Human reproduction is based on the sexual union
of a man and a woman. Nonetheless, scientific research
on fertility (births), fecundity (the ability to give
birth) or contraception (birth control) is mainly devoted
to women and practically ignores men. Some studies
on male fecundity have been carried out, however.
These focus on the role of men in three aspects of human
fecundity: couple infertility, the question of a possible
male fecundity decrease with age and the
hypothesis that the fecundity of younger male generations
may be diminishing.