It seems to me that it doesn't weigh against it very much. A genetic change that causes a not-too-big increase in altruistic behaviour towards likely kin is unlikely to hurt your chances of survival and reproduction a lot.
The first organism with the genetic change doesn't need to be exceptionally well supplied with offspring or anything. (Unless this is an r-selected species for which surviving at all is exceptionally lucky; in that case, it needs to be about as lucky as the bearer of any other not-too-dramatic genetic change has to be.)
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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