When the Sapiens they arrived in the Middle East and Europe, met the Neanderthal .
These humans were more muscular than the Sapiens , they had more developed brains, and were better adapted to cold climates. They used tools and fire, were good hunters and apparently cared for the sick and infirm ( some archaeologists have discovered Neanderthal bones that lived for many years with severe physical handicaps, demonstrating that they were being cared for by their relatives ).
The Neanderthal they are often portrayed in a caricature, as archetypes of the crude and stupid "cave people", but recent evidence has changed the image that was given of them.
FUSION THEORY
According to the Theory of Fusion , when the Sapiens they spread to the lands of the Neanderthals , mingled with them until the two populations merged completely. If things went this way, then it means that Eurasians are not pure Sapiens . They are a blend of Sapiens and Neanderthal . Similarly, when the Sapiens they reached East Asia and crossed paths with the local Erectus , so the Chinese and Koreans are a mixture of Sapiens and Erectus .
REPLACEMENT THEORY
On the other hand, the Replacement Theory it tells a very different story, made up of incompatibility, revulsion, perhaps even genocide. According to this theory, the Sapiens and other humans had different anatomies , and most likely different mating habits and even different body odors.
They would have had little sexual interest with each other.
And even if a Neanderthal and a Sapiens had fallen in love, they would not have had fertile children, because the genetic gap that separated the two populations was already unbridgeable.
The two populations remained completely distinct, and when the Neanderthals became extinct, or were killed, their genes died with them.
According to this conception, the Sapiens they replaced all previous human populations without merging with them. If things went like this, the lineage of all contemporary humans can be traced back, in an exclusive way, to East Africa .
This diatribe has many consequences. From an evolutionary point of view, 70,000 years are a relatively short time interval.
If the Replacement Theory is valid , all human beings have roughly the same genetic background, and the racial distinctions between them are negligible.
But if the Theory of Fusion is valid. , there can undoubtedly be genetic differences between Africans, Europeans and Asians, dating back hundreds of thousands of years.
Over the past few decades, the Theory of Replacement has dictated the law in the field.
It possessed a more solid archaeological foundation, and was more politically correct (scientists were unwilling to open the Pandora's box of racism by claiming the significant genetic diversity among modern human populations). But that ended in 2010, when the results of four years of research to map the Neanderthal genome were published.