Conclusions
The different online simulations presented on this website all lead to the same result, namely that there is a purely mathematical predisposition to altruism in structured populations.
The most important conditions, besides a structured population, are an external selection pressure on each individual and a certain degree of migration among the groups.
Structured Populations
From the population's perspective, structured populations, whether divided into groups with limited exchange or based on neighborhood proximity, favor altruistic agents over egoistic ones from a purely mathematical perspective. Under suitable but realistic conditions, this automatically leads to stable populations with a large proportion of altruists.BTW, every natural population is structured in some way, so that not every individual interacts with every other individual in the same way. This model condition is therefore much closer to reality than the assumption of a mixed population, as is often the case.
Selection pressure on each individual
A key factor in establishing altruism is general selection pressure that affects each individual.It is best to assume an abiotic environmental factor, such as temperature or water shortage. Interspecific factors also have this effect, for example through predators or parasites. However, intraspecific selection between group members, i.e., competition for resources or sexual partners, is unsuitable in this regard.
The selection acts explicitly and exclusively on the individual level. Benefits received from altruists strengthen individuals against the selection pressure, while costs weaken it.
Migration
In populations divided into groups, migration between groups plays an important role. Without migration, these groups are isolated populations that die out one after the other because at some point the egoists gain the upper hand. Too much migration, however, causes the variation between groups to be lost, the whole population becomes mixed again and, once the egoists prevail, the entire population is wiped out. Variation among groups is crucial for the stable persistence of altruistic traits in the population.With the right amount of migration, weakened groups, where egoists have gained the upper hand, are filled by individuals from thriving groups, i.e. primarily altruists.
What's about kin and group selection?
The most common concepts among biologists for the evolution of altruism are kin selection and inclusive fitness, which state that helping relatives gives shared genes an advantage. That's probably right, but the concentration of relatives is also just the mathematical consequence of the structured populations, and so the probability of interacting with relatives increases. It is kin assortment by chance rather than kin selection. It is also not necessary for the evolution of altruism that relatives recognize each other, for example, by their green beards (which would probably be ruined by defectors recognizing non-relatives).
Therefore, kin selection correlates with altruism, but both - kin selection and altruism - are just consequences of the dynamics of structured populations.
The concepts of Group- and Multilevel Selection are based on the assumption that groups compete with each other. However, the simulation models shown here demonstrate that competition between groups is not necessary for the evolution of altruism, but rather that the existence of groups or other structures within populations alone is sufficient for this. (Competition between groups can promote the evolution of altruism, however.)
Ultimately, altruism is a game of poker
The altruism in the population is promoted by the probable or stochastic reciprocity supported by the structuring of the population. Altruistic individuals "bet" with good odds that there will be mostly other altruists in their group. Some, however, are unlucky and find themselves in groups with too many defectors. These are the pawn sacrifices of their altruistic strategy. But under the right conditions, their odds are good and the altruists win the game. Thus, an evolutionary poker game may solve the Darwinian puzzle of altruism.
References and further reading
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