According to kin selection theory, which boat would be most beneficial to save?

In the context of kin selection theory, the primary focus is on the reproductive success of individuals related by blood ties. This theory suggests that individuals can increase their own genetic contribution to future generations by helping relatives survive and reproduce, thereby indirectly passing on similar genes.

Choosing the scenario with one sister, one half-brother, and three cousins is optimal because of the genetic relatedness within this group. Siblings share an average of 50% of their genes, half-siblings share about 25%, and cousins share around 12.5%. In this case, the individuals in the chosen boat are a mixture of closer and more distant relatives. The sister and half-brother provide a higher relatedness factor to the individual compared to the other options. The presence of three cousins adds some genetic relatedness but is less impactful than the direct sibling relationships.

This combination of both closer (sister and half-brother) and relatively close (cousins) relationships maximizes the potential for genetic success, which is the key principle of kin selection. Thus, from the perspective of maximizing inclusive fitness, this choice represents the most advantageous option for saving.