Mammals are subdivided into three major subclasses; Prototheria, Metatheria and Eutheria. Prototheria are the egg laying mammals. Metatheria are the mammals whose young ones are born while immature or undeveloped and must cling to their mother until they are big enough to survive on their own. Before they are born, the young ones are usually attached to the yolk. For the Eutheria, their young ones form embryos and are attached to their mothers through placenta in the womb. The three subclasses are similar in that all of them are warm blooded, are four limbed and breathe air. In all the above subclasses, young ones depend on their mother for food. Their bodies are either covered with hair, fur or bare and have a constant body temperature. Their lower jaws are a single bone and have three bones in the middle ear. The three subclasses are different in their mode of reproduction. Prototheria lack teats but feed their young ones from mammary segregations. Moreover, unlike other mammals, they have a singe opening for excretion and reproduction. Metatheria have a pouch where the young ones stay until they are fully developed. Eutheria is the only class that is able to live in the three environments, terrestrial, air and water, and the placenta transfers nutrition to the young one from the mother.
The order primates have distinct traits. They have five fingers on each hand and five fingers on each toe, a longer gestation period compared to other animals of their size, forward facing eyes and have stereoscopic vision, well developed skeletal features related to arms and legs. Many primates are omnivorous. These traits are important in that the fingers and toes are useful in grasping and manipulating bits of food as they feed. The long gestation period helps them in ensuring their young ones are well developed before they are born. Primates are omnivorous in that they can feed on different types of food available on different environments. The positioning of the eyes is for the purpose of making decision stimulated by vision; the stereoscopic vision helps them to make proper distant judgments especially when they are moving from one position to another. Primates have a collar bone and two separate arm and legs bones for better limb movement and accurate motion. Primates are successful in that they are intelligent and use that intelligence optimally to survive and get food. Primates are usually protective of their young ones this makes them survive for future generations. Since primates are omnivorous, they are able to adapt to different diets.
Hominoids comprise of apes and humans, and are different from other primates in that they have larger and complex brain sizes and have no tail. They have distinctive molar teeth which have five pointed crown and the shoulder blades are at the back. The hominoids characteristic are important for the evolution of human because they help humans to be well adapted to the environment. The semi-erect posture was important since humans evolved to an erect posture.
Activity budget is a way of representing animal behavior by recording the period of distinct activities such as eating, sleeping, grooming and reproduction. Activity budget is important to primate communities for understanding their lifestyles and how they interact with the environment. It indicates how they utilize their energy and time in various activities. It helps establish the relationship between time spent on certain activities with season, habitat and availability of resources. Activity budget helps in determination of the reasons due to nutritional change as well as the relationship between body size and diet type.
Primates are social animals since they engage in play and other social behavior. The social character is delightful and psychologically important to the primates. There are numerous advantages of primates being social which include helping reinforce relations among themselves, helping them be able to efficiently communicate, developing beneficial artistic behavior and development of social groups that are important for basic survival. The social behavior has a disadvantage in that they develop dominance hierarchies where some animals keep lower positions from mates, food and other resources. The social behavior is helpful in development of adaptations in humans. Communication among humans has enabled them to develop universal communication signs, sounds and language. Grooming is a social element that is responsible to togetherness of humans.
Polygyny is a mating system where the male primate is able to mate with many females. Since primates are social animals they normally cluster together. Primate’s females are in constant search of food unlike males who search for mates, and this makes the females to come together. For polygyny to occur the males will normally have the role of protecting the female and the parental care vested on the male primate is usually low. Humans practice monogamy and has evolved because one male can economically defend one female and spatial distribution of females. Humans practice monogamy because the male’s parental care is very important to female reproduction, and joint male and female care is important to the young ones.
Reference
Craig Stanford, John S. Allen, Susan C. Anton (2009). Exploring Biological Anthropology: The Essentials. Prentice Hall. 2nd Ed.