Final answer:
The meerkat male's inclusive fitness from saving two sisters and three nieces/nephews is calculated at 2 units after taking into account the loss of potential direct fitness from not producing his own offspring.
Step-by-step explanation:
The concept being described in this question is inclusive fitness, which is an important idea in the study of evolutionary biology and behavioral ecology. Inclusive fitness refers to an individual's total effect on proliferating genes by producing its own offspring and by providing aid that allows close relatives to reproduce as well. Specifically, it combines direct fitness—the number of genes an individual passes on through its own offspring—and indirect fitness—the additional number of genes passed on by helping relatives raise their offspring.
The meerkat male in the question ultimately saved the lives of five close relatives by sacrificing his chance to produce offspring. According to Hamilton's rule and the principles of kin selection, his behavior would be favored by natural selection if the cost to his direct fitness is less than the benefit to his inclusive fitness, adjusted for relatedness. Given that a meerkat's siblings share, on average, 50% of their genes, the saving of two sisters represents one unit of inclusive fitness each (2 * 0.5). The three offspring of another sibling would each represent a quarter unit of inclusive fitness (3 * 0.25) since nieces and nephews share about 25% of their genes with their uncles. However, this benefit is counterbalanced by the loss of his potential three offspring, which would have contributed directly to his inclusive fitness. So, the calculation would be as follows: 2 * 0.5 (sisters) + 3 * 0.25 (nieces/nephews) - 3 (his own offspring) = 2 units of inclusive fitness.