SO ENDS this first of two weekends on coevolution. It seems intuitive that two interdependent creatures could affect each others evolutionary trajectory. Thus the continuity of the germplasm into the future — that driver of life — is not simply affected by successful mating and gene reshuffling, but by what type of company you keep, wittingly or not. This includes the microbiome of multiple creatures in and on your body. This is an exemplar of Darwin’s tangled bank seen through the lens of time, dynamic and active.