First and Last Men Part I - Adam's Kindred
The Image of the Caveman
It is an odd thing to consider that only a couple centuries ago there existed among neither the public nor the sciences any particular notion of prehistory. There was history, of course, a field both venerable and respected, but nothing before it. The annals of the Old Testament traced back the lines of man to the very dawn, or so it seemed, and little in the way of archaeology or palaeontology had ever arisen to complicate this picture. The histories seemed complete, a record from dawn till dusk. The process of discovery is rarely gentle. The advent of geology, palaeontology and complex archaeology have resulted in nothing less than a total reinterpretation, if not revolution, in our view of human history. If the old narratives were not destroyed, they were rendered at least vastly more complex than hitherto thought. From this process of discovery and transformation has arisen an entirely new cultural vocabulary, never before known: Extinction, evolution and the vastness of time became concepts enmeshed in popular thought. For the first time in millennia, people spoke of the mammoth and the sabretooth. For the first time in history, of the dinosaur. Yet of all the new images and ideas, perhaps the most startling was also the most familiar: the man before Man, the dweller in the grottos, the ur-person. The Caveman.
Inseparable from the mammoth and the marching ice remains the picture of the people--or near-people--who witnessed them. It is not exactly a flattering image. Brutish, primitive, sluggish savages, beneath even the level of barbarism and scarcely above the simian. The Caveman is an insult, and a caricature. He is nearly a comic figure. As with so much in life, first impressions often last. Despite the movements of science and the steady tide of revelations, despite the interval of over a hundred years since the first paintings of the dumb Neanderthal, still that picture lingers. But the science has moved. Today we know more about our ancestors (and near relatives) than would have been conceivable even a scarce few decades ago. In terms of mere numbers, our treasure of named species and genera has vastly increased. In terms of more specific details, of how they lived and died, where they went, and not merely what but also who they were, our knowledge is likewise greatly grown. In this article, we will explore the world the first Homo sapiens encountered upon beginning their global trek. We will trace the biology and, yes, culture, of those strange beings they met; creatures which push, as they must have pushed then, the boundaries of what it means to be human. And we will discuss their fate, the process by which our ancestors set out in a world rich in kindred species and settled in one where they stood alone. How Man became the Last Man.
Fig 1. Le Moustier by Charles R. Knight - painted in 1920. The painting shows a group of Neanderthals (Homo neanderthalensis) living in a cave in Southern France.
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Adam’s Kindred
Today, our species occupies something of a lonely perch in our tree of relatives. Nearest to us are the chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), whose ancestors split from ours some 6 million years ago (5). Yet this was not always so. When our earliest true Homo sapiens ancestors made their first, probing thrusts out of Africa, 80-100,000 years ago (6), they encountered a world rife with kindred species, like and yet not. In Europe and West Asia, they encountered the Neanderthals (Homo neanderthalensis), in eastern Eurasia and flooded Sundaland, the mysterious Denisovans, and on the isles of Indonesia, the archaic, pygmoid species of Luzon, Flores and possibly other places beyond (7,8,9). The Americas were as yet unpopulated, Sahul possibly so (9), but for most of their trek, our ancestors found the world populated.
The initial settlement of Afroeurasia by various hominid lineages is a complex and still-debated story. Much of the difficulty, at least in communicating the narrative, stems from the long-lasting and multivalent nature of Homo erectus. The earliest fossils ascribed to this species date to Africa, well over a million years ago, and nearly all later hominid lineages, including Neanderthals, Denisovans and modern humans, appear to have descended from these African H. erectus (10). And yet, populations ascribed to H. erectus persist well beyond this, continuing even long after taxa such as Homo neanderthalensis and sapiens had speciated off from them. The result is a strange and confusing situation, wherein Denisovans can be described both as descending from, interbreeding with, and outlasting varying populations of Homo erectus, and where studies in one context may describe the descent of H. sapiens from H. erectus, whilst in another questioning whether the two species ever met. In summary, sometime shortly after 1 million BC populations of ancestral, African-derived H. erectus moved north into Eurasia, where one lineage underwent adaptive changes, giving rise to the later Neanderthals and Denisovans, whilst certain other groups remained more conservative in form and culture, becoming the Asiatic H. erectus of the last glacial period (10, 11). Of those who remained in Africa, some would eventually give rise to the earliest populations of anatomically modern humans.
Approaching the Late Pleistocene, 120kya, and thereby the very cusp of modern human expansion, we find the world as such: From Europe through the Levant and north into Central Asia, Neanderthals populate the land, dwelling in small and disparate clan-groups (27). In the vales of the Altai Mountains, they find their furthest extent, meeting there with their cousin species, the Denisovans. Of the latter, much is wrapped in mystery. The East in general remains a debatable region, where the borders of species and their relative relationships are often unclear--the consequences both of poor preservation and rising seas.
Before proceeding, a few words may be given on taxonomy and terminology. Throughout this article, we have persisted both in the use of the phrase “our ancestors”, implicitly over and against those hominids which were not, and in the use of the term “modern humans”. There are many researchers nowadays to whom both of these decisions would seem ill-advised. Regarding references to ancestry, it would be pointed out that we now know the earliest H. sapiens were not alone in contributing to our genetic heritage. As will be explored in more detail later, research in the last few decades has revealed a degree of hybridisation between the first H. sapiens leaving Africa, and at least some of the aboriginal hominids they encountered on their way. That is to say, strictly speaking, the category of “our ancestors” includes (at least for certain human ethnicities) both Neanderthals, Denisovans and at least one other thus-far unspecified taxon. That we nevertheless persist in excluding them from the category is a matter both of reasoning and convenience. Neanderthals did indeed leave some genetic contribution in later human populations, but the phrasing there betrays the point: Theirs was a contribution, a fraction. It did not approach an equal melding, let alone the creation of an entirely new hybrid species. The Neanderthals, Denisovans and other kindred taxa bred into the expanding human population. They left a genetic footprint but did little to alter the phenotype. The earliest H. sapiens to enter Europe and Asia were, by all accounts and for all intents, alike to us in body, mind and behaviour. The species they replaced were not. As for the use of “modern humans”, this is a distinction of convenience which, far from dehumanising our fellow hominids, instead allows us to acknowledge their claim to humanity, whilst retaining distinction. “Modern humans” may be labelled as such, not because they were “modern” by comparison with other contemporaneous taxa, but because they belonged to the same species as do those humans today who are, chronologically, modern.
The Neanderthal World
Of all the archaic hominids, none are more famous than the Neanderthals, nor more scientifically well-attested and studied. Homo neanderthalensis displayed a considerably greater morphological robustness than modern humans, including the Cro-Magnon populations that replaced them (2, 27). They possessed rounded, markedly large skulls, upwards of 1500 cm3, with stocky facial features and comparatively short limbs, features in large part adapted to a mobile lifestyle in cool environs (27). In particular, the build of their faces, though theorised in the past to represent perhaps adaptations against animal bites, appear in fact to allow the movement of significantly more air through the nasal cavities than in modern humans. This would aid both survival in cold, dry climates, as well as generally compensating for Neanderthals’ high energetic expenditure--substantially above that of modern humans (1,3).
In such conditions as the Neanderthals’ endured, environmental factors and caloric requirements played essential roles in shaping social structure. Low density, small group sizes, high mortality and low fertility were all characteristic of Neanderthal populations (27). Though the assemblage of large groups is naturally beneficial in terms of allowing for divisions of labour, collective rearing of young and a general societal security net, it remains a matter of costs and benefits. For the Neanderthals, it appears that the energetic demands of single individuals may have been so high that the aggregation of large social bands was simply not economically feasible (27). It would have required a greater supply of food than any one region could realistically proffer. The result was a small, widely scattered population, distributed in miniscule, mostly isolated social units. The average Neanderthal group seems to have numbered only around 20 individuals, with some evidently below 10, approaching the very limit of minimal viability (27). Neanderthals do appear, like humans, to have associated in larger, tribal or ethnolinguistic regions, wherein disparate groups occasionally exchanged goods and partners for marriage (4). Yet even these would seem to have been of a significantly smaller order, and the conclusion seems difficult to avoid that isolation was the norm in the Neanderthal world. Perhaps unsurprising, inbreeding, at times of a severe sort, was not uncommon among Neanderthal tribes, where exogamy was not always an option (27).
And yet, in face of this, for hundreds of thousands of years, they had endured, despite hardship and varying fortunes. Theirs was a broad range, from Europe to the Levant and into the hills and plains of Central Asia (12, 27). It was not constant across time, nor evenly distributed across space. Their patterns of occupation showed a notable north/south and east/west gradient, with the southwest of Europe by far the most densely and consistently populated. Interestingly, whilst Neanderthal distribution appears to have been strongly contingent on climatic oscillations, Neanderthal population-levels were not – that is, declines in climatic conditions corresponded to contractions in the range at large, but not marked reductions in the on-the-ground populations. They were widespread, hardy, intelligent and thoroughly adapted to their environment. And yet, by 20,000 BC, they were gone. We will explore the nature and dating of their disappearance in more detail later, alongside that of all their related taxa which vanished alongside them. First, however, these too must be surveyed.
The Mystery of the Denisovans
Nothing frustrates the scientist and historian more than a void. Uncertainty of data may prompt debate and novel thinking. It is the anvil on which new careers are forged. Yet with a complete vacuum, there is little that can be done, save that one activity which most academics abhor: speculation. We do not know absolutely nothing about Denisovans, though this changed only as late as 2010 (14). We have a few, woefully partial remains from scattered locations across Asia and across time--a mandible here, a stray tooth there. We have the burgeoning science of evolutionary genetics, which in fact proved entirely instrumental in the discovery of the Denisovans’ very existence. And yet, if we do not know nothing, we know frustratingly close to it. Nothing approaching a complete skeleton has ever been discovered, and the species has yet to even receive a scientific name. All the same, the Denisovans, mysterious as they be, are a crucial piece in hominid history, and in our own ancestors’ first migrations. By the Late Pleistocene, they were evidently the primary hominid lineage throughout most of Asia, and seemingly the sole representative in much of it (15, 16, 17). They ranged from northern China and Siberia to the highlands of Tibet, the jungle-plains of Indonesia and possibly beyond. They appear to have encountered and interbred with the ancestors of modern human populations on at least two occasions--in the north, among archaic Eurasian lineages that would also give rise to modern-day Amerindians, and in the south, where Denisovan ancestry peaks in the isles of Melanesia (15, 17).
Of their own ancestry, they appear to have descended from the same northward movement of Homo erectus that produced the Neanderthals. Their lineage broke from the ancestors of the latter circa 400kya, though the two species still met and interbred as late as 120kya (18). Like the Neanderthals, at least some populations of Denisovans appear to have been big-game hunters, employing similar forms of primitive stone tools (15). It is difficult to say much about the specifics of Denisovan culture, or how it varied from region to region and period to period, yet it seems reasonable to assume certain characteristics with their close relatives the Neanderthals. If nothing else, their repeated interbreeding with modern humans indicates presumably a reasonable degree of cultural and behavioural sophistication. Relevant to note in this context is that there existed within the Denisovans multiple lineages, of which the “Sunda Denisovans” of Southeast Asia were genetically distinct, though conspecific, with their relatives to the north (17). That this genetic separation was reflected in a separation of material culture and possible phenotype seems probable. Yet the story does not end here, for genetic evidence hints at--though it does not demonstrate--the existence of yet more far-flung populations, beyond the mainland of the Sunda shelf, among the southern isles, and perhaps even in ancient Sahul itself. This prospect we will discuss in the next section of the article.
Fig 2. Tourists visiting Denisova cave, which has become famous for its hominid remains - Particularly those of the Denisovans
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Denizens of the South Seas
For some time now, it has been known that our early kindred did not all stop where the mainland ended. In 2004, the discovery of a new species of archaic hominid was announced--Homo floresiensis, the ‘Flores Hobbit’ (19). At only a meter tall, its small stature suggested prolonged adaptations to an insular, jungle-dominated habitat, not unlike modern pygmoid populations, and a connection here has been suggested (20). The differences between H. floresiensis and all modern pygmies, indeed all modern humans, are however substantial. Beyond merely its diminutive size, the species has a remarkably low cranial volume, even compared to primitive, pre-Homo Australopithicus, with robustly shaped limbs likewise indicative of the latter taxa (19,22). The feet of H. floresiensis, though similar in general structure to other hominids, resemble those of chimpanzees and bonobos more closely in dimensions (23). Nor do investigations of the species’ dental morphology entirely clarify this, as they too retain a peculiar mixture of archaic and derived traits (22). In conclusion, then, its identification as a unique species from H. sapiens seems secure (21). The greater question becomes whether it descends even from the same Homo erectus populations that produced the other known hominids of Pleistocene Asia, or if it derives from a yet more primitive branch, affiliated with archaic Homo habilis or even beyond the genus Homo (19, 21).
Whatever its taxonomic positions, archaeological evidence indicates that creatures culturally similar to H. floresiensis were present on Flores Island as early as 700kya (24). Nor were they alone in Maritime Southeast Asia, for 2019 heralded the announcement of another insular taxon, Homo luzonensis, this time from the Philippines (8). Already three years prior, findings from the isle of Sulawesi indicated that some as-yet unnamed population of early hominids may have reached the very brink of Australasia by the late Middle Pleistocene (25). Into all of this archaeological data, we now must throw that proverbial apple of discord: genetics. We have already discussed the crucial role the study of population genetics played in the discovery of the Denisovans, and it is here that they re-enter our story. Thus far, all the hominid populations attested have remained at least within the orbit of ancient Sundaland, on isles which could reasonably be termed its insular periphery. Sulawesi is the southeasternmost location with any definite hints of settlement, and even that lies within, not east of, the region of Wallacea which separates the Asian from the Australasian world. Yet it is a very peculiar fact that Denisovan ancestry in modern humans peaks, not in mainland Asia, nor on the isles of Indonesia, but among the Papuans of Oceania (9). This could conceivably be explained away as an artifact of successive waves of human colonisation moving through the region, yet there comes an additional complication. Papuan ancestry shows signs, not of one but of two separate peaks of Denisovan ancestry, stemming from two widely divergent populations. The nature of the genetic introgression indicates heavily that one of these mixing events happened in Sundaland, whilst the other happened east of Wallacea (9). That is, in Sahul. It indicates, in other words, that Pleistocene hominids were present not merely on the brink of Australasia, but within it. Among the short-faced kangaroos, marsupial tigers and enormous diprotodonts of ancient Australia may have lived an enigmatic population of archaic human, utterly unattested save for their genetic legacy. The data indicates also that this population was highly divergent from the other two, northerly Denisovan-lineages, having split from them only shortly after their collective break with the Neanderthals, and warranting therefore perhaps their own species.
We do not in this article have time to explore one of the most obvious and startling implications of these findings: If archaic hominids were present across the islands of Southeast Asia and even into Australasia, how did they get there? In the next article of this series, we will tackle in full the subject of Pleistocene seafaring.
To The Victor
We come now, in the end, to the end. We have surveyed the life, range and relationships of our early relatives and ancestors largely to prepare for this one, obvious question: why did they vanish, when we remain to discuss them? We cannot in every case, with every population, provide an answer of equal detail. In many places, our data is simply too scanty or nigh-non-existent to paint anything but the murkiest picture. Yet we are not totally without recourse, and the Neanderthals in particular have provided an unusually detailed look into at least one people we replaced.
It has in the past been posited that Neanderthal populations were already moving towards extinction prior to the entry of H. sapiens. This now seems false. Not only were their numbers generally stable, but they had in fact been trending upwards in the last millennia of their existence. The size of the Neanderthal metapopulation and the intensity of their occupation appears to have peaked as late as circa 60kya, and therefore only shortly before their rapid extinction (27). Not only that, but there is evidence of a period of back-and-forth between the two species. In the Levant, an exceptionally early thrust of H. sapiens seem to have expelled the aboriginal Neanderthal population already circa 120kya. And yet, between 90-80kya, Neanderthals returned, replacing the newcomers and going on to inhabit the region for another 25,000 years, until the final, great pulse of human movements (12). Even in Europe itself, some limited evidence points towards early, probing migrations in this same period, all of which evidently failed (27). The picture, then, is not utterly uncomplicated. In the contest of Cro-Magnon man and Neanderthal, the outcome might swing either way, at least at the level of individuals and small groups. Nevertheless, nuanced though it may be, the overall picture remains clear. Between 50-60kya, a new wave of human movements began. One of an entirely different magnitude, to which nearly all modern populations beyond Africa owe their primary or sole descent. Before this wave, the Neanderthals, Denisovans, and all other prior groups were swept away, never to return.
That the replacement of Neanderthals by H. sapiens should have been assisted in part by a pre-occurring population-decline, owing to adverse climatic conditions, is a conceivable, even plausible scenario. We know they were on the increase only 10,000 years prior, but perhaps we may allow some drastic change in fortunes in the years following. As with so many other discussions of species-extinction and the co-variable roles of climatic and human impacts, however, this seems perhaps to miss the point: A scenario in which Neanderthal-populations are seen to have undergone continuous swings in size, growing in periods of favourable conditions, shrinking in times of adversity, and in which their replacement by modern humans corresponds with one such down-swing, is still one in which the arrival of H. sapiens is the ultimate efficient cause of extinction. Unless it could be shown that the climatic trends depressing Neanderthal populations would have led to their eventual extinction, even in lieu of human settlement, the former must be considered at most a contributing factor. There exist, to our knowledge, no attested instances of firmly established advanced hominid species being utterly extirpated without replacement by another, succeeding hominid taxon. Not in Asia, not in Africa, not in Europe. Even on Flores, an earlier species of possible H. erectus affinities appears to have been replaced in short order by the ancestors of the ‘Hobbits’ (26). The claim that this would nevertheless have occurred with the Neanderthals is therefore entirely unprecedented. That it should have occurred, coincidentally, with every single population of non-human hominid in Afroeurasia starting 50kya seems nearly incredible. That this last period of unprecedented metapopulation-collapse furthermore just so happened to coincide with H. sapiens’ dispersal may, then, reasonably be considered extraordinary. In the absence of equally extraordinary evidence to redeem the notion, it is, in frank terms, not a serious contending idea.
Fortunately for us, what data we do have would appear to furnish, if not an exhaustive, then at least a suggestive picture. We do not know what crucial factors separated our ancestors from our kindred species, so similar in most respects. As the nature of archaeological and zoological preservation renders an answer to this question literally impossible, we will leave such speculations to the philosophers and theologians. What we can observe, however, is the reality. Neanderthal populations were as we have discussed small, isolated, vulnerable. Inbreeding was rife, their environmental footprint often minimal. It would be unfair to label a species that persisted for hundreds of thousands of years ‘ephemeral’, but their touch on the land appears to have been light. It is notable, for instance, that the arrival of H. sapiens to western Europe appears to have resulted in an immediate corresponding decline in the effective population size of cave bears--competitors, presumably, for space (27). The estimated size of even the earliest Cro-Magnon populations was larger than that of the preceding Neanderthals by a vast margin, and whatever fundamental cognitive differences divided our species, this was the evident fruit: In terms of social coordination, hierarchical structuring and institutional development, modern humans seem to have been simply more capable. When the last great push out of Africa finally began, roughly 50-60kya, the result was decisive. On Flores, the layers of earliest human presence post-date exactly those of the last H. floresiensis (28), in Asia, this is the first and last date of Denisovan introgression, and in Europe, the westwards movement of modern humans starting 50kya corresponded region-for-region with the disappearance of Neanderthals (13).
Whatever the reason, whatever the process, the pattern is evident. Man became the Last Man, not by fortune or mere stochastic processes, but by what would have resembled most probably a process of tribal war, displacement and extermination. In the next article in this series, we will be exploring this great and violent trek of human migrations in detail, both the history of debate and the current consensus, the mysteries and the revelations. For now, it may be said that to the victor went the spoils.
Fig 3. An attack on a Neanderthal (Homo neanderthalensis) village by marauding Homo sapiens of the Aurignacian culture. Set in the Late Pleistocene of the Balkans just after human arrival.
Terms of use: Artwork by Hodari Nundu and Commissioned by The Extinctions
References
1. Wroe et al. (2018). Computer simulations show that Neanderthal facial morphology represents adaptation to cold and high energy demands, but not heavy biting
2. Harvati, K. (2001). The Neanderthal taxonomic position: models of intra- and inter-specific craniofacial variation
3. Froehle, A. & Churchill, S. E. (2009). Energetic Competition Between Neandertals and Anatomically Modern Humans.
4. Pearce, E. & Moutsiou, T. (2014). Using obsidian transfer distances to explore social network maintenance in late Pleistocene hunter–gatherers
5. Disotell, T. R. (2015). Phylogenetic Relationships of Hominids: Biomolecular Approach
6. López et al. (2015). Human Dispersal Out of Africa: A Lasting Debate
7. Sutikna et al. (2016). Revised stratigraphy and chronology for Homo floresiensis at Liang Bua in Indonesia
8. Detroit et al. (2019). A new species of Homo from the Late Pleistocene of the Philippines
9. Jacobs, G. S. (2019). Multiple Deeply Divergent Denisovan Ancestries in Papuans
10. Dembo et al. (2016). The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods
11. Rogers et al. (2017). Early history of Neanderthals and Denisovans
12. Been et al. (2017). The first Neanderthal remains from an open-air Middle Palaeolithic site in the Levant
13. Timmermann, A. (2020). Quantifying the potential causes of Neanderthal extinction: Abrupt climate change versus competition and interbreeding
14. Krause et al. (2010). The complete mitochondrial DNA genome of an unknown hominin from southern Siberia
15. Brown et al. (2022). The earliest Denisovans and their cultural adaptation
16. Chen et al. (2019). A late Middle Pleistocene Denisovan mandible from the Tibetan Plateau
17. Stringer, C. B. & Barnes, I. (2015). Deciphering the Denisovans
18. Slon et al. (2018). The genome of the offspring of a Neanderthal mother and a Denisovan father
19. Brown et al. (2004). A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia
20. Perry, G. H. & Dominy, N. J. (2009). Evolution of the human pygmy phenotype
21. Argue et al. (2006). Homo floresiensis: Microcephalic pygmoid, Australopithecus or Homo?
22. Morwood et al. (2005). Further evidence for small-bodied hominins from the Late Pleistocene of Flores, Indonesia.
23. Junger et al. (2009). The foot of Homo floresiensis
24. Brumm et al. (2016). Age and context of the oldest known hominin fossils from Flores.
25. Gerrit et al. (2016). Earliest hominin occupation of Sulawesi, Indonesia
26. Brumm et al. (2010). Hominins on Flores, Indonesia, by one million years ago.
27. French, J. C. (2021). Palaeolithic Europe – A Demographic and Social Prehistory. (Cambridge World Archaeology). Cambridge: Cambridge University Press
28. Sutikna, T., Tocheri, M. W., Morwood, Ml J., Saptomo, E. W., Jatmiko,, Awe Due, R., Wasisto, S., Westaway, K. E, Aubert, M., Li, B., Zhao, J -X., Storey, M., Alloway, B. V., Morley, M. W., Meijer, H. J.M., van den Bergh, G. D., Grün, R., Dosseto, A., Brumm, A. R., Jungers, W. L., Roberts, R. G. (2016) Revised stratigraphy and chronology for Homo floresiensis at Liang Bua in Indonesia. Faculty of Science, Medicine and Health - Papers: part A.3778.