When did humans stop evolving?
Answers
Answer:
When did humans stop involving then that humans have seen their end...
Explanation:
The basic rationale behind the conclusion that human evolution has stopped is that once the human lineage had achieved a sufficiently large brain and had developed a sufficiently sophisticated culture (sometime around 40,000–50,000 years ago according to Gould, but more commonly placed at 10,000 years ago with the development of agriculture), cultural evolution supplanted biological evolution. However, many evolutionary biologists have not accepted this argument, and indeed some have come to exactly the opposite conclusion. For example, Cochran and Harpending2 argue that “human evolution has accelerated in the past 10,000 years, rather than slowing or stopping, and is now happening about 100 times faster than its long-term average over the 6 million years of our existence.”
The answer to the question of whether or not human evolution has stopped has medical implications. To those who advocate that human evolution has stopped, modern medicine is just one more example of cultural evolution supplanting biological evolution. For example, advocates of human evolution having stopped believe that we no longer adapt to infectious diseases through natural selection; rather, we adapt culturally through the development of vaccines, antibiotics, and public health policies. Under this view, the common systemic diseases that we suffer from, such as type II diabetes, heart disease, etc., arise from our biological adaptations to a pre-agricultural environment that have persisted into the present because human evolution has stopped. Indeed, Armelagos3 has argued that human health has actually declined in many ways since the development of agriculture because we are stuck in bodies that are biologically adapted to a Stone Age environment.
In this review, I will argue that human evolution has not stopped, and our ongoing evolution has many medical and health implications. The rationale for the cessation of human evolution has three fundamental flaws. First, it is based on the premise that cultural evolution eliminates adaptive evolution via natural selection. However, all organisms adapt to their environment, and in humans much of our environment is defined by our culture. Hence, cultural change can actually spur on adaptive evolution in humans. The second flaw in the argument is the false premise that evolution is the same as adaptive evolution. Evolution is a change in the type or frequencies of genes or gene combinations in the gene pool over time, with the gene pool being the set of genes that are collectively shared by a reproducing population.4 Natural selection is a powerful mechanism for altering the frequencies of genes in the gene pool, but patterns of dispersal, system of mating, population size, and other factors can also cause alterations in the gene pool. Evolutionary change is determined not by one evolutionary mechanism operating in isolation, but rather by the several mechanisms interacting in concert.4 Human culture has dramatically changed the relative strengths of these other evolutionary mechanisms, once again spurring on much recent and ongoing human evolution. Third, traits are developmentally correlated, so that even a neutral trait can evolve due to selection on another trait. Hence, when cultural innovations weaken or eliminate natural selection on a trait, this alters the balance of evolutionary forces in a manner that induces further, albeit non-adaptive, evolutionary change in the neutral trait.