SPEAKER: Now, we've been talking about the importance of paleontology and its relationship to geology. And from that record, we obtained fossils and we interpret these fossils biologically in terms of their relationships to one another and, where possible, their behavior. We also examined the concept of evolution, and this is the basis of our biology. By putting together the concepts of paleontology and evolutionary theory, we're now ready to look at the issue of our own origins as primates.
The great Swedish taxonomist, Linnaeus, in the 18th century, placed all of the primates-- that is the monkeys, the apes and ourselves, as humans-- into a single order that he called the primates. And this distinguished that group from other orders to which belong the carnivores or the herbivores and the animals that are very distinct from ourselves that we would never confuse as being in any way directly related to us.
By putting humans into the order, primates, Linnaeus did something that no one had conceived of before. But the basis for this lumping together of monkeys, apes, and humans was based primarily upon the physical morphological differences and similarities that he saw when comparing those groups with members of other orders. That is the primates share certain anatomical and behavioral characteristics.
What are these characteristics of primates, living and extinct? Well, for one thing, primates have very good optic senses. They have stereoscopic vision, which allows them to see depth, and that's important when you're living in the trees and must make rapid decisions in moving from one branch to another, perhaps escaping a predator. This vision is also color vision. The eyes of primates are generally oriented toward the front of the face, toward the front of the head, rather than to the sides of the head, as occurs in fish or in other animals where there is not overlapping visual field.
Primates are characterized by a reduction of their sense of smell, yet the brains of primates are somewhat larger than we would expect in relationship to their total body size. So if we look at the cranial capacities of horses or cows or armadillos, we're going to find cranial capacities that are in proportion to the sizes of those animals. That is pretty much as we would expect. But among the primates, we find that these cranial capacities are somewhat larger.
The adaptive factor here of larger cranial capacities among the primates may relate to their behavioral patterns. We find primates in different kinds of environments. Most of them live in trees, and in the forest canopies, some live in the very highest branches on the very small twigs. And they're small animals. You could hold them in the palm of your hand. Others are lower in the forest canopy, and some down toward the base, and there are some, such as baboons, who spend most of their time on the ground but go to trees for protection and for sleep and also for foraging for fruit.
We, as human beings, do not spend much time in the trees. We are fully adapted to locomotion on the land, although we can do some climbing. But our primate ancestors certainly were adapted to a tree environment. And not only that, but while they were confined, in the past and in the present, very much to the tropical belt, they also had adaptations that allowed them to exploit different environments. So we find them not only just along the lines of the equator, but we find them in the northern and southern temperate latitudes.
One of the other characteristic of primates is that they're social. They live in groups, and with a few exceptions, such as the Gibbons, who are monogamous, most of them have multiple mates over the course of their lives. And the social organization is based upon a hierarchy dominance recessive form of relationship between both males and females and among males and females. This behavioral characteristic of the primates is something that is difficult to establish in the fossil record, to be sure. But certainly, it is characteristic of most of the primates that we see living today.
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Since the time of separation of the evolutionary lines of apes and humans about 5 million years ago, some fossil specimens of the skeletal remains of our earliest ancestors have been preserved and discovered. Putting together the pieces of the puzzle of human biological history is the task of paleontologists, geologists and anthropologists.
In this room we explore how these scientists can reconstruct the past from their studies of the geological contexts in which fossils are found, the dating of the specimens, their comparative anatomy with extinct and living species of our taxonomic order, the Primates, and the lifeways and behavior patterns of the first members of the human family within the Primates.
By looking at reproductions and pictures of this fossil record, including representations of pre-human Primate species, we learn about our prehistoric beginnings among those populations of first two million years of our evolution, as identified as Ardipithecus, Australopithecus and the earliest members assigned to our own genus- Homo habilis and Homo rudolfensis.
This video is part 10 of 13 in the Human Paleontology series.