Due to this reproductive isolation, New World monkeys and Old World monkeys underwent separate adaptive radiations over millions of years. Therefore, it is thought that monkeys arose in the Old World and reached the New World either by drifting on log rafts or by crossing land bridges.

At the time the platyrrhines arose, the continents of South American and Africa had drifted apart. There is still quite a bit of uncertainty about the origins of the New World monkeys. Old World monkeys are called Catarrhini-a reference to their narrow noses. New World monkeys are also called Platyrrhini-a reference to their broad noses (Figure 1). By 40 million years ago, evidence indicates that monkeys were present in the New World (South America) and the Old World (Africa and Asia). (credit: Xavi Talleda)Īnthropoid monkeys evolved from prosimians during the Oligocene Epoch. It makes a call that sounds like a lion roaring. By the end of the Eocene Epoch, many of the early prosimian species went extinct due either to cooler temperatures or competition from the first monkeys.įigure 1. The howler monkey is native to Central and South America. Evolutionary changes continued in these early primates, with larger brains and eyes, and smaller muzzles being the trend. These early primates resembled present-day prosimians such as lemurs. The first true primates were found in North America, Europe, Asia, and Africa in the Eocene Epoch. They were found in North America and Europe in the Cenozoic and went extinct by the end of the Eocene. Plesiadapiforms were proto-primates that had some features of the teeth and skeleton in common with true primates. Fossils of this primate have been dated to approximately 55 million years ago.

The oldest known primate-like mammals with a relatively robust fossil record is Plesiadapis (although some researchers do not agree that Plesiadapis was a proto-primate). These proto-primates remain largely mysterious creatures until more fossil evidence becomes available. The existing fossil evidence (mostly from North Africa) is very fragmented. They were roughly similar to squirrels and tree shrews in size and appearance. The first primate-like mammals are referred to as proto-primates. In general, prosimians tend to be nocturnal (in contrast to diurnal anthropoids) and exhibit a smaller size and smaller brain than anthropoids. Anthropoids include monkeys, apes, and humans. Prosimians include the bush babies of Africa, the lemurs of Madagascar, and the lorises, pottos, and tarsiers of Southeast Asia. Order Primates is divided into two groups: prosimians and anthropoids. Other characteristics of primates are brains that are larger than those of most other mammals, claws that have been modified into flattened nails, typically only one offspring per pregnancy, and a trend toward holding the body upright. These adaptations include, but are not limited to: 1) a rotating shoulder joint, 2) a big toe that is widely separated from the other toes and thumbs, which are widely separated from fingers (except humans), which allow for gripping branches, 3) stereoscopic vision, two overlapping fields of vision from the eyes, which allows for the perception of depth and gauging distance. This arboreal heritage of primates has resulted in hands and feet that are adapted for brachiation, or climbing and swinging through trees. Characteristics of PrimatesĪll primate species possess adaptations for climbing trees, as they all descended from tree-dwellers. The characteristics and evolution of primates is of particular interest to us as it allows us to understand the evolution of our own species. They range in size from the mouse lemur at 30 grams (1 ounce) to the mountain gorilla at 200 kilograms (441 pounds). Non-human primates live primarily in the tropical or subtropical regions of South America, Africa, and Asia. Order Primates of class Mammalia includes lemurs, tarsiers, monkeys, apes, and humans.

Explain why scientists are having difficulty determining the true lines of descent in hominids.

Describe the derived features that distinguish primates from other animals.

By the end of this section, you will have completed the following objectives:

Old world vs new world monkeys