1. Sapiens: A Brief History of Humankind
Chapter One

2. In the Beginning
Big Bang billion ya  physics- fundamental features of the universe
300,000 years later chemistry- interactions of molecules
3.8 billion ya Earth is formed along with biology
Approximately 70,000 ya Homo sapiens (human wise) create elaborate structures called cultures (history)

3. Three Important revolutions that shaped History
Cognitive Revolution: considered the start of history (70,000 ya)
Agricultural Revolution: 12,000 ya
Scientific Revolution: 500 ya
We will focus on prehistoric progression

4. Origin of Humans Genus homo refers to humans
Humans evolved from a genus of apes called Australopithecus (Southern Ape) about 2.5 million ya in East Africa
About 2 million ya, these archaic humans dispersed to many different places such as North Africa, Europe, and Asia.
Different areas caused unique evolutionary trends due to different climates
Cold climates of Northern Europe vs hot climate of Indonesia’s jungles
Resulted into different species
At least six different species of humans existed on the Earth a hundred millennia ago

5. Homo neanderthalensis
Man from the Neander Valley
Humans that migrated to Europe and Western Asia
They were bulkier and more muscular and adapted to the cold climate of Ice age Western Eurasia

6. Homo erectus
‘Upright Man”
Lasted for almost 2 million years
Homo erectus is attributed with the longest existence of any human species ever
Homo sapiens will most likely not break this record, if we even last for thousands of years

7. Human Islanders Homo floresiensis
These humans migrated to an island easily accessible from the main land when the sea level was low. However, some were trapped on the island of Flores when the sea level rose. Resources were scarce, so natural selection favored smaller people, and they became dwarves.
Max height: one meter, Max weight: 25 kilograms
Made stone tools and hunted dwarf elephants on the island
Homo soloensis- ‘Man from the Solo Valley’
Built for the tropics on another Indonesian island

8. The Human Brain
The first human brain was about 600 cubic centimeters, which is significantly larger than mammals that weight 60 kilograms with an average brain size of 200 cubic centimeters.
Modern sapiens brains tend to be 1,200—1,400 cubic centimeters
Neanderthal brains were bigger
Of course, brains are expensive. Brains of other apes only cost 8% compared to our 25%
This forced early humans to spend more hunting and gathering and sacrificed muscular strength

9. Other Human Traits
Bipedalism made scanning for over tall grass for prey or predators much easier
Arms were made available, which could be used for throwing stones or signaling
Hands could also be utilized for intricate tasks and create sophisticated tools
Selective pressure favored concentration of nerves in hands and well developed muscles in palms and fingers
Tools date back to 2.5 million ya

10. Costs of Human Adaptations
Bipedalism lead to backaches and stiff necks, and large cranium does not help the situation
Women suffer more from these adaptations
Upright gate means narrower hips. Babies heads were only getting bigger as well, so death by childbirth was a major hazard.
Women who gave birth to premature babies tended to increase their chances of survival. This is why babies seem to be a lot less developed compared to other mammals at birth. They also require much more care.
Colts can walk soon after birth
It was also challenging for women to gather resources and raise kids at the same time, so building strong social ties was vital. It took a village to raise a baby.

11. Middle of the Food Chain
For about 2 million years, humans feared predators, rarely hunted large game, and mainly depended on gathering plants, collecting insects, hunting small game, and scavenging the remains of kills committed by bigger carnivores.
Humans most likely used stone tools to extract bone marrow from the remains big prey like a giraffe. Bones would be the remaining resources left after other more capable scavengers (hyenas) took their share.
Only until 400,000 years ago did humans start to hunt big game, and 100,000 years ago that Homo sapiens jumped to the top of the food chain.
This jump was so quick that the ecosystem was not able to limit Homo sapiens growth. Prey normally have time to adapt to predators becoming more capable. This sudden change caused many historical calamities (ecological catastrophes to deadly wars).

12. Domestication of Fire 800,000 ya fires were used to keep warm
300,000 ya Neanderthals started to used fire more frequently and for multiple purposes.
Light
Warmth
Defense against predators. Our power did not have to come directly from our bodies. This set us a part from other animals.
Modifying neighborhoods by burning down thickets, which could then grown into prime grasslands that could support more game
Could also harvest could animals, nuts, tubers

13. Cooking
Cooking made indigestible food sources digestible. Wheat, rice, and potatoes became huge parts of the diet.
It also cleansed food by killing germs and parasites that infested food (tapeworms and salmonella).
It cut down on time spent of chewing and digesting. Insects, fruits nuts, and carrion could be consumed easily within an hour vs chimpanzees that spend five hours a day chewing raw food.
More efficient food sources led to smaller teeth and more importantly, a smaller intestinal track. Less energy spent on digestion made room for a larger brain according to some scholars.

14. Where did everybody go?
150,000 ya East Africa was populated by Homo sapiens that look just like we do today.
70,000 ya Sapiens migrated from East Africa to the Arabian peninsula. From there they took over all of the Eurasian landmass. This area was already occupied by other humans. What happened to them?
Two theories attempt to explain this phenomenon.
Interbreeding theory and Replacement theory

15. Interbreeding theory
Claims Homo sapiens were attracted to other species and mingled with them. Eventually, both species would merge. This means that today’s sapiens aren’t purely sapien but a mix.
Sapiens encountered Neanderthals in the Middle East and Europe. Neanderthals were more muscular, had larger brains, and were better suited for the cold climate. Like Sapiens, they used tools and fire, were capable hunters, and nursed their sick (remains of Neanderthals with physical handicaps suggested they still lived for many years). They definitely could have been viable breeding option.
This theory would also claim that Chinese and Koreans are mixture of Sapiens and Erectus.

16. Replacement theory
Claims that Sapiens and other humans had different anatomies as well as different mating behaviors and even body odors. Therefore, there would be little sexual attraction, and there would be no chance of producing fertile offspring.
This indicates that genocides may have occurred, or that other humans could not compete with humans in terms of fighting for the same resources.
If this theory is true, we can all trace back our lineages to East Africa, 70,000 ya. We would be ‘pure Sapiens’.

17. So is it interbreeding or replacement?
What are the political implications of the interbreeding theory?

18. Maybe a bit of Both?
1-4% of the modern day population in the Middle East and Europe is Neanderthal DNA.
Up to 6% of human DNA of modern Melanesians and Aboriginal Australians is Denisovan DNA.
While these number aren’t very large, they are still significant. It suggests that some successful breeding did occur, however, it must have been limited. Still, a conclusion of a merger seems very unlikely.
Important note: further research is still required for more definitive conclusions.
derthal/discussion

19. Possibilities of the Exit of other Humans
Sapiens were better hunters and gatherers than Neanderthals due to better technology and advanced social skills. Sapiens might haven multiplied and spread so much that they depleted Neanderthal’s food sources and drove them to extinction. Some Neanderthals might have joined Sapien groups to survive.
Or Homo sapiens did not tolerate Neanderthals due to phenotypic differences and decided that violence and genocide was the best route to take for the competition of resources. Think of modern times. Homo sapiens might have executed the first and most significant ethnic cleansing.

20. Final notes
Homo sapiens have been the only humans on Earth for that past 10,000 years.
Homo soloensis were the first to go with remain dating back 50,000 ya.
Homo denisova disappeared soon after
Neanderthals lasted until 30,000 ya
The last humans to die off were dwarfs from Flores Island
What would culture and religion be like if other species of humans survived?