Our species, Homo sapiens, is the last hominin standing. Until recently the prevailing theory of how we became the last surviving hominin is that modern man evolved in Eastern Africa in a relatively small population that was isolated by geographical elements like mountain ranges or rivers. This isolation let various gene mutations work through the process of natural selection to evolve the hominin line to modern man and then at some point we spread out and took over the entire world replacing the other living hominin species. The time frame for most of adherents to this ‘Out of Africa’ theory is about 70,000 years ago. Something like that. Some say about 120,000 years ago or so there was a migration wave out of Africa but it was a much smaller one and those migrants most likely died out or were inconsequential.
Multiregional and Assimilation Theories
However, there are competing theories and it now appears the Out of Africa theory is going to go by the wayside. New discoveries in the past couple of years are changing minds. With the major pushback of the timeline for the birth of sapiens going from 200,000 years ago to quite possibly 500,000 years ago it seems more and more likely that the Multiregional or Assimilation model for how Homo sapiens became the last surviving hominin makes more sense.
Let’s take a very brief look at each one.
The Assimilation Model says that archaic humans did indeed first evolve in Africa but their migration into the rest of the world contributed significantly through gene flow to the evolution of other hominin species that lived outside of Africa to the extent that they all evolved in parallel with archaic humans. There was a constant gene supply coming out of Africa via migration to enable this instead of some ‘wave’ leaving Africa in a short amount of time.
The multiregional model says that Homo erectus migrated out of Africa and subsequently evolved to Homo sapiens because all hominins maintained extensive ties with each other and traded and gene exchanged occurred frequently. So basically, all hominins evolved together more or less along the same timeline but sorta with fits and starts which included regional differences.
Defining Modern Man
A big challenge to a complete understanding is how do you define modern man in the first place? Is it more along the lines of morphological or do we consider cognitive ability also and if so how much? It is now becoming more apparent, through recent discoveries and analysis, the Homo sapiens species birthed about 500,000 years ago. However, that does not mean we had the same cognitive ability then. Modernity of man did not occur for hundreds of thousands of years after we anatomically evolved. It’s perfectly acceptable to call early man, archaic modern man or archaic sapiens. There was indisputably a cognitive evolution to modernity that followed the physical evolution of man. Somewhere along the line, and we don’t know exactly when, a big mutational change happened with the wiring of our brains. This change precipitated modernity for man and ushered it in.
Having said that, even archaic sapiens where cognitively different than the other hominins 500,000 years ago.
A New Theory
Here is the new theory taking shape. It is a combination of multiregional and assimilation models. It goes something like this.
About 500,000 years ago Homo sapiens birthed in Africa but not from a single founding population. It was from gene pool contributions from here and there around the continent most likely starting with Homo heidelbergensis and even throw in some Homo erectus. (the multiregional model)
Keep in mind that evolutionary advances or the changes going forward in time of a species are accomplished through natural selection. But in order for that change to be selected it has to be there in the first place. So, the first step for a change is gene mutation. Gene mutations take place all the time, the vast majority are neutral and don’t have much effect. Some create a disadvantage for survival and are bred out of a population. However, some are advantageous gene mutations and those are kept in the mix by natural selection. That is a quick overview but you get the idea.
We now have conclusive proof, in the way of stone tools, that early hominins were in central China by around 2.12 million years ago.
The likely suspect is Homo erectus. This means that well over 2 million years ago hominins had made their way out of Africa setting up migration pathways to all the lands of Europe and Asia. Let’s face it, if they could walk 7,000 km to Central China from Africa they could walk to Northern Europe and all the places in between.
It makes sense that this migration was more or less continuous. There was never a time when hominins made a collective agreement to stop migrating out of Africa.
Hominins kept migrating uninterrupted out of Africa starting over 2 million years ago.
The hominin line is a wandering bunch of folks. Because of bipedalism and the cognitive ability to make and use tools they could exploit and survive in just about any geographical area they wandered into.
Back to the birth of Homo sapiens.
We now know that hominins were widespread across Africa. Let’s say there were a thousand population centers. When I say population centers I am talking about a valley or certain area where a small number of tribes lived with 10-15 individuals. These population centers had regular contact and exchanges with neighboring populations. They traded and also exchanged tribe members for mating, etc. Heck, in actuality there was a continuous flow of exchanges between all population groups all over the continent.
Let’s say in area 1 a certain gene mutation proved to have a survival advantage. That gene would have made it into the gene pool and been passed to other groups of hominins in neighboring areas 2,3,4 and so on eventually spread out over all of Africa. Slowly but surely this took place and while some groups of the hominin population faded away the groups with the most advantageous of survival traits grew.
All the while the migration of hominins out of Africa is still going on, so the new genes giving improved survival chances are spreading everywhere there are hominins. Keep in mind this process takes tens of thousands of years in most cases.
So, in Africa the processes of evolution to becoming Homo sapiens is faster than outside of Africa simply because the exchanges of genes between individuals would be greater in the geographical region of Africa than out of it given, even though migration continued to occur, the opportunity for gene flow was less as the total number of migrating hominins would have been much lower than the total gene pool of hominins that stayed in Africa where the changes were being advanced. Another way to put it is the evolutionary processes moving towards sapiens was far greater in Africa than outside but nevertheless outside of Africa it still moved in that direction.
The multiregional model is being used to describe what happened in Africa as we evolved to sapiens. Once Homo sapiens were to the point of what we now recognize as archaic modern man the migration out of Africa, which had never stopped, took on a new significance. At that point there appeared a fundamental survival advantage to being sapiens.
What that advantage was is not up for debate, a different way of being gave archaic sapiens a huge survival advantage.
How huge was it? Well when this group started migrating out of Africa their gene pool took over everywhere they went, to the extent all other hominin groups were ‘assimilated’ into the sapiens legacy. So, at that point the Assimilation model takes precedent as the dominant force behind Homo sapiens being the last hominin standing.
The fundamental difference that the archaic sapiens had was not physical. In fact, we know from skeletal remains going back over 2 million years that Homo erectus was basically us, except for the cranial size.
Is that some outrageous claim, no it’s the truth. Here I am in the summer of 2018 standing next to the Nariokotome Boy remains.
He currently resides at the Chicago Field Museum. This Homo erectus boy was about 10 years old and lived over 1.6 million years ago. Had he been full grown he would have been 6 feet 1 inch tall (1.86m). Coincidentally, I am 6 feet 1 inches tall myself. I am the one with clothes on.
Had he lived to adulthood we would have been the same except for the head size. If I were walking around with his tribe back then people would have said, “Man, that Bob sure has a big head doesn’t he.” (Yes, they did have language and talked to each other.) On the other hand, if Nari were to be walking down the street today, fully clothed in modern attire, he would not have drawn any stares at all. His cranial size falls within the modern range, all be it on the small end.
Archaic humans did not have any physical advantage over any other hominin they encountered. None.
Even going back to Homo heidelbergensis (a hominin that predates Neanderthals), our skeletal structure including cranial size is identical, our cranial capacity has been the same size from 800,000 years ago on.
Dexterity of hands, the same, etc., actually Neanderthals and H. heidelbergensis, if anything, had the physical advantage over us as they were a lot stronger and more heavily muscled than archaic humans.
Around 400,000 to 500,000 years ago fully realized archaic H. sapiens migrated out of Africa and began in earnest to assimilate the 4 other hominin species. (4 that we know of so far). They were H. erectus, H. heidelbergensis, H. neanderthalensis and Denisovans.
Homo floresiensis was also a hominin species that survived until 50,000 years ago but there is no indication (DNA or otherwise) that they had contact with archaic sapiens. There was one more hominin alive at the time and that was Homo naledi. As yet there is no indication of any breeding going on with them but they certainly were living in the same areas as sapiens did at the same time.
So, What Was It?
The dominant characteristic of archaic sapiens that enabled them to assimilate the other four species of hominin had to be cognitive and not physical. What exactly was that cognitive feature?
Now, it’s not enough to say that archaic sapiens were smarter and therefore able to dominate the others. After all H. erectus had been around for over 2 million years before sapiens showed up and they were making out just fine thank you very much. H. heidelbergensis whose range was from Europe to Africa was around for hundreds of thousands of years before sapiens. Neanderthals and Denisovans both survived for hundreds of thousands of years.
It seems that the skill set to survive for hundreds of thousands of years with all the ice ages and other environmental changes that took place was pretty well set and mastered by the other living hominins.
The answer is rooted in the nature of the social culture of groups and the way individuals related to one another. All groups have a culture specific to them. The very definition of Anthropology is the ‘The study of man’. And the majority of that study is with the various cultures of man.
However, ‘Culture’ itself is not a physical entity, it is a conceptual construct held in the mind of man. This does not, I repeat does not make it any less ‘real’ than the chair you are sitting in or the device you are reading this on. Additionally, the different cultures of man undergo evolution just like physically any species does. Cultures evolve and change, often quite rapidly compared to physical changes.
The cognitive change that enabled sapiens to assimilate all the other hominin species was the expansion of consciousness relating to cultural complexities. One of those relates most notably to group size.
There was an expansion of consciousness in H. sapiens that increased dramatically their social and emotional intelligence leading to the behavioral changes that increased their survival changes exponentially.
How does this apply to human evolution and the rise of H. sapiens? As the cognitive limit for groups went from 10 – 15 individuals to upwards of 48-50 individuals, the survival advantage of larger groups became an overwhelming advantage when facing smaller groups.
It has long been accepted that hunting and gathering tribes or groups of pre-H. sapiens numbered roughly 10-15 individuals. By studying contemporary hunting and gathering groups it is clear they can comfortably live and thrive in groups of 35-50 individuals. Ok, but how much more complex could it be living in larger groups?
Social scientists who have studied group dynamics have a formula for the complexity of relationships that exist within groups. The formula to determine the number of possible relationships is – [ N x (N-1)] / 2. For a group of say 10, it would be 10 times 9 divided by 2 which equals 45. So, there would be 45 different sets of relationships in a group of 10. With a group of 15 it would be 15 times 14 divided by 2 equals 105 relationships. With a group of 48 it would be 48 times 47 divided by 2 equals 1,128 different sets of relationships or approximately 25 times the amount of relationships to be involved in and keep track of over the smaller group of 10 and 11 times the amount of relationships of a group of 15.
This increase of social and emotional intelligence of H. sapiens was one of the main critical factors enabling them to assimilate all other living hominin groups.
The larger groups of 48 - 50 would have had distinct survival advantages over smaller groups of 10-15.
When I talk about the larger size tribes being dominate I am not talking about physical conflict between tribes. Far from it. Physical conflict as in fighting and killing was the last thing early man wanted to engage in. When a small tribe of 10-15 individuals lost a mature adult, it caused a severe impact on the survivability for that group. Losing 3 probably meant the end of it. Open conflict was the last option anyone wanted. Even larger tribes have a hard time sustaining the loss of one individual in their prime.
Let’s create a little scenario. A group of 15 Neanderthals is hanging out in a valley and doing ok. One day they look up and see 48 individuals walking towards them. That alone might be a frightening experience because they may have never seen 48 individuals together at one time before. What they don’t do is grab arms and rush to battle. They wait and see what’s up with the expectation of maybe trade or some sort of exchange.
On the other hand, you have a group of 48 entering the valley and thinking this is a place they could hold up and rest and live for a bit but see another group of 15 individuals at the far end of a meadow. They would not be as concerned for their overall safety as they had the numbers on their side but still everyone knows a conflict will result in deaths that would hurt the group’s survival chances. They too would want trade and exchange instead of death and destruction.
Death and destruction are no one’s first choice so let’s drop the theory that H. sapiens ‘invaded’ territories and wiped out the native inhabitants.
Did not happen that way. What did happen was they communicate thru gesture and sign language to the extend they could exchange goods and maybe services and even mates.
The larger group would have assimilated some of the smaller group in an exchange of mates. No one leaves the relative safety of a larger group for less safe and harder life of a small group. So, if we are keeping score, survival advantage – sapiens.
Another thing about larger tribes is they eat more. They, by sheer numbers, will deplete the surrounding area of the food supply faster than small tribes would. After a certain period of time the 48 sapiens would have taken all the eatable flora and fauna within a few days walk and had to move on. At that point the smaller Neanderthal tribe would also realize the food supply was gone for them too. So, they either picked up and went to find another territory for themselves or would tag along with the larger group of sapiens. After all they got along reasonably well and safety in numbers and all that and one of the Neanderthal family members could have mated with an individual in the larger tribe.
When I say safety in numbers, again, I am not talking about fear from other hominins I am talking about protection from other predators like bears, lions, etc. A bear might attack a small group with only 3-4 adults but facing 20-25 armed adult men most likely ended up with the tribe having a new bear skin rug. Advantage – sapiens.
As far as hunting goes Neanderthals survived in their range for hundreds of thousands of years so they had a good handle on how to hunt the fauna in their territory. The only advantage I see that sapiens had could have been in the numbers of a particular hunting party or the amount of hunting parties the tribe could have sent out at one time. Basically, though I would think hunting is a wash. Ditto gathering. Sure, the more hunters and gathers could bring in more food but that also meant more mouths to feed. Advantage – neutral.
There is another cultural advantage with a larger group and it centers around knowledge and distribution of labor. In smaller groups individuals have to do more, larger groups can divide up tasks and specialize. This creates a bigger knowledge base in various areas that can be passed along. The knowledge base increases because you have several individual tribe members concentrating on certain tasks and they can exchange ideas and invent new strategies for carrying out that task whatever it is. In other words, they sit around and shoot the bull and try out new things. Some work some don’t but a knowledge base is built up faster that way when you have more minds involved. Advantage – sapiens.
Here is something else to consider.
Europe is 10 million square kilometers, USA is 9 million square kilometers. The range of Neanderthals included present day Europe and the Middle East combined. The total estimates for the population of Neanderthals that lived at any point in time vary wildly from a high of 150,000 to a low of 5,000 individuals. Let’s take the high end and say when H. sapiens migrated into Europe 500,000 to 400,000 years ago with groups of up to 50 individuals the Neanderthal population was 150,000. Can you imagine only 150,000 people living in an area the size of the United States? I mean come on, that’s practically too hard to wrap your head around. Lots of room to roam, that’s for sure. There was plenty of room for new groups of people to move in, occupy and get established.
Hey Good Looking
There is another resistance point the assimilation model runs up against and that is apparently, some think, a stumbling block for the inclusion of Neanderthals or other hominin tribes into H. sapiens tribes is based on looks.
The argument goes something along the lines of the ‘lesser’ hominins would have looked too different, too ugly, too this, too that, blah, blah, blah. That is just simply not true and rooted in very old prejudices that are apparently hard to shake.
As I have pointed out H. erectus had a smaller skull but other than that you, right now, as you go about your daily business have basically the exact same skeletal structure as H. erectus, H. heidelbergensis, Neanderthals, and Denisovans.
Even recognizing that point as valid, the argument goes, yeah but looking at their faces would have been too much to handle, blah, blah, blah. Admittedly the skull shape has changed some. That’s a given here. But not so much as to be grotesque or weirdly out of shape. That is point number one about the skull. But the larger perspective on this is the variety of facial configurations that contemporary humans enjoy is every bit as diverse as early archaic sapiens had themselves or would have encountered with other hominins.
Point number two about the shape of the skull is you couldn’t see it anyway. If you stood the five hominins we are talking about right next to each other what you would see for the men is they all had long hair and most likely long beards. In other words, most of the face is covered up anyway. The hair also camouflages the shape of the skull.
As to body shape and size, every group has the same variety of sizes, some are taller, some are thinner, etc. I doubt any were fat. They all lived on the Paleo diet after all.
Line up the women and you’d see basically also the same thing. They did not have beards but their long hair would mask the tiny differences in skull shape. Again, given the hardships of the life style and diet they didn’t carry much body fat. All the women had larger breasts than the men and larger hips of course but really how much of that did you see under the ‘clothing’ they wore?
As to their clothing, everyone dressed the same. Animal skins. No going to the mall. They all clothed themselves in animal skins and fur of some sort. Imagine going to one of their parties and everyone is dressed the same, the horror!
I mean let’s step back and get a look at this. Even allowing for different tailoring of the animal skins a group of hominins standing around is looking pretty much the same. Certainly, the differences were not enough to recoil from.
And the final point (speaking of partying) is once the DNA code was cracked we know for a fact Homo sapiens, Neanderthals and Denisovans mated among themselves. Don’t know about H. heidelbergensis and H. erectus yet because scientists have not been able extract their DNA because of the fossil ages we have for them. But if we use a little common sense and accept what I have been talking about it is highly likely they mated with them also.
To that point this year (2018) scientists have discovered unknown hominin DNA in a group of West Africans. Eight percent of the genetic ancestry from the West African Yoruba population has this unknown or ‘Ghost’ DNA.
It has not been proven in the lab yet but the speculation is that the ghost DNA is from H. heidelbergensis.
Looking at all the photos of contemporary humans in this post you might think that displaying photos that show older people might be misleading because you have read that the average age or life expectancy for archaic hominins was about 25 or so.
That 25 year old age statistic is very misleading for this reason... The infant mortality rate among hunting and gathering groups is approximately 43%. That is astoundingly high by modern standards but studies of hunting and gathering groups has proven this number. And that number is derived from contemporary hunting and gathering groups. One has to assume that 500,000 years ago it was the same or higher.
For the sake of argument let’s say it is 50%. So, if a child dies at 5 and an adult dies at 55 the average age is 30. In hunting and gathering groups if an individual makes it past puberty they have as good a change to make it to old age as we do. There are Neanderthal remains were it can be determined they lived into their 60’s.
Back in the Day, as the saying goes, when I was getting my Anthropology degree we were taught that the Homo sapiens species birthed around 35,000 to 50,000 years ago. Seems silly now doesn’t it. Through the successive decades that timeline has been pushed back to where we are now which is 500,000 years ago. This timeline seems speculative right now but reasonable given recent discoveries.
By the same token the ‘Out of Africa’ model for how sapiens became the last hominin standing was the accepted theory. We have not wrapped it up 100% yet but the outline I just presented is about 99.9% wrapped up. The process of assimilation during the continual migration of hominins from Africa for over 2 million years makes more sense given all the recent discoveries scientists have made in the last decade.
I am positive the Assimilation model will become more widely accepted in the next few years. After all, and you knew this was coming, “resistance is futile”.