Mammalian traits: body hair, mammary glands, live birth, dentition. Generalized traits: mammalian traits other lost over time. Adapted to environment: limbs and locomotion, erect posture + bipedal, range of limb movement (rotation of forearm) Neocortex: brain portion involved- higher mental function + use many sensory organs. Evolutionary factors: characteristics of primates- adapted to arboreal (life in trees) Arboreal hypothesis: other animals are also arboreal, haven"t evolved. Behavioral ecology: study of the evolution of behavior + biology/natural selection. Social structure: size + sex ratio of group of animals. Matrilines: groups that consist of female, daughters + offspring. Predation: vulnerable to predators (depends on size, social structure + predator) Communication: conveys information in the form of a message. Affiliate behaviors: amicable associations between individuals reinforce social bonds. Intragroup: group within a group, not opposed to between groups. Altruism: behavior that benefits another individual but at risk to self. Reproductive behavior females receptive to males only on estrus.