  We study the global in time existence of solutions to the parabolic-elliptic
Patlak-Keller-Segel system of multi-species populations. We prove that if the
initial mass satisfies an appropriate notion of sub-criticality, then the
system has a solution defined for all time. We explore the gradient flow
structure in the Wasserstein space to study the question of existence.
Moreover, we show that the obtained solution satisfies energy dissipation
inequality.
