I am far from a geneticist (or in fact any form of scientist), but why do normal experimental controls not work in the case of this experiment? You perform the

I am far from a geneticist (or in fact any form of scientist), but why do normal experimental controls not work in the case of this experiment? You perform the odor exposure to half of your group and not the other half (the control group). Then you compare the results (measurement of the offspring) between control group and non-control group. Assuming that your group size is large enough that the measured difference can be considered statistically significant, then it doesn't matter what other variances there are - you have controlled for them.