To be fair it says "this tribe" which can be read "the collective" and for the collective to survive it is only required that enough members survive. It doesn'

To be fair it says "this tribe" which can be read "the collective" and for the collective to survive it is only required that enough members survive. It doesn't specify any particular individuals. Of course this is a fairly nuanced reading of the title and I initially thought the same as you. It's kind-of the same as saying "lions keep the antelope herds healthy" which is technically true, but only because they are the mechanism by which the less healthy antelopes stop being a part of the herd.