An 18-year-old boy today is equivalent to a 22-year-old boy 200 years ago. Parents often have this feeling: today's children are becoming more and more precocious physiologically. Research on human medical records in the scientific community has long confirmed that the age of menarche in girls is getting earlier and earlier, but there has been a lack of comparable data on the age of sexual maturity in boys. A new study from Germany's Max Planck Institute for Demographic Research indirectly fills this gap.

Research has confirmed that since at least the mid-18th century, boys have reached sexual maturity an average of 2.5 months earlier every 10 years. Goldstein, director of the institute, said: "The physiological maturity level of an 18-year-old boy today is equivalent to that of a 22-year-old boy in 1800." Goldstein believes that the main reason why men and women mature earlier and earlier is that Continuous improvements in human nutritional status.