This article draws on Dawkins’ theory of selfish genes and evolutionary stabilization strategies (ESS) to explain why some birds reproduce by laying eggs, and why birds that have been laid care for them as if they were their own. He explores the possibility that the ESS strategy may extend to interspecies interactions, shedding light on the survival strategies of genes through the trade-offs between laying and non-laying birds.
In The Selfish Gene, Dawkins argues that genes are the key unit of evolution, and he refers to the nature of genes to replicate and spread themselves as “selfishness.” He explains that the selfishness of genes has driven life to evolve and thrive. According to this selfish gene theory, all living things are nothing more than machines for the preservation and propagation of genes.
Dawkins also argues that when organisms fight for something, they follow an Evolutionarily Stable Strategy (ESS). When fighting for profit, either intraspecies or interspecies, the strategy used can be disadvantageous or advantageous depending on the strategy of the opponent. Within a species, an ESS that maximizes the average profit of each individual is implemented, and in interspecies fights, strategies that follow the ESS are likely to be chosen. If an individual emerges within an existing ESS system with a strategy that is more favorable to survival and reproduction than others, the proportion of ESS in the population can change. Dawkins suggests that this phenomenon can be explained at the genetic level.
As I read the book, I wondered if it was possible to connect the ESS strategy to the phenomenon of turbidity and extend the ESS strategy to cross-species problems. Although the book only mentions the phenomenon very briefly, it seemed like a topic worthy of discussion to our group. The text explains that cuckoos fledge by exploiting the blindness of the maternal instinct, but we wondered why the genes with this blindness were not culled and why special individuals did not emerge through mutation. If genes were selfish, it would seem that all birds should be clucking, but this is not the case.
The ESS strategy is an evolutionary stabilization strategy, and although it is discussed in the book as an intra-species concept, I wondered if it could be extended to an inter-species concept as it is a strategy stabilized by the selfishness of individuals. Despite my lack of biological knowledge, it also raised the question of why non-taciturn birds incubate other birds’ eggs instead of laying them. Also, in various examples, such as the prisoner’s dilemma and the ESS of males and females, the authors use numbers to determine the effectiveness of strategies. However, the criteria for determining the numbers is not clear. Although it was meaningful to try to explain the phenomena in the biological system with existing theories, I felt that there were limitations.
Therefore, I would like to extend the ESS theory to explain the interspecies phenomenon of turbidity by focusing on this aspect. The phenomenon of laying eggs, which is characteristic of some birds, seems to be consistent with Dawkins’ theory of selfish genes. By laying their eggs in other birds’ nests, they are able to concentrate their efforts and leave a large number of offspring. This seems consistent with the nature of genes to increase their own chances of survival. However, if laying birds benefit, other birds should also lay eggs according to the selfishness of their genes, which is why selfish genetics does not fully explain laying.
One way to solve this problem is the ESS strategy, which is described in this book as working only within species. However, since ESS is a strategy stabilized by the selfishness of individuals, it seems likely that it can be applied across species. Therefore, we hypothesized that “introducing ESS can explain turbidity” and searched for evidence. Since ESS is a strategy stabilized by an individual’s self-interest, it is likely to form a strategy stabilized by self-interest across species. Since the cuckoo’s selfishness is the result of its selfishness, ESS can explain it. While Dawkins’ explanation was not enough to explain the existence of non-cuckooing birds, if ESS can be applied across species, it could explain why non-cuckooing birds exist in nature.
The Selfish Gene explains that genes make strategic cost-benefit calculations to decide whether or not to fight in competition, and that they avoid unnecessary competition by waiting for an opportunity or avoiding fighting. Maynard Smith believes that different strategies coexist among populations and an evolutionarily stable strategy (ESS) emerges. According to this theory, the stable strategies that emerge from a population’s struggle are left to natural selection, and individuals that engage in deviant behavior are culled.
As a concrete example, suppose there are two groups in a population: hawks and doves. The hawks are combative and unwilling to give in to other individuals, while the doves are peaceful. Assume that the winner of a fight receives 50 points, the loser receives 0 points, being seriously injured receives -100 points, and wasting time receives -10 points, and that these points are proportional to the survival of the genes. In an all-pigeon population, the winner gets +40 points, the loser gets -10 points, and the average score is +15 points because there are no fights and no time wasted.
Next, if a hawk appears in the population, the hawk will beat all the doves and score +50 points, while the doves will score 0 points because they avoid fighting. In this case, the average score of the population is +25 points. If the population is all hawks, the winner gets +50 points, but the loser is seriously injured and loses -100 points, making the average score -25 points. In the end, the most stable strategy is implemented when the ratio of hawks to doves is 5:7.
Now let’s extend this strategy to an interspecies situation. We can set up two egg-laying strategies for birds: “turbulent” and “non-turbulent”. A turbinator lays its eggs in the nest of another species, while a non-turbinator incubates both its own eggs and the eggs of a turbinator. In this case, you can set a score of +100 points if the eggs of the turbot hatch, +30 points if the eggs of the non-turbot hatch, and -20 points if they fail to hatch.
In an ecosystem with all non-taxoliths, all taxoliths score 30 points, giving an average score of +30. If a turbulent larva is added to the mix, the turbulent larva gets 100 points and the non-turbulent larva gets 30 points, for an average score of +65. On the other hand, in an ecosystem with all turbellids, egg laying is repeated, resulting in an average score of -20. Therefore, the optimal balance is achieved when the proportion of turbellids and non-turbellids remains constant.
From this, we can conclude that the optimal outcome occurs when there is a constant ratio of turbinates to non-turbinates. The reason why non-taxolans incubate the eggs of other birds can also be seen as a kind of “selfish behavior” for genetic selfishness. Alternatively, it could be that the birds diverged from the same ancestor, resulting in the evolution of differentiated taklans and non-taklans within the species. In this way, the logic of ESS can be applied between species, leading to speciation.
