Human natural selection adding to 'nearsightedness epidemic'

Natural selection among humans is adding to the'epidemic' of nearsightedness, with each successive generation in the UK gaining more than 100,000 extra cases. It is estimated that around half of the world's population -- some 4.9 billion people -- will suffer from the distant visual impairment by the middle of the century. Much of the problem is environmental -- with increased screen time and not enough spent outdoors using our long-distance vision often blamed. However, US experts have found that many of the genetic variants that increase the risk of nearsightedness, or myopia, are also associated with reproductive benefits. Thus, those with these genes are likely to have more children, and from a younger age, increasing the relative prevalence of myopia-causing genes in the population.