For men, fertility is in healthy cases an ever-present condition, from puberty on. Even though studies have shown that men who parent a child after crossing the age of 50 run a higher risk of having offspring with mental illness, many men do so, well into their sixties. For women, the partial monthly cycle of fertility gradually slows down and ends during menopause, which usually is completed by their early fifties.
A recent study by researchers at the University of Miami has found that women, when they are at their most fertile points during any given month, tend to stay away from male relatives so as to avoid any evolutionary hint of inbreeding. The behavior has long been observed among other animal species, and when the cell phone records of four dozen participating women were analyzed retroactively, they revealed the same pattern of behavior. Women were 50% less likely to call their dads during high fertility days.
Optimum Fertility Ages
Meanwhile, the constant coverage in the media of older women having babies is creating a distorted view of the normal female fertility cycle. At age 25, women have already lost 80% of the eggs they were born with. By 35, that figure has reached 35%. Several hundred Canadian women were surveyed about their knowledge of their own fertility, with data confirming that they were under a generally false impression of their potency in later years. Few seemed to realize that by 30 years, the monthly likely success rate of pregnancy was 22% and would drop to 18% by age 35 and 5% by age 40.
Overall, the tipping point in terms of fertility for women is 35, while for men it is the age of 40. First-born children of older mothers also were found to face more health risks.
vvvvv PBS.org – Fertility Through Life, Retrieved December 1, 2010 from http://www.pbs.org/wgbh/nova/baby/fert_text.html
Daily Mail – “Women ‘Avoid Their Fathers When They Are At Their Most Fertile to Reduce the Risk of InBreeding'”, December 1, 2010, Retrieved December 1, 2010 from http://www.dailymail.co.uk/sciencetech/article-1334631/Women-avoid-fathers-fertile.html
Vancouver Sun – “Women Reach Best Before Date at 35″, November 29, 2010, Retrieved December 1, 2010 from http://www.vancouversun.com/health/Women+reach+best+before+date/3898874/story.html