Sapiens by Yuval Noah Harari. Well, this has to be the most thought-provoking and perspective-changing book I’ve read so far. I came across this book in my college days after a recommendation from my friend. Since then I’ve read this multiple times and was fascinated by the depth and the perspective of Yuval about human history, every single time.

This is Part 1 (The Cognitive Revolution) in the four-part series of book summary of Sapiens by Yuval.

The Cognitive Revolution

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1) An Animal of No Significance

• Animals much like modern humans first appeared ~2.5 million years ago.
• Prehistoric humans were insignificant animals with no more impact on their environment than gorillas, fireflies or jellyfish.
• Just 6 million years ago, a single female ape had two daughters. One became the ancestor of all chimpanzees, the other is our own grandmother.
• Homo sapiens—the species sapiens (wise) of the genus Homo(man).
• The rise of sapiens kickstarted the Cognitive Revolution about 70,000 years ago.
• Until about 10,000 years ago, many different human species coexisted.

Skeletons in the Closet

• The depiction of man evolving from hunched over to upright incorrectly displays human evolution as a linear trajectory. In fact, the species lived simultaneously.
• Homo sapiens are just one of many different species of humans that once lived. The earth of a hundred millennia ago was walked by at least six different species of man.
  1. Homo neanderthalensis (Neanderthals) lived in Europe and western Asia.
  2. Homo erectus (Upright Man) populated eastern regions of Asia and survived there for 2 million years making it the most durable human species ever.
  3. Homo soloensis (Man from the Solo Valley) occupied the island of Java in Indonesia.
  4. Homo floresiensis were dwarf humans, reaching a max height of only 3.5 feet and weighing no more than fifty-five pounds. They lived on the Indonesian island of Flores.
  5. Homo denisovalived in Siberia.
  6. Homo rudolfensis (Man from Lake Rudolf) evolved in East Africa.
  7. Homo ergaster (Working Man) evolved in East Africa as well.

There may be many more lost relatives of ours still waiting to be discovered.

The Cost of Thinking

• All humans have extraordinary large brains compared to other animals.
• Big brains are a huge energy drain. Human brains account for 2-3 percent of body size, but use 25 percent of energy.
• We paid for our large brains by spending more time searching for food and muscle atrophy.
• Upright walking on two legs is another singular human trait.
• Our hands evolved to perform intricate tasks and produce sophisticated tools.
• 100,000 years ago, Homo sapiens jumped to the top of the food chain so quickly that the ecosystem did not have time to adjust.
• Most animals at the top of the food chain made it there gradually over millions of years. Humans, however, jumped to the top relatively rapidly. This means that the rest of the food chain wasn’t ready and neither were we. Hence we feel anxious and stressed because we aren’t used to being at the top.

Having been one of the underdogs of the savannah, we are full of fears and anxieties over our position, which makes us doubly cruel and dangerous. Many historical calamities, from deadly wars to ecological catastrophes, have resulted from this over-hasty jump.

A Race of Cooks

• 300,000 years ago, humans were using fire on a daily basis.
• Fire allowed humans to cook, which made many more foods digestible.
• Chimpanzees spend five hours a day chewing raw food. Humans spend one hour eating cooked food.
• Since long intestines and large brains are both massive energy consumers, it’s hard to have both.
• By shortening the intestinal track and decreasing their energy consumption, cooking inadvertently opened the way to the jumbo brains of Neanderthals and Sapiens.

Our Brother’s Keepers

• 70,000 years ago, Sapiens from East Africa spread from the Arabian peninsula, and from there they quickly overran the entire Eurasian landmass.
• The ‘Interbreeding Theory’ suggests that Sapiens bred with other human populations and people today are the outcome of this interbreeding.
• The ‘Replacement Theory’ suggests that Sapiens could not breed with other humans and killed them off either directly by force or indirectly through competition of resources.
• The reality is probably a combination of both theories.
• 1-4% of the unique human DNA of modern populations in the Middle East and Europe is Neanderthal DNA.
• Homo sapiens wiped out the Neanderthals because “They were too familiar to ignore, but too different to tolerate.”. It is the most significant ethnic-cleansing campaign in history.
• Tolerance is not a Sapiens trademark. In modern times, a small difference in skin colour, dialect or religion has been enough to prompt one group of Sapiens to set about exterminating another group. Would ancient Sapiens have been more tolerant towards an entirely different human species?
• Whether Sapiens are to blame or not, no sooner had they arrived at a new location than the native population became extinct.

2) The Tree of Knowledge

• 70,000-30,000 years ago witnessed the invention of boats, oil lamps, bows and arrows, and needles. The first objects that can reliably called art date from this era, as does the first clear evidence for religion, commerce and social stratification.
• This time period is referred to as the Cognitive Revolution.
• We don’t know what caused it. The best guess is a random genetic mutation.
• Homo sapiens conquered the world thanks to our unique language.
• Our language evolved as a way of gossiping. Homo sapiens is primarily a social animal.
• Gossip is essential for cooperation in large numbers.
• A truly unique feature of our language is the ability to transmit information about things that do not exist.
• As far as we know, only Homo sapiens can talk about things we have never seen, touched, or smelled. Think religions, myths, legends, and fantasies.
• Fiction allows us to imagine things collectively. A common belief helps us cooperate flexibly in large numbers. That’s why Sapiens rule the world, whereas ants eat our leftovers and chimps are locked up in zoos and research laboratories.

Our language is amazingly supple. We can connect a limited number of sounds and signs to produce an infinite number of sentences, each with a distinct meaning. We can thereby ingest, store and communicate a prodigious amount of information about the surrounding world.

The Legend of Peugeot

• Chimps can’t form groups of more than 50 or so. For humans, the group size is usually 150 or so. Beyond that, you can’t rely on gossip and personal communication. You need something more to get large numbers of people working together.
• Larger numbers of strangers can cooperate successfully by believing in common myths and beliefs.
• The way people cooperate can be changed by changing the stories as myths we tell.
• In academic circles, stories are known as fictions, social constructs, or imagined realities.
• Unlike lying, an imagined reality is something that everyone believes in, and as long as this communal belief persists, the imagined reality exerts force in the world. This glue has made us the masters of creation.
• Ever since the Cognitive Revolution, humans have been living in a dual reality: the physical reality and the imagined reality.

People easily understand that ‘primitives’ cement their social order by believing in ghosts and spirits, and gathering each full moon to dance together around the campfire. What we fail to appreciate is that our modern institutions function on exactly the same basis.

• Two Serbs who have never met might risk their lives to save one another because both believe in the existence of the Serbian nation, the Serbian homeland and the Serbian flag.
• Corporations are modern day figments of our collective imagination.
• Limited liability companies are legally independent from the people who set them up, or invested money in them, or managed them.

Telling effective stories is not easy. The difficulty lies not in telling the story, but in convincing everyone else to believe it. Much of history revolves around this question: how does one convince millions of people to believe particular stories about gods, or nations, or limited liability companies? Yet when it succeeds, it gives Sapiens immense power, because it enables millions of strangers to cooperate and work towards common goals.

Bypassing the Genome

• Archaic humans only changed their behavior, invented new tools, or settled new territory as a result of genetic mutations or environmental pressures.
• Ever since the Cognitive Revolution, Sapiens have been able to change their behavior quickly, transmitting new behaviors to future generations without any need of genetic or environmental change.
• Because Homo sapiens’ shared myths were not genetically based, they could adapt and change their behavior as soon as they adapted their new belief. They didn’t have to wait millions of years for a genetic change.

History and Biology

• The Cognitive Revolution is the point when history declared its independence from biology.
• Historical narratives replace biological theories to explain our development.

3) A Day in the Life of Adam and Eve

• As far as we know, the humans of 30,000 years ago had the same physical, emotional, and intellectual capabilities that we have today.
• Evolutionary psychology claims that most of our psychology was developed during the period before the Agricultural Revolution about 10,000 years ago.
• Ever since the Agricultural Revolution, there hasn’t been one predominant way of life for all humans. There have only been options from a variety of cultures.
• It’s hard to guess how the ancients lived because there are so few artifacts.
• The Stone Age should more accurately be called the Wood Age, because most of the tools used by ancient hunter-gatherers were made of wood.
• It’s also problematic to extrapolate the lives of modern forager societies to ancient ones.
• Today’s forager societies have been influenced by neighboring agricultural and industrial societies.
• Modern forager societies have survived mainly in areas with difficult climate conditions and inhospitable terrain. This may provide a very misleading model for understanding ancient societies that roamed fertile areas.
• Lastly, the most notable characteristic of hunter-gatherer societies is how different they are from one another.

The Original Affluent Society

• Dogs were the first domesticated animal. About 15,000 years ago.
• The human collective knows far more today than the ancients. But at the individual level, ancient foragers were the most knowledgeable and skillful people in history.
• The ancients were as fit as marathon runners and had the physical dexterity that people today are unable to achieve even after years of practicing yoga or t’ai chi.
• They worked just 35-45 hours a week.
• They enjoyed more diverse experiences throughout their days.
• Ancients ate a varied and nutritious diet.
• The instinct to gorge on high calorie food is wired into our DNA.
• Ancient foragers also suffered less from infectious diseases. Most of the infectious diseases that have plagued agricultural and industrial societies (like smallpox, measles and tuberculosis) originated in domesticated animals and were transferred to humans only after the Agricultural Revolution.
• The wholesome and varied diet, the relatively short working week, and the rarity of infectious diseases have led many experts to define pre-agricultural forager societies as ‘the original affluent societies’.
• Their world could still be harsh and unforgiving. High child mortality, minor accidents by today’s standards could be a death sentence, and confrontations with other foraging bands could be extremely violent.
• In ancient human groups (over 10,000 years ago) there was very little privacy, but also very little loneliness.
• The human collective today knows far more overall than the whole population of 15,000 years ago. However, at the individual level we are much more specialized today. Ancient foragers were the most knowledgeable and skillful people in history.

4) The Flood

• 45,000 years ago Sapiens crossed the sea to Australia. Experts are hard-pressed to explain this amazing feat.
• The moment the first hunter-gatherers set foot on an Australian beach was the moment that Homo sapiens climbed to the top rung in the food chain on a particular landmass and thereafter became the deadliest species in the annals of planet Earth.
• The settlers of Australia transformed the ecosystem beyond recognition.
• Within a few thousand years, of the 24 Australian animal species weighing 100 pounds or more, 23 became extinct.

Guilty as Charged

• Change in weather patterns 45,000 years ago is weak evidence to support such a massive extinction.
• When climate change causes mass extinctions, sea creatures are usually hit equally hard. Yet there is no evidence of any significant disappearance of oceanic fauna 45,000 years ago.
• Mass extinctions, like the one seen in Australia, occurred again and again in the ensuing millennia whenever people settled another part of the Outer World.
• Large animals breed slowly. Plus, Australian giants had no time to learn to run away. They would have been surprised to find themselves in danger to punitive humans.
• Sapiens may have also used fire to intentionally burn large areas to create open grasslands.

The End of Sloth

• The settling of America – across the Siberian peninsula through Alaska into Canada and the United States down through Mexico and Central America into the Andes and the Amazon and all the way to the tip of South America – was one of the most rapid and incredible invasions by a single species the world had ever seen.
• Within 2,000 years of Sapiens’ blitzkrieg across America, North America lost 34 out of its 47 genera of large mammals. South America lost 50 out of 60.

Noah’s Ark

• Homo sapiens drove to extinction about half of the planet’s big beasts long before humans invented the wheel, writing, or iron tools.
• Perhaps if more people were aware of the First Wave and Second Wave extinctions, they’d be less nonchalant about the Third Wave they are part of now.
• If we knew how many species we’ve already eradicated, we might be more motivated to protect those that still survive.

If things continue at the present pace, it is likely that whales, sharks, tuna and dolphins will follow the diprotodons, ground sloths and mammoths to oblivion. Among all the world’s large creatures, the only survivors of the human flood will be humans themselves, and the farmyard animals that serve as galley slaves in Noah’s Ark.

Continued in Book Summary: Sapiens (Part 2)