Ladies in waiting
Keeping the commoners happy is easy when you have pharmacology on your side. Complex caste systems exist throughout the animal kingdom, but is it purely social feedback that keeps us all in our places? Vergoz, Shreurs and Mercer report that a pheromone prevents worker honeybees from forming aversive associations while they serve the queen in a recent article in Science.
In the honeybee society, the females do all of the work. Young females attend to the queen and her hive. Later in life, they leave the hive to collect nectar and pollen (the average honeybee lifespan is 4-6 weeks). Queen mandibular pheromone (QMP), which is produced by the queen and transferred to the rest of the hive by her caretakers, prevents the ovarian development of other females.
Honeybees show both appetitive (positively reinforced) and aversive (negatively reinforced) learning. In response to odors, honeybees can be trained to extend their tongues in anticipation of a sweet reward or extend their stingers in anticipation of a shock. Octopamine and dopamine are important in appetitive and aversive learning, respectively. QMP alters brain dopamine levels. Does QMP affect aversive learning?
The authors found that QMP blocked aversive, but not appetitive learning in 6-day-old female bees. However, QMP had no effect on aversive learning in 15-day-old female bees.
How does QMP affect aversive learning? The QMP component homovanillyl alcohol (HVA) blocked aversive learning, whereas another QMP component hydroxybenzoate (HOB) did not. HVA is similar in structure to dopamine, so HVA may be responsible for the QMP-mediated reduction in brain dopamine and the decline in dopamine-mediated aversive learning.
Why block aversive learning in subordinates? The authors speculate that QMP prevents young attendants from forming aversive associations with the queen and therefore promotes loyalty and diligence. Perhaps the age-dependent decline in QMP's effect on aversive learning induces older honeybees to leave the hive.
It is highly unlikely that humans have an Orwellian pheromone mediating subservience. However, there probably is a QMP keeping us in our societal places: the Quantity of Money in our Pockets.