only time will tell how current changes will affect the future.