UPDATE: I called a dicty worker and got this answer.
The solution to the “altruism” problem requires two things. First, stalks and spores are formed only when there’s a shortage of food (bacteria, usually). That means that all the genes in all of the individuals in the area will not leave copies if there’s no way to disperse those genes away from the locale of famine.
Second, dicty individuals that are more related to each other are more likely to get into the spore-forming top, but if you share ANY genes for this behavior with other individuals in the spore body, you’re still better off being part of the stalk than simply dying, for there’s still a chance that some of your genes will be in slightly related individuals that form the spores. Better to take that chance that ensure that you leave no descendants.
ZeFrank has another biology video, this time on the slime mold (one with an amoeba life stage) Dictyostelium discoideum. This is a strange microorganism that usually reproduces asexually, but can do so sexually. In one stage of the asexual reproduction, the cells aggregate into a slug which then turns into a stalk that produces spores that disperses genes. Some of the cells that aggregate, however, don’t get to reproduce as they form the stalk instead of the reproductive top of the stalk. It seems, in other words, like a form of altruism.
I used to know the answer to this conundrum, because a cell certainly doesn’t want to help other cells reproduce at the cost of its own reproduction.. (If they were genetically identical it wouldn’t matter, but I don’t think they are.) And I don’t think ZeFrank gives the solution.
I know some readers here work on “Dicty”, as they call it, so we’ll have an answer soon.