Merely 50% of German infants born in the nineteenth century ever reached the age of five, as opposed to 99.6% in 2020. Does this mean natural selection of humans is coming to an end, or are humans still evolving?
Around ten to twelve million years ago, the primate lineage split. These two lineages evolved separately to become the variety of primates today.
Members of the first group were the early version of what we know today as gorillas, chimpanzees, and bonobos, and orangutans. This group, which moves around on four legs, mostly remained in forests, inhabiting treetops. Members of the second group, however, transformed in an “unusual” way. Unlike members of the first group, members of the second group evolved into primates that inhabit the land, walk on two legs, and possess brains multiplied in size. This second group is the group that, through evolution, gave rise to modern humans.
Weakening Natural Selection
In recent history, Humans, unlike other species, interrupted the natural selection, which is one of the main pillars of evolution.
Today, the death of a child of an infection or a disease is a rarity in industrialized countries. However, this was not always the case. For instance, in 1870s Germany only about 50% of live-born infants reached even the age of five. This rate is 97.3% for 1970, and 99.6% for 2020. Figures may be different, but this trend is the same anywhere else in the world too. Does this mean human evolution is coming to an end?
Are Humans Still Evolving?
Although natural selection is a crucial factor in evolution it is not the only one. Therefore, although humans are having far less offspring, and natural selection becomes less and less relevant for humans, mutation and genetic drift are still at work.
Firstly, human reproduction cells, namely, eggs and sperms, inevitably mutate over time. In most cases, these mutations have a negative impact on the offspring, but in some other cases, it results in trait variations. In other words, the mutation will cause a new trait that didn’t exist before.
Secondly, the human gene pool is affected by some external factors such as a random change in the frequency of a gene in offspring, a devastating natural or human-made disaster that wipes out a considerable number of people, a political decision that affect human reproduction.
Changes caused by random mutations in reproductive cells and severe events that indiscriminately kill a considerable number of local populations, and in combination with rare occurrences of natural selection will continue to result in the evolution of humans. Yes, humans are still evolving and will continue to evolve in a world where nearly all of us are fit to survive.