The lactase mutation, which allows the digestion of milk to keep into adulthood, appeared in approximately 90 % of Europeans. ‘Presumably,’ Pritchard said, ‘a few thousand years from now, if selection pressure continues to be the same, everyone shall possess [the selected mutation].’ Classifying all of the genes by their biological features, the researchers listed the top 16 categories that experienced the strongest indicators, including olfaction , reproduction-related processes and carbohydrate rate of metabolism, which includes the lactase gene. Other processes that show signals of selection consist of genes related to metabolism of international compounds, brain development and morphology.Research is not well funded on the impact of recreational medicines on fertility, but common medicines like cannabis and cocaine do influence hormones negatively, capability of sperm to visit through the oviduct, and male production of sperm. Cannabis provides been shown to disrupt the advancement of the mind and nervous system, predisposing the baby to neuropsychiatric illness in life later. Avoiding all pharmaceutical and recreational medicines allows the body to keep optimal hormone amounts and foster a strong reproductive system, thereby supporting fertility. Exposure to toxins in the home and work environments Polluting of the environment, cleaning supplies, pesticides, personal care products, exposure to heavy metals, plastic elements such as BPA and phthalates, and Teflon-coated cookware, can be contributing factors to infertility.