President Yoweri Museveni of Uganda is about to sign into law a vehement anti-gay law after “medical experts presented a report that homosexuality is not genetic but a social behaviour,” according to a tweet from Ofwono Opondo, a Ugandan government spokesman. It is sad and ironic that Mr. Museveni will do so just as scientists at the annual meeting of the American Association for the Advancement of Science report that they have robustly confirmed my original finding of molecular linkage between male sexual orientation and a specific genetic region, Xq28.

Pres Museveni has told NRM MPs he will assent the Anti-Homosexuality Bill into law — Ofwono Opondo (@OfwonoOpondo) February 14, 2014

The President’s action, which would result in lifetime imprisonment for homosexual acts, is based on a report that was issued in the form of a press release with no supporting evidence, citations or analysis. I am writing to urge my fellow scientists at Makerere University, the Ministry of Health, and throughout Uganda to reconsider and issue a revised report. Here is my response to the 6 conclusions that my Ugandan colleagues enumerate in their study:

1. There is no definitive gene responsible for homosexuality.

The presence or lack of a single gene says nothing about the overall extent to which a trait is influenced by heredity. There is also “no definitive gene responsible for” skin color, height, handedness or many other innate human characteristics because these traits, like sexual orientation, are influenced by multiple genes acting in concert with one another. That doesn’t make the traits non-genetic, it just makes them complex.

In fact, twin and family studies indicate that genes are the major known factor responsible for individual sexual orientation in both males and females, accounting for 25 to 50 percent of the overall variation and 50 to 100 percent of the ascribable variation; the sources of the remaining variation are unknown, but are most likely to be biological and stochastic factors since they are not affected by rearing environment or social surroundings.

It is also known that at least part of this genetic variation is due to genes at Xq28, as well as on chromosome 8, as molecular linkages at both locations have now been replicated and confirmed. Again, this does not mean that there is a single “on-off” switch for being gay – any more than there is for being right or left handed – but simply that there are DNA sequences that contribute to the molecular and neurophysiological pathways involved in the development of sexual orientation.



2. Homosexuality is not a disease, but merely an abnormal behavior which may be learned through experiences in life.



There is no scientific evidence that homosexual orientation is a learned behavior any more than is heterosexual orientation. Indeed the absence of a significant shared environmental component in twin studies provided statistical evidence that this is not the case.

3. In every society, there is a small number of people with homosexuality tendencies.



This is correct, but it points to precisely the opposite overall conclusion of the report. Cross-cultural universality is an indication that a trait has origins that are shared by all humans, most likely genetic. Traits that differ from one culture to the next are more likely to be learned.

4. Homosexuality can be influenced by environmental factors, such as culture, religion and peer pressure among others.



Although sexual activity can clearly be influenced by environmental factors, including laws, the underlying orientation is immutable.

5. The practice needs regulation like any other human behavior especially to protect the vulnerable.



The most vulnerable are those who would be put into prison for the rest of their life for expressing their natural love for another person.

6. There is need for further studies to address sexuality in the African context.



Indeed. It is now well know that the push for Ugandan anti-homosexuality legislation was conceived of and lobbied for by right-wing, fundamentalist, anti-gay and anti-science religious groups from the United States. It is an important time for African scientists, and indeed scientists around the world, to stand up for a more rational and less biased view of human sexuality.

Dean Hamer is a Scientist Emeritus at the National Institutes of Health, and co-author of the New York Times book-of-the year The Science of Desire: The Search for the Gay Gene and the Biology of Behavior.