The course is split into seventeen lectures and further into four main segments.
Part I: The Cognitive Revolution –
Part II: The Agricultural Revolution
Part III: The Unification of Humankind
Part IV. The Scientific Revolution
This week’s lecture introduced the course and introduced the Human family. From the Syllabus on line :-
Lecture 1: The Human Family
One hundred thousand years ago, at least six different species of humans inhabited planet Earth. Our species, Homo sapiens, was just one among them. Who were the others? Where did they come from? And what happened to them? Why is there today only one species of humans—Homo sapiens?
As with all lecture notes that I put on my MOOC blog the notes are to help me remember. I sometimes use my own words and sometimes those of the lecturer. The process of writing the blog helps to to assimilate the information.
What is History?
Dr. Harari started by stating that he will be presenting his own understanding of history. He appreciates that his view is not the same as all other historians. It will be superficial, due to time, and controversial because this is how he understands it.
About 13 billion years ago, matter, energy, time, and space, came into being in what is known as The Big Bang. The story of these fundamental features of our universe is called physics. Physics examines how matter, energy, time, and space interact with one another and behave.
About 300,000 years after their appearance matter and energy started to combine into complex structures which we call atoms. These atoms then combined into even more complex structures which are called molecules. The story of atoms, molecules, and their interactions is called chemistry. Chemistry examines what happens when an oxygen atom comes into contact with a hydrogen atom or when a solid molecule comes into contact with a water molecule.
About 4 billion years ago on a planet called earth certain molecules combined to form even larger and more complex structures which we call organisms, or living creatures. The story of organisms is biology. Biology examines how for example a lion or a giraffe function and what happens when a lion comes into contact with a giraffe.
About 70,000 years ago, organisms belonging to a very particular specie, our species, Homo sapiens started to come together and combine and form even more elaborate structures, which we call cultures. The development of these human cultures is history.
What is a Human?
Humans existed long before history. History began, according to evolution about 70,000 years ago. Animals, much like modern humans, first appeared about 2 and a half million years ago in East Africa. For most of these 2 and half and million years our human ancestors were just another kind of animal. There was nothing special about humans. There was no hint that their, great, great, great grandchildren would one day, walk on the moon, or split the atom, or understand DNA, or write history books. Prehistoric humans were unimportant creatures, they did not have more impact upon the world than gorillas, or fireflies, or penguins.
Animals are said to belong to the same species if they mate with one another, giving birth to fertile offspring. Horses and donkeys look quite similar but their offspring, which are called mules, are always sterile. They are two completely different species and cannot exchange genes between them; they are evolving in different directions. A Bulldog and a Cocker Spaniel look very different from one another, but they can produce fertile puppies. Bulldogs and Spaniels are considered members of the same species
Species that evolved from common ancestors are bunched together by biologists under the title genus. For example, lions, tigers, leopards and jaguars are different species within the genus Panthera. The scientific name of each animal has two parts, first, the genus, and then the specie. Lions for example have the scientific name Panthera leo. The scientific name of our species is Homo sapiens, which means the species sapiens, a Latin word meaning wise, of the genus Homo, a Latin word meaning men.
Genera are grouped by biologists into larger collectives which are known as families The dog family includes dogs and all kinds of wolves, foxes, and jackals. All members of the family trace the lineage back to some ancient ancestor who is the great, great, great grandmother or grandfather of all of them. Homo sapiens belong to a biological family called, the family of great apes. There are some other members of this family still living today. Our closest relatives include chimpanzees, gorillas, and orang-utans, of these, chimpanzees are the closest
Homo sapiens tend to call ourselves humans as if we are the only humans. But there used to be many other human species on planet Earth. Human simply means animals that belong to the genus Homo that is man in Latin. Humans first appeared in East Africa, about 2 and a half million years ago. They evolved from an earlier genus of apes called Australopithecus, meaning southern ape. At first Australopithecus was the only human specie, but, about 2 million years ago, some of these archaic men and women left east Africa and spread around the world, settling various areas in North Africa, the Middle East Europe and Asia. In each area they encountered different conditions, a different climate, different geography, animals and plants. In order to adapt they began to evolve in different ways. This created completely different human species. For example, humans who reached northern Europe needed to adapt to the very cold climate and all kinds of big animals like birds and mammoth and mastodons. The result was that over the years many different species of humans evolved in different parts of the world to which scientists assigned Latin names.
In Middle Eastern Europe there was a specie of humans which scientists call Homo neanderthalensis, meaning man from the Neander Valley. The name was given because the first remains of these ancient humans were discovered by archaeologists in the Neander Valley in Germany. They also gave these humans a nickname, which everybody, the Neanderthals. Neanderthals were well adapted to the cold climate of ice age Europe and the Middle East which was much colder than it is today. Neanderthals were bigger, more muscular than us. They had insulating layers of fat covering their bodies to give them better protection from the cold and they even had bigger brains that we have.
On the island of Java in Indonesia, evolved Homo soloensis. This means, in Latin again, man from the Solo Valley, because the first remains were discovered by archaeologists in the Solo Valley on Java Island . Java had a tropical climate so Homo soloensis evolved to become better adapted to living in the jungles and swamps of tropical Java.
On another Indonesian island, the very small Island of Flores evolved a very unique and interesting human specie which is called by scientists Homo floresiensis, man from Flores Island. Homo floresiensis were dwarfs. Flores used to be connected to the mainland. At some time, the sea levels rose and Flores was disconnected from the mainland. Flores is a small island and there is not much to eat so big people died first as they needed more food. Smaller people managed to survive better. Over the years the people of Flores Island became smaller, and smaller. It’s estimated, according to the bones that scientists have found that Homo floresiensis reached a maximum height of no more than one meter and the maximum weight of 25 kilograms. Nevertheless, these tiny people were humans. They were able to manufacture and use all kinds of tools like spears and so forth. They even managed, at least from time to time, to hunt the small elephants of Flores.
From an article on Nature.com I read that animals bigger than rabbits get smaller when food supplies are short and smaller animals get bigger. The rats on Flores Island were as big as rabbits.
All human species shared several defining characteristics that make them all humans. They all had large brains. Mammals weighting 60 kilograms usually have a brain of about 200 cubic centimeters but a homo sapiens today at that weight has a brain averaging between 1200 and 1400 cubic centimeters. The brains of earlier humans were smaller, but even the brain of the earliest men and women, in East Africa about two and a half million years ago, was still very large compared, say, to the brain of a tiger or a pig of an equal weight.
This disproportion of a very big brain compared to body size only increased as humans evolved. A big brain, aside from its advantages is also a very big problem. First of all, you have to carry it around and you have to protect it so it’s encased within a massive skull. It’s burdensome to the body to carry around this big head. What is even harder is to fuel the brain with energy. In homo sapiens, the brain accounts for about 2 or 3% of total body weight, but it consumes 25% of the body’s energy when the body is at rest. The brains of other apes, like chimpanzees or gorillas, require only 8%.
Ancient humans paid for their larger and larger brains in two main ways. First they had to spend more time looking for food. Secondly as the brain got bigger, humans became less muscular. A chimpanzee cannot win an argument with a homo sapien but can rip one apart as if it were a rag doll. A chimpanzee that weighs 60 kilograms is estimated to be at least five times stronger than a human being of equal weight. Giving up on muscles in exchange for brain it wasn’t necessarily such a good deal. Human brains kept growing but apart from some flint knives and pointed sticks, humans had very little to show for them. Why the brain became so big, is one of the greatest mysteries in evolution.
Another quality which is common to all human species, Neanderthals, Homo erectus, Homo floresiensis and, of course us, is that we walk upright on two legs. It’s easier to explain the advantages of walking upright than the advantages of big brains. When you stand up it’s much easier to scan the Savannah in search of prey, enemies and predators. Once your hands are free you can use them for many other new purposes, like signalling, throwing things and making things. Human hands evolved increasing concentrations of nerves, and finally small finely tuned muscles in the palms and the fingers, which enables humans to preform very complicated, very delicate tasks with their hands. The first evidence we have for humans producing and using tools dates back to about two and a half million years ago in East Africa. The manufacture and use of tools is a defining characteristic by which archaeologists recognize ancient humans.
Walking upright also has its downside. Firstly the skeleton of our primate ancestors evolved for millions upon millions of years to support a creature that walked on all fours and had a relatively small head and brain. When humans moved to walking upright and simultaneously had bigger brains and bigger heads this created very lot of stress on the spine, the skeleton, and the muscles in general. The skeleton and muscles evolved but it has never been perfect. Even today, people still suffer a lot from back aches, stiff necks and all kinds of other problems in the skeleton and muscular system which result from a moving to an upright position.
Women paid extra for walking on two legs. One of the things that happens when you walk upright is that you’re hips have to be relatively narrow. In women this also means that the birth canal must be narrow. This created a huge problem because at roughly the same period the brains and the heads of the babies became bigger. How to give birth to babies with big heads, through a narrower and narrower birth canal was a big problem. One of the outcomes was that women and children began to die more often during child birth. The solution to this problem was to give birth to babies earlier and earlier when they are still small and especially when their head and brains are still very small and supple. Women who gave birth relatively late had a greater chance of dying in childbirth. The pregnancy period of women became shorter and shorter and women began to give birth earlier and earlier. Today women give birth much earlier comparatively than any other animal. Humans are born prematurely. They emerge from the womb when many of the vital systems, especially the brain are still not developed.
Impacts of premature birth
Because human children are born prematurely, they need a lot of care and attention from their elders, parents, siblings and so forth in order to survive. There’s a famous saying, that it takes an entire tribe to raise a human. This is why humans evolved very strong social ties with one another, natural selection favored humans who were capable of forming strong social ties and living in tribes.
The second important impact is that humans can be educated socialized to a far greater extent than any other animal. Humans emerge still very mouldable. We can educate our children to become Christian or Buddhists, Capitalist or Socialist, war-like or peace loving.
We tend to assume that having a large brain, being able to produce and use tools, having a complex societies are huge advantages, and it is obvious, why humans that possess all these advantages became the most powerful and most important animals on earth. The surprising and important fact is that humans enjoyed all these advantages for more than two million years and remained weak and marginal creatures, without much impact on the environment. There were less than a million humans about a million years ago and they were not the top predators of the ecosystem. They were preyed upon; they were hunted by bigger animals such as lions, bears, and alligators. Humans were not very good hunters. They were rarely able to hunt by themselves big animals like giraffes or elephants. Most humans subsisted by eating vegetable foods and small animals. They also ate the leftovers of other animals. Humans as scavengers would use stone tools, not to hunt animals, but to crack open the bones of dead animals in order to get the marrow. Some researchers believe that eating marrow was the original niche, or specialty of humans in the world.
From about 400,000 years ago several species of humans like neanderthals begin to hunt large animals on a regular basis. Only in the last hundred thousand years, with the rise of our species, Homo sapiens, did humans jump from the middle to the top of the food chain and became top predators of planet Earth. This spectacular leap from the middle to the top of the food chain had enormous consequences. Humans were not used to being at the summit of the food chain and they were not adapted for this position. Other animals at the top of the food pyramid, like lions, sharks, and alligators evolved to fill this position over millions of years. Human kind ascended to the position of top predator of the planet almost overnight, in evolutionary terms. It was not enough time for humans to adapt to this new position. Many historical calamities, and things about the way that humans behave towards others and toward the environment, from wars to the ways that people treat the ecosystem, result from this jump. That we now fill a position in the ecosystem which is completely different from the position of our ancestors until a very short time ago and we are not used to it, and not well adapted to it. Sometimes we think about ourselves, human kind, as a pack of wolves that somehow got hold of tanks and atom bombs. This is wrong, It is better to think about ourselves as a herd of sheep who due to some evolutionary accident learned how to make and use tanks and atom bombs. Armed sheep are far more dangerous than armed wolves because they are not used to it.
How humans became top dog.
Domestication of fire.
Perhaps the first significant step on the way to the top was the domestication of fire. We don’t know exactly when, where or how humans did this but, from archaeological evidence, we know that by about 300,000 years ago some humans, like neanderthals and later homo sapiens, were using fire on a daily basis.
Fire had important advantages to offer humans. It gave them a source of light and warmth. It gave the first really effective weapon against dangerous animals. Fires could also be used to start changing the environment to fit our ancestor’s needs for example, you could use fire to burn down forests then humans could walk in and collect and eat the cooked dead animals.
The most important thing that fire did was that it enabled humans to cook. Cooking was of immense importance. It opened up a whole range of previously inedible foods such as, wheat, rice, and potatoes. Cooking kills germs and parasites that infest food especially in meat so this also protected humans from poisoning and death this way. It also reduced the time and energy that humans have to invest in chewing and digesting their food. This means that humans can survive with smaller teeth, with less powerful jaws and with shorter intestines.
Some scholars believe that there is a direct link between the beginning of cooking, the shortening of the human intestines, and the growth of the human brain. The two greatest consumers of energy in the body are the brain and the digestive system (stomach and intestines). It’s quite difficult to have both very long intestines and a large brain at the same time, because they compete for the limited energy of the body. Although brains had grown before, the really big jump in size came only in the last 300 to 400,000 years, with the appearance of species like the neanderthals and homo sapiens. This is exactly the time that people began to cook. Once you cooked your food, your intestines became shorter and then your brain really got big.
Many scholars and scientists say that the first really significant gulf between men and all the other animals was the domestication of fire. The power of almost all the other animals depends upon their body. Some animals can use natural forces to increase the power. For instance animals can harness the power of water currents, or the power of winds, but even when animals do that there is still a very close connection to the physical abilities of their bodies. Eagles, for example, can use winds, and thermal columns to fly. But, they can’t control their location. The maximum carrying capacity is still proportional to their wingspan. When humans domesticated fire, it broke the link between the power of the animal and the size and power of the body of the animal. Humans gained control of an obedient and potentially limitless force.
However, it should be emphasized, that even after the domestication of fire, humans were still not the most important animal in the world. The real jump to the top of the food chain had to wait a few hundred thousand years more to the appearance and the spread and the triumphs of our species, Homo Sapiens.
At that time there were still many species of humans on planet Earth. Despite having fire they still remained relatively insignificant animals. The real revolution in the status of humans came only after the appearance of Homo Sapiens. We evolved in East Africa sometime between 300,00 and 200,000 years ago. Almost all scholars agree that by 150,000 years ago, east Africa was populated by Homo sapiens. Scholars also agree that around 70,000 years ago, some of these sapiens left East Africa and reached the Middle East, and quickly spread all over the Eurasian land mass. When Homo Sapiens arrived in the Middle East, most of Eurasia was already populated by other humans, by the Neanderthals and Homo Erectus, and Homo Soloensis, and so forth. What happened to them is one of history’s biggest and most important questions. There are two conflicting theories.
This argues that as sapiens spread around the world they bred with other human species and people today are the result of this interbreeding. For example, when sapiens reached the Middle East and Europe, they encountered the local population of Neanderthals. They were more muscular and better adapted to the cold climates of Europe and the Middle East than sapiens. They also had bigger brains than the brains of sapiens. They used tools, fire, and were quite good at hunting all kinds of animals.
When homo sapiens spread into Neanderthal lands, in the middle east and Europe they bred and the two populations basically merged to form a single population. If this is indeed the case, this means that Europeans and Middle Eastern people are not pure sapiens. But they are in fact a mixture of sapiens and Neanderthals. Similarly when sapiens reached China about 60 thousand years ago, they met and bred there with the local population of Homo erectus so that Chinese and people in east Asia in general are also not pure sapians, but a mixture of sapians and erectous. The only people who are really pure sapian are maybe Africans.
Replacement theory tells a very different story. It tells a story of incompatibility or revulsion and perhaps even of genocide. According to the Replacement Theory, there was no sex between sapiens and other human species, like the Neanderthals or the Erectus. Sapiens and Neanderthals had different anatomies. They most likely had different mating habits and had very little interest in having sex with somebody from the other species. Even had children together these children were infertile.
The populations of different species remained completely distinct. When the Neanderthals died out, their genes died with them. According to this view, sapiens replaced the other human populations in the world without merging with them. If this is the case, this means that all living humans today, not just Africans, are pure sapiens. All living humans today share exactly the same ancestors.
From an evolutionary perspective, 70,000 years is a relatively short time. It is not enough time for important genetic changes to accumulate.
If replacement theory is correct and all humans today are the descendants of the same African ancestors. All living humans today have roughly the same DNA. Racial distinctions between Africans, Europeans, Chinese and Aboriginal Australians and therefore the differences between them are negligible.
If Inter-Breeding theory is correct, there might be genetic differences between races that go back hundreds of thousands of years. There might be significant differences between different populations of humans today not only in physical qualities, but also in mental and psychological qualities. This is obviously political dynamite, it’s a problematic notion that there might be deep genetic differences between different populations of humans today. Because of the political implications and also because of the firmer archaeological evidence replacement theory was the most prevalent until recent years.
In 2010 the results of a four year effort to map the neanderthal genome were published. Geneticists were able to collect enough intact neanderthal DNA from fossilized bones to map the entire Neanderthal genome. They then compared the Neanderthal genome with the genomes, the DNA, of living people. The results stunned the academic community. About 4% of the unique human genes of modern people in the Middle East and Europe are Neanderthal genes. A few months later DNA extracted from the fossilized finger bone from Meso Denisovan cave showed that up to 6% of the unique human genes of modern Melanesians and aboriginal Australians are actually Denisovan genes.
It’s important to keep in mind that these are very new results. There is more evidence and more research being done all the time. We should be careful about jumping to conclusions. If these results are valid it means that there were at least some sexual encounters between sapiens, neanderthals, and the denisovan that resulted in the birth of fertile offspring.
That doesn’t mean that replacement theory is completely wrong. Since Neanderthals and Denisovans, according to these new findings, contributed only a very small percentage of our modern DNA, it is impossible to speak about a real merger between sapiens and other species. If there was actual merger between the populations we should have seen 40%, 50%. Although the differences between sapiens and neanderthals were not large enough to completely prevent fertile intercourse they were still sufficient to make its pretty rare.
Ancient populations of sapiens and other species may have intermingled but they did not merge, they remained distinct groups. They were not completely different species like horses and donkeys. On the other hand it would also be a mistake to view them as simply different populations of the same species like bulldogs and spaniels. Biological reality is not black and white. Every two species that evolved from a common ancestor were at one time two populations of the same species like bulldogs and spaniels. With time the two populations became more and more different from each other until they became completely distinct species and went their separate evolutionary ways. During this process there must have been a time when the two populations were different from one another but still capable of having sex, and producing fertile offspring.
There is still an important question to answer. If the Neanderthals did not simply merge with Sapiens, what exactly happened to them?
One possibility is that Neanderthals became extinct because Homo sapiens out-competed them. About 40,000 years ago sapiens from the Middle East arrived is a place where Neanderthals lived. They needed to eat and started hunting the local deer and picking the local mushrooms, nuts and fruits. This is exactly the food that Neanderthals relied on to survive. The two species started to compete for the same food resources. If sapiens were already more sophisticated than Neanderthals in their techniques of hunting and gathering they would have more of the food and their population would grow whereas other species would die out.
Another possibility is that the competition between sapiens and Neanderthal for the same food resources was not peaceful and quiet but escalated into violence, war and genocide. This is quite a likely scenario because tolerance is not a sapien trademark. In modern times, even a small difference of skin color of dialect or religion have been enough to prompt one group of sapiens to go about exterminating another group of sapiens. It is unlikely that ancient sapiens would have been more tolerant towards neighbors of a completely different human species.
We don’t know which if either of these possibilities is correct. It might have been different in different place. Whatever happened the Neanderthals and the other humans disappeared. Their disappearance was one of the most important events in history. It changed everything, it changed the way that sapiens understand themselves, their place in the world, and the relations to all the other animals. Homo Sapiens have grown so accustomed to being the only human specie around that it’s hard to conceive of any other possibility. The lack of brothers and sisters makes it very easy for us to imagine that we are the epitome of creation, and that there is a gap separating us from the rest of the animal kingdom.
When Charles Darwin in the 19th century indicated that Homo Sapiens were actually just another kind of animal, people were outraged. Even today, many people around the world refuse to believe it. Sapients is just one more kind of animal that evolved in a slightly different way, but not so different from the other animals. Had the Neanderthals survived along us, would we still imagine ourselves to be a very unique creature separated from all from the rest of the animal kingdom? Perhaps this is exactly why our ancestors wiped out the Neanderthals and the other human species. They were too familiar to us to simply ignore them, but they were too different from us to tolerate their existence. So the solution was to exterminate them. We don’t know it for sure, it’s just a speculation.
What we do know for sure Is that whether sapiens are to blame or not, no sooner had sapiens arrived at a particular location on planet Earth the native population of other human species became extinct. The last remains of Homo Soloensis on the island of Java, are dates to about 50,000 years ago, just when Homo sapiens arrived in Java. Homo Denisova disappeared shortly thereafter about 40,000 years ago. The Neanderthals disappeared about 30,000 years ago. The last ones vanished from Flores Island, about 12,000 years ago. They left behind some bones, some stone tools, a few genes in our DNA, and a lot of unanswered questions.
They also left behind us, Homo sapiens the last surviving human species.
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- In Europe, Neanderthals Beat Homo Sapiens to Specialized Tools (blogs.discovermagazine.com)
- Prehistoric Cats – Part 1
Orang-utan study suggests that upright walking may have started in the trees (notexactlyrocketscience.wordpress.com)
- Meet the Denisovans, indigenous Australia’s Siberian kin