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Human evolution can seem like a phenomenon of the distant past which applies only to our ancestors living millions of years ago. But human evolution is ongoing. To evolve simply means that mutations – the accidental changes to genes that happen normally in the process of copying DNA – are becoming more or less common in the population over time.
These changes can happen by chance, because the individuals who reproduced happened to carry a particular mutation somewhat more often than individuals who didn’t have children. They can also happen because of natural selection, when carriers of a specific mutation are better able to survive, reproduce or tend to their family members – and therefore leave more descendants. Every biological adaptation, from the ability of humans to walk upright on two feet to flight in birds, ultimately traces back to natural selection acting on these minute changes, generation after generation.
Humans - Question - Individuals - Mutations - Descendants
So humans are definitely still evolving. The question is whether we are still adapting: Are individuals who carry harmful mutations living less long, reproducing less – ultimately leaving fewer descendants? For instance, terrible eyesight may have been a major survival disadvantage living on the savanna, but with glasses and laser surgery, it’s unlikely to prevent people from living a long life today. How commonly then are mutations under selection in contemporary humans?
Because adaptations involve tiny changes in the frequencies of mutations from generation to generation and their fortune plays out over tens to hundreds of thousands of years, they are incredibly hard to study directly – at least in long-lived organisms such as people.
Evidence - Evolution - Footprints - Adaptation - Genome
So while there is overwhelming evidence for human evolution and unequivocal footprints of adaptation in the genome, rarely have scientists been able to directly observe natural selection operating in people. As a result, biologists still understand very little about...
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