The cognitive revolution, about 70,000 years ago, offered homo sapiens the chance to spread all over the world. As every book says, the major breakthrough was the invention of “fire”. The fire enabled the sapiens to cook food and reduced the amount of energy human body needed (both to digest food and to withstand cold).

This excess (saved) energy helped the brain to develop further. By then the human brain used more than 25% of body energy and grew drastically; though the brain is just 2-3% of our total body weight, it consumes >20% of our body energy, even today (can't believe, isn't it? 😉). This larger brain led him more intelligence, imagination, and very important communication.

His communication skills brought in “language”. His imagination gave birth to thousands of stories, religions, and beliefs. All this combined, helped him to grow as a group (society), with a lot of interaction and collaboration between each other. We used this cognitive ability to withstand our dangers and survive better, while the other species were eliminated.


However, the author does not acknowledge the agricultural revolution as a "progression" that man made. In fact, he even calls it as "history's biggest fraud.". He writes as "The Agricultural Revolution certainly enlarged the sum total of food at the disposal of humankind, but the extra food did not translate into a better diet or more leisure. Rather, it translated into population explosions and pampered elites. The average farmer worked harder than the average forager, and got a worse diet in return"

He also defends his anger with a fact that an average man was roughly 5'10" tall and the woman was 5'6" before the agricultural revolution. Then sooner, within 3-4 generations, the average heights dipped to 5'5" for male and 5'1" for female. Many researches show that it was mainly because of his diet switch from more proteins to carbohydrates, combined with less physical movement. This is quite a fact, Isn’t it😞?

Scientific Revolution: 

Till the year 1500, human’s acquaintance to objective science was quite confined. Till 15th century, no human had even dreamt of circumnavigated the earth, but this changed when Magellan successfully returned to Spain in 1522. Prior the year 1500's, he just believed that the sky is only for the birds and angels. But he broke his own beliefs on 20 July 1969, by entering into the moon.

During the last five centuries, humans increasingly came to believe that they could increase their capabilities by investing in scientific research. This wasn’t just blind faith – it was repeatedly proven empirically by many historical technology milestones from engineering to medicine.

On the other extreme, he started pushing science and technology on war and nuclear bombs;  started making strides in biotechnology by modifying the genes of vegetables and animals, with no clear boundary of what is good and what is forbidden to do. He keeps trying to change things with mortality, by cloning and Artificial Intelligence. Thus, even after becoming the primal species of the world, human still stays more than ever dissatisfied and irresponsible who don’t know what they want!.

Harari ends the book talking about the future of humankind including how the world needs to come together to solve truly global problems such as global warming, and the rise of artificial intelligence.

As I said, the book is a heavy read, not something you want to take along on a beach vacation😇. But if you have little interest in science and want to know how the humans evolved, you’ll absolutely love this book, it’s extremely interesting, engaging and informative. I confess it again; this riveting and myth-busting book cannot be summarized… (what I have written so far is too small) you will simply have to read the full book.