(a) The Precursors of Modern Human Beings Look at these four skulls. A belongs to an ape. B belongs to a species known as Australopithecus (see below). C belongs to a species known as Homo erectus (literally ‘upright man’).
D belongs to a species known as Homo sapiens (literally ‘thinking/wise man’} to which all present-day human beings belong. List as many similarities and differences that you notice, looking carefully at the brain case, jaws and teeth. The differences that you notice in the skulls shown in the illustration are some of the changes that came about as a result of human evolution. The story of human evolution is enormously long, and somewhat complicated.
There are also many unanswered questions, and new data often lead to a revision and modification of earlier understandings. Let us look at some of the developments and their implications more closely. It is possible to trace these developments back to between and mya. We sometimes find it difficult to conceptualise such long spans of time.
If you consider a page of your book to represent , years, in itself a vast span of time, pages would represent , years, and a pages would equal million years. To think of million years, you would have to imagine a book , pages long! That was when primates, a category of mammals, emerged in Asia and Africa. Subsequently, by about mya, there emerged a subgroup amongst primates, called hominoids.
This included apes. And, much later, about . mya, we find evidence of the first hominids. While hominids have evolved from hominoids and share certain common features, there are major differences as well.
Hominoids have a smaller brain than hominids. They are quadrupeds, walking on all fours, but with flexible forelimbs. Hominids, by contrast, have an upright posture and bipedal locomotion (walking on two feet). There are also marked differences in the hand, which enables the making and use of tools.
We will examine the kinds of tools made and their significance more closely later. Two lines of evidence suggest an African origin