Sapiens 1 -- The Human Family

Notes from a former student, generously posted online

Lesson 01 - part 2 -- There have been many "humans"

• Defines species (sapiens), genus (homo), family (great apes)
• Many other human species have existed and co-existed with us sapiens on earth

Lesson 01 - part 3 -- Costs and benefits of big brains, upright walking

• Defining characteristics of all human species: large brains (even the earliest humans)
• If big brains are better, why did evolution not produce other species with big brains?
• Costs of having big brains:  consumes a lot of fuel, meant giving up muscle mass
• So, why did humans evolve with bigger brains?  Nobody knows.
• Upright walking:  
•  benefits:  far-sight + hands-free
•  costs: "half-baked" babies, requires social ties
• Because humans are "half-baked" at birth, great potential for malleability, education
• For 2 million years, despite these advantages, humans were "weak and marginal" creatures in the middle of the food chain, very little impact on the environment; mostly scavengers
• Early Stone tools were not for hunting, but for scavenging, breaking bones for marrow
• Only about 100k years ago did humans emerge to the top of the food chain and become top predators; psychological/social consequences = we are ill-adapted to this position because of the rapid leap (wars, ecological disruption, etc.)

Lesson 01 - part 4 -- Fire = first significant leap away from other animals

• How did humans make the leap to the top of the food chain 100k years ago?
• Domestication of fire by Neanderthals and Sapiens -- the best advantage of which is cooking
• new foods became available -- wheat, rice, potatoes, etc. which we can't digest otherwise
• protective vs. parasites
• reduced time/energy required for digestion
• Some scholars link cooking --> shorter intestines --> growth of the brain
• For other animals, their power is dependent on the size/shape of their bodies, but with fire, humans broke the link (though humans overall remained relatively "insignificant" animals)

Lesson 01 - part 5 -- The real revolution in the status of humans = Homo Sapiens

• Emerged in East Africa, sometime between 300k-200k years ago
• Around 70k years ago, some Sapiens left East Africa, reached the Middle East and spread across Eurasia
• What happened to all the other human species that inhabited Eurasia at that time?
• Inter-breeding theory 
• Replacement theory, argues that different species couldn't produce fertile offspring
• If the 1st theory is correct, there may be important genetic differences between races.  In recent years, the 2nd theory prevailed -- we are all from the same Sapien ancestors -- until the Neanderthal genome was mapped in about 2010
• So, Neanderthals and Sapiens could not have been distinct species (like horses and donkeys)
• What happened to the Neanderthals?  Either starved (lost the competition for food resources) or genocide (as Sapiens are not known for tolerance)
• What if the Neanderthals had survived?  And there were different species of humans co-existing today?
• This "revolution" -- the emergence of Sapiens as the only species of human -- changed the way we see ourselves as separate from other animals (no brothers and sisters) and the apex of creation.