Incidence of chlamydia, a major cause of infertility. The high polygyny rate among the “female farming� peoples of sub-Saharan Africa may have favored the evolution of STDs. Is this where we should look for the precursor of the hypothetical “gay germ�? (source) Heritability for male homosexuality is low to moderate (30 to 45%). There is... Read More

U.S. General Social Survey (analysis by Jason Malloy), - only groups of 40 or more individuals included - homosexual category includes bisexuals Jason Malloy has looked into the U.S. General Social Survey for rates of homosexuality by national origin and by gender. Not surprisingly, he found that different national origins have different rates of homosexuality,... Read More

What causes exclusive male homosexuality? This is the question I’ve addressed in the last few posts. The answer is still elusive although there seems to be consensus on some points. One such point is the relative importance of inborn causation versus environmental causation. In men, an exclusively homosexual orientation has a heritability of 30-45%. A... Read More

Steve Sailer has entered this debate with a post on the chimerism theory, i.e., the idea that male homosexuality arises when a male fetus absorbs cells from a female twin that has died during early fetal development. Chimerism appears to be more widespread than previously thought, but its actual incidence remains unknown (also see this... Read More

In a previous post, I suggested that something in the environment had begun to alter male sexual development in Western countries by the turn of the 20th century. Among a small minority of men, probably those already weakly predisposed to heterosexuality, the result was a shift to exclusive male homosexuality, i.e., development of a female-like... Read More

In my last post, I argued that large quantities of estrogen were flushed into lakes and rivers across North America and northern Europe between the introduction of modern sewer systems in the late 19th century and the shift to secondary and tertiary sewage treatment after the 1960s. By separating out solid fecal waste and rapidly... Read More

What is the main source of estrogen in the environment? Birth control pills? An industrial compound with estrogenic properties, like DDT, PCBs, and dioxins? No, it’s women’s urine. The stuff that gets flushed down toilets millions of times a day. There is also testosterone in wastewater but at much lower levels, being less water?soluble (Tabak... Read More

One point is often raised about male homosexuality: it has always been with us. True, but has it ever changed in its nature or prevalence? Well, more gays have been ‘coming out of the closet.’ People are practicing openly what used to be done in secret. But have there also been more fundamental changes? Such... Read More

Are there other theories on the origins of male homosexuality? Yes, quite a few. These theories generally fall into two categories: those that explain the relatively small variance due to genetic factors (30-45%) and those that explain the larger variance due to some environmental factor. Conceivably, we could be looking at an interaction between the... Read More