Word: sperms
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...that produce lots of good babies doesn't need any competition from other, lesser females setting up a nest nearby. Even the queen herself is not allowed to fool with the gene pool once it's been set. She mates only once in her life and stores all the sperm she'll ever need for the thousands of eggs she'll produce. (See pictures of the insect world...
Then again, the history of protected sex, in the broadest sense, used to be a whole lot yuckier. Take the practice of women in ancient Egypt who resorted to using crocodile dung as a spermicide. Modern research has shown that crocodile dung actually created optimum conditions for sperm because of its alkalinity, but the sheer grossness of the practice might have worked - if only by completely ruining the mood. (See pictures of animal attraction...
...chest, it was your wife's problem," says Barry Behr, an associate professor of obstetrics and gynecology at the Stanford Medical School and director of Stanford's in vitro fertilization laboratory. Even now, he said, though about half of infertility cases are caused by male factors, such as low sperm count or motility, there are many more tests to evaluate a woman's fertility than...
...contrast, men make new sperm about every 90 days, Behr says, so the logic has been that there should not be that much difference between a young man's sperm and an old man's. Indeed, men as old as 94 have been known to father children...
There are many possible explanations for the decline in male fertility, from a decrease in the number of sperm and their motility to lower testosterone levels to the effects of other age-related diseases like diabetes, which is associated with erectile dysfunction and lower levels of testosterone. But researchers think that genetic factors may be behind the link between paternal age and a child's risk of bipolar disorder and psychiatric disorders like autism and schizophrenia, whose origins are increasingly being attributed to DNA. Although sperm may be no more than 90 days old, the cells that make sperm...