Uganda’s Anti-Gay Law: The Missing Science

Ugandan reads Red Pepper.jpg

Rebecca Vassie/AP Photo

People reading a list of alleged gays in Red Pepper, Kampala, Uganda, February 25, 2014

After Uganda’s Parliament passed a harsh anti-homosexuality bill in December, increasing numbers of gays in the capital Kampala said they were being evicted from their houses and taunted and threatened by their neighbors. Western leaders, who give Uganda some $1 billion in foreign aid annually, warned President Yoweri Museveni that if he approved the legislation–which punishes “aggravated homosexuality” with a life sentence—it would greatly complicate diplomatic relations. But this week, Museveni signed the bill anyway.

Museveni’s considerations were clearly political. Now in his twenty-eighth year in office, his popular support is plummeting and conservative Christians are among his few remaining allies. His government is wracked with corruption and he himself has recently been accused of stealing $5 million per month from the national workers’ pension fund; his henchmen have harassed and possibly murdered rival politicians; his troops are involved in bloody conflicts in several neighboring countries, including South Sudan, which could explode into a regional conflict, and there is widespread discontent even within his own political party.

At times like this, a dictator’s thoughts often turn to the moral behavior of others. During a similar period of turmoil in the 1970s, then President Idi Amin banned mini-skirts—meaning skirts that don’t cover the knees, even when a woman bends over. Any woman found wearing such a skirt would be forced to eat it, Amin announced. (It’s not known if anyone was ever subjected to this punishment.) The decree was annulled when Amin was overthrown, but Museveni recently pulled it off the shelf. It easily passed in Parliament, which Museveni largely controls, and he has signed it into law once again. Activists in Uganda say that since the law came into effect, some women have been stripped on the streets for wearing clothes considered revealing by their attackers.

Although Museveni pretended to hesitate over the anti-gay bill, behind the scenes, he has long supported Uganda’s anti-gay movement. In November 2013, before the bill was even put to a parliamentary vote, he secretly gave a group of pastors $500,000 to mobilize anti-gay sentiment around the country through their congregations and on local radio stations. Uganda’s largely illiterate population, convinced that gay recruiters were out to sodomize their children, were overjoyed when Parliament passed the bill, and they are celebrating again now that the president has signed it into law.

In fact, the bill has also given Museveni a new political weapon. The day after he signed it, hundreds of alleged gays were outed in the pages of Red Pepper, a tabloid scandal sheet whose major shareholder is Museveni’s half-brother. Many of those accused are no doubt government critics and opposition supporters. They now could face life in prison.

Museveni claims that he decided to sign the bill into law because he concluded there is no scientific evidence that homosexuality is determined by a person’s genes, and is therefore “deviant” behavior. Psychiatrists at the American Psychiatric Association, citing studies showing that identical twins are more likely to share a homosexual identity than fraternal ones are, maintained that sexual preference is partly genetic. But a team of Ugandan doctors assembled by the Health Ministry argued that since homosexuals tend to produce few if any offspring, a “gay” gene could never be maintained in human populations, so being gay must be voluntary. Museveni sided with Uganda’s government-convened doctors. “There is no scientific proof yet that people are homosexuals by genetics,” Museveni said in an official statement before he signed the bill into law. “It is on the strength of that I am going to sign the bill.”

Gays are “disgusting,” Museveni told a CNN reporter. “But I was willing to ignore that if there was proof that that’s how they’re born…but now, the proof is not there!”

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Rebecca Vassie/AP Photo

President Yoweri Museveni after signing the anti-gay bill, Entebbe, Uganda, February 24, 2014

I’ve been working in Uganda on and off for twenty years and have friends in Ugandan politics. A few weeks after the bill passed parliament in December, I received an email from an MP I know asking for scientific evidence that homosexuality was genetic. He was involved in the debates over the bill and wanted to counter the president’s supposed scientific reasoning that homosexuality was some sort of deviant choice. We both knew that Museveni’s considerations weren’t guided by science and that any rational argument would fall on deaf ears; we also both knew that it doesn’t make any difference whether homosexuality is genetic or not. Consenting adults should be allowed to do what they want in private.

But my friend’s request reminded me that I—an amateur biologist, with a long-ago Ph.D. in the subject—have been thinking about Museveni’s Darwinian puzzle for years. I’d even come up with a scientific hypothesis to explain why homosexuality, and all sexual preference for that matter, is probably at least partly genetic. I sent my friend a letter about this hypothesis, and although it obviously failed to convince Uganda’s leader, I share it here, in case it helps others grappling with this issue understand why homosexuality should be subject only to nature’s laws, not human ones.


The existence of a significant number of gays in human populations around the world could be a consequence of the fact that a high degree of diversity in sexual preference is necessary to ensure our survival. In other words, what is hardwired into our genes isn’t homosexuality itself, but the human tendency to exhibit a wide range of sexual preferences. Scientists refer to this as “hypervariability” and it may well give rise, in some irreducible number of cases, to men who fall on the masculine-preference end of the spectrum and become gay, and women who fall on the feminine-preference end and become lesbians.

We know intuitively that sexual preference varies a lot: some people go for Sumo wrestler-types, others for Diana Vreeland’s skinny fashion models. This is a good thing for at least two reasons. First, we can’t all marry Javier Bardem; thankfully not all of us want to and happily settle for someone else. Second, a wide range of sexual preferences ensures that human populations will remain genetically diverse overall, avoiding genetic “bottlenecks” and lowering the risk of genetic diseases.

Sexual preference may be analogous to the immune system. In the 1950s and 60s, Peter Medawar, Gerald Edelman, and others discovered that everyone’s immune system is unique. The complex collection of genes that determine how each one of us will respond to a particular germ are incredibly diverse and no two of us have exactly the same set of such genes—not even identical twins. That’s because the building blocks of our immune systems are created partly upon conception when sperm and egg meet, partly during embryonic development, and partly after birth in response to real-world germs.

By having diverse genetic responses to germs, humans are better able to avoid extinction in the face of new epidemics. Any new germ that comes along almost certainly won’t kill all of us, because some people will have just the right genes to fight it off. In fact, such battles between germs and human populations probably gave rise to our highly variable immune systems in the first place.

We know far less about sexual preference than we do about the immune system. But if sexual preference is also determined by some combination of our personal genetic makeup and our own early experience, it will be difficult to identify actual “gay genes” until we understand how the brain governs social behavior, which won’t be soon. However, if “hypervariability” mechanisms like those of the immune system are also involved in creating the diversity in sexual preference evident in every human population, then we can no more expect gay people to consciously alter their sexual preferences than we can expect them to alter their immune systems.

Many other theories have been proposed to explain the persistence of homosexuality in human populations, but there is little evidence to support any of them. One popular explanation is that gays, unburdened with their own children, provide assistance to their kin in child rearing, and thus promote the persistence of their own genes. However, studies have failed to show a greater rate of fitness or survival in people with gay uncles and aunts. By contrast, there is strong evidence that having a living grandmother increases a child’s chances of survival.

What about the “hypervariability” theory? As far as I know, this is the first time it has been proposed, and except for the protean nature of human sexual preference itself, the only evidence I’m aware of to support it is this: when I was in graduate school, a fellow-biology student named Prim Singh did a fascinating experiment. He was studying the sexual preferences of rats and found that a big factor was the odor of other rats’ urine. Both male and female rats (who were all straight, as far as I remember, although rats can be gay) were attracted to other rats whose pee smelled different from their own. Prim discovered that the smell was determined by the Major Histocompatibility Complex (or MHC), a set of genes that also determines some of the variability in the rats’ immune systems—and in ours. In other words, diversity in sexual preference was genetically determined in these rats, using some of the same genes that created the diversity of their immune systems. This helped ensure the rats didn’t fall for close relatives and destroy themselves by inbreeding.


People select sexual partners according to complex criteria, and the smell of each other’s urine may not even come into it. But if diversity in sexual preference is also programmed in our genes, then gay people are all the more essential members of the human family. Whatever the case, they should be respected, not condemned. Alas, President Museveni’s decision to sign the anti-homosexuality bill suggests he wasn’t really interested in the scientific debate. He needs those Christian soldiers on his side.

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