Sapiens Chapter 4 Summary – The Flood

Chapter 4 of Sapiens follows the story of Homo sapiens directly from where we left off in Chapter 3.

.stk-67693a2{margin-bottom:0px !important}.stk-67693a2-container{box-shadow:0 5px 30px -10px rgba(18,63,82,0.3) !important}.stk-9cbdf58{margin-bottom:0px !important}Sapiens Chapter 3 Summary – The Flood

Who were our ancestors? What did they really feel? How did they live? The answer to these questions shape our identity even today. Find the truth…

In this chapter called The Flood, Harari paints a remarkable picture of human exploration in the prehistoric times. It gives an account of the ingenuity and will power of our ancestors. But, at the same time, he also compares the spread of humans to a flood. A flood of death and destruction for entire ecosystems that were not prepared for our arrival.

Prior to the Cognitive Revolution, humans of all species lived exclusively on the Afro-Asian landmass. Few islands near the shores may have been settled as early as 850,000 years ago, but humans did not had the resources to venture into open sea. As a result, there were no humans in America, Australia or other remote islands such as Madagascar and New Zealand.

Organisms of distant lands such as Australia or Madagascar evolved in isolation for millions upon millions of years. The plants and animals found there had very different shapes and nature when compared to their Afro-Asian counterparts. The sea-barrier was a great wall separating the multiple ecosystems from each other.

However, all of this was about to change soon.

The Invasion of Australia

After the Cognitive Revolution, Sapiens acquired the technology and more importantly, the vision to break out of Afro-Asia and spread to the so-called Outer World.

As per estimates, some 45,000 years ago, humans succeeded in colonization of Australia. Though experts are hard-pressed to explain this remarkable achievement, reasonable theories suggests that the Sapiens residing in the Indonesian archipelago developed the first sea-faring societies.

This was an unprecedented transformation.

Every other mammal that went to sea before us had to evolve for ages to adapt to survive underwater. The Sapiens in Indonesia became sea-farers without going through any of that evolution process. They simply built boats and learned how to use them.

According to Harari, this was an event almost as important as the voyage of Columbus or the Apollo 11 expedition to the moon. It was the first time any large mammal species had crossed from Afro-Asia into Australia.

However, this was just the beginning.

Even more important is what the human pioneers did in the newly discovered continent. The moment the first hunter-gatherer set foot in Australia was the moment that Homo sapiens climbed to the top of the food chain and became the deadliest species in the history of the planet.

Australia was a strange universe full of strange creatures that included a 200-kilogram kangaroo, a marsupial lion as big as a modern-day tiger and flightless birds twice the size of ostriches. The giant diprotodon weighing around 2-2.5 tons roamed the forests and dragon like lizards walked in the undergrowth.

The Prehistoric Australian Ecosystem

Within a few thousand years, all of these giants vanished from the face of the Earth.

Food chains throughout the entire ecosystem of Australia ruptured and rearranged around the new apex predator. It was the most important transformation of the Australian ecosystem for millions of years. And it happened because of Homo sapiens.

Are Homo sapiens Innocent?

Some scholars have attempted to exonerate our species of the crime by placing the blame on the vagaries of climate change.

However, there are several important pieces of evidence that make the climate change theory weaker.

Firstly, Australia’s climate did change 45,000 years ago but it wasn’t a major upheaval. The resulting weather patterns were not strong enough to cause such a massive extinction of flourishing species.Secondly, when climate change causes mass extinctions, sea creatures are also equally impacted. However, there is no evidence of oceanic fauna disappearing 45,000 years ago. Homo sapiens were a terrestrial menace at the time and did not had the capability to impact ocean life in such a drastic manner.Thirdly, mass extinctions similar to Australia have occurred again and again in the ensuing millennia whenever people settled a new part of the Outer World. For example, the megafauna of New Zealand survived the so-called climate change 45,000 years ago, but suffered devastating blows as soon as the first humans stepped on the island. A similar fate befell the mammoth population of Wrangel Island in the Arctic ocean.

In short, whenever there was a mass extinction, humans were involved. Judging by our horrendous track record, Homo sapiens can be labelled as ecological serial killers.

Harari goes on to explain how ancient humans were able to cause such massive ecological disasters even with stone-age technology.

First reason was the slow breeding of large Australian animals such as diprotodons. Even if humans started killing one diprotodon every few months, it would be enough to cause deaths to outnumber births and eventual extinction of the species.

A Diprotodon found in Australia 45,000 years ago

In fact, it would have been relatively easy for humans to hunt the giant Australian animals. In Afro-Asia, other animals had learned to stay away from humans. However, the Australian animals had no time to learn to run away from humans. Technically, humans don’t look particularly dangerous in appearance. The fear of humans simply did not evolve fast enough in the Australian animals and before they could understand how dangerous we really were, they were wiped out.

Second reason was fire agriculture that Sapiens had already mastered. Faced with an alien and threatening environment, the Sapiens would have burned vast areas of thickets and forests to create open grasslands. This completely changed the ecology of large parts of Australia in a very short amount of time.

The fire theory is proven by the abundance of Eucalyptus trees in Australia since they re-generate particularly well after fire. This sudden change in ecology destroyed the existing food chains and pushed more animals towards extinction.

The Footprints of Sapiens

Wherever the Sapiens went, mass extinctions followed.

The same thing happened when humans reached Americas. North America lost 34 out of its 47 genera of large mammals and South America lost 50 out of 60 after the arrivals of humans.

The wave of extinctions also began in the Pacific Ocean when Polynesian farmers settled the Solomon islands in about 1500 BC. They killed, directly or indirectly, hundreds of bird species, insects, snails and other local inhabitants.

Not for nothing are humans known as the deadliest species on the planet.

Harari finally concludes the chapter by hoping that we might learn from our mistakes and alter our behaviour so that more species such as whales, sharks and dolphins do not go extinct due to our industrial activities. Otherwise, humans would remain as the only large animals on the planet surviving the flood of humans.

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