Evolution is change over time. Human origin simply means biological change over time. It is the lengthy process of change by which our physical and behavioural traits from apelike ancestors millions of years ago. There are mainly three theories about the human origin. They are:-
1. Single-origin theory
2. Multi-regional theory
3. Assimilation theory
1. Single-origin theory
This theory is also called replacement theory and out-of-Africa theory. According to this theory, modern humans first evolved in Africa and dispersed to different parts of the world. Anatomically modern humans evolved about 200,000 years ago having some biological or cultural advantage that allowed them to move to the rest part of the world. it is said that they replaced hominins like Neandertals, Denisovans etc.
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| Human migratory route |
2. Multi-regional theory
This theory is opposite to the single-origin theory. According to this theory, instead of modern humans, homo Erectus evolved in Africa and spread to different parts of the world.
3. Assimilation theory
This theory is strongly supported by Genetic data which suggests that while there is a replacement, there is also interbreeding. It appears that modern human DNA not only contains 1-6 % of the DNA of Neandertal and Denisovan but also has important benefits to modern humans.