Human Evolution Before Lucy

Lucy

Lucy is an Australopith discovered in 1974.  She got her name because the song ‘Lucy in the Sky with Diamonds’ was playing as she was being excavated.  Properly, Lucy is a female of the species Australopithecus afarensis, several hundred pieces of bone fragments representing 40 percent of her skeleton were eventually found.  Lucy became famous as a representative of the Australopiths and in the field of human evolution the best known early man fossil in the world.  She has been dated right about 3.2 million years ago.  The life span of the species A. afarensis has been dated between 3.9 and 2.9 million years ago.

Here is Lucy…

Lucy fossil remains

There is another Australopith that predated Lucy, Australopithecus anamensis first discovered in 1965, this Australopith’s life span has been dated 4 to 4.5 million years ago.  Nearly one hundred fossil specimens are known from Kenya and Ethiopia, representing over 20 individuals from this species.

This is interesting, here is a skull of a A. anamensis and this is pretty much what it looks like when discovered.

australopithecus anamensis skull

Not the same skull shown above but next is another anamensis skull after being cleaned up and reconstructed.  The white areas are the places bone was missing.  You can see there is quite the process involved in restoring and reconstructing ancient fossils.  It can take years to extricate the bone fragments from the rock encasing them.

reconstructed Australopithecus anamensis skull

What about the hominins that came before the Australopiths?  How many were there and really what’s the deal with them anyway? 

The thing about the Australopiths is that among Anthropologists they are widely considered to be bona fide early hominins, part of our human legacy, whereas before them there have been discoveries of several different fossil finds that could be possible hominins but the evidence is not conclusive as we shall see.

The Starting Point In Time

The starting point for the first exclusive ancestor to modern man and human evolution starts with the split from the last common ancestor to both humans and chimpanzees.  When the ancestral line split and chimpanzees and humans went their separate ways that is the point we start at.  As you can imagine that was a long time ago and fossil evidence is sparse at best and the estimates for the exact time of the split varies wildly.  Some say it could be 13-14 million years ago and others say more like 7-8 million years ago.

I think the 7-8 million years ago is the more supported view at this point until some new fossil discoveries are made. 

And yes, there is actually an acronym for it… CHLCA or chimpanzee-human last common ancestor.

Let me just say right here that the next post I make is going to be about the sexy and intensely interesting Linnaean taxonomy. I am not going to tip my hand on that but honestly, it’s riveting.

 Whenever the split occurred it broke the Tribe: Hominini into two branches or sub-tribes.  The human sub-tribe is called Homininia and the chimp sub-tribe is called Pania.

At this point we are only concerned with human evolution so if you are in the sub-tribe Homininia you are called a hominin.  All of the species belonging in the human legacy are hominins.  Below the sub-tribe classification, you have Genus and Species and even sub-species to designate individual species.  Most commonly species are named by their Genus classification first and then the species name. The Genus is always capitalized and the species is not.  This is called binomial nomenclature.

Graecopithecus freybergi

The first hominin we currently know of after CHLCA is called Graecopithecus freybergi.  The original mandible was found in 1944 but not extensively studied until 2017.  G. freybergi could very well be the first hominin even though the fossil evidence is based on only two finds.  However, after extensive state of the art dating and analysis it seems reasonable at this point they could be included as hominins. 

Here are the fossils found from two different locations, a lower jaw from Greece and an upper premolar from Bulgaria...

Graecopithecus freybergi fossil remains

The dating puts G. freybergi is around 7.2 million years ago which fits nicely in the time frame for CHLCA and makes it a nice candidate for the first pre-human..

The most interesting aspect of this find is that Graecopithecus freybergi was found in Greece and Bulgaria and not in Africa.  This brings into question the long held belief that the human lineage began in Africa.

At the time period we are talking about, 7.2 million years ago, large portions of Europe where open savannas.  This most likely was pivotal in helping in the evolution of G. freybergi and it’s split from the chimpanzees.  The open grasslands of the savannas promoted upright walking and other evolutionary changes.

You might look at the photo above and think, “Wait a minute.  Is that all they have to go on?  How can anyone determine anything with so little fossil evidence?”  Well scientists can determine quite a bit with a small sample size especially if that sample size is from the jaws and teeth.  I am not going to get into all the comparative analysis done but using teeth and mandibles is one of the best ways to classify hominins.  From lengthy and detailed comparisons of these fossil remains and other hominin fossils quite a bit can be deduced.  

There will probably be more fossil remains of this species unearthed in the future.  For now G. ferybergi  has already expanded the vision of human evolution to include the possibility that the first hominins evolved in Europe and not Africa.

Sahelanthropus tchadensis

Right on the hells of G. ferybergi is Sahelanthropus tchadensis discovered in 2001.  This species is dated to 7 million years ago and again it is represented by just a few bone fragments consisting of nine cranial specimens.  Even with this sparse fossil evidence we can see human like qualities such as small canines and some facial features.  But the most telling feature is the position of the foramen magnum.  The foramen magnum is the hole at the base of the skull.  It is positioned far enough forward to indicate bipedalism.  Being bipedal is a significant milestone along the path to being human. This species is thought to be ancestor to Ororrin tugenensis. 

Some pictures of a reconstructed Sahelanthropus tchadensis  skull...

reconstructed skull of Sahelanthropus tchadensis

 Sahelanthropus tchadensis  skull fragments

Orrorin tugenensis

Orrorin tugenensis first discovered in 2000 it has been dated to 6 million years ago.  It is represented by 20 specimens of fossil remains from five individuals at four different sites in the Tugen Hills in Kenya.

The analysis of the remains indicates bipedalism and tool use of the hands.

A photo of the skull fragments found...

Orrorin tugenensis skull

More bone fragments from Orrorin tugenensis...

Orrorin tugenensis  bone fragments

I think this is a good point in the story to point something out.  These five species in this post suffer from the same malady and that is the meager amount of bone fragments that have been discovered to date for each individual species. 

I think Orrorin is a great example of this because of the various conclusions that have been postulated from the evidence. It ranges from Orrorin being a direct ancestor of humans to speculation that the species lived before the ape and human split and could be an ancestor to both human and chimp lines.  Some think it could be such a direct link in the human legacy that it would move the Australopiths to a side branch of the hominin family line.

In other words it’s all over the place.  Until Paleoanthropologists have unearthed more complete examples of each species the interruption of what we have will vary.  One thing is clear however and that is they are all part of the story no matter how they each fit in.

Ardipithecus kadabba

Ardipithecus kadabba discoveries occurred between in 1997 and 2002 and is dated between 5.7 to 5.5 million years ago. Thought to be the direct ancestor to Ardipithecus ramidus. 

Here is the fossil evidence discovered so far...

Ardipithecus kadabba bone fragments

Analysis of the bones do indicate the creature could have been bipedal but more discoveries would be welcomed here.

Ardipithecus ramidus

Ardipithecus ramidus first discovered in 1994 and is dated to 4.4 to 4.2 million years ago.  There are 110 bone specimens from 35 individuals for A. ramidus. This creature is thought to be bipedal and a possible ancestor to the Australopiths.

Here is a picture of the skull bone fragments that have been found...

Ardipithecus ramidus skull fragments

And from all that here is a reconstructed skull simulation...

Ardipithecus ramidus  reconstructed skull

The Time Gap and the CHLCA

There is a time gap between what is generally considered 7-8 million years ago for the CHLCA and the first Australopith, anamensis, dated to as old as 4.5 million years ago.  So we have a gap of about 2.5 to 3.5 million years were there is not a definitive set of fossils or rather species that can be placed in the human legacy.  The five species I just talked about are possible candidates to be included but each of them have their own issues.  A list of pros and cons for each one leaves the question open.

Were any fully bipedal?  Partially bipedal?  The evidence seems to indicate that all of them had the capability.  That is one reason they have been considered to be hominin in the first place.  Bipedalism being a major milestone. 

If none of these five species are in a descendant line to modern man then the gap still exists.  They could be transition species or when more discoveries are found each one could be considered a hominin.

With so little evidence to work with it’s amazing the information derived can be so extensive.  But the analytical techniques used are quite considerable.  The comparative analysis between older species and younger ones is invaluable when looking at attributes like being bipedal.  The comparisons of individual bone structure sheds light on methods of locomotion and even the ability for tool use.

As you can see by the time assigned to the discoveries, most were in the past 20 years or earlier ones re-examined in the last ten years.  Newer techniques for exploration are being tested out and perhaps some day a cool ground sonar will enable Paleoanthropologists to find fossils they might have not been able to.  Until then the time between the  CHLCA and the first Australopiths has the above mentioned species as viable candidates to fill in that gap.

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Kevin Lakins

Love the information. Love the scientific updates based on new findings and re-examined earlier discoveries that causes adjustments to previous generally accepted ideas. I appreciate that scientific knowledge allows itself to be corrected or amended as new information comes to light.
Like your posts and web sight. Bought some gallery of skulls shirts that ? look great ?
Thank you ?

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