Where Are All the Panins?

Have you heard of the word hominin?  Even if you don’t know exactly what a hominin is, you have probably heard of it before.  Hominins are a tribe of organisms that include modern Homo sapiens as well as all species that have been apart of our lineage since we diverged from a common ancestor with chimpanzees and bonobos (and they have been discussed on this blog before).

What about the word panin?  Unless you are a professional biological anthropologist specializing in primatology or paleoanthropology, it is unlikely that you have heard this word.  This is because despite our ever growing knowledge of hominin evolution from fossils in eastern, southern and central Africa, we have almost no remains of panins – the tribe of organisms that includes chimpanzees, bonobos as well as all species that have been apart of their lineage since they diverged from a common ancestor with our species.

In fact, despite having collections of literally thousands of hominin bones – from Sahelanthropus tchadensis (a hominin that existed 7 million years ago) to Homo floresiensis (a hominin that existed up until approximately 17 thousand years ago), we only have two teeth from a panin.  From this fossils we know that it lived in East Africa less than a million years ago and was likely an ancestor of the modern day chimpanzee.  Although we can only know so much from a few teeth, the morphology of these fossils suggest that it was not that much different from contemporary chimpanzee populations.

However, this is a major problem for primatology and for our understanding of hominoid evolution.  Whenever fossil hominins are analyzed they are always compared against the modern day chimpanzees and analyzed for ancestral and derived traits.  This is done because it is assumed that the common ancestor that we share with chimpanzees and bonobos was more chimp and bonobo-like than human-like.  Also, in primatology, whenever a chimpanzee or bonobo engages in a behaviour or is characterized by a trait that we also do or possess, it is argued that it was present in the common ancestor.  This because it is a parsimonious answer, but also because it is ‘sexy’ (meaning the idea creates an interesting and marketable narrative for the public).  However, in both cases we cannot rule out convergent evolution.  Chimpanzees and bonobos have also evolved over the past 5-8 million years and we cannot assume that they are time machines that represent what our common ancestor with them looked like.

In my mind other anthropologists can continue to hammer this point home, but in practice the only way to stop engaging in these practices is to find more panin fossils.  Over the past 15 years our understanding of hominin evolution has improved dramatically and we are now on the verge of gaining deep perspective on when the first hominins emerged and what pressures there were that led to bipedalism and larger brain size.  However, our knowledge of panin evolution is embarrassingly impoverished.  We do not have any idea how many panin species there have been over the past 8 million years, or what environments their clade experimented within.  We have no knowledge on their distribution (other than that the only fossils discovered indicate that chimpanzees ancestors had a range that extended further east in Africa than contemporary populations do).

The discovery of more panin fossils would unleash a wave of new perspectives and hypotheses to consider and would literally force anthropologists to re-write the textbooks for hominoid evolution.  Perhaps most importantly, it will force people to conceptualize the journey to becoming human in a different way.  Frequently, I will encounter individuals who believe chimpanzee are our ancestors.  They are in fact our closest relatives, not our ancestors.  Finding panin fossils will help the public (and the scientific community) remember that chimpanzees and bonobos also have an equally long evolutionary history, which may reveal that our assumptions are correct (meaning that they have undergone very little change over the past 5-8 million years), or I think more likely, it will reveal that their clade underwent a series of changes that we are currently ignorant to.

Whatever we find, it is exciting for me to remember that there is still so much we have to learn about our evolutionary history, and part of that is attempting to understand the evolutionary history of our closest relatives – the panins.

 

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About Cadell Last
Hello. I'm probably drinking coffee and reading.

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