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PinkMonkey Online Study Guide-Biology

CHAPTER 12 : HUMAN EVOLUTION

12.0 Introduction

All humans are members of the species Homo sapiens (Latin = "man who is wise"). Today, man may be considered a dominant species on the earth due to his:

(1) Accumulation of achievements (e.g., language, tools and methods developed to feed and, shelter, organization in groups, achievements in arts, commerce and science); and

(2) Cultural and biological evolution due to biological attributes or characters such as (a) excellent stereoscopic vision(b), a large brain with a unique capacity for learning and reasoning. (c) hands that can grasp and manipulate objects. (d) upright bipedal (two-footed) posture. (e) specialized teeth for an omnivorous diet. (f) presence of the foramen magnum below the cranium so that the head can be moved about freely. These biological characteristics appeared gradually over 70-80 million years of primate evolution.

Homo sapiens belongs to the mammalian Order-Primates which also includes tree shrews, tarsiers, lemurs, lorries, monkeys and apes. The primate order is divided into :


(1) Sub-order - Prosimi (Pro = almost, Simians-apes) e.g. lemurs, lorries, tarsiers, shrews.

(2) Sub-order - Anthropoidea (Anthrop = man, oid = like) e.g. monkeys, apes, humans are closely related species are placed in super family - Hominoidea (man-like). Present and past Hominoids having man-like features are placed in family - hominidae. There were at least two species of the genus Homo (Homo habilis and Homo erectus), but the only living survivor is Homo Sapiens.

We place ourselves in the order Primate because we resemble the Primates more than any other animal. Before we get to know our ancestors, the major groups of primates (Figure 12.1 A) related distinctly to human evolution are :

Tree shrews - which resemble those mammals from which the primates arose.

Tarsiers - with long tails, long hind limbs, stereoscopic vision, improved grip form, the most advanced prosimians because they are like the monkeys.

Lorises and Lemurs - which colonized early in their evolutionary history, until humans arrived some two thousand years ago.

Monkeys - can walk upright, they are relatively intelligent, live in groups, females care for the young, they have larger brains than prosimians, and have stereoscopic and color vision.

Apes - are the closest kin to humans in size, form, physiology and behavior. They have bigger brains, and brachian style of locomotion (swing by their arms as shown in figure 12.1B) which is related to the evolution of an erect body posture and elongation of arms. Apes and humans constitute the hominoids. Besides humans, gibbons, orangutans, chimpanzees and gorillas are the only living forms of hominoids. Gibbons and orangutans are arboreal brachiators. Orangutans, chimpanzees and gorillas, when on ground walk on all fours, supporting their weight on their fists, (called - knuckle walkers). Chimpanzees and gorillas are more intelligent, can use simple tools and have the ability to learn sign language.

Studies of DNA sequences have shown that humans are more closely related to chimpanzees than to any other primates. Human and chimp DNA are 99 percent identical; but that is not to say that the humans have descended from fossil chimps. Fossil records shows that humans and apes have both descended from a common ancestor, or such genera as Dryopithecus, Ramapithecus and Sivapithecus which lived in Africa and Asia. A brief account of various genera related with human evolution is adressed in section 12.3.

Table of Contents

12.0 Introduction
12.1 Palaeontological Evidences - Our Ancestors
12.2 Ancestral Forms of Homo Sapiens

Chapter 13





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