Friday, September 28, 2012

Slave Rebellion Among Ants

This is the 150th anniversary of Abraham Lincoln's Emancipation Proclamation.  The Preliminary Emancipation Proclamation was issued on September 22, 1862, followed by the Final Proclamation on January 1, 1863. 

I have offered a Darwinian interpretation of Lincoln's Emancipation Proclamation in my paper on "Biopolitical Science," which has just been published as a book chapter in Evolution and Morality, edited by James Fleming and Sanford Levinson (New York University Press).  I also have a chapter on slavery in Darwinian Natural Right.  I have also written some blog posts on slavery, usually near the yearly anniversary of the birth of Lincoln and Darwin on February 12th, because Darwin was an abolitionist who cheered Lincoln's Emancipation Proclamation.

My argument is that the history of the debate over slavery manifests a natural moral sense rooted in the biological nature of human beings,  As part of that argument, in Darwinian Natural Right, I compared ant slavery and human slavery.  The similarities suggest that slavery among ants and humans manifests a natural inclination to exploitation.  The differences suggest that the uniquely human opposition to slavery shows a natural resistance to such exploitation.

Biologists identify slavemaking ants as social parasites, who live by exploiting the labor of their slaves.  Slavemaking ants attack the nest of an opposing colony.  They kill the queen and capture the larvae, pupae, and younger adult workers.  The captives are taken back to the nest of the raiders.  Those that are not killed become slave laborers in the nest of the captors.  The slaves do all the necessary work for the colony such as foraging for food, rearing the brood, and maintaining the nest.  Some slavemaking ants are so totally dependent on slave labor that they are incapable of doing any work other than going out for slave-raiding.

Although in most cases of ant slavery, the slavemakers and the slaves belong to different but related species, there are some cases--such as the honeypot ants--where the ants enslave members of their own species.

The success of this enslavement depends on the coercion of the slave raid and the manipulation of the slaves.  When the enslaved pupae mature, they imprint on the unique odor of the colony of the slavemakers, so that the slaves are tricked into serving the colony as if it were their own.

Similarly, human slavery depends on coercion and manipulation, where manipulation might come through a paternalistic ideology of the masters in arguing that they are acting in the best interests of the slaves.  In the American South before the Civil War, some of the defenders of slavery actually pointed to ant slavery as evidence that all slavery was natural.  But this rhetorical manipulation doesn't work as well as the chemical manipulation does for the ants.  Human beings are naturally adapted to detect and punish exploitation, which is indicated by the human history of slave rebellion and moral condemnation of slavery.

Since ant slavery lowers the fitness of the slaves, biologists have wondered whether slave ants ever rebel against their enslavement.  Three possibilities have been considered and rejected.  First, the slaves could try to return to their home colony.  This is unlikely because once they emerge as adults, the slave ants will have the odor of their slavemakers' colony, and thus the slaves would be unable to find their home colony, and even if they did find it, they would be rejected because of their alien odor.  Second, the slaves could refuse to work or desert the slavemakers' colony.  This has not been observed.  Third, the slaves could reproduce themselves.  But this cannot work since the slavemakers' suppress the reproduction of slave workers.

There is now some evidence, however, that some slave ants have found a successful strategy for rebellion.  Some slave ants destroy a large proportion of the slavemaking pupae under their care, which reduces the population of the slavemakers' colony.  This form of slave rebellion does not directly enhance the individual fitness of the slaves, but it does favor their inclusive fitness by improving the chances that their collateral relatives in nearby colonies will be less exposed to slave raids.

This looks like the evolution of antiparasite adaptations.  Human beings show this as well.  The difference is that human beings can evolve moral emotions against exploitation, and these moral emotions can be expressed as a moral rhetoric of condemning slavery as unjust.  "As I would not be a slave," Lincoln declared, "so I would not be a master.  That is my idea of democracy."


Achenbach, Alexandra, and Susanne Foitzik.  2009.  "First Evidence for Slave Rebellion: Enslaved Ant Workers Systematically Kill the Brood of their Social Parasite Protomognathus Americanus," Evolution 63 (4): 1068-1075.

Pamminger, Tobias, et al.  2012.  "Geographic Distribution of the Anti-parasite Trait 'Slave Rebellion'"  Evolutionary Ecology (published online: June 13, 2012).

Other posts on insect politics can be found here and here.

1 comment:

Anonymous said...

"Human beings are naturally adapted to detect and punish exploitation, which is indicated by the human history of slave rebellion and moral condemnation of slavery."

But slavery existed for thousands and thousands and thousands of years. Surely the argument would be that humans are naturally adapted to exploit and reward exploitation. And on the other hand, those in slavery naturally want freedom. (My intuitions about the use of the word "naturally" get very weak here.) So at best you could say that humans naturally seek their own best interest. Plus, I don't think you can ignore the fact that slavery was finally abolished during the industrial revolution where machines could replace human labor, rather than that some moral epiphany happened to happen at that time where we suddenly deduced that slavery was morally wrong.