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Daniel LiebermanA modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Daniel Lieberman was born and raised in the northeastern United States. He attended Harvard University, where he earned his undergraduate degree in anthropology in 1987. He went on to receive two master’s degrees, one in biological anthropology from the University of Cambridge and one in Anthropology from Harvard. In 1993, Lieberman earned his PhD in anthropology from Harvard.
Early in his career as a paleoanthropologist, Lieberman worked as a professor and researcher. He began his teaching career at Rutgers University and George Washington University before moving on to teach anthropology at Harvard. Through his research, Lieberman has explored multiple areas of interest, such as skull and tooth structures and biomechanical forces on bones. He, along with research colleagues, went on to study how endurance running evolved in humans. Lieberman has written multiple academic texts, including The Evolution of the Human Head (2011) and Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding (2020).
Given his educational and professional background, Lieberman is considered a renowned expert in paleoanthropology. Part 1, in particular, showcases Lieberman’s previous research work. As mentioned above, much of Lieberman’s research has focused on examining skeletal structures and how they evolved. His discussions on hominin evolution center on these types of features: For instance, he is able to infer dietary changes through accompanying changes in tooth size and skull shape. Lieberman’s extensive research, along with his academic pursuits and teaching career, add to his academic authority and increase the credibility of the text.
Four early hominin species are discussed in Chapter 2. The four species are thought to be descendants of the last common ancestor between humans and chimpanzees. The last common ancestor has not been discovered, which may be because it evolved in the African rain forest, an environment which rarely allows for fossilization.
The oldest known early hominin species is Sahelanthropus tchadensis, which may have evolved up to 7.2 million years ago. The species was discovered by Michel Brunet and his team in 2001 in Chad. Most information about the species has been gleaned from a fossilized cranium nicknamed “Toumaï.” Orrorin tugenesis was found in Kenya, and it evolved around 6 million years ago. Not much is known about this species as only a few fossilized remnants have been discovered.
More is known about the Ardipithecus, which were found in Ethiopia by Tim White and his research team. Ardipithecus kadabba is thought to be older, existing 5.8 to 5.2 million years ago, while Ardipithecus ramidus lived around 4.5 to 4.3 million years ago (33). Ardi is the best-known early hominin and is the partial skeleton of a female Ardipithecus ramidus.
Lieberman asserts that some relevant information can be inferred from the small number of early hominin fossils, which, he writes, could fit into one shopping bag. The fossils suggest that hominins diverged from other apes because of climate change; however, these changes were relatively minor—“If a surviving relict population of very early hominins were to be discovered, we’d be more likely to send them to zoos than boarding schools” (44). Lieberman identifies bipedalism in early hominins as the first in a series of evolutionary changes that led to the emergence of modern humans.
Chapter 3 focuses on australopiths, or members of the Australopithecus genus. Several species of australopiths have been discovered, and they are divided into gracile and robust species, with the latter having some larger features, like larger teeth. The three known robust species include Au. aethiopicus, Au. boisei, and Au. robustus. The five known gracile species are Au. anamensis, Au. afarensis, Au. africanus, Au. sediba, and Au. garhi. A chart in Chapter 6 includes a sixth species listed as a gracile australopith—Kenyanthropus platyops, but this species is not discussed within the text.
All of the australopith species evolved and lived in Africa during a period of climate change. Lieberman posits that, as with early hominins, australopith evolution was a result of climate change. Fruits, which are the primary food source for apes, were less available, so hominins evolved features that adapted them to eat different foods and to efficiently travel longer distances while foraging.
Lucy, a famous Au. afarensis, is the best-known representative of the genus, but hundreds of other specimens have been found. Given the substantial fossil records, experts are able to infer more about the australopiths compared to the earlier hominins. Lieberman also emphasizes that many of the traits found in australopiths are visible in modern humans: “These diverse and fascinating ancestors occupy a special place in human evolution because their efforts to feed themselves changed what we are adapted for in ways still evident every time we look in a mirror” (49). The initial diversification of hominin diets and the respective evolutionary features provide some of the framework for later discussions regarding what humans are evolved to eat.
Early Homo species evolved after the australopiths, and they are discussed in Chapters 4 and 5. In Chapter 4, Lieberman centers on H. habilis and H. erectus, who evolved to have larger brains, smaller snouts, and more human-like teeth, legs, feet, and arms as compared to the earlier australopiths. Other noted Homo species include H. heidelbergensis, H. rudolfensis, H. floresiensis, H. neanderthalensis, and the Denisovans. These species developed during the Ice Age, a period of global cooling that started about 2.6 million years ago.
H. erectus, characterized by its larger brain and human-like limbs and teeth, was the first species discovered outside of Africa. It evolved in Africa at least 1.9 million years ago and has been found in Georgia, southern Asia, China, and Europe. Lieberman suggests that climate change drove the evolutionary changes seen in the Homo species. He and other experts infer that H. erectus also evolved to practice hunter-gatherer lifestyles, perhaps partly due to their larger brains. Adopting such a lifestyle may have helped the species increase their reproduction rates, which led to their dispersal throughout Asia and Europe.
H. floresiensis, which was found on the island of Flores is quite small relative to the other archaic Homo. This is likely because the species was confined to an island, and animals on islands tend to become relative giants and dwarfs.
H. neanderthalensis, or the Neanderthals, were larger than Homo sapiens, or humans. They practiced hunter-gatherer lifestyles, and they dispersed northward into Europe and Asia. One primary difference noted between Neanderthals and humans is that early humans practiced symbolic behaviors. Humans and Neanderthals interbred, and some modern humans have Neanderthal DNA. Humans also interbred with the Denisovans—another Homo species that lived in Asia and that have not yet been assigned a scientific title.
The discussion of the early Homo species is important for understanding how hominins transitioned from foragers constrained to African woodlands and grasslands to intelligent hunter-gatherers able to survive in more diverse habitats.