Breaking the time barrier: Clive Gamble revisits the moment at which archaeologists realized that human prehistory was far longer than biblical scholars had imagined; and links this to today's debates about the antiquity of the human mind with its capacity for self-aware thought.
On a spring afternoon in 1859 two successful English businessmen were about to make history in a gravel pit in northern France. Joseph Prestwich, at forty-seven the older by eleven years, had a day job in the wine trade. But his passion was unravelling the geology of northern Europe; tracing the history of glaciations by mapping surface deposits with the evocative name of 'the drift'. His younger companion, John Evans, had tremendous energy and a most impressive set of side-whiskers. Roman coins were one of his archaeological obsessions and he had earlier bought some found by workmen in this pit on the outskirts of Amiens on the Somme River. He ran the paper company in Hertfordshire that his wife, Harriet Dickinson, had inherited. She had died the year before leaving him with five young children. The eldest, Arthur, would later inherit the family fortune and make his name discovering the Minoan civilization of Crete.
What had brought Prestwich and Evans together on May 2nd, 1859, was a quest for something much older than the Bronze Age and numismatics. Their interest lay seventeen feet below the ground surface and four-and-a-half feet up from the base of the river terrace cut into the chalk slope. Sticking out of the gravels was the unmistakable edge of a worked flint tool. They were so excited by this find that they had asked for three representatives of the Societe des Antiquaries de Picardie to be present as witnesses and, moreover, arranged for a photographer to record the discovery.
The remarkable photograph that resulted captures the moment in the history of archaeology when the time barrier to a human antiquity of geological proportions was conclusively broken. But even so who is pointing to the flint and who is sitting in the wheel-barrow remains a bit of a mystery; the lack of side-whiskers seems to rule Evans out and neither figure matches pictures of Prestwich. Perhaps they are two of their French colleagues Pinsard, Dufour or Garnier?
The flint itself was never illustrated, perhaps because as Prestwich recalled, 'this implement is rougher and more imperfect than the generality of the specimens ... It is an unfinished implement'. Only the best-looking artefacts were made into published plates, a costly process. No doubt the flint sits today, unremarked upon, in a museum drawer along with the many handaxes the men collected and bought from the workmen that day and on later visits.
Evans and Prestwich were excited not because they had found a stone tool, many hundreds of which were already known, but because it was the first recorded and witnessed in situ. This one was poking out of the same gravels that had yielded bones of extinct animals such as mammoth and woolly rhino. It was undisturbed until Prestwich prised it out, noting carefully that its thickest edge was inner-most, making it impossible for someone to have pushed it into the gravels.
Prestwich had been alerted by another geologist Dr Hugh Falconer that the discoveries in Abbeville and Amiens by the collector Jacques Boucher de Perthes (1788-1868) might be what were needed to prove beyond doubt the association of ancient humans and extinct animals. Boucher de Perthes, now an old man of seventy-one, had been collecting handaxes and making notes on their geology for many years. He had put forward a theory in 1847 that these flint tools were evidence of ancient man in Europe. But he had lost his credibility for his exaggerated claims for ancient flint sculptures of horses, bears and humans. In fact these were all naturally shaped flints.
On May 1st, Evans endured a rough crossing from Folkestone to Boulogne to join Prestwich that evening to meet Boucher de Perthes in Abbeville. They spent the morning of May 2nd touring the pits in the town and examining the large collection of artefacts amassed by their host. Then during a 'most sumptuous dejeuner a la fourchette', as Evans recalled, a telegram arrived from Amiens, thirty miles away. The news was good. The workmen, briefed by Prestwich, had made the discovery that had eluded him during his visit a few days earlier; a flint tool had been found in the section waiting to be dug out. They quickly bid adieu to their eccentric host, boarding a fast train to meet the photographer and the French antiquaries in the pit near the seminary of St Acheul. The following day they were on the boat train arriving back in London by midnight. This had been a whirlwind visit.
The next month saw some frenzied but well co-ordinated activity. Evans set off on May 6th for a business trip that took him to Dublin, Belfast and Manchester returning home a week later. In the meantime Prestwich went back to St Acheul with palaeontologist John Flower to recover more artefacts and extinct animal bones. They planned a three-pronged attack on the learned societies whose endorsement they needed to prove a great antiquity for humans. Prestwich spoke first to the Royal Society on May 26th, only three weeks after their momentous discovery. Evans, the expert on flint tools, would elaborate on his preliminary findings which were available to Prestwich with a full account to the Society of Antiquaries of London on June 2nd. Flower provided further proof to the Geological Society on June 22nd.
But before any of these three lectures took place, something quite unexpected happened. Sometime between his return from Ireland and Prestwich's talk to the Royal Society, Evans stumbled across a short letter, illustrated with two fine engravings, which had been sent to the Society of Antiquaries in 1797 and published in their journal Archaeologia three years later. It had been written by John Frere, a Fellow of both the Society of Antiquaries, founded in 1707, the oldest institution dedicated to understanding the past, and the Royal Society founded by Charles II in 1660. Frere was a landowner in Suffolk. His letter, accompanied by two flint handaxes, records their discovery in the brick pit at Hoxne in that county. What marks out his brief communication is his comment on their stratigraphic position, his conjecture that they were 'weapons of war' and his conclusion based on the evidence that they came from a 'very remote period indeed; even beyond that of the present world'. Although politely thanked for his letter by the Society it was promptly forgotten.
How Evans came across Frere's letter is not recorded. Did a librarian bring it to his attention? Did he trace it after seeing the handaxe that still survives in the Society of Antiquaries collection? Once aware of it, he and Prestwich went immediately to Hoxne where, as Evans recorded, they met an old quarry workman who repeated Frere's claim by referring to the handaxes as 'fighting stones'. Not surprisingly, Hoxne figures prominently in both their papers to their respective learned societies. It was their final proof of human antiquity because it repeated the same set of discoveries--bones and stones in situ--that had been made on the Somme.
How was the discovery received? In his diary Evans betrays his nervousness. He had almost lost his voice since May 2nd as a result of all his travels. The audience at the Antiquaries was formidable and included Faraday, Murchison, Babbage, Huxley and Lyell among others. This was cutting-edge science laid before some of the greatest practitioners of the time. With obvious relief he wrote that 'our assertions as to the finding of the weapons seemed to be believed'. Frere's letter was the key since, as Prestwich noted, he was an 'antiquary unfettered by geological theories'. Frere had had no axe to grind about antiquity, just some observations concerning evidence. Prestwich and Evans' papers were also well received because they avoided the most contentious issue, the age of the artefacts. Prestwich was clear on this point,
... the evidence, as it at present stands, does not seem to me to necessitate the carrying of man back in past time, so much as the bringing forward of the extinct animals towards our own time.
They had no way to estimate how old the finds were, but as Evans put it:
Thus much appears to be established beyond a doubt; that in a period of antiquity, remote beyond any of which we have hitherto found traces, this portion of the globe was peopled by man; and that mankind has here witnessed some of those geological changes by which these so-called diluvial beds were deposited.
But they left nothing to chance in convincing those with the greatest scientific and social clout. In June they arranged for the doyen of British geologists Sir Charles Lyell, up until then a critic of great antiquity for humans, to visit the Somme. More handaxes were found, one of which survives in Edinburgh University with Lyell's name and the St Acheul location written on it. Lyell was convinced, and at a packed session of the British Association for the Advancement of Science held at Aberdeen that September in the presence of Prince Albert, he added his authority to the case:
A vast lapse of ages, [separates] the era in which the fossil implements were framed and that of the invasion of Gaul by the Romans.
And that was the end of the matter.
What happened then? Well there was the publishing sensation on November 24th, 1859 of The Origin of Species by Charles Darwin; a work that side-stepped human evolution but whose implications for the subject were clear. Fuller discussion came with The Descent of Man in 1871 published a year before the French archaeologist and political maverick Gabriel de Mortillet used St Acheul as the type site for those stone handaxes. And so the term Acheulean came to describe one of the most enduring and widespread of archaeological cultural traditions. A tradition set, literally, in stone.
Evans continued with his business and antiquarian interests, his achievements recognized with a knighthood in 1892. His massive book The Ancient Stone Implements of Great Britain first published in 1872 is a classic and established the modern study of Palaeolithic archaeology. Prestwich, meanwhile, left the wine trade in 1874 to become Professor of Geology at Oxford, a post he held for fourteen years and which crowned his reputation as one of Britain's greatest geologists. He was knighted in 1896, the year he died.
How important are the sites of St Acheul and Hoxne for Palaeolithic archaeologists today? The pit by the seminary has long gone but a number of important archaeological discoveries were made in its vicinity as gravel continued to be dug for many years. In the 1990s the Somme evidence was thoroughly reassessed by a French team led by Main Tuffreau and Pierre Antoine. Their work on the age of the deposits began with Prestwich's sections across the valley and the staircase of river terraces that he had carefully noted. Their aim was to tie the phase of aggradation, when huge quantities of gravels were laid down, and the subsequent phase when they were cut through making river terraces, to the timescale established independently from research into cores drilled into the muds of the ocean floor. These sediments contain small marine organisms, foraminifera, whose tiny skeletons act like blotting-paper when they are alive soaking up the oxygen isotopes present in the sea water and preserving the ratio between [O.sub.16] and the heavier [O.sub.18]. When this ratio is plotted along the length of a core what emerges is a wiggle-curve of changing values. Moreover these wiggles show a cycle, of repeated values. Sir Nick Shackleton in the 1970s saw the significance of these wiggles as a signal of changing Ice Age climates; when they are rich in [O.sub.16] oceans were large and hence climate was warm. When [O.sub.18] dominated, the lighter [O.sub.16] had been evaporated and used to build ice sheets at the poles. Here was a deep-sea stratigraphy of climate change, comparable to the staircase of terraces cut into the Somme Valley
Such deep-sea stratigraphy was undreamt of in 1859 just as our ability to put ages to these cycles would have been. This has been done by linking the earth and the ocean through measurements of changes in the Earth's polarity; literally when the North Pole became the South Pole. 790,000 years ago the Earth's polarity switched from reversed to what we now know as normal. This can be measured in volcanic rocks on land, as well as the marine sediments, and those same rocks can be dated by scientific methods that use the rate at which isotopes such as potassium and argon (K/Ar) decay. This boundary, the Brunhes-Matuyama (shortened to the B-M), provides a stratigraphie marker of which Prestwich would have approved. Above it are eight climate cycles each consisting of a warm interglacial and a subsequent glaciation. Hoxne and the Amiens terrace at St Acheul sit in the fifth cycle after the B-M boundary.
Hoxne provides more detail on the interglacial section of this cycle, now dated to between 427,000 and 364,000 years ago. The lake at Hoxne yielded pollen that showed it existed in a warm climate during which there was a marked succession in the vegetation with conifers and cold tolerant trees giving way to deciduous forests. Of all the eight interglacials since the B-M boundary, this one has the most climatic similarities to the present. However, the differences are also plain. The population of England 400,000 years ago was probably 3,000-5,000 people at most. The animal faunas indicate the rich grazing and diversity of habitats that existed. At the time Hoxne was visited by the handaxe users, the grasslands resounded to the footfalls of extinct varieties of elephant and rhino, horse and a large fallow deer. Macaque monkeys could be found in the forests, and along the rivers an extinct giant beaver was building dams. Furthermore, even though no fossil evidence for humans has yet been found at either Hoxne or the Somme, discoveries at sites of similar age reveal them as likely to have been Homo heidelbergensis, dating from 600,000 years ago and powerfully built, as indicated by their robust bones and skulls.
400,000 years would have been an inconceivable amount of human history to Lyell and Evans. Prestwich, as we have seen, wanted to bring mammoths and rhino forward rather than push humans back in time. But back in time they have gone, though we now think in terms of even longer timescales for human prehistory. We now trace the beginning of hominin evolution, which began with the split from the chimpanzees, to six million years ago; the first stone tools, to 2.5 million years old from Gona in Ethiopia; or even to the first appearance of our lineage Homo, to sometime soon after in Africa and outside that continent at Dmanisi in the Republic of Georgia 1.8 million years ago, and the earliest occurrence of Acheulean handaxes found at Olduvai Gorge in Tanzania, to 1.4 million years ago.
However, although Hoxne and St Acheul may not today be breaking Palaeolithic time-barriers the evidence they contain is challenging another fundamental barrier to understanding the past: when did hominin brains become human minds?
Currently archaeologists are split into two camps in a fierce debate. There are those who favour a very late date indeed for this transition; during the Neolithic with its villages, crops and domestic animals that begins just 12,000 years ago in the Near East. They see as crucial the built environment of houses with their opportunities for secrecy, privacy and a closer connection between people and material symbols, as are found for example at the early Anatolian town of Catalhoyok in Turkey or the crowded tell-site of Abu Hureyra on the banks of the Euphrates. In Trevor Watkins' opinion, 'the world's earliest village communities were also the first to develop fully modern minds and a fully symbolic culture'. Here people engaged with their material worlds in new ways and thus new minds were fashioned.
Palaeolithic archaeologists disagree. They point to an older human revolution one that predated the Neolithic by at least 50,000 years. It was at this time, argues Richard Klein, that our brains underwent significant neural changes. Paul Mellars points to a wealth of evidence for art, ritual in the form of burials and a global diaspora when Homo sapiens moved out of Africa to reach Australia, the Pacific and the Americas. Excavating in Blombos Cave on the coast of South Africa, Christopher Henshilwood found engraved pieces of ochre pigment and pierced marine shells that were almost certainly strung on a necklace, and dated by thermoluminescence to more than 77,000 years ago. At the other end of Africa, Nick Barton's excavations in the cave at Taforalt, Morroco, has discovered similar pierced shells in layers dated to 82,000 years ago. These finds date from long before any move to a sedentary life based on agriculture. These data are downplayed by Neolithic archaeologists, like Colin Renfrew who refers to a sapient paradox when anatomically, and also culturally, the Palaeolithic people at Blombos and Taforalt may have had modern cognitive powers but they failed to do anything with them.
Both positions betray an old prejudice that modern minds must be associated with Homo sapiens and not earlier hominins such as Homo heidelbergensis and their descendants the Neanderthals who became extinct when people like us first entered Europe. From this standpoint the argument is about which Homo sapiens had modern minds; the Paleolithic hunters or the Neolithic farmers. I don't know exactly what Prestwich and Evans would have thought of the matter, or even that they considered it all, but judging by the social standards of their day there was not much good to be seen in peripatetic hunters who were considered to be at the bottom of the ladder, more animal than human. Evans in particular, I feel, would have bet his numismatic collection on the farmers.
Trying to break this mind-barrier involves placing the evidence in a different framework; one where Hoxne and St Acheul occupy an important position.
During the evolution of hominids from six million years ago to Homo sapiens, the brain trebled in size. This process, known as encephalization, required changes in diet and physiology as such big brains need higher quality food such as meat. So, why did the larger brain evolve at such a cost?
One answer, suggested by evolutionary biologists Robin Dunbar and Leslie Aiello, points to the social lives of our ancestors. Dunbar and Aiello have shown that the brain sizes of different species of monkey correlate very strongly with group size. The bigger the brain the bigger the primate group. When humans and extinct hominins were added to the same graph it became clear that during human evolution the number of other individuals that could be remembered, monitored and engaged with had doubled; from about seventy, the primate maximum, to 150. And this last number constantly recurs in the organization of human groups and networks, forming the building block for our demographically huge and intricately inter-connected urban world.
How did this doubling occur? Social contacts among apes are maintained by finger-tip grooming. To go beyond sixty to seventy contacts runs into problems of finding enough time in the day to groom everyone in your social circle. The solution is to develop a different form of communication; Aiello and Dunbar argued that language fits this need.
The implication of their argument was dramatic. The big rise in brain size between 600,000 and 400,000 years ago, when Homo heidelbergensis lived at Hoxne and St Acheul, strongly suggests they had language to support their social lives. We don't know what they talked about when they knapped those handaxes and sat around some of the oldest hearths known at sites such as Beeches Pit and Schoningen, in eastern Germany, where Harmut Thieme also found well-crafted wooden javelins and spears; but it probably consisted of social gossip.
But have we broken the mind-barrier? Apparently not. Those Homo sapiens who painted cave walls and buried their dead festooned with beads and covered in ochre must have had language. However, several Neolithic archaeologists do not regard them as having modern minds. The Hoxne hominins, with their much simpler cultural inventory, therefore stand no chance.
The time-barrier to accepting human antiquity was broken almost 150 years ago. The prejudice that supports the mind-barrier is still waiting to fall. This time however it will not depend on a single discovery but rather a change in outlook. As we begin to understand just how the brain works, we see that emotion plays a pivotal role not only in dealing with others but with the material world--whether of stone handaxes or of computer handsets. The mind may have less to do with the manipulation of symbols than proponents of both the human and Neolithic revolutions maintain. Instead of being mind readers, perhaps humans' great evolutionary skill has been to understand, amplify and manipulate the emotions of others and to shape them during childhood.
Prestwich and Evans were excited, and yes, emotional, about their discoveries in 1859. But since then we have only allowed a rational account of the social lives of our ancient ancestors. Once the mind-barrier is broken, the prospect for the next 150 years of Palaeolithic endeavour is truly exciting-just as the patient wait by Evans and Prestwich for an in-situ flint tool brought dividends. And it will be broken. Antiquaries, after all, have time on their side.
L. Aufrere, 'Figures des prehistoriens, I Boucher de Perthes' Prehistoire, 7, I-134, 1940; J. Evans, A History of the Society of Antiquaries (Oxford University Press, 1956); C. S. Gamble, Origins and Revolutions: Human Identity in Earliest Prehistory (Cambridge University Press, 2007); D. K. Grayson, The Establishment of Human Antiquity (Academic Press, 1983); C. Stringer, Homo Britannicus: the Incredible Story of Human Life in Britain (Penguin, 2006); J.J. Wymer, The Lower Palaeolithic Occupation of Britain (Wessex Archaeology, 1999).
Clive Gamble is a Professor at the Centre for Quaternary Research in the Department of Geography, Royal Holloway, University of London. This article is adapted from a lecture he gave in 2007 as part of the tercentenary celebrations for the Society of Antiquaries.
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|Date:||May 1, 2008|
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