Sapiens: A Brief History of Humankind

Sapiens: A Brief History of Humankind

I've read all of Harari's books, but the first third of Sapiens is still the most impressive.

Cross-read these notes with the Smithsonian's Human Origins project, since some timelines and theories will complement and also disagree with Harari's research.

As always in evolution: A lot of paths in the tree of life can seem logical and inevitable, but that doesn't mean they happened.

Make it your own

  • History is the story of the development of human cultures.
  • Three revolutions shaped the course of history. The cognitive revolution kickstarted it 70.000 years ago. The agricultural revolution sped it up 12.000 years ago, and the scientific revolution 500 years ago might end history or start something totally new
  • Human = animal belonging to the genus ‘homo'


  • Why didn’t cats develop larger brains? Why are brains so rare in animal kingdom? Brain = Drain. 3% of bodyweight => 25% of total energy. That’s 3x the rest time energy of apes. This led to humans having to spend more time looking for food, while their muscles atrophied.
  • From Biceps to Neurons. Analogy: Government moving funds from defense to education.
  • The brain kept growing for 2 Million years, but during that time we didn’t have much to show for except knives and pointed sticks. We don’t know what drove evolution forward in this direction.

Walking and premature Birth

  • Walking upright is a signature human trait. It’s easier to scan the savannah for enemies and food. Arms freed up and whoever could do more (stone throwing, signaling etc.) with his arms was more successful.
  • It was hard to develop towards standing upright —> the scaffolding had to support a larger cranium. We paid with backaches and stiff necks. Women especially since upright walking required narrower hips, constricting the birth canal…at the same time when baby heads were getting larger. Death at childbirth become a major hazard. Women who gave birth earlier survived AND were able to give birth to more children.
  • Humans are born prematurely when most vital systems are still underdeveloped. We are helpless, dependent for many years on the elders for education, protection and sustenance. This fact has contributed greatly to our extraordinary social abilities and also social problems. It takes a village to raise a child (or a tribe to raise a human). Evolution favored those who could form close social ties. In addition, since we are born underdeveloped we can be educated and socialized far more than other animals. We can be shaped surprisingly well, while other mammals come out of the womb pretty set.


  • Evolutionary pressure lead to finely tuned palms and fingers. With the increased concentration of nerves humans could produce tools (*2.5M years ago). Archaeologists take tool production as criteria to recognize ancient humans.
  • We think that complex social structures, superior learning, tools and large brain are big advantages. But humans had those for a full 2M years in which we remained weak creatures
  • Humans from 1M years ago were in constant fear of predators - eating leftovers from stronger carnivores, insects, plants. Some Researchers believe that our original niche was to use stone tools to crack open leftover bones (after stronger animals took everything they could) to extract the marrow.


  • Domestication of fire (800.000yrs ago) was a big step. It gave warmth, light and protection from wild animals. Food that we couldn’t digest in natural form – wheat, rice and potatoes – became part of our diet.
  • It also became easier to chew and digest cooked food. While chimpanzees spent 5hours a day chewing raw food, we could do it in 1 hour. So: more kinds of food, less time eating —> need for smaller teeth and intestines.
  • Some researches believe that the shortening of the intestinal track and the growth of the brain are directly related. Long intestines and large brains are massive energy dumps - it’s hard to have both. Fire also democratized destruction. Previously humans were limited by their body. Now a 15 year old girl could burn down an entire forrest.
  • We are right now manipulating the lives of lesser beings on this planet - the animals
  • "Wheat domesticated us."


  • Our language is unique in its suppleness. Animals can communicate things like ‘Attention, a lion’, but we can tell a friend about the lion hunting gazelles this evening at the lake close to here.
  • Why did Homo Sapiens develop advanced language? One theory is that it was just a random genetic mutation that could as well have happened to the neanderthals. A second theory is that language enabled and was evolved as a way of gossip.
  • According to this, we are primarily a social animal. Knowing who in the tribe hates who, who sleeps with whom, who is honest and who is dangerous is far more important than knowing about lions and bisons. The information we must process and obtain to know all the relationships in just a small tribe is enormous (related: Dunbar’s Number)
  • But the most unique feature of our language is to speak about things that don’t exist. FICTION. Gods, myths, religions appeared the first time with the cognitive revolution 70.000 years ago.
  • Not only can we imagine things, but we can do so collectively.
  • Common myths (such as nations, religions) enabled us to cooperate with complete strangers that share that myth.
  • We're collaborating on larger scales, with other humans we never physically met.
  • The "imaginary" things we made up are slowly starting to transform the "real" world there is.
Loosely related: Complexity increases non-linear for every new node in a network

Other Species

  • There were many other species of humans - we aren't unique.
  • Example: Homo Floresiensis. People reached the island Flores when sea levels were extremely low and it was easy to reach. When sea level rose again, some were trapped on the island which was poor in resources. Big people died first. Over generations people of Flores became dwarves. 1 Meter and 25kg maximum.

The Insecure Species

  • Only about 400.000 years ago humans started hunting large game on a regular basis and only the last 100.000 years with the rise of homo sapiens, we jumped to the top of the food chain. This leap from the middle to the top of the food chain had enormous consequences. Lions and sharks evolved into that position slowly, gradually. The ecosystem was able to develop balances that prevent lions and sharks to wreak too much havoc. As lions became deadlier while gazelles evolved to run faster, hyenas to cooperate better and rhinoceroses to be more bad-tempered.
  • The ecosystem didn’t have time to adjust for humans. Humans themselves failed to do so. Most top predators are majestic creatures, filled with self-confidence after million years of domination. Humans are more like banana republic dictators. Our fears and anxieties over our position makes us more cruel and dangerous. Historical calamities, from wars to ecological catastrophes might have resulted from this over-hasty leap.

Energy / Conversion

"An even bigger problem was that people didn’t know how to convert one type of energy into another. They could harness the movement of wind and water to sail ships and push millstones, but not to heat water or smelt iron. Conversely, they could not use the heat energy produced by burning wood to make a millstone move. Humans had only one machine capable of performing such energy conversion tricks: the body.

In the natural process of metabolism, the bodies of humans and other animals burn organic fuels known as food and convert the released energy into the movement of muscles. Men, women and beasts could consume grain and meat, burn up the carbohydrates and fats, and use the energy to haul a rickshaw or pull a plough.

Since human and animal bodies were the only energy conversion device available, muscle power was the key to almost all human activities. Human muscles built carts and houses, ox muscles ploughed fields, and horse muscles transported goods.

The energy that fueled these organic muscle-machines came ultimately from a single source – plants. Plants in their turn obtained their energy from the sun. By the process of photosynthesis, they captured solar energy and packed it into organic compounds. Almost everything people did throughout history was fueled by solar energy that was captured by plants and converted into muscle power."


"Most people claim that their social hierarchy is natural and just, while those of other societies are based on false and ridiculous criteria. Modern Westerners are
taught to scoff at the idea of racial hierarchy. They are shocked by laws prohibiting blacks to live in white neighborhoods, or to study in white schools, or to be treated in white hospitals. But the hierarchy of rich and poor – which mandates that rich people live in separate and more luxurious neighborhoods, study in separate and more prestigious schools, and receive medical treatment in separate and better-equipped facilities – seems perfectly sensible to many Americans and Europeans.

Yet it’s a proven fact that most rich people are rich for the simple reason that they were born into a rich family, while most poor people will remain poor throughout their lives simply because they were born into a poor family”

[^1]: Not sure this is correct. According to the Smithsonian, we had additional brain growth during the last 800-200.000 years [Smithsonian: Human Origins] ( "Human Brain Development")

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