[jpeloquin]

The concept of indirect fitness must be more complicated than explained here. The article explains it as a worker bee sharing 75% of her genes with her sisters, but only 50% with a child, so there is selection pressure for workers to be sterile and self-sacrificing. But few genes actually differ between individuals, so the percentages are much higher. E.g., I share ~ 99% of my genes with each one of you reading this. Assuming honey bees' genetic variation is not much more extreme than human variation, we're talking about 99.5% vs. 99.75% sharing, which sounds more like an explanation of why altruism would be preferred in general rather than uniquely affecting bees.

The article does eventually circle around to acknowledge this, but it's easy to miss and very underdeveloped compared to the discussion of kin selection: "So why do bees die when they sting you? Perhaps because they're disposable parts of a larger super-organism which has evolved by multi-level selection."

[GuB-42]

It doesn't matter how much bees have in common. The idea is that in bees, altruistic traits, that is those that produce more sisters by helping the queen have a 75% chance of being passed, because sisters share 75% of a worker bee genes. Most of the genes are the same, of course, bees won't become dogs or anything like that, but a few of them differ, and these are the one that matter.

Could worker bees be fertile and have a selfish traits that let them have more children, they would only have a 50% chance of passing these, because children share 50% of genes.

So: 75% of altruistic genes pass vs 50% of selfish genes. Altruistic genes win. Humans can't pass 75% of their genome this way, so that altruistic genes have no intrinsic advantage over selfish genes.

[jpeloquin]

Right, "sharing" here must mean DNA that was cloned from the same ancestral DNA strand, not merely that it shares the same informational content. I got lost in the analogies that frame things in terms of what's "better" for the organism and lost sight of this.

The most important thing from the perspective of replication of a DNA strand is the number of copies of DNA passed to the next generation, and future generations, right? Which would be 0.75 * (mean marginal increase in next-generation sisters) + 0.5 * (mean # offspring). The probability that these next-generation individuals actually get to reproduce in turn would also factor in somewhere.

What's also interesting is that if we take the point of view of the queen (through whom the altruistic genes must pass), the queen's reproductive strategy is relatively few children + hordes of sterile helpers + killing her own sisters. So are we talking about a fitness advantage of altruistic traits (maximizing # sisters), or a fitness advantage from selfish traits [maximizing P(fertile child survival) I guess, since # children is small] that produce hordes of sterile helpers?

Edit: Circling back to the organism perspective, in the sense of "I would gladly give up my life for two brothers or eight cousins.", how many bees is it worth giving up one's own life for in that specific sense? We do have a common ancestor after all and thus a non-zero R-factor.

[prerok]

Hmm, I understand this difference in genes differently.

You and I probably share 99% of effective genes, but still the difference in genes is much greater because there we are comparing the entire DNA. There is a lot of non-affecting DNA. And that is what they analyze when comparing DNA of two individuals in forensics.

[jpeloquin]

Based on the information I found, the % difference between two randoms humans in terms of base pairs (including non-coding DNA) is even less than the difference in terms of genes, so the distinction does not materially alter the discussion. Also the article framed its explanation in terms of genes, not base pair sequence.

"Between any two humans, the amount of genetic variation—biochemical individuality—is about .1 percent." https://www.ncbi.nlm.nih.gov/books/NBK20363/

https://book.bionumbers.org/how-genetically-similar-are-two-...

Forensic comparisons are mostly about comparing the number of short tandem repeats at handful of loci, a very small part of the the whole genome.

If you have any information that indicates the DNA similarity between people is less than 98–99% I would love to hear it. I have not personally analyzed the sequences from the 1000 genome project to check, and am relying on summaries written by other people.

[prerok]

I see, thank you for the explanation!