Genetically programmed, but with options

This is a guest post by Adam Calhoun (@neuroecology), a very talented science writer and fellow member of UCSD Neurosciences. 

Australia has been having a problem with discarded beer bottles. It turns out that the Australian Jewel Beetle finds these bottles so attractive that they will mate with them until they die from dehydration. The bottles, so fine with their seductive golden shading and arousingly dimpled bottoms, are the ultimate beetle aphrodisiac. So gorgeous are these bottles that the Jewel Beetles have been known to continue mating even while being eaten alive by ants. Unfortunately for them, they have been genetically adapted to a different environment than the one they currently find themselves in, and their genetic programming has been hijacked. What they once found so deeply enticing about their fellow beetles, they now find in empty beer bottles instead.

Much of our behavior – not just insect behavior but our behavior – is driven by our ‘genetic programming’. Take a look at the list of things that are ‘cultural universals’. Language, color, family and friend groups, toys, weapons, play, song, dance. These are all things that we do no matter who we are. These are some of the things it means to be genetically human.

And yet – despite all this genetic programming we still make choices. It is easy to think of genetic programming as something that cannot be overridden, but experience modifies us all. Our genetics and architecture are but a framework that our lives are built around.

Take the example of courtship. We find our partners in many ways: flirting, fashion, dancing. Strangely enough, researchers recently analyzed the movement of human dancers to find which come-hitherly gyrations were the most seductive (Neave et al., 2010). Large, variable head and torso movements combined with quick twisting of the knees were what really drove people crazy. Yet despite the fact that song and dance are seen in every single culture ever, we wouldn’t call it a fixed genetic program. After all, krumping and line dancing are hardly the same thing.

We like to assume we are quite different from the baser animals, and nothing at all like insects, but here is how a male fly captures the attention of his desired lady fly: he begins to sing. Vibrating his wings, he emits a purring song which we can only assume that the female finds heavenly. A genetically programmed song, one might say.

Except, as with everything, it is highly sensitive to feedback. Philip Coen and colleagues recorded the precise movements of male flies while they puttered about a small arena, attempting to woo a lady fly (Coen et al., 2013). These lady flies were only concerned with the male’s singing and not his dashing good looks as they were all born blind. The songs are a combination of a sort of ‘chirp’ and ‘warble’, either repeated loud emissions or tones that go up and down and up and down.

It turns out that their songs were controlled by both their own movement as well as the movement of the female fly. As the female fly moved further away, the male would frantically chirp-chirp-chirp at it. When the female was closer and or as she slowed down, the male would resort to its crooning warble. The Dance of Flies is subtle in its specifics.

At its root, this courtship is very much genetically programmed. A small set of neurons contain with them the gene fru. When activated, these fru neurons cause the animal to sing (Clyne & Miesenböck, 2008). But not just the male: the female, too. Despite the fact that she would never do so in nature, the proper neural command can make a singer out of anyone. The singing, then, may be a genetic program but it is under the control of neurons. And if there is one thing we know about neurons is how well they learn, how much they respond to the outside world.

The truth is, all our behavior is genetically stereotyped. But any program must be able to react to a wide range of situations, and there is no way to do that without learning and choice. We are all slaves to what we can perceive – but anything we can perceive we can do something about. If we choose to.

 

References

Clyne & Miesenböck, 2008. http://www.sciencedirect.com/science/article/pii/S0092867408002158

Neave et al., 2010. http://www.northumbria.ac.uk/static/5007/neave_dance.pdf

Coen et al., 2013. http://www.nature.com/nature/journal/v507/n7491/full/nature13131.html

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