In Harari's book, people are referred to by scientific names as 'Homo Sapiens' or 'Sapiens' rather than 'Human'. He gave a striking reason for this - through evolution, several species of 'humans' were born from apes. The wild humans of the Neanderthal valley of Europe became nonexistent 30,000 years ago, the one-foot-high dwarf humans of the Indonesian island of Florin also became nonexistent ... the people of the Donovan caves in Siberia also became nonexistent. Today there is only one species that survives - Homo Sapiens, we. So, the author is not just willing to call the Sepians a human race, they are just a species of human. 

Harari begins with the first chapter entitled "An Animal of No Significance", Sapiens have been living on Earth for millions of years, during which time they have received more of a hunting role than a hunter. They do not have the strength, they do not have the ability to fly, they do not have extraordinary eyesight, they do not have the size of huge elephants. They can't drown in the sea; they can't survive in the cold. Other animals begin to become self-sufficient within a few months of birth, and sepians cannot do that! They just have a head, a big brain! That's the problem again. It's hard to move fast with this big head, meanwhile, no necessary work is done with intellect. Sapiens may win an argument with a chimpanzee, but in a face-to-face fight, the chimpanzee can tear him apart like a toy in a matter of seconds. The only specialty of human beings is that talent has not been used for millions of years! Carrying this 1,400 cubic centimeter brain, weak, slow creatures have had to pay the ultimate price for thousands of years in a terrible world - the author calls it - 'cost of thinking'! 

Gradually the Sepians learned the use of stone and wood. Hareri narrates the story of how Stone Age people lived and how they behaved - mentioning fossils and archeological finds from various places as sources. 

The 'agricultural revolution', which began 12,000 years ago, is one of the greatest events in history. Harari showed how people did not get the food and security they wanted in an agrarian society. On the contrary, most of the lives have become more threatened due to these new structures of villages, states, empires formed due to permanent residence. 

Harari gradually mentions how one religion after another began to emerge which helped unite the people scattered all over the world. He saw the discovery of "money" among human beings as one of the great revolutions. Even if you give a monkey a hundred dollar note exchange for a banana, he is not going to accept it – because to the monkey the dollar note is just a worthless paper. But people have created the economic system by using their extraordinary thinking - they generally believe that a hundred dollars are worth it, their belief is the value of that money. The author says that even the enemies of the United States are willing to accept a dollar note - because they know that its value is guaranteed by the US Treasury itself. So, the money is above all politics. In the chapter "The Scent of Money", the author mentions some interesting facts about how even the Christian Crusaders, who were at war with the Muslims, did not object to the adoption of 'Arabic dinars written in Kalima'. 

As far as the eye can see, there are huge grasslands covered with green grass, which may have merged into a forest in the distance. Some giraffes are eating in the grass in the gentle breeze of the morning. Suddenly a group of lions came out from behind the long grass, disturbing the calm grassland! Some of the giraffes ran away but one of them fell down with a giant scratch by a lion. The meal started. After a while, the lions started their journey towards the forest. When the tail of the last lion disappeared into the forest, the hyenas came out of hiding. They began to swallow the leftovers of the lions. The foxes arrived when the hyenas had gone elsewhere, looking for meat in the grassland. When the evening foxes have eaten away, only the giraffe's bones are left. When the meat-eaters went to seek shelter all night, a few two-legged animals came out of the forest. Hairless, slender animals are wrapped in tree bark and leaves to survive the winter. They come silently to find out if there is anything left to eat in the body of the dead giraffe. When they don't find anything, they start breaking the bones with the picked-up stones. At the same time, they keep a watchful eye all around, so as not to suddenly become prey to any animal!! 

Another morning, July 16, 1945. 

A few strange airplanes fluttered their wings over a desert in New Mexico. Suddenly, the heart of the desert shook. The calm desert became stormy, the light of a thousand suns shone at once. The first nuclear explosion shocked the world. 

A couple of two-legged animals standing on a hilltop 150 kilometers away saw the light with strange eyes. In the distance, sparks and smoke gathering like mushrooms, witnessing that they have opened the gates of hell. Man has entered the nuclear age. One of them, scientist Oppenheimer muttered a few words, 

"... Now I've become Death, the destroyer of worlds ...." 

On July 16, 1945, mankind again took part in a new war. This war was for wealth - for domination. Today man has succeeded in creating the absolute domination of nature. 

But, how did a weak two-legged animal lying under the food chain discover nuclear physics!? How did he dominate all creatures? The story of all this is told by 'Yuval Noah Harari' in his book 'Sapiens'.