About 40% of men with male infertility have a condition that does not fall neatly into any of the known causes. Many of these may be genetic but medical science has not yet worked out the genetic causes fully. In fact it is just scratching the surface. Some of these causes may be environmental yet science is still only beginning to understand the complexities of environmental toxins and their relationship to fertility not only in man but in other species as well. Effects on a fetus prior to birth that are not genetic may result in male infertility later in ways that scientists do not fully understand yet. Even if the causes remains a mystery, techniques currently available can still help these men father children in the majority of cases.