Friday, September 18, 2015
How Group Selection Works
To say that a human being must breathe, eat, and defecate, all on a regular basis, in order or write poetry, does not reduce poetry to respiration and digestion; it simply reminds us that poets are biological beings. Biological processes such as these may rarely be relevant to the interpretation of poetry but they are constantly relevant to an historical interpretation of households and cities. Caesar cannot recline and enjoy his feasts if food does not come in and poop go out and neither can Rome.
If you want to understand the idea of justice, as Plato’s Socrates sets out to do in the Republic, you will sooner or later have to account for the existence of human souls and human communities and that cannot be accomplished without evolutionary theory. My position (big surprise) is that the latter completes Socrates’ account.
I have been reading David Sloan Wilson’s Does Altruism Exist? It reminded me of a fairy tale I composed some time ago to illustrate group selection. I offer it here.
Consider a group of imaginary primates living and hunting in small groups in an area covered by tall grass. I’ll call them puds. Some of the primates in each group are taller than the grass. Others are smaller than the grass.
Now consider that this population of puds is subject to two selection pressures. The puds are preyed upon by a large avian animal. I’ll call it a dragon. Dragons cannot spot a single tall pud but can easily spot more than a handful when the group is moving. When a dragon descends on a pud group, however, it can feed on large and small with equal ease. Groups with a lot of tall puds are at a disadvantage, so that is selection against those groups.
Within each group, tall puds have an advantage. They are stronger and can forcibly mate with more females than their shorter male pud compatriots. So in any group with both tall and short males, the taller will proliferate over time. So that is selection against small puds.
If the groups remain isolated from one another, the species is on the road to extinction. Every group will eventually have enough basketball stars to attract a dragon and so every group will be eaten and the dragons will go on disability.
What will save the puds is that some of them will survive a dragon attack. The survivors will find other survivors and form new groups. Groups with more short pud fellows will survive longer and grow larger, increasing the supply of small puds in the total population. If, however, every group has at least a few tall guys, the cycle will continue.
One thing that might alter the trajectory is if the puds are smart enough to figure this out. A bunch of small puds might realize that the two tall puds who made it to the founding council are a problem and vote them off of the island. This rule, whether a product of pud culture or a slowly evolving disposition, would tilt the playing field in favor of puds against dragons. How bad it would be for the latter depends on how tall genes are distributed in the population.
I thought this up before I knew a lot about the research into group selection. I intended it only as a demonstration that group selection was logically possible. D.S. Wilson’s book gave me an example that neatly matches my fairy tale. Pond skaters (Gerridae) are insects that skate across water in search of prey. The males come in two flavors: rapists and gentlemen. The former force themselves on any female they meet. The latter wait until a female approaches to mate.
Within groups of skaters, the rapists have an advantage. They mate more often and produce more offspring. So their sons proliferate in the group. However, their appalling behavior doesn’t leave the females with enough time to feed, so they lay far fewer eggs than they would if they were well fed. The result is that groups with more gentleman grow faster than those with more rapists.
What keeps the gentleman in business is that females have some choice. When groups are forming, females are more likely to join a group with more gentlemen. That simple, biologically trigger preference, rewards chivalry with the precious coin of reproductive success.
This explains so much. It explains why cooperation is so difficult and how it is possible. It explains why rules of justice are necessary among human beings and other social organisms and how justice is possible.
Something more important now occurs to me. The balance between group selection and individual selection can tilt either way. When it tilts toward the group, eventually you get the assimilation of individual organisms into a new whole, as when a multi-cellular animal emerges from a cooperation of cells. When it tilts the other way, the community with its social interactions disintegrates into individual competitors.
Human beings are social animals but we are also individuals. The entire field of justice and morality emerges from this fact. All human activity, including poetry and politics, is possible because within group selection and between group selection balanced out, over a long period of our life on this earth.