You probably also know about the Neanderthals. For a long time they were considered primitive brutes, but today we know that they were intelligent, inventive and caring people who lived for around 400,000 years in Eurasia (which means both Europe and Asia), had the largest brains of all humans and mastered the challenges of many glacial periods. Therefore it surprises scientists that they disappeared, and most of them still believe they went extinct.
The Neanderthal Children Theory explains these two mysteries by putting what we know today into a new context which, in my opinion, makes a lot more sense than the theories of others.
For hundreds of thousands of years, many species of humans lived in the world, but most of them went extinct, merged with others or evolved into other species. One of them was Homo heidelbergensis who lived in Europe for a long time until they evolved into Neanderthals more than 400,000 years ago. This coincided with an interglacial during which temperatures were milder, but after a few thousand years the next glacial period gripped Europe, and the Neanderthals started producing clothes. The earliest tools for making clothes are 400,000 years old and were found in present-day Italy.
Between 400,000 and 300,000 years ago they also produced sophisticated spears, called the Schöningen spears, which required a lot of co-operation, proving that they already must have had a complex language.
Fire was important for most if not all human species. Many of them had learned to control and use fire, but they all depended on fires in nature, like wildfires or lightning. As far as we know, Neanderthals were the first people before modern humans who had figured out how to light a fire.
Neanderthals looked after their sick and old and were the first known species to bury their dead; it looks like some of them were even laid to rest with gifts and flowers.
While they ate some vegetables with their meals, they mostly lived on meat. Some hunted big game like bison and reindeer or cornered herd animals in the mountains which they pushed over the edges. Many of those who lived at the sea also hunted seals and dolphins.
Most of them lived in caves, but others also built tents from mammoth bones. They also cleared forests for their settlements.
In order to attach stone spearheads to wooden shafts, or knives to handles, they developed a superglue from birch bark which required a complicated chemical process.
Neanderthals were the first musicians. The oldest instrument, a bone flute, was found in present-day Slovenia and is 45,000 years old.
Neanderthals also were the first seafarers. Their tools have been found on Crete, an island that lies 40 km from continental Europe.
Neanderthals appreciated beauty and adorned themselves with jewellery, ornaments and feathers. They also created cave art.
Neanderthals spread all over Eurasia, and in the East they met another species, the mysterious Denisovans. This is a species we know merely from the genetic record; the only fossils of them ever found were a handful of finger bones. But it appears that both species were quite similar, and that they met and mixed frequently.
Around 200,000 years ago Homo sapiens emerged in Africa. They were not doing very well in the beginning, and around 150,000 years ago something happened that brought their numbers down to just a few, which is called a bottleneck event. As a result, all living humans are the direct descendants of one woman who (or at least whose children) survived this event.
The genetic record shows us that some Homo sapiens and Neanderthals already met and mixed 100,000 years ago, but there is no certainty about where this happened. One possibility is the Levant, the area that connects Europe and Africa, where both species were present. It is here that we come across the first known Homo sapiens burial 100,000 years ago; they may have copied the custom from their Neanderthal neighbours, but their fossils show so many Neanderthal traits (such as brow ridges) that they were thought to be Neanderthals at first. Maybe these people were already the children of Homo sapiens and Neanderthals.
Another possibility is the Strait of Gibraltar. Many Neanderthals lived in the caves of Gibraltar from where they could see Africa, just 14 km away across the water. We haven’t found any evidence yet, but can you imagine that these adventurous, innovative and seafaring people could resist the temptation to explore another continent?
In the Contrebandiers Cave on the coast of present-day Morocco, a few hundred kilometres from the Strait of Gibraltar, scientists have found bone tools for the making of clothes which look very much like those of Neanderthals and which are around 100,000 years old. Maybe they were made by Homo sapiens who had already met Neanderthals and learned their techniques (probably in the Levant), or maybe Neanderthals indeed crossed the Strait of Gibraltar, and some of them decided to stay, mix in with the local Homo sapiens and show them how to make clothes.
Beginning around 48,000 years ago, when the Sahara became inhabitable again, the first Homo sapiens arrived in Europe during a bitter glacial period. The reasons are unknown, but I imagine that they were displaced by other Homo sapiens and pushed northwards.
Over the coming years they spread all over Eurasia, but in the long run they were unable to deal with the harsh conditions, and most of their lineages went extinct.
But some of them met Neanderthals who showed them the skills they needed, such as making fire, sewing clothes and building shelters.
There were only a few populations of Neanderthals who were scattered all over Eurasia. As they kept taking in Homo sapiens and mixing with them, they soon were outnumbered, and after a few thousand years all Neanderthals had mixed with Homo sapiens, and no pure Neanderthals were left. This process is called assimilation.
This Neanderthal assimilation created modern humans. Homo sapiens became smarter and more cultivated, and in the beginning their brains became larger. But after the last Neanderthal had been assimilated, they only had each other, and since then our brains become smaller again.
From Eurasia modern humans spread all over the world, including back to Africa where in the meantime those Homo sapiens populations without Neanderthal genes have gone extinct.
Now the two big questions are answered: meeting the Neanderthals was what made us smarter and turned us into modern humans, and Neanderthals didn't go extinct but were assimilated, so they do live on in all of us.