Almost all of the responses here putting this down as "not that big a deal" are completely missing the point. It's extremely easy to say that evolution should d

Almost all of the responses here putting this down as "not that big a deal" are completely missing the point. It's extremely easy to say that evolution should do a thing, but if you cannot provide a mechanism to explain how such a thing is passively selected for, then evolution doesn't care. Evolution has no intelligence. There is no designer. This is probably the most important aspect of evolution to understand and the one hardest to grasp intuitively. For example: say you had a savannah with grass and tall trees populated by 4-legged horse-like animals that survive by grazing on the grass. We can look at such a scenario and say that it would be advantageous for some sub-population of those horse-like animals to grow longer and longer necks until they were capable of also grazing on the trees (doubling their available food supply, relative to their neighbors), but it will never happen! In each generation there will be a distribution of neck lengths, and as there is no advantage to those with slightly longer (but not long enough to reach the trees) necks, the distribution will remain unchanged. This is the basic Hardy-Weinberg principle. The only way you get giraffes is if the trees start out much shorter, so that the horse-like animals are capable of grazing on them. Then the trees that are slightly taller will have an advantage, and the distribution of tree heights in the population will shift. This will give an advantage to the horse-like animals with longer necks, causing their distribution to shift, and on, and on. This is the basic Red Queen hypothesis. So saying that an organism that has an inherent capacity for adaptation, or one that knows to cooperate with neighbors, would be better able to survive than the alternatives doesn't mean crap. If you cannot provide a mechanism (backed by a mathematical model) of how such traits arise, then evolution doesn't care. That is what makes this work so particularly interesting. The authors are providing a model to explain how a mechanism for the selection of cooperation could occur.