The Oldest Known Fossils for Humans

I have to admit I am feeling pretty smug right about now.  I have been saying to anyone who would listen (very few) that the accepted timeframe for Homo sapiens is way off. The 200,000 years ago mark for the beginning of the species just felt to me like it was way too young.  A time more like 400,000 years ago was what I have been espousing for years and now with the Jebel Irhoud find in Morocco I feel vindicated.

This week the results from the dating analysis of the Jebel Irhoud site in Morocco of the Homo sapiens fossils found there were released and they are astonishing at the very least.  The time range given to the bones and the associated tools is 280,000 to 350,000 years ago.  This dating shatters a long held belief that H. sapiens were only 200,000 years old.

Jebel Irhoud mine in Morocco The cave site in Morocco.

In 1961 miners working the Jebel Irhoud site found a fossilized skull and other bone fragments.  At first they were thought to be Neanderthal and only 40,000 years old. After that the site became abandoned.

In 2004,  Jean-Jacques Hublin from the Max Planck Institute for Evolutionary Anthropology reopened the site looking for more fossils.  His team found a partial skull and other bone fragments from 5 individuals.  In total there are 22 specimens from five different individuals.

jaw bone from Jebel Irhuod caveHomo sapien jaw bone from the Jebel Irhoud cave.

The only difference between skulls of man today and the fossils they found is that the Jebel fossil skulls were lower at the top and somewhat elongated at the back.  They had slightly larger brow ridges also.

reconstructed Homo sapien skull from Jebel IrhoudReconstructed skull

The team also found many stone tools some of which showed signs of being in a fire or heated.  This turned out to be very fortuitous as it allowed the team to date the stone tools using a technique called thermoluminescence.  This dating put a timeframe on some of the tools to be 350,000 years old.  Dating the sediments that the fossil bones were found in gave the team a date of 286,000 years ago.

Stone tools from the Jebel Irhoud cave site.Stone tools from the Jebel Irhoud cave site.

It is now extremely clear that the beginning of timeframe for Homo sapiens is most likely between 350,000 and 400,000 years ago.

The Study of Human Fossils

To help understand the significance of the Jebel find better let’s dig down (pun intended) into the fossil record for Homo sapiens a little deeper.

Paleoanthropology is the study of the origin and the evolution of the hominin lineage (human evolution).  With Paleoanthropology, the main pillar of the science is built upon the actual physical skeletal remains unearthed that you can hold in your hands, the fossil evidence.  The comparative study of these fossils is essentially what Paleoanthropology is all about.  The two main questions to be answered once you have an actual fossil in hand are what species is it and how old is it. 

Virtually all hominin fossils are bone fragments. 

Rare is the complete bone.  It is very challenging to identify which species a hominin bone fragment might belong to.  However, once the species is identified it helps with establishing the timeline for that particular fossil found because you have an established baseline for that species to go on.

hominin bone fragmentsHominin bone fragments

New hominin fossil finds can even turn out to be a new species altogether. 

Since 2003 there have been three new species of hominin discovered, Homo floresiensis in 2003, Denisovan in 2010 and Homo naledi in 2013.  With the discovery of a new species the difficulty of establishing a timeline is even greater.  Anthropologists bring out the whole arsenal of dating techniques with every find of course but as you can imagine the timeline for a new species is critical to establishing at what point in the human lineage the new species fits into.

Establishing a timeline can take quite a bit of time itself.

The date for the Homo naledi fossils discovered in 2013 was not announced until May of 2017.  And when it was announced it was a shocker.  At the time of the find the fossils where thought to be anywhere from 2.5 million to 1 million years old.  They turned out to be only 250,000 years old.

Because establishing a date for fossils can be so critical to the study of them and how they fill out the big picture, great care and time are taken to do that. 

It has been my observation that scientists take a very conservative approach to dating fossils and don’t get wild and crazy at all.  That is why the dates for the Jebel Irhoud fossils are all the more surprising.  You can feel confident that the announcement of the time for the Jebel fossils to be as old as 350,000 years ago was not made to grab headlines.  That is what years of study and analysis gave us.

The sophistication for fossil dating has really come a long way since the dawn of the digital age.  There is a very high degree of confidence in the final outcome of any analysis.  That was not always the case.

The evolution of dating Homo sapiens.

35,000 years ago, 50,000 years ago, 100,000 years ago, 160,000 years ago, 195,000 years ago, 200,000 years ago, 259,000, 300,00 years ago, 338,000 years ago and finally 350,000 years ago, what do all these different timeframes have in common? 

These are the different dates attached to the age of modern man, the age at which homo sapiens is believed to have evolved and could be declared a separate species (speciation).   But how could all these times be correct?  There seems to be quite a bit of difference between each date.  That’s because the beginning date for the species of Homo sapiens has itself evolved through time and it is has always been getting pushed back to an earlier date.

Example One

We can start with the first archaic human skull which was discovered in 1868 in Cro-Magnon, France. This Homo sapiens fossil, then called Cro-Magnon, was dated to be between 32 and 35,000 years old. And in keeping with the then current dating methods this site and remains where thought to be 32 to 50,000 years of age. 

Example Two

Another Cro-Magnon man was discovered in 1932 at Mount Carmel, Israel.  This find was at first thought to be 40,000 years old but decades later with better dating methods the skull was established at 100,000 years old.

Example Three

In the mid 1970’s, while I was getting my Anthropology degree, the general consensus for early humans was 35K to 50K.  Then in the beginning of the 1980’s new methods of radioactive dating were developed.  The Israel finds were revisited and found to be 100,000 years old.  This was an astonishing push back for the beginning of modern man as it doubled the timeframe.  So we see with even with the first two finds of archaic humans we have pushed the timeline back from 35,000 to 100,000 using  modern dating methods of Thermoluminescence. The findings were published in 1988.

Example Four

In 1967 and 1974 at two sites in the Omo National Park in Ethiopia, human skull caps where discovered.  It took 30 years to date the finds but in 2004 the dates where verified and they came in at 160K and 195K.  This again pushes the date back effectively doubling it from the 100,000 mark to 195,000 years ago . 

Example Five

So now we are at 195K and in walks Mitochondrial Eve.  Mitochondrial Eve, a fictional character, was established through the study of genetics in 2009. She is the most recent woman from whom all living humans descend in an unbroken line purely through their mothers, and through the mothers of those mothers, back until all lines converge on one woman.  The date for Eve was between 152 and 234 thousand years ago.  A general estimate given the Omo finds was tagged at 200,000 years ago for Mitochondrial Eve.  This DNA evidence along with Omo finds provided a solid foundation for establishing the 200,000 years ago mark as the beginning of modern man.  This dating has been the benchmark as the consensus of opinion on the age of modern man for the last 13 years or so.

Example Six

However, that foundation of 200,000 years ago has had cracks in it for a while now.  Florisbad is a Middle Stone Age locality in Free State Province, South Africa.  In 1932 the discovery of a largely intact archaic Homo Sapiens cranium was made. Again because of dating methods at the time the dating was basically guess work.  Then in 1996, enamel samples from the tooth went through the electron spin resonance technique which allowed researchers to date the skull to around 259,000 years old.

Example Seven

And now we come to Y Chromosomal Adam who is the male counterpart to Eve.  Y-chromosomal Adam is the name given to the most recent common ancestor (MRCA) from whom all living people are descended through the male lines of their family tree. Up until 2013 genetics had given the date to Adam of basically the same as Eve which is around 200K give or take.  Then an African American man submitted his DNA to a family tree website for testing and astonishingly it tested for 338,000 years old.  His heritage points to Western Cameroon in Africa. Researchers went there and found 11 other men with the same date, 338,000 years old, in their DNA.  This has been baffling to scientists since then as it did not fit into any accepted model for Homo sapiens.

And so here we are at The Moroccan site, called Jebel Irhoud with the latest and greatest find of them all, actual skeletal remains.  And as these things go it is a major find with 22 specimens from five different individuals. A very significant amount of material to study. 

And after all the years it took to analyze the fossils the conclusion of the timeframe for them is 300 to 350K.  Considering what I have just outlined for you I think it’s reasonable to take the earlier date of 350K rather than the later end of the spectrum.

I have long thought that when it’s all said done we will establish the date for Homo sapiens as right about 400K give or take a few thousand.  I do think the Jebel skulls are archaic human skulls and probably right at the end of a transitional period of evolution when H. sapiens evolved from H. heidelbergensis.

The thing that has always bothered me about the 200K date is we know from fossil evidence that we have fully formed sapiens skulls that are identical to modern man at the 200K mark.  So given the nature of speciation and evolution in general it’s hard to believe there wasn’t a long period of time for the actual transition to take place between one species to another.

We did not evolve in one generation from H. heidelbergensis to H. sapiens.  Even given the stair-step nature of evolution a sudden change due to gene mutation would not be that radical.  It actually does take some time.   

So, my thinking is, given everything we’ve discussed and taking the date mark to be 350K and adding on 30K to that to be conservative, it still leaves us with a 380K date which is right up against the approximately 400K I have long thought. Further finds will bare this out I am sure.

One of the more enlightening aspects of the Jebel Irhoud find is the location itself.  The Jebel Irhoud site is in Morocco which is located in the Northwestern corner of Africa.  This is thousands of miles from Eastern Africa.  Along eastern Africa from Ethiopia and the Horn of Africa south to South Africa is where the birthplace of mankind is considered to have taken place.  There had never been archaic H. sapiens fossils found anywhere else.

Now we see that H. sapiens basically had the run of the whole African continent as long ago as 350K plus, a time when the Sahara desert region was a lush grasslands with rivers and lakes.  This is highly significant for several reasons.  Frist of all it opens the possibility of finding hominin remains in other parts of the continent and certainly other modern man fossils. However, those further finds might be a long time coming.

It is way too dangerous in most of Africa currently to launch fossil hunting expeditions.  The lawlessness and the threat of terrorism is too great.  The same goes for most of Middle East.  It would be irresponsible to take a team out in the field for the majority of that territory.  So, we will have to wait on that but one of the gifts from the Jebel Irhoud find is that we now know all across Africa is potentially fertile ground for hominin exploration.

There is another significant aspect of the Jebel Irhoud find that has even bigger implications and it centers around migration.

We know from the fossil record that 1.6 million years ago Homo erectus migrated out of Africa and into Europe and Asia.  Given what we now know, Homo sapiens occupied all of Africa 350,000 years ago it seems highly likely they had migrated out of Africa also. 

Given the tendency for hominin wandering it also seems likely they made it into Europe and Asia just like Homo erectus had.  After all, during that same time period we know that Neanderthals occupied Europe and Eurasia ,  Heidelberg Man occupied Europe, Eurasia and Africa, Denisovans occupied Europe to Asia and Homo Erectus occupied Europe to Asia to Africa and lastly Homo floresiensis lived in Southeast Asia.  Why wouldn’t H. sapiens do the same?

I believe they did migrate out of Africa as much as 200,000 years before the commonly accepted date of 120,000 years ago.  Why not? They certainly wandered all around Africa by 350,000 years ago. (The first wave of the ‘Out of Africa’ theory of human migration has H. sapiens leaving Africa 120,000 years ago.)  

Stick with me a little longer because I want to share something else with you about what this Jebel Irhoud find could mean.

In April of this year a published report in Nature outlined an Archaeological site in California that is believed to have circumstantial evidence of human occupation 130,000 years ago.  The generally accepted timeframe for human migration to North America is approximately 14,000 years ago. 

The 14K figure has had holes blown in it for some time.  Another site, Bluefish Caves (Yukon Territory) is dated at 24,000 years ago and in Chile a site dated 18,500 years ago.  There are other sites in South America dated even older and pieces of artifacts from Texas dated to 40,000 years ago.

Now I have to tell you that Anthropologists by and large are very skeptical about these claims.  They stick to the 14K story line.  That story goes (very briefly) like this.  During the last ice age a land bridge was formed between Siberia and Alaska giving humans a path to migrate to North America which they did 14,000 years ago.

The time of 14,000 years ago nearly marks the end of the last ice age.  That particular ice age started almost 80,000 years ago and during the whole time there was amble opportunity for humans to migrate from Siberia to North America.

Not only that but there was another ice age from a time of approximately 200,000 to 150,000 years ago that was every bit as cold and created the same land bridge from Siberia to Alaska. 

 

Let’s review.

Homo sapiens occupied and migrated across Africa 350,000 years ago.  By that time 5 other species of hominin lived in Europe, Eurasia and Asia.

Most assuredly H. sapiens migrated out of Africa 350 - 300,000 years ago. This gave them plenty of time to move into Europe, Eurasia and Asia.  And why wouldn’t they as every other hominin did?

An ice age that lasted between 200,000 and 150,000 years ago created a land bridge between Siberia and North America.

Ask yourself this question. Why is it any more improbable humans migrated to North America 150,000 years ago at the end of that ice age than it is that they migrated to North America 14,000 years ago at the end of a subsequent ice age?

The absence of evidence is not evidence of absence.

What that means is just because they haven’t found Homo sapiens fossils in Europe, Eurasia or Asia before 120,000 years ago does not mean they were not there.  It just means they have not found them yet. The circumstantial evidence and logic are strong. 

In my opinion, they will find the fossil evidence sooner or later just like they found the skulls of Jebel Irhoud.

 

 

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Jay Boyle

Thanks for a very interesting and compelling review of early Homo Saipan evolution and paleontology review. Makes sense to me.

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