In the US, up to 20% of infertile couples have unexplained infertility. It also allows females to avoid mating with infertile males. The infertile eggs become male honey bees. They appear to be intolerant only of very infertile and acidic soils. Women with Turner syndrome are almost universally infertile. He even claims that whoever cannot make babies is a male, including infertile women. Many people of sub-Saharan Africa choose to foster their children to infertile women. They also have responsibilities for eating fungi-infected or infertile eggs, and fanning the eggs. Many species of plants have mycorrhizae to assist with nutrient uptake in infertile conditions. The region as a whole is noted for its sandy, infertile, and poorly drained soils. The soils of this area are quite infertile. It is seldom found on dry, compact, or infertile soils. The family is largely composed of plants that can tolerate acidic, infertile conditions. This causes them to become infertile or even die. Smokers are 60% more likely to be infertile than non-smokers.