πŸ“– Sapiens

6M β€” Our last common grandmother

We are members of a large and noisy family called the great apes. 6 million years ago, a single female ape had two daughters. One became the ancestor of all chimpanzees, the other is our grandmother.

Biologists label organisms with a two-part Latin name, genus followed by species: families > genus > spices.

  • Families: trace their lineage back to a founding patriarch.
  • Genus: species that evolved from a common ancestor are bunched together under the heading 'genus' (plural genera). They show little sexual interest in each other and their offspring will be infertile. Hence their DNA will always move along through separate evolutionary paths β€”Β i.e. horses and donkeys produce mules, which are sterile.
  • Spices: share same DNA pool and when they mate with each other they produce fertile offspring β€”Β i.e. bulldogs and spaniels

For example, lions, tigers, leopards, and jaguars are different species within the genus Panthera.

2.5M β€” The genus Homo

The genus Homo evolved from an earlier genus of Apes called Australopithecus. However, the most important thing to know about prehistoric humans is that they were insignificant animals with no more impact on their environment than gorillas, fireflies, or jellyfish.

Humans had extraordinarily large brains compared to other animals. Modern Homo sapiens sport a brain averaging 80 cubic inches, but Neanderthal's brains were even bigger and also more muscular β€”Β which disproves that natural selection favored intelligence.

It did, though, favor earlier births. And, indeed, compared to other animals, humans are born prematurely. Raising children required constant help from other members. Evolution thus also favored those capable of forming strong social ties.

  • 2.5M years ago, animals much like modern humans first appeared, but for countless generations, they did not stand out from the myriad other organisms that populated the planet.
  • 400K years ago, we start hunting large game regularly.
  • 300K years ago, generalized use of fire, most humans start using it daily.
  • 200K years ago, Homo sapiens first evolves in East Africa.
  • 150K years ago, East Africa was populated by Homo sapiens that looked just like us.
  • 100K years ago, humans quickly jumped from the middle to the top of the food chain.
  • 70k years ago, Homo sapiens from East Africa spread into the Arabian peninsula, and from there they quickly overran the entire Eurasian landmass. For some reason, our dominance as the only human species starts here.
  • 10k years ago, Homo sapiens remains mostly the exclusive human species around.

From about 2.5M years ago until around 10K years ago, the world was home to several human species. Very much like today, there are many species of bears: brown bears, black bears, grizzly bears, polar bears.

We are used to thinking about ourselves as the only humans, but there were up to 6 different Homos for a long time β€” of course, all of them human.

The question is: why? There are two competing theories:

  • Replacement Theory: a story about genocide and different mating habits between species; implies that all living Homo sapiens have roughly the same genetic baggage, and racial distinctions among them are negligible.
  • Interbreeding Theory: a story about attraction and sex, implies that there might well be genetic differences between Africans, Europeans, and Asians that go back hundreds of thousands of years. This is political dynamite, which could provide material for explosive racial theories.

It turns out we share a small percentage of genetic code with Neanderthals and Denisovans, which suggests that both theories could be right. 50k years ago, Sapiens, Neanderthals, and Denisovans were almost, but not quite, entirely the same species. We were not completely different species, like horses and donkeys; but also, not just different populations of the same species, like bulldogs and spaniels.

❓ "The" question: what would have happened β€”Β from a societal point of view β€”Β if other human species were still around?