 However, open questions about URLanization mechanisms in animal groups remain: Evolutionary adaptation towards  group-level optima (group-level selection), often implicitly assumed in the criticality hypothesis, is in general not a reasonable mechanism in fission-fusion groups composed of non-related individuals.
<clarity>  However, open questions about URLanization mechanisms in animal groups remain: Evolutionary adaptation towards  group-level optima (group-level selection), often implicitly assumed in the criticality hypothesis, is in general not a reasonable mechanism in fission-fusion groups composed of non-related individuals.
 However, open questions about URLanization mechanisms in animal groups remain: Evolutionary adaptation towards group-level optima (group-level selection), often implicitly assumed in the "criticality hypothesis", appears in general not a reasonable mechanism in fission-fusion groups composed of non-related individuals.