Studies on the ontogenetic origins of human knowledge suggest that cognition does not arise as a blank slate. On the contrary, the human mind appears to be built on a set of core knowledge systems that represent significant aspects of the environment such as physical objects, living beings, spatial relationships, and number. Core knowledge systems are evolutionarily ancient, and they can be investigated from a comparative perspective. I shall discuss evidence showing precocious abilities in nonhuman species to represent (a) inert objects with their basic mechanical properties, (b) the cardinal and ordinal aspects of numerical cognition, and (c) the geometrical relationships among extended surfaces in the surrounding layout. Controlled rearing studies suggest that the abilities associated with core knowledge systems of objects, number, and geometry are observed in animals in the absence (or with very reduced) experience, thus supporting a nativistic foundation of such cognitive mechanisms.