Evolution through natural selection in humans

Humans are evolving to improve fitness in ways that were not expected. With the help of genetic study, it is found that those genetic mutations that were harmful for Humans or that cause life shortness are being deleted via natural selection. In evolutionary terms, having a long life isn't as important as having a reproductively fruitful one, with many children who survive their adulthood and birth their offspring. So, harmful mutation that exert their effects after reproductive age could be expected to be 'neutral' in the eye of evolution, and not selected against. Studies shows that evolution is weeding out such mutations. It was also found that those people who live a long life, it is expected that certain groups of mutation which individually would not have a measurable effect but together accounted for health threats, were absent. Delay in puberty and childbearing was also found associated with those people who live a long life.