Sex differences in human physiology
Female fertility declines after age 30 and ends with the menopause. Female physical experiences vary depending on external forces such as diet, marriage patterns, culture, and other aspects. In Western nations menstruation begins to affect females at 13 and menopause starts around 51. In non-industrialized countries, on the other hand, most females begin menstruation at a later age. More lactation in the lifetime of non-western females inhibits ovulation and extends the number of fertile years. Pregnancy in the 40s or later has been correlated with increased risk of Down syndrome in the children. Males are capable of fathering children into old age. Paternal age effects in the children include multiple sclerosis, autism, breast cancer and schizophrenia, as well as reduced intelligence. Adriana Iliescu was reported as the world's oldest woman to give birth, at age 66. Her record stood until Maria del Carmen Bousada de Lara gave birth to twin sons at Sant Pau Hospital in Barcelona, Spain on December 29, 2006, at the age of 67. In both cases IVF was used. The oldest known father was former Australian miner Les Colley, who fathered a child at age 93.
Yanomami
The start of "menstruation" symbolizes the beginning of womanhood. Girls typically start menstruation around the age of 12-15. Girls are often betrothed before menarche and the marriage may only be consummated once the girl starts menstruating, though the taboo is often violated and many girls become sexually active before then. The Yanomami word for menstruation ("roo") translates literally as "squatting" in English, as they use no pads or cloths to absorb the blood. Due to the belief that menstrual blood is poisonous and dangerous, girls are kept hidden away in a small tent-like structure constructed of a screen of leaves. A deep hole is built in the structure over which girls squat, to "rid themselves" of their blood. These structures are regarded as isolation screens.