The Dead Speak
Ancient bones come back to life revealing the past of mankind. These ancient bones and artifacts of time tell a powerful, irresistible story. Paleoanthropologists and Archaeologists converse with these ancient bones and what they have found is nothing less than the epic saga of mankind.
The legacy of life on earth is revealed to us through fossils. We only know about our human legacy through the study of hominin fossil remains that have been discovered. From the first accidental finds of Neanderthal bone fragments to the sophisticated analysis of DNA contained in the fossilized bones from the hominin cache of fossils we currently have, the constant is the fossil itself. It’s really hard to imagine what our understanding of the history of life on earth would be like without fossils to enlighten us. What a great gift fossilization has been.
First off fossilization is very rare. You might think, ‘Wait a minute, there are fossils everywhere.’ There are a lot of fossils that have been found but compared to the quintillions of animals that have lived on earth relatively few fossils have been found. There are certain stringent conditions to be met for a living being to fossilize after death. No doubt there are millions, maybe tens or hundreds of millions of species in the history of life on earth that lived and died and left no fossil record.
Most people think of fossils as bones but fossils can be any trace of a living ancient organism. A fossil could be a footprint, a cast of a bone even soft body parts can be preserved under optimal conditions, i.e., frozen or encased in amber.
In the study of man the fossil history is the study of bones and other associated artifacts. The understanding of man through the study of fossils is the same as the understanding of life on earth through the study of fossils. There are pieces missing, some species are underrepresented but at this point we have a really good understanding of what happened and the timeframe for it.
The Process of Fossilization
Whether or not an organism becomes fossilized depends mostly on the environment surrounding it when it died. Deserts and arid caves are good. Being entombed by a cave-in or rockslide is good also. Tar pits have been good preservers of bones. Basically what is good is to have the organism encased away from the elements (water and oxygen) as much as possible and as soon as possible.
Not all bones fossilize equally well. Hominin bones with a lot of surface area, lightweight bones and small bones have a much less chance of becoming fossils than teeth, jaws, skulls and the bigger leg and arm bones. Teeth actually have the best chance. Rib bones while actually pretty big are more porous so they don’t fossilize well. Smaller bones are also more likely to get crushed or washed away or otherwise lost to time.
The following is a picture of the fossil remains of 'Lucy', an australopithecine 3.2 million years old.
Dead Men Do Tell Tales
There have been enough fossil remains found to fill out a big picture of human evolution. It would be nice to see more transitional forms to help connect the dots. However, transitional periods take place over a shorter timeframe which offers a decreased chance for leaving a recoverable example.
The vast majority of hominin fossils have been found in Europe, parts of Asia and Africa.
There are still large parts of Africa, Eurasia and Asia that for a variety of reasons have not been explored for hominin fossils. So it is possible, especially given the recent finds in the past two decades, that different species of hominin are yet to be discovered. Even searching in the same areas that have yielded fossils before can still be productive.
Some of the things we learn from fossils.
- Evolutionary processes and trends
- relatedness to other species
- body shapes and sizes
- species type
- physical capabilities
- growth patterns
- like expectancies
- inferences about size and shape of muscles
- understanding locomotion
- Positioning of eyes, ears, nose on the skull
- age of individual
- age of species
- how quickly children grew
- even some social behaviors can be determined
comparative hominin brain sizes
- Australopiths 400-500 cc
- Homo erectus 850-1100 cc
- Homo heidelbergensis 1250 cc
- Homo neanderthalensis 1300-1600 cc
- Homo sapiens 1250-1400 cc
Fossils can’t prove that one species evolved from another, but when we find a succession of them over time with slight modifications, it is difficult to deny the appearance of evolution.
Connecting The Dots
We have talked a lot about different aspects of Human evolution so far in this paper. We’ve talked about time, DNA, natural selection, speciation, extinction and we’ve outlined all the hominin species discovered.
Now I am going to give you what I think is the most probable path to modern man and it is not a straight line as such but a path nonetheless.
Australopithecus africanus, 3.3 million to 2.1 million years ago,
evolved to Homo erectus, 1.9 million to 70,000 years ago,
evolved to Homo heidelbergensis, (most likely) 1.3 million to 200,000 years ago,
evolved to Homo sapiens, 350,000 to present.
Pretty simple really. There are transitional fossils that have been found between Australopithecus and Homo erectus. In my opinion there are transitional fossils between Homo erectus and Homo heidelbergensis that have been found but some call them Homo antecessor. The time for Homo sapiens is somewhere between 300,000 and 350,000.
My own personal opinion is that the time for Homo sapiens will be pushed back to about 400K when it’s all settled. I would like to repeat (from an early paper) that “Absence of evidence is not evidence of absence.” Just because we have not found the fossil evidence of H. sapiens in the 400K range doesn’t mean that there isn’t any. It just means to me that we haven’t found it yet. And yes, I know the DNA and all that but still some estimates when looking at the DNA are in the 300K plus range. The study from DNA is great but so is the fossil evidence which is more definitive. (Don’t tell any Paleogeneticists I said that as they are all wonderful people.)
I keep pushing back the timeline on all hominin species because the more we discover and unearth hominin fossils the farther back the timeline gets pushed. Also, I would like to point out that when I was in college the timeline for H. sapiens was 50K to 45K. At that time we called them Cro-Magnon, a term that has fallen out of favor. Presently with the DNA we are looking at 300K for H. sapiens, so it changes but always in the direction of being older.
Out of Africa
It is universally accepted that Africa is the birthplace of humanity. It is also universally accepted that Homo sapiens evolved in Africa first. Therefore, the spread of H. sapiens throughout Europe, Eurasia and Asia is called the ‘Out of Africa’ theory.
But before H. sapiens left Africa, H. erectus did. The next picture shows the migration out of Africa for Homo Erectus.
Homo erectus left Africa and spread throughout Europe, Eurasia and Asia. They pretty much were everywhere and if you can believe the breaking news they may have been the first to reach North America 130,000 years ago or most likely even before that time. From 200,000 to 140,000 years ago during an ice age there was a 'land bridge' that would have allowed migration into North America.
There was a period of time between 300K and 200K when seven hominin species walked the earth.
They are in order of age;
- H. naledi
- H. erectus
- H. heidelbergensis
- H. floresiensis
- H. neanderthalensis
- H. denisova
- Homo sapiens.
There was interbreeding going on, especially between Neanderthals and sapiens, Denisovan and sapiens and between Neanderthals and Denisovans. And strangely enough Denisovan could have interbred with a ‘mystery hominin’. DNA indicates they interbred with an unidentified hominin that could either be H. erectus, H. heidelbergensis, H. floresiensis, H. sapiens or some other as yet unknown hominin. That’s the thing about DNA analysis on ancient bones, it’s not definitive but they can tell Denisovan interbred with some other hominin that just can’t be identified as yet. It may be one we know about or it may be a totally unknown hominin. My money is on it being one we know about once a better sample of Denisovan DNA can be found to analyze.
The Big Picture Of How Human Evolution Unfolded
In Africa about 7 million years ago the hominin lineage split from the chimpanzee lineage. Sahelanthropus tchadensis could be the first hominin or it could be Orrorin tugenensis.
The following picture is the totality of skeletal remains we have of O. tugenensis.
It most likely was the case that one or both are the earliest hominins. During the approximately 3 million year gap from the split with chimpanzees to the first australopiths there were no doubt some other species, maybe several that led to the Genus: Australopithecus.
The australopiths had a good run with several branch offs that eventually went extinct but one of them, Australopithecus africanus, evolved into Homo erectus. There is good transitional evidence dated 2.5 to 2.3 million years ago showing the evolution between africanus and erectus. By 1.9 million years ago Homo erectus established itself as the first Genus: Homo.
The recent discovery of Homo naledi (2013) could establish this new found species as the first Genus: Homo. The dating on the remains found has been established as recent as 250,000 years ago. The early date is has still not been established but based on morphological analysis it could be 2 million BCE. So naledi could will be the first Homo species.
Physically erectus looked just like modern man except for the head, their brain size being about 3/4ths of modern man. In height they grew to six feet and were heavily muscled. They ran like the wind and more importantly could run for long distances, after all that’s how they got dinner by running down prey. And they were very adventurous travelers. Erectus left Africa and populated Europe, Eurasia and Asia.
While in Europe H. erectus evolved into Homo heidelbergensis, while in Asia they evolved into Homo floresiensis. They were such a successful species that even after branches had broken off and evolved into new species they continued to live on until around 70,000 years ago.
In Asia H. erectus evolved into Homo floresiensis. Discovered in 2003 on the island of Flores in Indonesia, floresiensis has been given the name ‘The Hobbit’ because it only grew to 3.5 feet (1.07m) tall. Its brain size is comparable to the australopithecines. The lifespan of this species is 700,000 to 50,000 years ago.
Europe is where Homo heidelbergensis evolved some 1.2 to 1.3 million years ago from H. erectus. They then traveled as far as India and to Africa. In Africa they grew to over seven feet (2.13m) tall. Heidelberg Man, as he is known as, had a brain size roughly comparable to modern man.
While in Europe Heidelberg Man evolved into two offshoots, Homo neanderthalensis and Denisovan. He lived on until about 200,000 years ago.
Neanderthals lived in Europe and Eurasia and a little east of Eurasia. Recent DNA studies suggest a timeline for them starting around 765,000 years ago to 28,000 years ago. Their brain size was larger than modern man’s. While on the average somewhat shorter and thicker than us, Neanderthals looked like modern man in every respect except the head was somewhat elongated and the skull had a receding chin. If you saw one walking down the street dressed appropriately, it would not ring any alarm bells.
Little is known about the Denisovans. Only a handful of fossil fragments have been discovered. Their range was from Europe to Asia and they were contemporary to Neanderthals as far as we know at this time.
And then we come to us, Homo sapiens. We evolved in Africa and unless a as yet undiscovered species turns up we evolved from H. heidelbergensis about 350,000 years ago (maybe earlier). We are taller and slimmer than Neanderthals and with a slightly smaller brain size.
So there you have it. Australopithecus to Homo erectus to Homo heidelbergensis to Homo sapiens, with many off shoots having gone extinct along the way.
But how did modern man, Homo sapiens, become the only surviving hominin when at one time there were seven living hominins?
The Last Hominin Standing
So, was it our big brains? Actually Neanderthals had a bigger brain, Heidelberg Man about the same size and possibly Denisovans too. Was it our superior fighting strength? Neanderthals were stronger, so were Heidelberg Man and most likely H. erectus too and as far as we know Denisovans were more like Neanderthals than us. Was it our winning personality? Absolutely yes!
We are talking about three species that were charmed because Heidelberg Man and Homo naledi were basically not a factor being weighted heavily down in the extinction vortex at the time sapiens started to rise and H. floresiensis was very isolated and in all likelihood had no contact with modern man. The three other hominins would be H. erectus, Neanderthals and Denisovans.
When I say it was our winning personality I mean that we charmed the pants off these guys… literally.
Today modern man (except for indigenous sub-Saharan Africans) can have up to 2.5% Neanderthal DNA and in Southeast Asia there can be 4% to 6% Denisovan DNA mixed in. We do not have at this time any DNA from H. erectus so it’s impossible to say if sapiens interbred with them but speculation is they did.
I would assume that 100,000 years ago those percentages of DNA were higher as the gene flow was happening but after the other species died out and their gene pool was not around the percentage started to decline except for the genes that were kept because of the survival advantage they gave us.
You can imagine all the different scenarios of sexual encounters from perhaps the simple and friendly exchange of men and women to wild parties around the campfire to abduction but one thing is clear...
Homo sapiens are like the Borg from Star Trek lore, when we encountered another species we assimilated them.
And like the Borg, Homo sapiens were unrelenting in their spread out of Africa and throughout the world. We now occupy every nook and cranny, every available land space on earth no matter the climate or harsh conditions. Modern man is an unstoppable force and woe unto any species that gets in our way. In the 4.5 billion year history of the earth there have been 5 major extinction events. There is a growing consensus among scientists that we are in the mist of the 6th great extinction period caused solely by the size of the human population, 7 billion 400 million and growing.
But that is a different subject altogether. What we want to know and talk about now is the spread of modern man out of Africa into Asia, Eurasia and Europe.
The Out of Africa Single-Origin Hypothesis.
The single-origin hypothesis postulates that Homo sapiens evolved in East Africa 350K years ago. There was a first wave of migration into Eurasia and Asia around 120 to 150K years ago. A second and larger wave swept out of Africa in the 60 to 70K range. This larger wave spread throughout the world and by 28k to 40K years ago Homo sapiens became the only hominin species left standing.
The First Wave Out Of Africa
In the first wave of H. sapiens’ migration they made it all the way to China thru the middle east and Arabian Peninsula. There is not much hard evidence of widespread occupation of Europe but considering they trekked all the way to China I would imagine they occupied Europe too.
A second and larger wave of migration took place around 60-70,000 years ago.
It’s hard to imagine that that at some point during the first wave of migration it stopped for over 50,000 years and then started up again. I think a more likely scenario is that the climatic conditions were favorable during the beginning of the first wave and then conditions changed, which did not stop migration but slowed it down. Ice ages could have played a part as well droughts.
However, it is clear that around 70,000 years ago the big migration out of Africa took place. What major global or environmental event could have caused a change in H. sapiens that precipitated this migration?
Speculation about something major happening to sapiens 70,000 years ago has been swirling around for quite some time. For a while it was assumed that the Toba super-volcano eruption during that time period had caused a nuclear winter for the earth and this decreased the human population down to a genetic bottleneck number. That in turn created the conditions for rapid evolutionary advancement.
After further digging into this (pun intended) it seems that yes indeed the eruption of the super-volcano Toba did cause a nuclear winter but it did not have the devastating effect on humans or precipitate a cognitive revolution as once thought.
From the beginning time period of Neanderthals and Homo sapiens they started to make and use increasingly intricate body adornment and created artwork. The hunting weapons improved in many respects. They learned how to harvest the bounty of the sea. And with the expanded awareness they no doubt expanded their ability to communicate through a richer and more subtle language expanding the complexities of culture.
During the first wave out of Africa sapiens most certainly interacted with the other hominins when they encountered them. For the longest time it was thought they fought and killed other hominin species when they encountered them and that’s why they took over the world, most notably it was thought through warfare that sapiens made the Neanderthals vanish. However, after the Human Genome Project was complete in 2003 and subsequent breakthroughs of the analysis of fossil DNA we now know that interbreeding was one of the major influences of extinction for the other hominins at the time.
If you look at the way tribal cultures interact in historical times it is well within the human nature to war and fight with neighboring tribes. I am sure some of that went on between sapiens and Neanderthal tribes at the time. But the preponderance of human interaction is not to just run up and kill someone the first time you see them. It’s just not the way humans act now and there is no reason to believe they acted that way back in the day.
It is way more likely for two groups to feel each other out and try to trade and communicate in a non-life threatening way unless some particular incident would incite violence.
After all we know Homo sapiens would fight each other and it stands to reason that in some cases Neanderthals, Denisovan and Homo erectus would fight among themselves also. So common sense would tell you sapiens would also on occasion fight with the other species but does not mean it was the normal interaction or the main contributing event that caused extinction.
Consider this, Neanderthals lived in tribes of a dozen to two dozen individuals whereas sapiens lived in groups of up to 125 to 150 individuals. The necessary resources needed to sustain a larger group required a much more extensive exploitation of the surrounding environment. At the same time, Neanderthals having a thicker frame and more muscle and a bigger brain actually needed on an individual basis more nourishment than an individual sapiens needed plus the population of Neanderthals was very low and spread out over a large area.
With a population size of 70,000 or less and with a possible 7,000 breeders spread out over an area from Europe to Eurasia and into India, it doesn’t take much to see how fragile the situation was for Neanderthal at the time. Take away a certain percentage of females or males during their reproductive years and use up their resources and you pretty much have the reason for their extinction right there. The same thing would apply to Denisovan and H. erectus.
Because if there is one thing we know about Homo sapiens they sure can procreate.
After moving into an area and establishing themselves the population would grow. As the population of sapiens grew they either assimilated or they marginalized other species to such an extent they entered the extinction vortex because they inevitably would drop below that critical minimum viable population. Also consider we are talking tens of thousands of years here, so plenty of time to affect these changes.
The most likely scenario.
- Evolution brings many advancements in technology and culture. It enables larger groups or tribes of up to 150 individuals.
- For a variety of reasons the larger tribes allow for more security and infant mortality drops resulting in population growth.
- Environmental conditions are conducive to migration out of Africa.
- Sapiens move out of Africa and encounter Neanderthals, Denisovans and Homo erectus living in Europe, Eurasia and Asia.
- Those encounters result in the eventual extinction of all other hominin species except for Homo sapiens.
- After the end of the last ice age about 12,000 years ago modern man discovers the way to domesticate plants and animals thereby providing a more abundant and steady food supply and the rest is rock and roll history.
A closing statement
The evolutionary advantage which enabled humans to eventually dominate the planet earth like no other life form is not a big physical adaptation or improvement but a qualitative expansion of the consciousness enabling us to conceptualize solutions to problems large and small.
We had already evolved physically to the point where we could take advantage of the expanded mental abilities to manifest any supplemental attributes needed to exploit any and all environments presented to us for the harvest of resources they provided. This flexibility coupled with our mobility made modern man an unstoppable force.
When we looked at the sea we no longer saw a formidable barrier we simply made boats. When we saw fish and other food sources of the sea we made nets and special spearfishing tools. When it got cold we sewed animal hides for protection, not only for clothes but shelter and on and on. Every problem or obstacle we encountered or ran up against in every environment on earth we used our brain power to conceptualize whatever solution we needed to overcome it and then manifested that solution.
And here we are, 7 billion 400 million strong. The abilities we have used to get us to this point have always been in the direction of exploitation. Now we have entered a new epoch, the epoch of the Anthropocene. The age of man. In this age the focus of mankind must turn from exploitation of the earth to the intelligent stewardship of the earth.
Once the collective consciousness of mankind sees that the continued massive exploitation of earth is counterproductive to species survival we will realign our survival strategy to enter an age of intelligent harvesting of renewable resources for an agreed upon sustainable population size.
This has already begun in the area of energy. Germany can already supply 100% of its energy requirements with renewable resources.
We will have to turn our attention to a fresh water supply and nutritious food supply next. This will happen and in a relatively short period of time speaking historically but in human life span terms it may take another couple of hundred years for the collective consciousness to fully embrace this new survival awareness.
Go ahead and call me what you will, a pie in the sky thinker, having a utopian vision, etc. However, I am not saying we are all going to be sitting around the campfire singing Kum ba yah. What I am saying is that when faced with hard challenges we as a species have been able to do incredible things that take massive planning and cooperation with thousands of individuals. The Great Wall of China is an example, walking on the moon, the Panama Canal, the Great Pyramids etc.
We are not at the brink right now but we are close, very close so big changes are coming. But big changes are nothing new. Just look at the last 200 years. Mind boggling changes all over the place. I will admit to being a glass half full guy though. This gives me the confidence to predict we as a species, when pushed to the brink, will step back and manage the situation quite well… as bumpy as that ride might be.