Unstoppable Us, Volume 1: How Humans Took Over the World

The science of evolution is central to Harari’s arguments in Unstoppable Us. Harari suggests that humanity’s “unstoppable” nature is not innate but that our world domination is the result of evolutionary changes and humanity’s ability to adapt to specific circumstances. Harari teaches his readers that this trajectory comes with consequences, both good and bad.

In developing this theme, Harari draws closely on the work of 19th-century naturalist and biologist Charles Darwin. Darwin first articulated the biological theory of evolution that shapes Harari’s book. This theory holds that organisms, including humans, are the products of natural selection. Organisms with superior traits or skills survive and reproduce, leading to the evolution of various species. To support this, Harari gives evidence that some of our modern biological instincts are legacies of evolution, an example of which is our urge to eat fatty, sweet foods even though our bodies do not always need them. Our ancestors, however, needed to consume sweet and fatty foods when they foraged because they did not know when their next meal might come. It was a survival method that persists in our neurobiology today.

Harari establishes his theme by explaining the evolutionary process, using whales as an example:

[T]he ancient ancestors of whales were land animals that were no bigger than a dog. Around 50 million years ago, some of these doglike animals started spending part of their time in rivers and lakes […] Their feet, which they no longer needed for waling, evolved into flippers. Their tails also changed to better help with swimming (146).

The book develops this theme by showing how evolution also applies to humans. For example, as early humans learned how to make fire and cook food, their bodies changed because they expended less energy on eating and digestion. Human brains grew, which facilitated new skills. Eventually, like whales, humans adapted to life on water when they developed rafts and canoes that allowed them to migrate into the Pacific and onto islands like Australia. Harari emphasizes that this human adaptability had profound consequences for the places to which Sapiens migrated, including Australia and the Americas. Their superior skills, like the ability to make fire and cooperate in large groups to acquire food, resulted from evolutionary processes and led to the extinction of much Stone Age megafauna. Virtually all the world’s large prehistoric animals were depopulated because of humans hunting them, according to Harari. This depopulation had a cascading effect on the ecology and environments of various areas of the globe, which changed forever.

Harari’s main theme directly challenges the views of creationists, who oppose Darwin’s theory of evolution. Harari’s work begins by contradicting religious ideas of human exceptionalism, showing that, according to evolution, humanity is an animal descended from primates. Creationism believes that the world is much younger than most scientists suggest and was divinely created within a matter of days. Creationists contend that ancient humans were the same as modern humans and did not evolve. Harari’s book, aimed at a young audience, navigates the challenges of scientific education in a pluralist society, where guardians, parents, and political figures may take issue with school or library reading materials that do not align with their worldview. However, Harari presents overwhelming scientific evidence for his key theme of evolution and adaptability and its role in making Homo sapiens an “unstoppable” force.