Chapter 4–A NEW PERSPECTIVE ON HUMAN ORIGINS
This chapter begins to get into the transition from early Ramapithecus to the fully modern human. It is made clear that this process did not follow a step-wise progression, but instead there was overlap and coexistence of multiple types of hominid for a very long time. By around 1 mya, only one hominid remained, which eventually gave rise to Homo sapiens. At the point this book was written, Homo habilis, Australopithecus boisei, and Australopithecus africanus had only turned up in Africa, although they mention that it is still possible their remains are buried deeply on other continents.
Some suggestions are offered in favor of an “out-of-Africa” hypothesis include the shrinking of a tropical zone that made the Eurasian continent unsuitable for hominids during the time period the discovered fossils are from.
It is made clear in this chapter that the authors are in favor of Homo habilis being the hominid that eventually would prevail as the direct ancestor to humans, but many questions still remain to be explained at this point in the book.
Chapter 5–THE HUMAN FAMILY UNEARTHED
In 1972, Maeve Leakey had her first child, and also reconstructed a tremendously important hominid skull that was found at Koobi Fora. This helped Louis Leakey to confirm his belief that the genus Homo was at least two million years old, which was much longer than commonly believed at that time. This skull came to be known as Skull 1470, and is the most complete specimen of its type.
The Lake Turkana area was clearly teeming with wildlife, which helps Anthropologists gain insight about how 1470 and his counterparts would have lived. The area was much wetter than it is now, with the waterside ecology being typical of where scientists have found hominid fossils in East Africa. The fossil record at Lake Turkana suggests that the three principal hominids coexisted for one million years at a minimum, and very likely much longer, as they had very different food tastes which would mean minimal competition. It is this competition for food that would eventually lead to one group surviving while another dies off.
The authors also emphasize the difficulties of fossil dating in this chapter, placing an emphasis on the East African sites being so useful because their fossils can be dated more reliably due to the volcanic ash layering from the Olduvai to the Hadar. This dating allowed them to confidently confirm that claim that the principal hominids were all present with each other, which is confirmed with other supporting factors. This period during the 1970’s was extremely rich in this strip of Africa, leading conclusions to be drawn that have taught us nearly all we know about our hominid ancestors to date. These discoveries also allowed Leakey to claim, with full confidence, that Homo erectus was African born and then made the journey into Asia, and later into Europe.
Chapter 6–LESSONS FROM BONES AND STONES
Chapter 6 reveals some truths about early hominids that were also ascertained through the study of these fossil findings. The first mentioned is that the angle between the knee and the shaft of the thigh was within modern human range, which led Owen Lovejoy to be able to say that our ancestors were walking upright as early as 3.5 mya. This meant that at least one type of hominid was walking around the Pliocene landscape upright. Lovejoy also reluctantly suggests that it may have been Homo who struggled with upright walking at first, debunking prior misconceptions about bipedalism being an advantage that allowed Homo to survive longer than australopithecines.
The teeth of the different early primates allowed these scientists to determine that they likely had much different diets. Yet, it was a commonality that they would live in social groups while individuals would have fed themselves, similar to how many primate groups function even today. Life among our Homo ancestors was probably significantly different, with the development of stone tools prevailing at least 2.5 mya. As time went on, the complexity of these tools became greater and greater.
Often, these hominids would have had to travel miles to find the right stones, which would have required significant planning as well as effort. Moreover, they knew how to retouch the tools to be used more often. The oldest of these man-made tools have been found at the Hadar Site. Yet, the most extensive collection is from the Olduvai Gorge in Tanzania, leading this period of stone tool-making to be named “Oldowan”. As the technology developed, the “Acheulian” age came about, best known for the hand-axes that were commonly used.