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  • Writer's pictureSinead Mackintosh

Human Genetic Adaptations

Since the human genome was first fully sequenced in the early 2000’s, scientists have been investigating what genes are particularly useful in our species. These genes have been selected for and are beneficial to the people or populations that have a valuable variation. In certain situations, having a particular variant (aka type) of a gene might be more useful and give that individual a competitive advantage over an individual who does not have a beneficial variant.

Examples of this include malaria resistance and lactose tolerance. Malaria is one of the oldest human diseases and still infects hundreds of millions of people and kills 1-2 million children in Africa annually. Therefore it is clear how malaria resistance would be a useful genetic trait to have. In the 1940s and 1950’s researchers, Haldane and Allison showed that the geographical distribution of sickle cell disease (see earlier post about SCD) is linked to malaria areas. This is because people who carry the sickle cell disease genes are resistant to malaria! Therefore it is beneficial to have the genes for sickle cell disease if it means that you are less likely to die of malaria. There is a price, though, sickle cell disease also affects millions of people in Africa and can be fatal.

Lactose tolerance is the ability to digest lactose (the sugar found in dairy products). It is present in young mammals but disappears typically in adults. But in some people, especially those of European descent, a mutation in the lactase gene (“LCT”) enables these individuals to digest lactose as adults. This mutation was useful when cattle were domesticated in Europe and produced nutritious, readily available milk. It is suggested that up to 80% of people with European ancestry have lactose tolerance.

These are just two examples of useful genetic adaptations in humans. Researchers are always investigating why certain traits vary between populations to shed light on human evolution’s past and possible future.

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