How can you say that? Almost every part of every organism functions simultaneously all the time. At the community scale, organisms cooperate and communicate continuously in real time. My eldest daughter is going through an ant obsession phase at the moment, their communities and how they coordinate hundreds of individuals simultaneously are amazing. Nature and natural selection are the ultimate optimizers - if there is any way for an organism or species to extract even the tiniest survival or reproductive advantage, nature ruthlessly optimises for it. Parallel function and behaviour is one of it's primary tools.