Darwin wasn't just provocative in saying that we descend from the apes - he didn't go far enough. We are apes in every way, from our long arms and tailless bodies to our habits and temperament.
Frans de WaalIf you are a cooperative animal you need to watch what you get. If you, or even a whole community, invest in something but then a few individuals receive a much larger return, it's not a good arrangement. If it happens consistently, it's time to look for an arrangement that is more beneficial. That's why we're so sensitive to how rewards are being divided.
Frans de WaalEmpathy probably started out as a mechanism to improve maternal care. Mammalian mothers who were attentive to their young's needs were more likely to rear successful offspring.
Frans de Waal