Since posting an excerpt of my
third fifthforthcoming tome The Beowulf Effect: Fossils, Evolution and the Human Condition I have been deluged by a Dr I. B. of Tennessee, notwithstanding inasmuch as which Dr J. G. of Sussex, and no doubt other people, for more. I’m now just about halfway through – having scribbled some 41,000 words, almost all on my iPad while on trains. I finished another chapter today, about how the fossil record of hominins is so sparse that it is effectively impossible for one to drape any particular narrative over it any more convincingly than any other. Here is an edited version of some of what I wrote earlier today. It’s still a bit rough in the places that are still steaming…
Our record of hominin evolution is important not by virtue of the fossils that have been found, because these are few – but by the oceans of ignorance that they punctuate. It is rare for any newly found hominin fossil to be greeted as if it were expected – as a ‘link’ in the chain that we knew had to be there, but was hitherto ‘missing’. In almost all cases, newly found hominin fossils open up new vistas, new possibilities, that scientists had not imagined to have existed before the fossils were found. This tells us that the hominin record is not only sparse, but so sparse that even the general course of events in human evolution cannot clearly be discerned – much less a coherent narrative.
What else might lurk in the vast gaps between the tiny islets of knowledge represented by the few fossils that have been discovered?
The case of Homo floresiensis is particularly instructive. This discovery revealed the presence of a peculiar hominin on a remote island that had evolved in isolation for at least a hundred thousand years, and possibly more than a million, and whose anatomy spoke of an evolutionary divergence from the hominin line before the emergence of Homo erectus, or even the genus Homo itself.
The implications of Homo floresiensis for understanding the scale of our ignorance are immense. This single discovery showed that hominins might have migrated from Africa perhaps a million years earlier than anyone had thought, which means a million years of entirely unknown hominin evolution in Eurasia as yet completely undocumented by fossils, and of which everyone had been completely ignorant.
It showed that the usual scenario of human evolution, concerning the emergence of Homo erectus and its migration out of Africa around 1.9 million years ago, is based very much on our idea of human evolution as a narrative of progression, with scant regard paid to the poverty of the evidence to support such a narrative.
Most of all, the discovery should prompt questions such as these: how likely to you think it is that researchers excavating in one cave on one island in Indonesia just happened upon the one and only species of peculiar, endemic, primitive hominin that ever existed in Eurasia? And given that Homo floresiensis lived until almost historical times, how likely do you think researchers just happened to have stumbled across the only species of archaic hominin to have survived so late? More likely, I think, is the alternative view, that the world was full of hominins of all kinds, some of them persisting until relatively recently, in geological terms. Given that fossilization is exceptional, especially for hominins, it would be no surprise if almost none of these species left any trace in the fossil record. The discovery of Homo floresiensis is proof enough, in the breach. If Homo floresiensis existed, then so must many others, in many other places.
This is not to say that the discovery of Homo floresiensis has not caused some scientists to take a new look at specimens that never quite seemed to fit into the conventional narrative. I’ve already mentioned skull material from Nigeria, representing a kind of archaic hominin that lived until recent times. Before Flores, scientists tended to dismiss this specimen as an oddity. Now Chris Stringer of the Natural History Museum in London and his colleagues think it might have represented a hitherto unknown kind of archaic human, surviving well into the era of Homo sapiens. Meanwhile, a number of skulls of ancient hominins from China have defied categorization. Early Homo sapiens? Not quite. Homo erectus? Not that, either.
The incredible growth of research into ancient DNA is beginning to shed some light on such matters. The sequencing of the genome of several Neanderthals shows that around four per cent of the DNA in modern Europeans come from that rugged acme of Ice-Age cave life. More startling still was the sequencing of DNA from an otherwise unremarkable hominin finger bone preserved in Denisova cave in southern Siberia. The DNA signaled the arrival of a hitherto unknown hominin species, distinct from both Neanderthals and modern humans, that had lived in eastern Asia until as recently as 30,000 years ago. The latest occurrence of a species as a fossil is never its last, so the Denisovans must have been around more recently than that. The latest evidence is that, in a way, they are still with us, because these archaic hominins have left traces of their genes in modern human populations throughout New Guinea and the western Pacific Ocean. The discovery allowed a whole host of questions to be asked, questions whose framing had not hitherto been possible – were some of the enigmatic Chinese skulls from Denisovans? What about some of the strangely archaic-looking skulls of the earliest-known colonists of Australia? Were they Homo sapiens, or perhaps Denisovans – or a mixture of both, or something else altogether? Largely thanks to Flores, the world of palaeoanthropology has, in the past decade, learned to appreciate the chilly magnitudes of the unknown unknown.
Is it possible that hominins other than Homo sapiens might still be living in the modern world, or, if extinct, perished only in historical times? The discoveries of Homo floresiensis and the Denisovans suggest that the question is not quite so outlandish as it might appear at first. After all, we know that the last known appearance of a species in the fossil record might antedate by some margin the actual date of a species’ extinction.
The Denisovans are known – so far – from just one locality, so their time range is hard to estimate, but we can get some idea of the likelihood of Homo floresiensis persisting into the modern age. The skeleton of Homo floresiensis from Liang Bua cave, the best and most informative specimen of the species so far known, has been reliably dated to around 18,000 years ago. Other specimens of isolated bones, all from different layers in the same cave but attributable to the same species, range from 14,000 to perhaps as old as 95,000 years. Extensive evidence from elsewhere on Flores shows that hominins were making tools on the island for at least a million years. At the top end of the sequence – catastrophe. A layer of volcanic rock speaks of a massive volcanic eruption around 12,000 years ago. Layers deposited more recently show no sign at all of Homo floresiensis or of other creatures endemic to the island such as giant lizards and tiny elephants. Leaving aside local Floresian folk wisdom of the ebu gogo, the Little People who lived in the mountains (tales found pretty much everywhere) it is very likely that the volcanic eruption did for Homo floresiensis just as random, localized disasters have almost certainly tipped other, isolated hominins into extinction. It is a teasing thought, however, that had the eruption not happened, Homo floresiensis might have lasted into modern times, and, because of all the chances and mischances of life, death and fossilization I’ve discussed in this book, it shouldn’t be so surprising were other species of hominin to be found living obscurely on Earth with us.
In my next chapter I am going to dissect the writings of the
cretinistscreationists who have for a decade or more been traducing the text of my former tome In Search of Deep Time (whose themes are related to The Beowulf Effect) – preferably without anaesthetic. I’m looking forward to that.