Their experiment was relatively simple. Isolated male flies were bred with 2-3 female flies, and the copulation latency, or the time between pairing and successful mounting, was recorded. This is a reasonable measure of male attractiveness because in D. simulans the female is in charge of the sex event—a male cannot copulate with an unwilling female. Granted, this was something of a desperation measure, the question being asked is, essentially, “If this was the last guy on earth, how long would it take for him to convince you to sleep with him?” A more convincing demonstration might have been to have females choose from different males, but as I am not a fly geneticist I’m not sure whether one could set up such an experiment. Additionally, it seems possible to me that the copulation latency might be affected by the attractiveness of the female, but I am not sure whether male flies are choosy. At any rate, the experiment might have been improved if repeated experiments with different females had been performed for each male to minimize bias arising from female attractiveness. This was done in the first part of the experiment, but not the second.
After maturing in isolation, so as to eliminate the possibility of learned behaviors affecting the results, the male progeny from these breeding events were isolated with females from a different population. The copulation latency was again recorded (no word on whether alcohol or dance music were supplied to help get things going). From these results, the authors concluded that the attractiveness of the father, as measured by the latency, contributes significantly to the attractiveness of the sons.
The authors did not provide much information on the nature of heritable features that give rise to attractiveness in their fruit flies, except to exclude body size as a factor. I myself don’t really know what the Brad Pitt of the fly world would look like, though maybe cousin Kathy has some idea, but wingspan, pheromones, and maybe some kind of auditory factor could all contribute and conceivably be heritable and account for the observations. A knowledge of the specific means by which “attractiveness” is transmitted isn’t relevant to the larger question of whether attractiveness is heritable, but matters when one wants to know whether the results in this model system can reasonably be extended to, say, birds or mammals.
Does this experiment tell us anything about the transmissibility of attractiveness in humans? Not necessarily. Mating behavior in humans is as much bound up in learned social behaviors as with unlearned biological ones. Many genes with the potential to result in male attractiveness are certainly heritable, but the diversity of lifestyles among humans means that the actual development of physical attractiveness from these potentials is uncertain. External non-heritable features (wealth, education, musical talent) also contribute significantly to human mating, which further complicates the issue. So I guess Dad is off the hook for this one, at least for the time being.
The article itself is relatively bare-bones and does not include any figures of raw data, which is something I never like to see. I don’t mean to impugn the authors—the journal may have decided not to make the expenditure. I think it would have been beneficial to see the correlation, and I can’t imagine any scientific reason not to include such a figure. Maybe it’s some biology thing.