Studies in the field of human behavioral genetics have shown that a it is always a combination of your genes and the environment lead to certain behavioral traits (see the last post on this blog http://meetyourself.co/2015/04/twins/).
However, there are a few cases in the animal kingdom, where a gene is directly responsible for a certain kind of behavior, regardless of the environment. Remarkably, in the fruit fly, Drosophila melanogaster (those annoying little things that swarm your untouched fruit basket), a gene, deliciously named ‘fruitless’ has been shown to play a direct role in the mating behavior of these flies! In an intriguing paper published in Cell around a decade ago, researchers found that by modifying this ‘fruitless’ gene, male fruit flies completely lose their ability to attract and mate with a female fly.
These little fruit flies that you invariably find in your kitchen display a remarkable courtship behavior, especially the males. This behavior is innately built into the make up of the male flies and is extremely elaborate and uniform. Picture this…first the male fly orients himself towards the female, before tapping her with his forelegs. Next he sings her a song that is species specific (obviously you and I cannot enjoy this musical fiesta). this song is produced by one wing of the fly, which he flaps around. Finally, the male indulges himself by licking the females genitalia before curling his abdomen in anticipation.
It is important to keep in mind that while the females have this gene as well, they do not display the behavior that the males do.
Amazingly, this paper showed that when the ‘fruitless’ gene in female flies was modified in the same manner that it is in the males, the FEMALES displayed the same courtship behavior that males do! Vice versa, when the ‘fruitless’ gene was modified in the same manner as in the female, the male flies completely lost their ability to perform the entire courtship ritual!
This study showed that it is indeed possible for one gene to influence a complex behavioral pattern!
Interestingly, in humans, the only gene that comes close to determining a behavior is the role of the serotonin transporter gene in influencing depression. Even this is very controversial.
Of course, we are extremely complicated creatures, and perhaps it will be difficult to find a scenario where one single gene influences some aspects of our behavior. However, these kinds of studies in other animals and insects suggest that these genes do exist on our planet.