A central assumption in joint action research is that in order toexplain how individuals act as part of a group, we must firstexplain how the group comes into existence. This assump-tion has led to an unnecessarily narrow research programme:research has focussed largely on interpersonal coordinationmechanisms. I outline an alternative approach predicated ona dynamic conception of the ecosystem. On this view, thereis no need to assume that actors must first constitute a groupagent with their fellows before entering into coordinated ac-tion. Such coordination can be more efficiently explained byrecognizing that all actions perturb the structure of the ecosys-tem itself in a manner that can alter the action possibilitiesavailable to neighbouring actors. This move allows us to over-come entrenched debates over the nature of shared intention-ality, and to instead focus on practical interventions in multi-actor settings.