The age at which our hair begins to gray and our skin loses elasticity is related to our genetic background; balding is a trait passed to a boy by his maternal grandfather; and there are also some forms of age-related hearing loss, rheumatism, osteoporosis and heart disease which appear across family medical histories.
我們什麼時候開始頭髮變白、皮膚失去彈性，都可能與遺傳有關係；禿頭，就可能會從祖父一代遺傳到孫子身上；又如某些年老性失聰、風濕症、骨質疏鬆症和心臟病，也常常追蹤得出家族病史。