Ok, I freely admit that’s click bait or something close to it for sure but except for sub-Saharan indigenous peoples we all have up to 4% of Neanderthal DNA in us. That only happened because humans and Neanderthals interbred. This is not new information. What is new as reported in New Scientist magazine in July of 2017 is the hook up occurred before 219,000 years ago.
When, where, how much and under what circumstances these occurrences took place is a titillating field for speculation. We can’t know exactly what took place but it is reasonable to make certain assumptions based on what we do know about human behavior. So, let’s look at what we do know.
When and Where
The timeline for the lifespan of early hominin species has shifted many times in the last 20 years. As scientists utilize newer dating methods and strategies it gives us a better understanding of when the different hominin species lived.
And that doesn’t even consider new finds. Consider the latest Homo sapiens revelation. At a cave site in Morocco a reevaluation of H. sapiens remains reveals the bone fragments were as old as 350,000 years. That is quite a pushback from the previously accepted time of 200,00 years ago for the beginning of H. sapiens.
The study of DNA from fossilized hominin bone fragments has revealed amazing results.
It is really hard to be able to analyze DNA from fossils but the field has yielded some fantastic finds. In July of 2017 the New Scientist magazine reports that utilizing DNA testing we now know that Neanderthals and humans were interbreeding over 219, 000 years ago in Europe. This timeline might have raised more than a few eyebrows had not the Moroccan H. sapiens been dated to 350,000 years ago. After all, before the Moroccan dating it was widely considered that H. sapiens were only 200,000 years old. That would put a crimp in the results of the DNA study placing them in Europe before 219,000 years ago.
The DNA analysis was done from a Neanderthal femur bone found in South-West Germany. But how did modern man get there as early as 219,000 years ago when the current thought is they evolved in Africa 200,000 years ago and stayed in Africa until around 60-70,000 years ago then migrated out of Africa and into the rest of the world.
To be fair there is an Out of Africa theory that says modern man migrated out of Africa in two waves. The first would be around 120,000 years ago and the second and larger wave at about 60-70,000 years ago. Still 120,00 years ago is about 100,000 years later than what the DNA now shows us.
However, with the new understanding that Homo sapiens had migrated throughout Africa as early as 350,000 years ago it is highly likely they also had left Africa by then too. Why would I say that? Because Homo erectus had left Africa some 1.6 million years ago and Homo floresiensis left Africa 700,000 years ago and perhaps next week we will discover another hominin left Africa around that time too. With the knowledge that earlier hominins had migrated out of Africa it just seems like common sense modern man did too. There is no reason to believe they did not.
We have no bone fossil fragments that support modern man in Europe 219,000 years ago. What that means is that there are no fossil fragments to hold in hand that place modern man in Europe at that time but it certainly does not mean he was not there then or even earlier. There will undoubtedly be newer and amazing fossils dug up in the future that support the DNA evidence. The fossilization of bone is a rare event in the first place and then they have to be found.
Speciation and Human Evolution
Speciation is when one species under certain circumstances changes or evolves into another species. This speciation can occur when species A evolves into species B in totality and therefore species A no longer exists. The more likely and frequent way is that under certain circumstances members of species A break off and evolve into species B and then species B will come back into contact and live contemporaneously with species A.
It also happens that species A will have multiple divergent lines break off from it. In this case species A could live contemporaneously with species B, C and D, maybe more depending on the life span of species A.
The most likely evolutionary sequence for modern man goes like this. Homo erectus to Homo heidelbergensis, then H. heidelbergensis to H. neanderthalensis and Denisovans and H. sapiens. So, if Homo erectus was the grandpa then Heidelberg man was the father and the children are Neanderthals, Denisovans and Us. Of course, the question is who is the oldest child. Apparently, we are the baby of the family.
This analogy breaks down and gets yukky when talking about interbreeding between species but it does give you an easily understood view of our human legacy.
How often and under what circumstances did Neanderthals and modern man have sexual intercourse?
For a long time there was a question as to what happened to the Neanderthals. They were apparently a well adapted species that vanished about the time it was assumed modern man moved into the Neanderthal’s territory with the big Out of Africa migration. Before the study of DNA was possible the basic assumption was H. sapiens moved into the Neanderthals territory and killed them off because they were competitors for the same resources and also because they viewed the Neanderthals as a different species and therefore had to kill them because of that difference. This scenario was to have taken place starting about 60-70,000 years ago. That’s pretty much been blown out the window once scientists established we interbred with Neanderthals. This a great example of how the study of DNA has changed a lot of views about mankind and his legacy.
The demise of the Neanderthal is a peaceful assimilation of them into the tribe of modern man rather than an eradication of them by it.
And this assimilation started way, way earlier than previously thought. To be sure even when different tribes of modern man encounter one another it can result in conflict. Most likely not though. Conflict at the tribal level results in damaging changes and upheaval and when that can be avoided it is.
Also consider that Neanderthals and H. sapiens are almost identical in looks and nature. European Neanderthals on average stood about 2 inches shorter than modern man. They were stockier and they had a larger head. That’s about it. They were identical in almost every way with modern man. When a tribe of migrating humans came into contact with a tribe of Neanderthals they would not have been taken aback by any differences in appearances. In fact, if you took your average Neanderthal and dressed him modern clothes and let him loose in the street he would not turn any heads at all. Some Anthropologists would make Neanderthals a sub species of humans and not a totally separate species at all. In the strictest scientific nomenclature we are called Homo sapiens sapiens. Neanderthals as a sub species would be called Homo sapiens neanderthalensis.
And please, let’s just stop debating language and Neanderthals. Of course they had language. Their anatomy is virtually exactly the same as modern man’s and they contain the same brain processing power we have. In fact, on average they had larger brains that we do. But they didn’t speak the same language as modern man. Really? That’s where you are going. Take a trip to Europe and see how many languages you understand. Try going to Asia or Africa and see how many languages there are. Just as in modern times ancient man spoke different languages according to geographical location.
The Broca area of the brain was well developed and the hyoid bone is identical to modern man, both of which are necessary for speech. In fact, it is highly probable that the ‘father’ of both Neanderthals and modern man, Homo heidelbergensis, had language as they too sported a fully developed hyoid bone and had a large brain size comparable to modern man’s.
Based on what we now know I am going to outline a picture of the events that I believe unfolded in our past in relation to the merging of Neanderthals and modern man.
Neanderthals broke off from Heidelberg Man about 500,000 years ago in Europe. H. sapiens broke off from Heidelberg Man about 400 to 350,000 years ago in Africa. We know that at 350,000 years ago sapiens had migrated around Africa. There is absolutely no reason to assume they had not also migrated out of Africa during the same time period or at the very latest 300,000 years ago but most likely before that.
When they left Africa, they made their way to Europe thru Eurasia. They also migrated to Asia. Once out of Africa they would have encountered Neanderthals in Eurasia and Europe. Keep in mind that they already would have been living in contact with the last survivors of Heidelberg Man in Africa and quite possibly Homo naledi and even Homo floresiensis and Homo erectus. In other words, encountering another hominin was not a novel experience to them. That coupled with the fact the Neanderthals they did encounter looked virtually the same as they did, allowing for superficial differences like skin color and eye and hair color.
You also have to keep in mind that Neanderthals and sapiens and for that matter even Heidelberg Man had highly developed cognitive abilities. They had extensive took kits, they enjoyed a complex social culture, they domesticated fire and employed language, they had music, medicine and cared for the elderly and infirm. These where not naked savages running around aimlessly grubbing out a living. They had a certain ancient cachet that allowed them live and grow and interact on a sophisticated level.
When the different tribes would encounter one another the first impulse was not to run over and kill the other ones. I mean really if that were the case how would any hominin species have survived.
Ninety-nine times out of a hundred this is what happened. One migrating tribe moves into a fertile valley. The tribe might be as large as a couple of dozen. They see another tribe in the distance. They check each other out for a spell and then one of them holds up his right arm with an empty hand, a universal sign of greeting without intent of hostilities, in other words a friendly but cautious ‘hello’.
The tribes approach each other, again cautious but not actually preparing to jump and kill. They meet and start to exchange greetings. They don’t speak the same language but there are universal ways of communicating thru sound and gestures. Gifts are offered and exchanged and perhaps the offer to stay the night as it were.
These were normal and average meetings that took place though out the ancient world. Now as far as sex goes it would have followed a normal pattern also. There were probably two or three families in each tribe during the time period we are talking about. With that being the case the norm was to exchange breeding individuals among tribes to avoid inbreeding. So, it is highly likely that maybe not the first night but if the tribes hung out for any period of time and there were unattached breeding age individuals and they were exchanged in some way. This was probably an exchange for a female unless there was an abundance of males in one tribe. A female could be traded for material goods or another female or male. These exchanges would result in offspring that carried both Neanderthal and H. sapiens DNA. This is quite common in hunting and gathering cultures. Individuals in small tribes cannot interbred or the long term survival chances will be hurt.
I am not going to be Pollyannaish about it. I realize that violence, even fatal violence would have taken place from time to time. Raiding parties to capture females were also a strategy to provide genetic diversity to a tribe. But by and large sexual diversity was something all groups knew they had to have and found ways to accomplish this without a constant stream of violence.
Given that after all these tens of thousands of years some individuals have as much as 4% Neanderthal DNA it is an indication that quite a bit of interbreeding happened. Consider this, with one Neanderthal and one H. sapiens they produce an offspring which would have 50% Neanderthal DNA and 50% H. sapiens DNA. Then that offspring breeds with a H. sapiens and has an offspring that will have 25% Neanderthal and 75% H. sapiens.
You don’t have to be a math wizard to figure out that if interbreeding only happened a few times that over the course of 300,000 years the trace of Neanderthal DNA in humans would be negligible. Given that we now think the last of the Neanderthals died out 30,000 years ago it still mathematically seems like there would have been a whole lot of interbreeding going on for humans to maintain a 4% portion of Neanderthal DNA.
In my opinion when H. sapiens moved into the Europe and began interbreeding with Neanderthals they basically established a relationship with them every bit as robust and fully developed as the relationships they had with other H. sapiens tribes.
Given that scenario you might ask then why didn’t the Neanderthals assimilate the sapiens and not the other way around. That is a good question and I will tell you why.
The New Scientist article says the DNA indicates interbreeding over 219,000 years ago. We know there was a big out of Africa migration around 70,000 years ago. That is a span of 150,000 years right there. During that time archaic humans were in Europe and breeding with Neanderthals producing offspring.
After 150,000 years of interbreeding there may have not been many purebred Neanderthals left. The only purebred humans would have been the ones still migrating out of Africa into Europe. So, the population of Neanderthals and humans in Europe where pretty well mixed. Throw in some Denisovan genes and maybe even Heidelberg Man genes and you have a nice mix.
Something very important to the world happened 70,000 years ago. Homo sapiens made an evolutionary jump in cognitive ability. Some call it the Cognitive Revolution or the Toba effect named after a massive volcanic explosion. The exact cause is not known but on the other side of 70,000 years ago humans came out with a vastly improved cognitive ability.
What this means to our topic is this. Part of the consequence of the new cognitive prowess was the social culture of humans took a leap forward in that they started to live in larger and larger tribes. Where before a tribe might be a couple of dozen individuals before it split into different tribes, now humans had the social wherewithal to live and thrive in tribes of up to 150 individuals.
When these large tribes migrated out of Africa into Eurasia and Europe they encountered the smaller tribes of Neanderthals and humans. It doesn’t take much to imagine what would happen when a tribe of 150 moved into your valley and your tribe was only a dozen or so. There is a total mismatch in the competition for resources.
Also, it’s easy to imagine how quickly a dozen individuals would be absorbed into the larger tribe. Consider this, in a tribe of 10 or 12 individuals there may only be one or two breeders. If they get assimilated into a larger tribe there goes the smaller tribe right away.
That is what happened to the Neanderthals and any previously pre-Toba effect archaic humans. They were assimilated into the new larger modern man tribes by sheer force of numbers.