Our family tree

Reference 1 is a review article about the evolution of apes to humans, more specifically about ongoing research into the many large apes of the Miocene epoch, say from 10mya (million years ago) to 2mya, by which time early forms of humans had arrived. Large apes which are only known from a rather fragmentary fossil record.

With my reading encouraged by at least four factors. First, we need to push back against what seems to be a rising tide of creationists across the Christian and Muslim worlds. Second, the way we humans came to be, starting off from good simian stock is of interest in its own right. Third, the classifications which emerge from evolutionary analysis are going to interest a former statistician with a finger in the pies of classification of both occupation and disease. Fourth, I am presently engaged with reference 5, which builds a evolutionary classification of the world’s languages. An overdetermined activity, as the shrinks would say.

The story of the present review seems to be that it is not enough to look at those of our relatives which are still about, the orangutans, the gorillas, the chimpanzees and the bonobos. We need to look at all the now extinct apes running around the world during the Miocene epoch, millions of years before we humans turned up; a world introduced at reference 3. I have learned that there were quite a lot of them on the north coast of the Mediterranean Sea, as well as being scattered across much of Africa and a swathe of south eastern Asia.

Part of the story being that humans did not evolve from any of these extant relatives and the hunt is on for the ‘Pan-Homo LCA’, that is to say the last common ancestor of humans, chimpanzees and bonobos, with the ‘Pan’ bit being these last two. An ancestor, from the figure above, which lived about 5mya. The blue-magenta junction.

Another part being that a critical step on our evolutionary path was learning to walk on two feet, from which so much else was able to follow. But we are some way off knowing exactly how and why this happened. As things stand, there are many ways in which this particular cake might have been baked.

And another being that there has been a shift in climate since the Miocene, meaning that there is less jungle and more woodland and savannah. Less of the soft, sugary fruit favoured by some simians. Furthermore, the climate is less stable. So animals which wanted to thrive needed to adapt, needed to be able to adapt.

While, for me, a dental curiosity was something called the canine honing complex, an arrangement of canines and premolars which allowed the upper canines to be sharpened by rubbing against a suitable hollow between the lower canine and the first pre-molar. It seems that early apes had much larger upper canines than we do, almost tusks, evidence of a much higher level of aggression, incompatible with the evolution of co-operative humans. Those more curious than me on this point can consult reference 4.

I think the take away for me is that this is all very difficult. It will take a lot more fossil hunting field work, particularly in that large part of Africa which has not yet been looked at properly for these purposes, a lot of which is not readily accessible, and then a lot more work back in the laboratories and institutes, before we get to a good understanding of the evolution of early man from the apes. Work of the kind which is evidenced at reference 6.

PS: the first version of the snap above, a png lifted from Wikipedia, took on an unhelpful black background when one clicked to enlarge. Hopefully, this jpg version from Microsoft's 'Snip & Sketch' tool will not do this.

References

Reference 1: Fossil apes and human evolution - Sergio Almécija, Ashley S. Hammond, Nathan E. Thompson, Kelsey D. Pugh, Salvador Moyà-Solà, David M. Alba – 2021.

Reference 2: https://en.wikipedia.org/wiki/Chimpanzee%E2%80%93human_last_common_ancestor. The source of the figure above. The orangutans had already gone their own way by time it starts, 10mya.

Reference 3: https://en.wikipedia.org/wiki/Miocene. 

Reference 4: Modularity of the anthropoid dentition: Implications for the evolution of the hominin canine honing complex – Lucas K. Delezene – 2015.

Reference 5: A guide to the world's languages. Vol. 1: Classification – Merritt Ruhlen – 1987.

Reference 6: https://en.wikipedia.org/wiki/Ardipithecus_ramidus. One of the pieces of the complicated jigsaw.