  In large groups, every collaborative act requires balancing two pressures:
the need to achieve behavioural synchrony and the need to keep free riding to a
minimum. This paper introduces a model of collaboration that requires both
synchronisation on a social network and costly cooperation. The results show
that coordination slows, and cooperativeness increases with the social
network`s local integratedness, measured by the clustering coefficient. That
is, in a large-group collaboration, achieving behavioural synchrony and
strategic cooperation are in opposition to each other. The optimal clustering
coefficient has no natural state in our species, and is determined by the
ecological environment, the group`s technology set, and the group`s size. This
opens the space for social technologies that solve this optimisation problem by
generating optimal social network structures.
