Men’s testosterone levels are largely determined by their environment during childhood, according to new research. The Durham University-led study suggests that men who grow up in more challenging conditions where there are lots of infectious diseases, for example, are likely to have lower testosterone levels in later life than those who spend their childhood in healthier environments. The study, published in Nature Ecology and Evolution, challenges the theory that testosterone levels are controlled by genetics or race. As high testosterone levels potentially lead to an increased risk of prostate enlargement and…