The higher primates such as chimpanzees, bonobos, gorillas, orangutans, gibbons and siamangs are the animals most like humans, and researchers looking for clues about culture in animals have focused a considerable amount of attention on them. The first widespread acknowledgment that apes exhibited culture was a study on social grooming among Tanzanian chimps by researchers William McGrew and Caroline Tutin, which revealed that different groups of chimpanzees exhibit unique grooming behaviors. Today, more than 40 populations of chimpanzees have been thoroughly studied, and scientists have found at least 65 categories of behaviors that are culturally transmitted, including varied technology, communication, play, food gathering or eating methods, and social behavior.