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Science/AAAS

Updatedplease see end of this post.

The archaeological site of Gesher Benot Ya’aqov has been in the news again recently, following the publication of a paper in Science, namely Spatial Organization of Hominin Activities at Gesher Benot Ya’aqov, Israel, authored by Nira Alperson-Afil et al, in which they reflect upon the organisational abilities of archaic humans in the Lower Palaeolithic of the Middle Pleistocene, who at GBY, represent the oldest known fisher-hunter-gatherers so far discovered in the archaeological record. It’s fair to say this paper has made something of an impact, with the general consensus being that archaic humans of this era were capable of organisational behaviours similar to that of anatomically modern humans, with one or two voices arguing that the evidence at Gesher Benot Ya’akov (GBY) is suggestive rather than conclusive.

This site of GBY offers us what appears to be a marked contrast to another site of around the same age, c. 780 kya, in the Aurora stratum, also known as the TD6 level at Gran Dolina, Atpauerca in modern-day central north Spain – I’ll add a brief word on that site later in this post, because apart from anything else, the fossils of 6 humans (suggested to have been cannibalised) have been found there, whereas there are no fossil remains of humans described at GBY. Labelled as H. antecessor, it may be that similar people dwelt by the shores of Lake Hula at GBY.

Apart from organisational behaviours, this site also documents a very early use and control of fire, which at c.800 kya, again appears to bridge a cognitive gap, while at the same time posing the question of why there appears to be a cognitive, or at least technological stasis from that point almost to the present day.

Briefly, the site in question GBY Level 2 was found to have been split into two main areas about 25 ft apart, one for the preparation of food such as fish, whilst the other was a hearth around which other activities such as stone tool manufacture, smashing nuts and eating are thought to have taken place. Moreover, because the site was sealed rapidly and very well preserved, numerous faunal and floral remains indicate that a wide range of foods and resources were regularly exploited by these people, from which it seems clear that they had long mastered the art of survival beyond the raw essentials.

Abstract:

The spatial designation of discrete areas for different activities reflects formalized conceptualization of a living space. The results of spatial analyses of a Middle Pleistocene Acheulean archaeological horizon (about 750,000 years ago) at Gesher Benot Ya’aqov, Israel, indicate that hominins differentiated their activities (stone knapping, tool use, floral and faunal processing and consumption) across space. These were organized in two main areas, including multiple activities around a hearth. The diversity of human activities and the distinctive patterning with which they are organized implies advanced organizational skills of the Gesher Benot Ya’aqov hominins.

Although the authors concern themselves primarily with implying that archaic humans at the site were showing organisational abilities on a par with modern hunter-gatherers, or foragers, the sheer range of foodstuffs and other materials found there also indicate a fairly complex diet – as opposed to one that mostly involved hurling spears at large mammals as a means of obtaining food – was not only available but fully exploited, with the possibility that certain sites were visited in line with their seasonal resources. There are differing opinions regarding the exact implications for the cognitive and organisational abilities of these early humans, with Vaughan Bell at Mind Hacks supportive of the authors, whereas John Hawks was less impressed.

Moreover, as has been mentioned in previous papers, there is clear evidence of the use of controlled fire on a continual basis, and what might be most surprising, is not that fish were also consumed, but that the lakeside dwellers were able to catch carp and other fish in the first place. It has often been stated that an advantageous trait of early modern humans in the Upper Palaeolithic was their more diverse diet which included fish, giving them a putative survival advantage over the Neanderthals (who are in fact documented as having eaten dolphin, seal and mussels on Gibraltar) – plus of course the cognitive ability to manufacture equipment such as barbed bone and ivory points, with which to acquire their prey.

I’m very grateful to have been sent a copy of a paper that would otherwise be inaccessible to me, on this occasion by Professor Naama Goren-Inbar, one of the authors, so as ever, I’ll add some detail from the text as well as adding some comment of my own. First up, a look at the site itself, its geologic past and the way in which it has fortuitously been preserved over such a vast expanse of time.

Gesher Benot Ya’aqov is located on the shores of the paleo–Lake Hula in the northern Jordan Valley in the Dead Sea Rift (7). The Early to Middle Pleistocene sediments document an oscillating freshwater lake and represent some 100,000 years of hominin occupation (Oxygen Isotope Stages 18–20) dating to 790,000 years ago (8, 9). Fourteen archaeological horizons indicate that Acheulian hominins repeatedly occupied the lake margins, where they skilfully produced stone tools, systematically butchered and exploited animals, gathered plant food, and controlled fire.

We focus on a hearth area and the lithic, botanical, and paleontological assemblages of Layer II-6 Level 2 (henceforth Level 2), one of eight superimposed occupational levels in Layer II-6. This sedimentary sequence was rapidly sealed, preserving the original location of different artifacts (evidenced by the fresh preservation state of the lithics, the preservation of mollusk embryos, the presence of conjoinable bones, and a lack of winnowing) (8, 10, 15, 16). Level 2 is 0.12 m thick, and we excavated across an area of 25.6m2 (3 m3). It yielded numerous stone artifacts made of different raw materials; a large assemblage of wood, bark, fruits, seeds, and nuts; and highly diverse lacustrine and terrestrial animal remains.

The immediate impression given is the sheer variety of activities and behaviours exhibited by an as yet unidentified species of archaic human, as they went about their daily lives. Although these were temporary occupations, it’s clear that a great deal of time and effort was needed to keep the camp supplied with resources required for the diverse food items to be sourced, acquired and prepared for eating. The presence of many species of wood remains offer further clues to an invisible part of the archaeology, with the likelihood that specific wood types were selected for various purposes – fire-wood, spears and fishing equipment come to mind, but before getting to those details, a quick word about how Level 2 at GBY was originally configured.

Towards the south-eastern end of Level 2, comprising 25.6 sq.m.,  the remains of a hearth have been found, around which various activities such as the making of stone tools from basalt and limestone, and the cooking and consumption of fish and crab, the remains of which have been found in abundance. Moreover pitted anvils are thought to indicate work surfaces upon which the repeated smashing of edible nuts took place, which were than placed in the fire as a means of making the tough skins easier to peel away, whilst also reducing the tannin content of the acorns, making them tasteless bitter.

At the north-western end, flint tools predominate, 99% of which were unburned, it is believed that fish and crab preparation may have been carried out – gutting the fish, cracking the crab and turtle shells before being taken over to the hearth, where they too were likely cooked.

The supplementary material  gives a better idea of exactly how many and what types of tools were in use – a total of 300 flint flake and flake tools, 165 cores and core tools of basalt and limestone, 4 flint hand-axes and 18 of basalt, 10 basalt cleavers,22 percussors and 4 pitted anvils.

What caught my attention as much as the spatial organisational capabilities of Lower Palaeolithic people at GBY was the fact that they caught fish at all, when we can see from the faunal and floral remains at the site, there were plentiful supplies of meat from mammals, as well as the freshwater crabs and turtles, whilst the range of fruits and nuts added yet more calories and nutrition to the varied diet. Catching fish from a lake is a markedly different activity from hunting terrestrial prey, or picking up turtles and crabs from lake or river margins, which required minimal pursuit, or indeed the gathering of fruits, nuts and seeds.

As the spatial organisation at GBY has already been extensively covered elsewhere, I’d like instead to consider other aspects of organisational activities that are implied by the archaeology, and which also hint that our cultural evolution may have progressed further towards modernity than is commonly portrayed.

Although there is no indication in the archaeology as to how they went about catching carp, catfish and sardines, presumably without recourse to modern technologies such as rods, lines and baited hooks, it’s likely that in addition to the lay-out of Level II, careful planning and organisation was needed in order to work out how to catch an elusive prey that lived in the water.

1,602 of the 2,578 of the carp remains found at GBY belong to an extinct species, Large Barbus sp.nov. around a meter in length, and as will be apparent from this link in which a smaller species is depicted, would have provided a substantial amount of food from a single kill, and judging by their estimated size, I would hazard a guess that these fish were big enough targets for a stealthy someone, handy with a barbed wooden spear to hunt in what may have been thickly weeded areas of shallow water near the lake shore. Whether this could have involved an individual standing in the shallows, or someone floating on a raft constructed from many of the types of wood also found at the site cannot be determined at this point.

It would be even more interesting to know whether these fish were lured to specific areas by use of bait – possibly derived from the many seeds and plant materials also found at Level II – as this again could add another layer to our perception of the cognitive abilities in archaic humans.

As we see from this account of a fisherman, Larry Robbins catching grass carp at Bark Camp Lake in Virginia, using acorns as bait:

One autumn day while fishing on the lake Robbins finally had his Newtonian break through. He happened to be watching when an acorn from an overhanging oak branch plopped into the water.

As he followed its descent into the shallows, a massive grass carp swooped out and ate it.  Evidently, acorns are a tasty seasonal treat white amur favor so highly that the sound of an acorn hitting the water in autumn is like a dinner bell to them. If a big grass carp is in the vicinity when one hits, it’ll usually nab the nut before it touches bottom.

After considerable trial and error, Robbins determined which acorns the fish preferred (white oak) and figured out how to bait a hook with an acorn in such a manner that the hook remained unobtrusive to the fish while also allowing for a solid hook set once the bait was taken. He scouted the shoreline for the places where white oak acorns were most likely to fall directly or even indirectly in to the water. And he was in business…

…Carp are naturally suspicious, spooky fish. And they fight like the devil when hooked.

Note that  a few acorns were found at Level II, with the observation that they had been modified by fire to facilitate the removal of tough skins and make them less bitter to eat – whether acorns were also deployed in their raw or cooked state as bait for carp is again an open question, as would be the way in which they would have been introduced to the fish in the absence of a baited hook.

N.B. Please see the added note at the end of this post regarding how these carp may have been caught, courtesy of angler George Thwaites, also a journalist for Kingsport News, Virginia.

Alternative methods might have involved the use of nets, or submerged traps constructed from the abundant plant and tree resources on hand, and I wouldn’t discount the use of some sort of raft, set afloat with spear-wielding humans aboard in pursuit of their prey, but despite the large size of the carp, these fish would still have been a tricky target. This can only be speculation, but I think these suggestions are parsimonious enough to at least merit consideration. If by some chance the humans had learned to manufacture and deploy some sort of rod and line equipment with a baited hook – the latter of unknown construction material – I’d be surprised, but then again, distant prehistory is forever offering up unexpected insights from its muddied depths.

Learning to lure prey into an area of one’s choosing in order to maximise the chances of a successful strike requires pre-planning, timing, and of course spatial organisation, so perhaps it is no coincidence that we find evidence of the way in which other activities such as the preparation and consumption of food were also constructed by means of discussion and decision amongst the planners. Landing a carp, as described above sounds like a complex business indeed, and yet these early lake fishers managed to procure enough to eat them on a regular basis. Of course, humans are by no means the only members of the animal kingdom to lure prey into traps, but the wider range of active and passive pursuit tactics in evidence by Homo maybe sets our ancestors apart from their faunal peers.

Although much is made of the appearance of bone and ivory barbed points and harpoons in the latter stages of the Upper Palaeolithic, a supposed indication of the cognitive upgrade ascribed to AMH, little consideration seems to have been given to the fact that such points could just as easily have been carved into wooden implements, at far earlier stages in the Palaeolithic, by archaic humans. We have almost no wood or timber remains that have survived intact from the Lower and Middle Palaeolithic, save for example, the Schöningen spears in Germany, dated to 400 kya, and more recently, the imprint of wood in the cave of Abric Romaní, dating to around 50kya, which hints strongly at built wooden structures used for shelter within caves – and which by implication suggests that such structures were assembled in the open air as well, as evidenced by other sites such as Terra Amata.

Another brief point to note is that GBY and Terra Amata may have been occupied on a seasonal basis, and although we can’t discern whether there was a strict order and timing to the visits of such sites, which meant that archaic humans basically lived in widespread but seasonally permanent set of locations, I think the people at GBY may well have had the cognitive wherewithal to organise themselves on an annual basis.

Atapuerca – Gran Dolina TD6, Aurora stratum, dated to 780 kya

For a look at how other humans alive at more or less the same time as those at GBY, it’s worth a quick look the contemporary levels at Atapuerca, specifically at the Aurora stratum, (click through to ‘Yacimienetos’) also known as the Gran Dolina TD6 layer, not only at which animals were being consumed, but also at what sort of humans may have been alive at GBY. Although Atapuerca is in north central Spain, a long way to the west of GBY, the remains of 6-10 individuals found at TD6 offer not only insights into human evolutionary traits like dental development at that time, but ask the intriguing question of whether humans were eating their fellows, as has been suggested by the way in which human remains replete with cut-marks have been found in association with other animal remains that show clear signs of butchery, and thus consumption. The humans at Gran Dolina have been labelled H. antecessor, but as no humans remains exist from GBY, we can only guess as to their exact identity.

The scene at Gran Dolina TD6 offers a very different view of life, perhaps one slightly skewed by the way in which the remains appear to have been tossed aside as rubbish, observations that the stone tools are rudimentary, and that cannibalism may have been practiced for gastronomic or other as yet unknown cultural reasons. As with GBY, there is every indication that a wide variety of mammals – mainly herbivores in this case – were available, so it’s unlikely – assuming the supply of food was consistently high – that humans would have been eaten of necessity.

Although there is no hint of laid-out camp-sites or longer term dwellings at Atapuerca, largely because the remains and artefacts there are found in the remains of caves, and anything left out in the open air would have had their traces obliterated by taphonomic processes. But I think it’s worth considering in the light of GBY that away from the caves, H. antecessor likely occupied sites nearby, in what was an abundantly rich and diverse bioscape. The long periods of occupation at Atapuerca indicate that it continued to attract humans, and I doubt they dwelt all that time without having some degree of spatial organisation as seen at GBY.

It has also been noted that all the faunal remains at TD6 are large mammals, that may have been hunted with spears, rather than smaller prey that would have required other methods of acquisition. Maybe we’re just seeing sites where certain types of animal were consumed in specific ways, whilst others were set near water, where different foods, perhaps similar to GBY, were processed and consumed – a possible hint at spatial organisation in itself.

It was only by sheer geologic serendipity that GBY survived at all, and provides an outlier to the general rules of what survives archaeologically over hundreds of thousands of years.

One of the first things I was taught (in the few evening classes I once attended) about the terminology of the Stone Age is that it could just as easily have been called the Timber Age – but because wood is organic, and except under very rare preservation circumstances, is completely invisible in the archaeological record, as over time it simply rots away. Thus our view of the past is greatly skewed by the stone remnants of points, axes, burins, scrapers, awls etc.,  that have survived all the way down from 2 million years ago, to the extent that all we see is stone, and judge our ancestors’ technological achievements accordingly. What they actually did with these stone tools is generally considered in the light of killing animals and processing the carcasses for food and other resources – but there is almost no indication as to how some stone tools could have been used to modify wood – were people simply felling timber for use as firewood, or lopping off suitable parts for use as spears, or attempting more ambitious ends – and more importantly, how far back in prehistory might such behaviours become part of everyday life?

Although at first glance there appear to be clear signs that early hominins at Gesher Benot Ya’akov possessed greater organisational and cognitive abilities than thought earlier, it’s worth making a notes on what isn’t in the archaeology, and how some of the activities bear comparison both with earlier hominins and primate relatives.

A quick look at what is absent from the site – there are no post-holes, or any indications from (sub)-circles, squares or rectangles of stones to indicate any kind of living or sheltering areas -of course, that doesn’t mean there weren’t any nearby that have since been lost, but there is no evidence for them.

Not much sign they tidied up after themselves either, and the fact they left some of the more massive flint axes behind is telling – they were seemingly cast aside, with no special symbolic significance attached to them as suggested elsewhere for hand axes of a later date, manufactured after 500 kya such as the rose lithic from Atapuerca some half a million years later – if indeed, that item wasn’t merely thrown away down a convenient hole.

As far as I can tell, there is no mention of whether the lithic assemblage has been analysed for phytoliths – given the number of wood samples found at the site, it would be interesting to know if certain tools, like the hand-axes had been used for cutting or modifying wood or grasses, or had only been used in a culinary context.

The fact that so many different food and plant types are present speaks more of forward and organised planning than maybe the demarcation zones of the site itself. Nuts and fruits are likely to have been brought in from afar, and some thought seems to have gone in to the idea that a central place should be sought and used in this way, on a regular basis, whether that was annual, or more or less frequently.

It’s difficult to imagine these people doing all this without some sort of language capabilities – the gathering of foods like fruits and nuts in anticipation of eating them at another location where other foods would also be brought, prepared, cooked and eaten indicates conscious forward planning. Carnivores also transport food, whole or in part to locations for consumption on a regular basis, but the range of foods tends to be prey fauna, and locations chosen for offering protection to the predator from other scavengers etc.

There is still a vogue amongst certain sets of esoteric writers of popular books to dub any ancient humans as ape-men, more often as not to prove some spurious point or other to promote modern humanity as the creation of aliens, gods or to have been subjected to some sort of cosmic ray emanating from outer space which altered their consciousness to some imagined and elevated state of awareness.

And whilst studies at GBY, Atapuerca Gran Dolina and Bilzingsleben and others clearly indicate that our predecessors were surprisingly sophisticated and even displayed traits of so-called ‘modernity’, we should be very careful when it comes to ascribing human uniqueness – time and again, we learn of some denizen of the animal kingdom displaying behaviours and cognitive ability we would hitherto have only applied to ourselves.

We can’t know at what point archaic humans used sites because they liked the location itself, rather than just for considerations of what food and other resources were to hand, and further, to what extent pleasure derived from visiting such palaeo-resorts may have contributed to archaic humans’ survivability and evolution.

One of the ongoing mysteries of humanity spending two million years sleeping outdoors every night is exactly how that was organised, if at all. Did everyone flop down wherever they happened to end up at the end of a given day, and if so, how did they go about protecting themselves? Contrary to popular opinion, there isn’t much evidence to suggest that early humans spent much time sleeping or even living in caves, still less that they built huts or other permanent shelters. Neither do we know at what point some people might have been assigned the task of keeping watch by night whilst their fellows were asleep, and to what extent rotas and duties were used to enforce such ideas, another activity that would require organisational skills.

The recent paper regarding Neanderthal sleeping arrangements, albeit a mere 50,000 years ago, along with other published material reminds us that it wasn’t only the daylight hours that affected our ancestors  – we’ve evolved to catch around 8 hours of uninterrupted sleep on a nightly basis, and a vital part of the Palaeolithic survival kit would have been the ability to ensure that those going to sleep for 8 hours stood a very good chance of waking up without having been maimed or even killed by opportunistic predators, or succumbing to the effects of exposure through inclement weather. This paper by Fank Hole, talking about Ohalo II c.23 kya, is also worth checking – Stone age bedding by the Sea of Galilee.

Bilzingsleben

The site would seem to bear some strong similarities with that of Bilzinglseben, dated to between 350kya and 400 kya, which although dates to considerably later, is also defined as a Middle Pleistocene site, with very similar artefacts, albeit 100,000 in total – and the floral and faunal remains indicate that these people also had a much more varied diet than simply that of big game hunters.

I’d intended to add much more about Bilzsinglsleben, but for the purposes of actually getting this post finished, I’ll have to leave that for later consideration – of particular interest there are the straight-line incised elephant bones and stones, which at c. 400 kya easily outstrip in age the incised ochre at Blombos, dated to c.77 kya, more of which another time. But that feature alone probably marks a significant step forward in behavioural terms, and offers intriguing contrasts to the older sites discussed above.

Ostensibly, very little seems to have changed in the way people went about their lives in the intervening half-million years or so, and that is puzzling, when we think how much has changed in the last 200k, 100k and 50kyr – the rate of cultural change has gradually accelerated,  and with the uptake of storage, horticulture and eventually agriculture, that rate of change has become faster still. David Deutsch giving a recent talk at TED, “A New Way to Explain Explanation” opined that it is only our modern ability, as witnessed by the so-called Scientific Revolution to perceive the unseen – geologic time, the atom and so on, that have allowed humans for the first time in evolutionary history to begin to find solutions and rational explanations for how the world actually works.

Although our perception of cultural evolution has probably been too closely tied to our physical evolution, and to a large extent this error persists, papers such as this conclusively demonstrate that seeking to define our modernity by concentrating solely on the Upper Palaeolithic are at best myopic and ultimately meaningless – everything deemed important in Palaeolithic evolution was in place well before 40 kya, an era commonly and wrongly attributed to the Human Revolution.

But we should also take care not to attribute tool use, basic understanding of fire, and planning to humans alone, especially when attempting to define human behavioural traits, so here’s cursory glance in the direction of our primate relatives – clearly the subject deserves far greater coverage, but for now a quick reference rather than long discourse will have to suffice for this post.

Tool Use and Fire Familiarity in Chimpanzees.

Attributing a predictive understanding of the properties of fire as being uniquely human has been called into question through the recent research by anthropologist Jill Pruetz, who made some interesting observations of the way in which Fongola chimpanzees of Senegal reacted quite calmly in the face of seasonal outbreaks of widespread burning. This doesn’t however imply that they know how to start a fire themselves, or would consider using it as a tool – for cooking food, clearing land or materials modification.

As mentioned earlier, a number of anvils and percussors found at the GBY site have been interpreted as having been used to process nuts, a behaviour also observed in chimpanzees – however, it is the combination of activities  – using fire to facilitate the removal of tough skins  – added to the realisation that heat processing also improved the flavour of acorns – along with using stone tools to crack open the nuts, which appear to set humans apart from their primate relatives.

I’ve set out to try and expand the debate about Gesher Benot Ya’akov by looking at the wider context while simultaneously drilling down to some of the detail about the site itself – and despite the rather rambling essay that has ensued, I hope that at least some value has been added to one of the most important archaeological sites of its kind at GBY. As far as I know, work there continues apace, and as time goes by and more data are published, I’m sure we’ll be returning for another look round at somewhere people once pleased to call home, if only on an ephemeral basis, 790, thousand years ago.

Due to a complete lack of good online images of the site itself, which is puzzling, I haven’t included any here – should that situation change, I’ll update this post accordingly.

Update 30 Jan. ’10 – My sincere thanks go to George Thwaites, who in addition to writing the linked article, Zen and the Art of Carp Fishing very kindly responded to an email question I sent him regarding how carp might have been acquired by the fishers of Lake Hula, 790 kya, with the following being his reply:

The man who took me fishing for the white amur (grass carp) insisted that the fish were dialed in on the sound of the acorns plopping into the water. In fact, I caught my fish beneath an oak tree under which they were accustomed to feeding. I assume the fish was conditioned to believe my bait had dropped from the tree. There were probably several other white amur competing for the same acorn. The bait had no time to hit the bottom. It was taken on the fall.

It seems possible that a stone age angler could have noted the areas where carp fed on dropping acorns and, by experimentation, learned how lure fish toward a pre-set net or fish trap by tossing acorns into the water.   Perhaps ancient fishermen on Lake Hula had the patience to condition an entire school of these carp, much in the same way domestic koi can be conditioned to respond to feeding. Such a process could have taken quite a few days.  Of course,  after the day “the trap is sprung” any survivors would be highly unlikely to fall for that tactic again any time soon (if they’re anything like modern carp). On the other hand, this method could result in multiple  fish being caught at once. Given that it would be a seasonal tactic (corresponding to the time acorns naturally drop) any carp that returned to the fishing site the following year might have been susceptible to an entirely new round of operant conditioning.

On the Holston River in nearby Rogersville, Tennessee, during the winter one can see the outline of what was a stone fish trap that  had been used by Native Americans for hundreds of years prior to the arrival of Anglo-European settlers. From the bridge above,  the large “vee wake” of the structure is unmistakeable. Assorted methods of luring, herding and trapping large numbers of fish were vastly more efficient for feeding a village than catching one fish at a time. I often wonder how much labor it took for the aboriginal anglers to build that fish trap, stone-by-stone and then to mend and maintain it, year after year. It occurs to me that hooking or spearing fish one at a time would have had the same appeal for them as it does to me: excellent recreation.  Sustenance is a serious business.

Hope this was of some help.

Well, I for one learnt a couple of things I didn’t know about how carp behave now and may well have been exploited by similar behaviours back in the Lower Palaeolithic and by subsequent by Stone Age folk thereafter – the idea of luring, herding trapping numbers of freshwater fish to feed several people at once is something I wouldn’t have guessed, for example.

Gesher Benot Ya’aqov – site description.

Reference:

Spatial Organization of Hominin Activities at Gesher Benot Ya’aqov, Israel, Nira Alperson-Afil, Gonen Sharon, Mordechai Kislev,Yoel Melamed, Irit Zohar, Shosh Ashkenazi, Rivka Rabinovich,1, Rebecca Biton, Ella Werker, Gideon Hartman, Craig Feibel, Naama Goren-Inbar – Science 18 December 2009: Vol. 326. no. 5960, pp. 1677 – 1680 DOI: 10.1126/science.1180695

Continual fire-making by Hominins at Gesher Benot Ya‘aqov, Israel – Nira Alperson-Afil, doi:10.1016/j.quascirev.2008.06.009

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