Kin selection is one of those special considerations derived from “selfish gene theory” that postulates that it is the degree of relatedness between organisms that will determine the likelihood that altruistic actions will occur. This also clearly implies the existence of a social group, of some type, so it isn’t expected that it would play a role between members of different species, or among asocial animals (although it could).

In general the idea of “kin selection” is that individuals are more apt to behave altruistically to “blood relatives” than to others in the interest of propagating their genes into future generations. A classic example occurs in eusocial insects where sterile females help maintain the colony for the reproductive queen.

However the use of eusocial insects is problematic since there is no possibility of an unrelated insect ever being present in the colony(1). Therefore there is no way to determine whether the behavior is due to simple proximity, kin relatedness, or response to the social group itself. In effect, there is no way to test kin selection theory in this case since every insect is, by definition, kin.

The nature of kin selection theory is described by Hamilton’s rule:

C < R x B

The values in this expression are interpreted such that C represents the cost in fitness to the actor and B the benefit in fitness for the recipient, while R represents the degree of genetic relatedness between the two. In this case, fitness is reproductive capacity.

Without getting into all of the calculations and terms of this relationship, one of the biggest questions focuses around the variable R. While this is defined as being the degree of genetic relatedness, there is nothing in this equation to require it, nor is it derived by any other means.

In other words, R could just as easily be used to describe the longevity of a relationship between individuals (kin or not), or it could be used to describe the ratio of brown-eyed to blue-eyed individuals. In all these cases, a solution could be derived, but it wouldn’t necessarily have any basis for extrapolation into the real world.

The most obvious problem with kin selection theory is that it requires that an animal be capable of assessing the degree of “relatedness” to an individual before acting. In the case of a strong familial group, this may not be difficult to determine, however the difficulty occurs when it becomes virtually impossible to distinguish an action as being based on “kin” versus the social group to which an individual belongs. This seems to have been shown in a recent study (2) where familiarity resulted in more positive interactions than kinship did, which coincides with most intuitive expectations.

There is little doubt that many social groups may have initially formed as families and extended families, so that there would be a high likelihood that there is a genetic relationship amongst a group’s members. This does not have universal application and consequently many of the members of a group may have no genetic relationship to each other. In this case their behavior must be construed as being oriented towards the survival of the group (or at least close individuals), rather than any notion of “kin”.

An additional difficulty occurs because in the quest for future mates, other social groups may be the source of such mates. As a result, the concept of “kin” must extend beyond the immediate genetic relationship to include others with whom future genetic exchange may occur.

Regarding the altruistic actions themselves, part of the confusion comes from considering altruistic behaviors as being anomalous and trying to rationalize their existence by postulating a kin relationship as evolutionary justification. In point of fact, many altruistic behaviors exist to ensure the survival of the group, because without the group there may be no individual chance of survival. Therefore, it may be quite reasonable for an individual to perform an act which is altruistic to ensure group survival, since their own survival would be jeopardized without the group anyway. It is also important that to recognize that costs or benefits are only potentially realized and cannot be assessed until after the action is taken.

By considering the potential cost of an altruistic act, we tend to overlook the fact that a “successful” altruistic act may convey great status to the individual and be of significant benefit. However this is rarely considered because it is presumed that altruistic actions that may have ulterior motives are somehow less altruistic or that they are only applicable to zero-sum circumstances.

In addition, motives or intent can play no role in assessing an action. Simply because we can never truly know what is behind another organisms actions. We can speculate or make assumptions, but it is impossible to know with any degree of confidence what the actual motivating factor is. The difficulty comes from having to infer a particular “state of mind” which can never be absolutely determined.

While it is relatively easy to see how “kin selection” can factor into animals that rear their offspring, it is a much more difficult assessment when evaluating adult behaviors. Related or not, how would one distinguish an act as benefiting a particular individual over the group to which they belong? It is obvious that all actions are largely going to be between individuals, so to suggest that there is such a specific reason for it, goes beyond our ability to assess it accurately.

Most importantly, there can be no action undertaken based on the certainty of a particular outcome. The altruist cannot know the consequences of their actions any more than that the benefit to the recipient can be assured. Therefore, we must conclude that whatever factors are at work, they must be less ambitious in explaining the cooperative nature of these species. While there is no question that genes are a fundamental element in natural selection, it may be that by placing undue emphasis on this aspect of evolution we are simply being too reductionist in our views.

(1) Notable exceptions related to aphids or other symbiotic relationship. However, these represent special cases much like domesticated animals to humans.

(2) Kin recognition versus familiarity in a solitary mustelid, the European polecat Mustela putorius