Zeuglodon, I'm not sure, are you agreeing that bacteria can make genetical copies of themselves?

Either way, I'm wondering about this r part. Is there empirical evidence that says those numbers 1/2, 1/4 and so on present themselves in nature? I read the Wikipedia article, but that only said

In 2011, experimentalists found empirically that Hamilton's rule describes very accurately the conditions under which altruism emerged in simulated populations of foraging robots. The accuracy of this first quantitative corroboration of Hamilton's rule is all the more impressive given that Hamilton's model made several simplifications that did not apply to the foraging robots.

But simulated populations of robots isn't really the stuff I'm interested in.

After all, if we were to sequence my genes and my sisters genes, and compare the sequences, we would find that they were much more than 50% similar. Genes are conserved, and my parents would have lots of genes in common that are identical even if they are not related in the everyday sense.

Suppose I have a half-sister, and we look at a gene where the sequence is identical between us. A gene has no clue were it came from, so from a genetic point of view, what does it matter if my half-sister got an identical gene from the same parent as I did, or from another parent?