Introduction to Other Human Species

4 min readMar 12, 2022


This is a part of a series of blog posts written based on concepts I read in a few books — Sapiens, Glimpses of World History, Discovery of India

The humans evolved in East Africa 2.5 million years ago, from another genus called Australopithecus (Southern Ape). Post that the evolution is not linear.

Migration to different places and encounters with different circumstances influenced the evolution of different species in different directions.

Homo Neanderthalensis (man from Neander Valley, called Neanderthal commonly) was strong as well as adapted to cold. They had bigger brains and more muscular bodies than Sapiens, and took care of their disabled and elderly. Homo Erectus was durable and lasted for 2 million years. It is likely that we’ll end up lasting for less than that. Homo Floresiensis grew on an island with less resources, so ended up becoming a species of dwarfs. There were also Homo Rudolfensis, Ergaster, and Soloensis.

The evolution was not in a straight line, but rather divergent. Till around 10,000 years ago, there were multiple species of humans on the Earth. The striking fact is not the existence of these species till recently, but rather the absence of these species today. It paints a dark picture of Homo Sapiens and their role in the disappearance of these species.

The Spread of Homo Sapiens

150,000 years ago, there were just around a million humans alive. At that time, there was for sure a species in West Africa that looked just like us. Their teeth and jaws were smaller than their ancestors because of the use of cooked food, and brains as big as ours.

70,000 years ago, Sapiens started spreading into the Arabian Peninsula, and very quickly spread to the entire Eurasia.

The End Of All Human Species Except One

There were multiple human species all across the Earth. However, wherever Sapiens reached, the other species kept going extinct. Soloensis went extinct 50,000 years ago, Denisova 30,000 years ago, Flores Island Dwarfs 12,000 years ago.

Theories Explaining The Disappearance Of Other Human Species

There are two theories for why all other human species disappeared:

  1. Interbreeding Theory
  2. Replacement Theory

Interbreeding Theory

Sapiens bred with different species till they all became one species. So the current Europeans are hybrid with Neanderthals, and Chinese / Koreans are hybrid with Erectus or another species.

A recent research shows that there is 1–2% Neanderthal DNA in both Caucasians and in East Asians. The DNA quantity and patterns of appearance suggest that the mixing was such that the offsprings were either sterile or largely infertile. Therefore only minor amounts of DNA spread from the mixing that happened.

Another research suggests that upto 6% of Aborigin and Malenasian unique human DNA is Denisovan.

Species biology is not black and white. Sapiens and the others were different species, but were at a biological boundary where they could produce some offspring.

In conclusion, interbreeding was so minuscule that it did not result in the extinction of other human species.

Replacement Theory

Sapiens ended up replacing all other species because of one or more of the following factors — genocide, war, or starvation because of scarcity of food to sustain 2 races.

The replacement theory has a bigger chance of being correct. Interbreeding was happening amongst other human species too, but it did not result in the extinction of so many species.

Replacement theory is also politically more correct because the other theory suggests that humans of different races are actually different at a DNA level.

How And Why Did Homo Sapiens Kill The Other Species?

While the replacement theory answers the question of what happened to the other species, it does not answer the following questions —

  1. How did Sapiens eradicate species who were bigger, stronger, well established, and also had tools and weapons to fight?
  2. Why did Sapiens engage in such large scale genocide?

These questions are complex, and deserve articles of their own. However, here is a brief overview.

How Did Sapiens Win? The Sapiens had linguistic abilities that allowed them to explain complex ideas to other people of their species. For example, instead of just saying ‘Run! Lion over there!’, they could say ‘There is a lion near the river, so avoid the river for now. We don’t have the ability to take on it individually. Let’s all group together and attack around sunset and kill it.’ . This allowed Sapiens to collaborate in large groups of upto 150. This collaboration allowed more sophisticated warfare and evolution of better weapons, and made Sapiens adaptable to different conditions.

Why Did Sapiens Engage in Genocide? Other human species lied in the Uncanny Valley in their resemblance to Sapiens. The other species were similar enough to humans to be considered a threat. At the same time, they were different enough to provoke a sense of tribalism and racism but a lot stronger. This type of species, that is similar enough to feel like a threat but different enough to invoke tribalism, is known to lie in the Uncanny Valley. It feels like a brutal, deformed version of oneself. If that was not enough, these species were often stronger than sapiens and invoked insecurity. Plus, humans (all, not just Sapiens) had the power of top-of-food-chain species, but with the personality and insecurities of middle-of-food-chain species. It proved to be a ruthless and brutal combination.