Bad Science: Homosexuality in flies "not hard-wired"

It always annoys me to no end when a scientific study comes to bad conclusions based on incomplete data, and it makes it even worse when the reporting is just as bad in not criticising the flaws in the conclusions.

Such was the case today with a new study that is making the rounds, and I learned of from PhysOrg. The title of the article says it all: "In fruit flies, homosexuality is biological but not hard-wired."

I braced myself for bad science, and there it was:

To test this, he and his colleagues genetically altered synapse strength independent of GB, and also fed the flies drugs that can alter synapse strength. As predicted, they were able to turn fly homosexuality on and off -- and within hours.

"It was amazing. I never thought we'd be able to do that sort of thing, because sexual orientation is supposed to be hard-wired," he said. "This fundamentally changes how we think about this behavior."

Basically, the scientists in the study found that if they genetically or chemically altered certain types of synapse activity within a fly's brain, they could "turn homosexuality on/off."

The data showed that otherwise heterosexual flies would start courting indiscriminately if this specific synapse strength was altered, and that's the key part of the data, barely hinted at by only one sentence in the article amidst the sensationalism:

"Homosexual courtship might be sort of an 'overreaction' to sexual stimuli," he explained.

I say hint because the data did not include tests on naturally homosexual flies. There was no control for the experiment and no negative test. This makes their conclusions fallacious and sensationalist.

The conclusion they can draw from the data is that when certain synapse strengths are modified, flies become hyper-sexual and display a tendency to mate indiscriminately in regards to sex. This hyper sexual behaviour fades when the synapses return to normal, and heterosexual flies again assert a preference for mating with the opposite gender.

The conclusion that they can turn homosexual behaviour on and off at will is bad science, and it really grinds my gears.