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In Sapiens, Admissions and Overstatements about Human Evolutionary Origins

Casey Luskin
Photo credit: World Economic Forum, via Flickr (cropped).

Editor’s note: Casey Luskin is reviewing Sapiens, by Yuval Noah Harari. Look here for Part 1.

The 2015 bestseller Sapiens: A Brief History of Humankind, by Oxford-trained historian Yuval Noah Harari, is extremely well-written and entertaining, but it adopts an unyielding materialistic evolutionary perspective on human history, and offers many unbacked claims. Despite these flaws, it makes intriguing admissions about our lack of knowledge of human evolutionary origins. For example, Harari admits, “We don’t know exactly where and when animals that can be classified as Homo sapiens first evolved from some earlier type of humans, but most scientists agree that by 150,000 years ago, East Africa was populated by Sapiens that looked just like us.” (p. 14) Harari is right, and this lack of evidence for the evolutionary origin of modern humans is consistent with the admissions of many mainstream evolutionary paleoanthropologists.

Explaining Our Brains

Another candid admission in the book (which I also agree with) is that it’s not easy to account for humanity’s special cognitive abilities — our big, smart, energetically expensive brain. This is especially difficult to explain if the main imperatives that drove our evolution were merely that we survive and reproduce on the African savannah. Here’s Harari’s account of how our brains got bigger:

That evolution should select for larger brains may seem to us like, well, a no-brainer. We are so enamoured of our high intelligence that we assume that when it comes to cerebral power, more must be better. But if that were the case, the feline family would also have produced cats who could do calculus, and frogs would by now have launched their own space program. Why are giant brains so rare in the animal kingdom?

The fact is that a jumbo brain is a jumbo drain on the body. It’s not easy to carry around, especially when encased inside a massive skull. It’s even harder to fuel. In Homo sapiens, the brain accounts for about 2-3 per cent of total body weight, but it consumes 25 per cent of the body’s energy when the body is at rest. By comparison, the brains of other apes require only 8 per cent of rest-time energy. Archaic humans paid for their large brains in two ways. Firstly, they spent more time in search of food. Secondly, their muscles atrophied. Like a government diverting money from defence to education, humans diverted energy from biceps to neurons. It’s hardly a foregone conclusion that this is a good strategy for survival on the savannah. A chimpanzee can’t win an argument with a Homo sapiens, but the ape can rip the man apart like a rag doll.

Today our big brains pay off nicely, because we can produce cars and guns that enable us to move much faster than chimps, and shoot them from a safe distance instead of wrestling. But cars and guns are a recent phenomenon. For more than 2 million years, human neural networks kept growing and growing, but apart from some flint knives and pointed sticks, humans had precious little to show for it. What then drove forward the evolution of the massive human brain during those 2 million years? Frankly, we don’t know. 

Sapiens, p. 9

Again, this is exactly right: If our brains are largely the result of selection pressures on the African savannah — as he puts it “Evolution moulded our minds and bodies to the life of hunter-gatherers” (p. 378) — then there’s no reason to expect that we should need to evolve the ability to build cathedrals, compose symphonies, ponder the deep physics mysteries of the universe, or write entertaining (or even imaginative) books about human history. Why should these things evolve? He said it, not me: “Frankly, we don’t know.” 

Human Cognitive Abilities: “Pure Chance”?

Here’s something else we don’t know: the genetic pathway by which all of these cognitive abilities evolved (supposedly). Now you probably won’t appreciate this fact if you read Sapiens, because Harari gives a veneer of evolutionary explanation which really amounts to no explanation at all. Here’s what he says:

The appearance of new ways of thinking and communicating, between 70,000 and 30,000 years ago, constitutes the Cognitive Revolution. What caused it? We’re not sure. The most commonly believed theory argues that accidental genetic mutations changed the inner wiring of the brains of Sapiens, enabling them to think in unprecedented ways and to communicate using an altogether new type of language. We might call it the Tree of Knowledge mutation. Why did it occur in Sapiens DNA rather than in that of Neanderthals? It was a matter of pure chance, as far as we can tell. But it’s more important to understand the consequences of the Tree of Knowledge mutation than its causes. What was so special about the new Sapiens language that it enabled us to conquer the world? 

Sapiens, p. 21

“We’re Not Sure” 

True, Harari admits that “We’re not sure” how all this happened. But he then proceeds to confidently assert that human cognitive abilities arose via “accidental genetic mutations” that “changed the inner wiring of the brains of Sapiens.” No discussion is attempted and no citation is given for exactly what these mutations were, what exactly they did, how many mutations were necessary, and whether they would be likely to arise via the neo-Darwinian mechanism of random mutation and natural selection in the available time periods. 

If we don’t know the answers to any of those questions, then how do we know that his next statement is true: “It was a matter of pure chance, as far as we can tell”? Of course the answer is clear: We can’t know that his claim is true. He doesn’t know the claim is true. He’s overstating what we really know. After all, evolutionary biologists have admitted that the origin of human language is very difficult to explain since we lack adequate analogues or evolutionary precursors among animals.

Yet for Harari and so many others, the unquestioned answer is that human cognitive abilities arose due to “pure chance.” This is an extremely important claim that he confidently asserts and it sets the stage for the rest of the book, which purports to give an entirely materialistic account of human history. For example, a few pages later he lets slip his anti-religious ideological bias. This is revealed in a claim he asserts as factually true, but for which no justification whatsoever is provided:

There are no gods in the universe, no nations, no money, no human rights, no laws, and no justice outside the common imagination of human beings. 

Sapiens, p. 28

Harari’s conjecture — “There are no gods” — forms the very basis for everything he says in the rest of the book. This naturalistic assumption permeates Harari’s thinking.

Next, “Did Religion Evolve, or Was it Designed, to Foster Cooperation?”