Turn-taking skills unique to humans?

In yet another "humans are unique with respect to...." type article Melis, Tomasello and collaborators do experiments showing that humans differ in their ability to carry out long-term collaborative relationships that involve taking turns. I've been reading de Waal's recent book "Are we smart enough to know how smart animals are?" (which I highly recommend), which suggests that the "unique to humans" implicit in the title of the article of the article may not be appropriate, for the article demonstrates a more 'advanced' behavior in humans only in a specific paradyme involving just the two species. Potential turn taking behavior in other social animals, invertebrates as well as vertebrates, is still a possibility. The experiments:

...gave pairs of 3- and 5-year-old children and chimpanzees a collaboration task in which equal rewards could be obtained only if the members of a pair worked together first to reward one and then to reward the other. Neither species had previously been tested in a paradigm in which partners can distribute collaboratively produced rewards in “fair” ways only by taking turns being the sole beneficiary.

Here is their abstract:

Long-term collaborative relationships require that any jointly produced resources be shared in mutually satisfactory ways. Prototypically, this sharing involves partners dividing up simultaneously available resources, but sometimes the collaboration makes a resource available to only one individual, and any sharing of resources must take place across repeated instances over time. Here, we show that beginning at 5 years of age, human children stabilize cooperation in such cases by taking turns across instances of obtaining a resource. In contrast, chimpanzees do not take turns in this way, and so their collaboration tends to disintegrate over time. Alternating turns in obtaining a collaboratively produced resource does not necessarily require a prosocial concern for the other, but rather requires only a strategic judgment that partners need incentives to continue collaborating. These results suggest that human beings are adapted for thinking strategically in ways that sustain long-term cooperative relationships and that are absent in their nearest primate relatives.