Elephants are among the world's most intelligent species. With a mass of just over 5 kg (11 lb), elephant brains have more mass than those of any other land animal, and although the largest whales have body masses twenty-fold those of a typical elephant, whale brains are barely twice the mass of an elephant's brain. The relationship between brain size and intelligence (if there is any such relationship at all) remains unclear. In addition, elephants have a total of 257 billion neurons. The elephant's brain is similar to that of humans in terms of structure and complexity—such as the elephant's cortex having as many neurons as a human brain, suggesting convergent evolution.Elephants express a wide variety of behaviors, including those associated with grief, learning, allomothering, mimicry, play, altruism, use of tools, compassion, cooperation, self-awareness, memory, and language. Further, evidence suggests elephants may understand pointing: the ability to nonverbally communicate an object by extending a finger, or equivalent. All indicate that elephants are highly intelligent; it is thought they are equal with cetaceans and primates in this regard. Due to the high intelligence and strong family ties of elephants, some researchers argue it is morally wrong for humans to cull them. The Ancient Greek philosopher, Aristotle, once said that elephants were ""the animal which surpasses all others in wit and mind.""