The Essential Tension

Abstract

IN THE preceding pages, we have travelled through crucial periods in the history of science and through a range of topics in the collective dynamics of biological systems. In each of the stops along our way, we have met, in various guises, what I describe as an essential tension: a balance between cooperation and competition, a balance between interactions at the local level – between cells or individual organisms, for example – and external pressures originating beyond these local interactions. We have seen how the balance of these apparently opposing drives plays a crucial role in the emergence of an ensemble of elements into a new individual in its own right. This shift is seen in the early theories of crowd formation, and in Durkheim’s theory of the origin of the division of labor in human society. It is seen in the balance between alignment with neighbors and collision avoidance that generates an immense murmuration of starlings flying over a field. It is seen in the simple shifts in gene expression that take volvocine algae and their relatives from a single-celled to a multicellular lifestyle. It is seen in the quorum sensing that induces individual bacteria to begin forming a biofilm mat and individual Dictyostelium amoebae to form a slug and then a fruiting body. It is seen in the induction of cluster formation by yeast under selective pressure for faster settling in a gravitational field. It is seen in the stretching and folding, in which trajectories exponentially diverge, only to be kneaded back together, that is inherent in the nonlinear dynamics used to model many of these complex biological systems. It is seen in the shift from competition to cooperation via the suppression of conflict that Michod and colleagues define as the key step from selection at the MLS1 to the MLS2 level, which takes an ensemble from being a collective of individuals to an individual collective. The tension between competition and cooperation manifests itself differently in each instance, and my emphasis on this common theme is meant as anything but a suggestion that these vastly complex scientific problems can be reduced to a simple formula. Rather, I have focused on this theme in order to highlight its importance as an Ariadne’s thread that may lead us to the center of the maze and, with luck, back out again.