Of course they do. To the extent that genes make you anything in particular, though the role of genetics in human behavior is pretty limited.
You’ve probably heard about the newly reported research in which a genetic link was found to homosexuality in a study of gay brothers. Kelly Servick has a good writeup on it here. The study looked at 409 pairs of gay brothers, and found a region on the X chromosome that was similar across the sample. This sort of shotgun approach, comparing a trait (in this case, gayness) with a bunch of DNA (I oversimplify) is very likely to get results that look real but are the result of random association. But, it is also possible to find real links. I am agnostic as to whether or not this study found something interesting. But I do have a few remarks to make about how you get to be gay.
Consider the following list of things:
<li>Sexual attraction (to whom you are attracted)</li> <li>Erotic response (what is erotic, including physically, to you)</li> <li>Attachment (with whom to you seek attachment, and of what kind)</li> <li>Sex drive (do you have it and where is it driving too?)</li> <li>Society norms (especially for your subset of society)</li> <li>The details of social norms, i.e., what categories of sexual orientation exist around you.</li> <li>Your relationship to social norms (your comfort level ... do you seek "normalcy" or prefer something else?)</li> <li>Whom you know or encounter and where they are with all of the above things.</li> <li>And many more things that ultimately may relate to sexual orientation.</li>
This list can be written in many different ways, and every item on this list really represents a number of other sub items. These things are not mutually exclusive and the list is not exhaustive of that which relates to sexual orientation. Feel free to provide your own lists in the comments, if you like.
Many, most, maybe all of these things have individual ontogenies for any individual. The ontogenies may start before birth. We are bathed (or not) in various maternal hormones in utero. We are bathed in our own hormones in utero. The effects the hormones have depend on the relationship between the amount of hormone and the abundance and distribution of receptor sites, and on the timing. The abundance and distribution of receptor sites itself is probably influenced by the process. It is very complicated. Differences between one individual and another may related to external or non-genetic factors. In fact that may be very common.
Hormonal effects and interactions continue after birth. Again, timing, relationships between kinds and relative amounts of hormones, and receptor sites, still apply. Causes may be numerous.
The above only applies to that related to hormonal changes, which may affect a number of somatic (body related) features including brain features.
Then there are the non-hormonal factors, including cultural and social ones. Again there are complexities to the ontogeny of an individual with respect to these factors. And, these complexities are dynamic; culture and society can change right underneath you. And the non hormonal and hormonal factors may interact.
Much of this can be thought of as a process of negotiation. One negotiates internally, one negotiates with one’s social groups, one negotiates with society, culture, even the law.
Here is a simplified model linking the DNA identified in this study to homosexuality. Various switches are turned on or off, buttons pressed or not, during a person’s development. They do everything in some individuals to “make a person be gay.” But there is one element missing. If you have the DNA profile associated with the sample of 409 brothers, you get to be gay. If not, you probably won’t be. But, the “yes-no” value (reminder: oversimplifying here) found in this DNA actually has another purpose. It has to do with how many hairs you have on the back of your hand. The variation across men in hand hair is accounted for by variation in these genes. But in some individuals (but not all) it also happens to be the final ontogenetic link in the chain to a particular sexual orientation that in the sociocultural context that the 409 pairs of men live in results in gayosity. In another society, another culture, at another time, it results in being more likely to be a blacksmith than a farmer.
Note: That was a made up example. But in the absence of a biologically, developmentally, sensible link between some DNA and a trait, we can certainly carry out amusing and instructive thought experiments.
This complexity of links between causes and effects is probably true for the vast majority of variation found in human behavioral traits. Not this exactly, but something like this. The steps involved can be characterized in a certain way with respect to a trait under study, but all or most of those steps actually relate as well to other things. Also, some of those steps might have multiple causes. A particular manifestation of sexual or erotic attachment may arise in one person for one reason, in a different person for a different reason. In other words, the list I provide above can take many forms, not just because I’m being vague about what is in the list. The list can simply be different for different people who end up with the same “trait” as we happen to define the trait for the moment.
There is a reason for this vague connection, or in many cases, lack of connection, between inherited genes and behavior. A strong link between genetics and behavior has been shown to be very highly adaptive in some organisms. Here’s an old example. In a particular species of fruit fly, the larvae have a gene with two alleles. One allele causes the larvae to forage tightly in space, making a lot of turns in its search for food. The other allele causes the larvae to forage widely, to make few turns, and cover a larger area. Each allele is adaptive in a particular context and the fruit fly species has diversity at this locus. So, the fruit fly female mates with multiple males, produces a diverse batch of offspring, and the ones with a particular pattern of alleles at that locus have higher fitness. For now. In a different environment, maybe a few generations later (as the orange juice they are feeding on changes its characteristics as it rots in that glass you left on your desk) the genetic arrangement with the higher fitness changes.
But, humans are different. Humans are like the fruit fly, needing different traits at different times, but instead of those traits being programmed by genes, they are learned. Added on to the individual by enculturation.
This applies to some extent to all mammals because mammals have brains that matter to behavior. It applies very much so to primates, especially apes, and even more to humans. We have diversity in behavior, but we get it from our cultures. We learn to be a functioning adult; it is not pre-programmed. There probably are some pre-programmed behavioral features, but those are the features that would generally apply. But even those may be largely divorced from genetic inheritance on the grounds that behavior generally does not emerge from genes coding for neural structures. Genes in humans can’t code for neural structures at the level of the cerebrum, because of the way cerebrum develops, and that is where most of the relevant behaviors exist.
We can be pretty sure this is the case because of the huge cost we pay for it. Childhood. Childhood may be the most important human adaptation, and it may be the most costly. Human females can die in childbirth. That is nearly unheard of among mammals, outside of humans and our domestic stock. The babies can die in childbirth as well. That is because of our oversized brainy heads. Human babies are born helpless and spend several years nearly killing themselves at an alarmingly high frequency, and only survive childhood because of the adult humans taking care of them (or in some cases, wolves or ocelots, I suppose). This is costly to the adults. It limits reproductive output in the adults. Childhood also limits the reproductive output of the child, because it extend the time before reproduction, and decreases the chance of survival until reproduction.
Childhood, a brain that learns, the heavy reliance on the things the brain learns, and the long time it takes to make all this work demands a brain that is not overly programmed genetically, and results in a species with an extraordinary characteristic found in no other species: we are a multitude.
If you look at numerous species in most mammal families, you will find a wide range of behavioral and ecological repertoire. Measure body size, sexual dimorphism, typical system of mating, food getting, diet, defense, inter and intra species competition, etc. across all of the geomyids or voles, across all the species of dogs or all the species of cats, across the antelopes, across the African forest monkeys, etc. and you’ll find many features such as those mentioned that vary very little within species, but vary greatly across them within that taxonomic group.
Then look at humans. They look more like a taxonomic family than a species. Human cultures vary in these and other features as greatly as larger mammalian taxonomic groups.
But, when you capture an infant at birth from one human group and have it raised by another group, the infant grows up with behaviors typical of the adoptive group, not its natal group. That pretty much falsifies the idea that variation in our behavior is linked to variation in our genes.
By the way, if you move new born antelope, rodents, primates, etc. between species you may get some of the same effect. Cross species adoption does result in a bit of a behavioral chimera sometimes. But, it is only possible between some species and tends to work when the interactive parts of the system happen to be aligned. A parent bird will feed mouth-gaping carp for a while if they’ve lost their mouth-gaping baby birds. Within mammals, we’d expect a fair amount of post adoptive learning across species, because, as I noted above, learning how to be typical member of your species applies to some degree to mammals in general, more so to primates, more so to apes, and vastly more so to humans. Vastly.
Imma let you get back to finding links between genes and behavior. But first, remember, culture rules.
Final note. Part of the reaction to this new research, and this has happened with all prior research on homosexuality, is in reference to the sociopolitical outcome. If you are born gay, Conservatives can’t legislate against you, but if it is a choice, you might be a criminal. That sort of thing. This is balderdash. The Nazi’s killed all those people because of their genes. Many value free choice. Some will see being born gay as being born broken. People who are born a certain way, in many sociopolitical contexts, are vilified for it. You can’t win the sociopolitical game by claiming a certain human behavior or trait is built in or choice. You win that game on its own terms. And, lately, we mostly are winning.