Many people used to get extremely upset at the ill-formed notion that “man descended from the apes.” Such words were much more likely to start fights or “monkey trials” than the correct notion that all living animals, including man, ascended or evolved from a single-celled organism which lived in the primeval seas hundreds of millions of years ago. Men are mammals, of the order called Primates, and man’s living relatives are the great apes. Men didn’t “descend” from the apes or apes from men, and mankind must have had much closer relatives who have since become extinct. Men stand erect. They also walk and run on their two feet. Apes are happiest in trees, swinging with their arms from branch to branch. Few branches of trees will hold the mighty gorilla, although he still manages to sleep in trees. Apes can’t stand really erect in our sense, and when they have to run on the ground, they use the knuckles of their hands as well as their feet. A key group of fossil bones here are the south African australopithecines. These are called the _Australopithecinae_ or “man-apes” or sometimes even “ape-men.” We do not _know_ that they were directly ancestral to men but they can hardly have been so to apes. Presently I’ll describe them a bit more. The reason I mention them here is that while they had brains no larger than those of apes, their hipbones were enough like ours so that they must have stood erect. There is no good reason to think they couldn’t have walked as we do. BRAINS, HANDS, AND TOOLS Whether the australopithecines were our ancestors or not, the proper ancestors of men must have been able to stand erect and to walk on their two feet. Three further important things probably were involved, next, before they could become men proper. These are: 1. The increasing size and development of the brain. 2. The increasing usefulness (specialization) of the thumb and hand. 3. The use of tools. Nobody knows which of these three is most important, or which came first. Most probably the growth of all three things was very much blended together. If you think about each of the things, you will see what I mean. Unless your hand is more flexible than a paw, and your thumb will work against (or oppose) your fingers, you can’t hold a tool very well. But you wouldn’t get the idea of using a tool unless you had enough brain to help you see cause and effect. And it is rather hard to see how your hand and brain would develop unless they had something to practice on--like using tools. In Professor Krogman’s words, “the hand must become the obedient servant of the eye and the brain.” It is the _co-ordination_ of these things that counts. Many other things must have been happening to the bodies of the creatures who were the ancestors of men. Our ancestors had to develop organs of speech. More than that, they had to get the idea of letting _certain sounds_ made with these speech organs have _certain meanings_.