Essentials of Physical Anthropology 9th Edition

Book Preface

One day, perhaps during the rainy season some 3.7 million years ago, two or three animals walked across a grassland savanna (see next page for definitions of terms on this page) in what is now northern Tanzania, in East Africa. These individuals were early hominins, members of the evolutionary lineage that also includes our own species, Homo sapiens. Fortunately for us, a record of their passage on that long-forgotten day remains in the form of fossilized footprints, preserved in hardened volcanic deposits. As chance would have it, shortly after heels and toes were pressed into the damp soil, a nearby volcano erupted. The ensuing ash fall blanketed everything on the ground. In time, the ash layer hardened into a deposit that remarkably preserved the tracks of numerous animals, including those early hominins, for nearly 4 million years (Fig. 1-1).

These now famous prints indicate that two individuals, one smaller than the other and perhaps walking side by side, left parallel sets of tracks. But because the larger individual’s prints are obscured, possibly by those of a third, it’s unclear how many actually made that journey so long ago. What is clear is that the prints were made by an animal that habitually walked bipedally (on two feet), and that fact tells us that those ancient travelers were hominins.

In addition to the footprints, scientists working at this site (called Laetoli) and at other locations have discovered many fossilized parts of skeletons of an animal we call Australopithecus afarensis. Because the remains have been extensively studied, we know that these hominins were anatomically similar to ourselves, although their brains were only about one-third the size of ours. They may have used stones and sticks as simple tools, but there is no evidence that they actually made stone tools. In fact, they were very much at the mercy of nature’s whims. They certainly could not outrun most predators, and their canine teeth were fairly small, so compared to many other animals, they were pretty much defenseless.