This question prompts for explanation on a topic, an interpretation of this topic is given. A simplified question statement is also given at the end for those who do not wish to read.
In the Self Gene by Richard Dawkins, it was suggested that genes are the fundamental units of evolution.
In one of the chapters of this book, animals such as the ants are discussed. These animals are specified to have the following properties:
- They live in colonies consisting of sterile workers and reproductive queens.
- Worker ants possess half of the genes from its queen and half its genes from the king, which is not living in the colony because it died after fertilizing the queen.
- The queen produces male "drones"--potential kings for future colonies. Drones are genetically identical to the queen.
The following interaction is suggested: worker ants, being less related to the drones than they are to each other, will manipulate the colony to increase the number of workers and reduce the number of drones present. They may do this by eating some drones before they hatch.
The reason why the workers do this is explained and interpreted as such: The workers wish to produce more individuals that are more closely related to themselves; other workers are more closely related to a worker than a drone is to that worker; therefore, the worker prefers another worker over a drone.
The Selfish Gene suggest that genes are the fundamental units of evolution, therefore a successful gene must be able to displace its alleles by being better at propagating itself.
Suppose gene-A incentivizes workers' drone-eating behavior, this gene in the short term and within one colony can produce a larger number of its own copy, but all of these copies are inside sterile workers, none of which can propagate gene-A.
When the colony containing gene-A spawns drones and potential queens, there are two cases to consider:
- Gene-A is present in drones: If this is true, then by incentivizing the occasional drone-killing by the workers, gene-A has reduced the number of gene-A carrying drones, this is deleterious to gene-A. When workers of the new colony is born, gene-A reduces the number of possibly non-gene-A-carrier drones and decreases the fertility of the new colony in general.
- Gene-A is present in female offspring: gene-A decreases the fertility of new queen, making her produce less gene-A carrying drones, this is again deleterious.
So far, gene-A has proven to be often deleterious to itself by restricting the number of reproductive individuals that may carry it. In terms of competition, gene-A may harm its alleles when the queen carries the allele and the king carries gene-A, but this will stop being beneficial when the number of gene-A and the number of its Alleles reach a 1:1 ratio, since after that point, the probability of harm is equal for both.
So, why is the drone-killing behavior still exhibited in animals such as ants?
Worker ants sometimes kill male ants in its colony because they are less related to the worker ants than the latter is to each other. Since worker ants can't reproduce, why do they bother about the number of close relatives who also cannot reproduce?