Mothers who consume excessive alcohol during pregnancy may have babies who are affected with a pattern of physical and mental disabilities known as fetal alcohol syndrome. Similarly, mothers who become addicted to drugs during pregnancy may have babies who show signs of addiction. Do these examples contradict the statement that traits acquired by the parents are not transmitted to the offspring?

Fetal alcohol syndrome and newborn addiction are developmental disorders that take place in the womb. Neither the mother's genes nor those of the offspring are changed by alcoholism or drug addiction, so the examples do not contradict the statement that traits acquired by the parents are not transmitted to the offspring. Properly understood, the principle is that traits acquired by the parents do not alter the parents' genes, and therefore do not affect the hereditary traits of the offspring.