We all, especially as kids, have collected visually interesting objects for no particular reason other than they ‘caught our eye’: at the beach; from ploughed fields; river gravel, or at the side of a path. They end up in sheds, attics and mantel shelves. In an online News and Views article at the Nature website Pamela Willoughby discusses the significance of a paper on an archaeological site in the southern Kalahari Desert, North Cape Province South Africa (Willoughby, P.R. 2021. Early humans far from the South African coast collected unusual objects. Nature, v. 323, online News and Views; DOI: 10.1038/d41586-021-00795-5). Jayne Wilkins and co-workers from South Africa, Australia, Canada, Austria and the UK have investigated a rock shelter, with floor deposits going back over 100 thousand years. The researchers have, in a sense, continued the long human habit of seeking objets trouvée by using trowels and sieves to excavate the shelter’s floor sediments. They found a collection of cleavage fragments of white calcite and abundant shards of ostrich shell. Ga-Mohana Hill is still a place that locals consider to have spiritual significance. The authors consider the original collectors to have had no other motive than aesthetic pleasure and perhaps ritual, and that this signifies perhaps the earliest truly modern human behaviour. Yet, in 1925 a cave on the other side of South Africa, in Limpopo Province, yielded a striking example of a possible ‘collector’s piece’ from much earlier times. It is associated with remains of australopithecines and has been dated to around 3 Ma ago (see: Earliest sign of a sense of aesthetics, November 2020).
Source: Wilkins, J. et al.2021. Innovative Homo sapiens behaviours 105,000 years ago in a wetter Kalahari. Nature, v. 323 DOI: 10.1038/s41586-021-03419-0
The Blombos Cave 300 km east of Cape Town is where the earliest signs of art produced by anatomically modern humans were found (see Snippets on human evolution October 2011). The most publicized was a shaped piece of ochre etched with a hashed pattern of lines (Henshilwood, C.S. et al. 2018. An abstract drawing from the 73,000-year-old levels at Blombos Cave, South Africa. Nature v. 561, online; DOI: 10.1038/s41586-018-0514-3). This and the ochre-processing workshop where it was found gave a date of about 100 ka, Now another item has hit the newsrooms; a ground piece of flinty silcrete that shows signs of being the product of knapping, on which has been drawn a similar pattern, which resembles the now ubiquitous ‘hashtag’ associated with Twitter. The level in the excavation from which it was removed gives an age of about 75 ka. Like the earlier artifact, it involved the use of ochre but in a way that has been said to be an example of drawing or painting, rather than etching. It is likely to have been produced by a sharpened piece of solid ochre, perhaps a kind of crayon
For some reason the object has been hyped as the earliest example of art and of advanced cognitive abilities. But the pattern is not as complex as that on the original etched ochre block from Blombos, or even those on a freshwater mussel from Trinil in Java that could have =been made by associated Homo erectus between 430 and 500 ka ago. This does not take the context at Blombos into account. There is ample evidence that ochre, along with charcoal and burnt seal bone, was being ground there and made into paint found in an abalone shell. It can be surmised that such paint was used for some kind of decoration that has not yet been discovered. That is quite possibly because it was used for body paint as similar materials are still widely used. Now anyone – male or female – who uses cosmetics today, be it foundation, lipstick, eye-liner and -shadow or the truly fabulous make-up used by the Kathakali performers of Kerala, takes an age to try and to decide on which of an almost imperceptible range of shades to apply. Ochres are like that, as any native Australian artist will tell you.
To me, the most likely origins of both kinds of Palaeolithic hashtag are: in the case of the ‘drawing’, checking the colour and ‘grindability’ of a sharpened piece of red ochre before use; and for the etched block, using a sharp tool to grind off small amounts from what may have been a well-used block of an especially valued hue.
A revised and updated edition of Steve Drury’s book Stepping Stones: The Making of Our Home World can now be downloaded as a free eBook
The week of 7 to 11 September 2015 was one of the most news-rich of the year. To name but two issues: the plight of tens of thousands of refugees fleeing Africa and the Middle East to Europe was made worse by total confusion, little action and downright obstruction by some of the most privileged governments on Earth ; in Britain one of the most exciting political dramas in decades – the leadership elections of the Labour Party – were reaching a climax of press and political skulduggery because of the unexpected direction both had taken. Something else burst onto the media scene that was, if anything, even more out-of-the-blue to the majority of people on Thursday 10 September: the remains of at least 15 individuals of a new hominin species found in a near-inaccessible cave were announced by a multinational team of geologists and anthropologists. The feature that ensured its wide publicity in competition with some pretty serious political and humanitarian developments was the suggestion that the corpses had been ritually laid to rest by beings that lived maybe 2 million years ago. This major scientific stir arose from the publication of two lengthy papers by the open-access, electronic journal eLife (Berger, L. R. and 46 others 2015. Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa. eLife DOI: 10.7554/eLife.09560. Dirks, P.H.G.M. and 23 others 2015. Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa. eLife, DOI: 10.7554/eLife.09560).
Homo naledi (naledi means ‘star’ in the Sotho language: the find was in the Rising Star cave system near Johannesburg) is known in more anatomical detail than any early hominin, and most closely resembles H. habilis and H. rudolphensis discovered 3 to 4 thousand miles away in Tanzania and Kenya. The Dinaledi deposit remains undated but likely to come out at around 2 Ma or older. The sheer wealth of anatomical detail, including complete foot- and hand-bone remains from individuals, evidence for a range of ages at death, and plenty of dental and cranial information, actually poses a taxonomic problem of comparison with remains of other early hominins. Most of them are fragmentary, and it seems likely that once a precise date is obtained H. naledi will assume greater importance in comparative anatomy. Comparison with australopithecines is easier because of their abundant remains, and H. naledi is clearly distinct from that clade as regards gait, chewing, overall physiognomy (see reconstruction video) and cranial dimensions, but does have some australopithecine affinities. They were certainly different from their near geographic neighbour Au. sediba, also found in a cave deposit within the great swath of Palaeoproterozoic limestones near Johannesburg, where the Cradle of Humankind UNESCO World Heritage Site is situated. The brain of Homo naledi was on a par with those of australopithecines as regards volume, yet larger than that of H. floresiensis: it does seem that brain size is not necessarily related to the uses to which it is put.
Interestingly, it is reported that only the most diminutive members of the research team were able to enter the chamber where the remains were found because of the narrowness of the connecting passage. Also, access from the main cave system involved an upward ‘U-bend’, so that although water could – and did from time to time – enter the chamber in the past, it is unlikely that coarse material such as large bones could simply have been washed in, the more so as the chamber is on a minor spur from the main system and its outlet is through small floor drains that could not sustain torrential flow. Nor is there any direct access from the ground surface to this part of the system. Some of the more fragile body parts, such as a hand, are still articulated, which suggests a non-violent movement to the chamber. There are no signs of physical trauma to any of the bones, ruling out action by carnivores or transport by violent floods, nor any indicative of de-fleshing as by cannibalism. However, before fossilisation, many of the bones had been gnawed by beetles and snails. This combination of features leads to the possibility that corpses may have been deliberately placed in the chamber. If they had been, then to get to deepest recess of the cave system and find the Denalidi Chamber required illumination: fire brands. That the chamber was actually a living space is highly unlikely because of its remoteness from the surface. One big question that cannot be answered is whether or not such possible disposal was by ritual or simply for sanitary arrangements. Another possibility, not considered by the authors is seeking refuge from predators and becoming trapped in the desperately constricted space.
The possibility of ritual burial is clearly what has seized headlines. Yet few palaeoanthropologists will accept that: only Neanderthals and anatomically modern humans are definitely considered to have adopted such a practice, in the last hundred thousand years. The association of a bifacial stone tool with 350 ka old H. heidelbergensis remains at Atapuerca in northern Spain has been suggested to be the earliest evidence for ritual burial, but is not widely accepted. There are no reports of artefacts in the Dinaledi Chamber.
The work done by an asteroid or a comet that hits the Earth is most obviously demonstrated by the size of the crater that it creates on impact, should it have survived erosion and/or burial by sediments. Since some is done in flinging material away from the impact, the furthest point at which ejecta land is also a rough measure of the power of the hit. All this and much more derived from the kinetic energy of the object, which from Newton’s laws of motion amounts to half the product of the body’s mass and the square of its speed (mv2/2). It’s the speed that confers most energy; doubling the speed quadruples the energy. At a minimum, the speed of an object from far-off in space is that due to acceleration by the Earth’s gravitational field; the same as Earth’s escape velocity (about 11.2 km s-1). In March 1989 Earth had a close encounter with Newton’s laws writ large; an asteroid about 500 m across passed us with just half a million kilometres to spare. Moving at 20 km s-1 it carried kinetic energy of around 4 x 1019J. Had it hit, all of this immense amount would have been delivered in about a second giving a power of 4 x 1019 W. That is more than two hundred times greater than the power of solar heating of the day-side of the Earth. A small part of that power would melt quite a lot of rock.
As well as the glass spherules that are one of the hallmarks of impact ejecta on Earth and more so on the Moon’s surface, some of the larger known impact craters are associated with various kinds of glassy rock produced by instantaneous melting. Some of this melt-rock occurs in thin dykes, but sometimes there is an entire layer of once molten ‘country’ rock at the impact site. The most spectacular is in the Manicougan crater in Quebec, Canada. In fact a 1 km thick impact-melt sheet dominates most of the 90 km wide structure and it is reputed to be the most homogeneous large rock mass known, being a chemical average of every rock type involved in the Triassic asteroid strike. Not all craters are so well endowed with an actual sheet of melt-rock. This has puzzled some geologists, especially those who studied the much larger (160 km) Vredfort Dome in South Africa, which formed around 2 billion years ago. As the name suggests this is now a positive circular topographic anomaly, probably due to rebound and erosional unloading, the structure extending down 20 km into the ancient continental lithosphere of the Kaapvaal craton. Vredfort has some cracking dykes of pseudotachylite but apparently no impact melt sheet. It has vanished, probably through erosion, but a relic has been found (Cupelli, C.L. et al. 2014. Discovery of mafic impact melt in the centre of the Vredfort dome: Archetype for continental residua of early Earth cratering? Geology, v. 42, p. 403-406). One reason for it having gone undiscovered until now is that it is mafic in composition, and resembles an igneous gabbro intrusion. Isotope geochemistry refutes that mundane origin. It is far younger than the rocks that were zapped, and may well have formed as huge energy penetrated to the lower crust and even the upper mantle to melt a sizeable percentage of 2.7 to 3.0 Ga old mafic and ultramafic rock.
Oddly, the same issue of Geology contains an article that also bears on the Vredfort Dome structure (Huber, M.S. et al. 2014. Impact spherules from Karelia, Russia: Possible ejecta from the 2.02 Ga Vredfort impact event. Geology, v. 42, p. 375-378). Drill core from a Palaeoproterozoic limestone revealed millimetre-sized glass droplets containing excess iridium – an element at high concentration in a variety of meteorites. The link to Vredfort is the age of the sediments, which are between 1.98 and 2.05 Ga, neatly bracketing the timing of the large South African impact. Using reasonably well-constrained palaeogeographic positions at that time for Karelia and the Kaapvaal craton suggests that the glassy ejecta, if indeed they are from Vredfort, must have been flung over 2500 km.
A means of assessing the cognitive abilities of hominins is through the objects that they created, whether tools or artefacts with apparent symbolic significance. The latter include pigments, coloured shells, beads, artwork or even deliberately parallel and crossing lines gouged on otherwise innocuous rock. Undoubtedly valuable to their creators, possibly treasured and passed on until lost or broken – most are fragile – symbolic artefacts are rare. So although they shout ‘thoughtful’, their age tells us little about when such a capacity first arose. Many archaeologists and palaeoanthropologists assert that creating and/or manipulating symbols may signify a link with being able to speak. Tools are a lot easier to find, probably as discards and lost items, and a well-described and understood sequence of forms and sometimes uses has been established, which extends as far back as perhaps 3 Ma – before the genus Homo appeared.
In terms of their meaning in terms of the consciousness of their makers and users, there are possibly four major recognisable steps. Chimpanzees and some birds can learn to pick up natural objects, such as stones and twigs, and use them: some bands of chimps even retain the knowledge. A step beyond that is preparing a natural object for use, as with breaking a pebble to create a cutting edge: something not exclusively human because it is possible that pre-human hominins created the earliest such Oldowan tools. Being able to visualise hidden potential inside something natural is altogether more advanced, and is represented by the iconic bi-face or Acheulean ‘hand-axe’. Its earliest makers, H. ergaster and erectus, literally brought such objects to light by skilfully knapping away the outer parts of substantial lumps of suitable rock. The knowledge endured for more than a million years but was eventually added to and superseded by a range of more delicate and specific stone tools, but more sophisticated tools represented the same ‘liberation’ of a simple idea held in rock. The fourth general cognitive leap was to add several resources together as composite tools, and arguably we have not long emerged from that phase with the creation of composite tools that help us design and make other tools: a machine-tool culture.
It is that penultimate step-up in consciousness that has been engaging archaeologists since they first realised that some small, sharp chips of stone were not waste but deliberately crafted for combination with wood or bone. Such ‘microliths’ have been found in intact arrows and sickles of the Meso- and Neolithic, but their range steadily goes back in time with more research. Unmistakeable microliths have now been discovered at the South African coastal site at Pinnacle Point, in an occupation layer that is 71 ka old (Brown, K.S. and 8 others 2012. An early and enduring advanced technology originating 71, 000 years ago in South Africa. Nature, v. 491, p. 590-593).
The Pinnacle Point technology was indeed sophisticated, microlith manufacture requiring fire treatment as well as choice of rock and careful shaping and sharpening. As well as extending the microlith culture back so far the team of South African, US, Australian and Greek archaeologists compared them with 28 later African tool kits. The designs have barely changed from 71 ka to those of the last few hundred years. Kyle Brown and colleagues show that the industrial method endured, thereby laying to rest the somewhat reactionary notion that the methods were lost again and again in Africa after separate inventions and were only taken up decisively by the supposed ‘advanced’ anatomically modern humans who colonised Europe…
It is difficult to see how the Pinnacle Point microliths could have been useful, unless hafted in arrows or throwing sticks – maybe even saws and sickles? Crucially, they predate larger blade-tools that could have been hafted to form spears. The focus must now shift to the Zambian scene where possible microliths are reported at two 250 ka sites. If confirmed, they would link the decisive fourth cognitive step towards humanity with the very origin of fully modern humans, rather than a much later, non-African dawning of ‘smarts’ along with language, advanced art and much else in the chilly caves of southern Europe.
Of all human-colonised continents Africa lags far behind the rest as regards spread and density of archaeological digs. Only the ‘famous’ sites attract resources for investigation. Imagine what might emerge once there are more local people with research skills, equipment and transport; and, dare I say it, more independence of action and the attendant confidence in their ability.
McBrearty, S. 2012. Sharpening the mind. Nature, v. 491, p. 531-532.
When and how humans acquired fire on demand and began to cook has long engaged story tellers and historians. Entertaining tales are those of the titan Prometheus, who stole fire from Zeus and then had his liver eaten by an eagle (http://en.wikipedia.org/wiki/Prometheus ), and of Bo-bo, who accidentally discovered the barbecue approach to the meat of pigs (http://www.amazingribs.com/BBQ_articles/dissertation_on_roast_pork.html). Despite the secretive pleasures of some French and Ethiopian gourmets, raw flesh is not widely appreciated, although a rare steak comes pretty close. There is nothing wrong with it apart from its usually being tough and prone to deliver spectacular evacuations. Cooking unfolds the proteins in meat making them easier to digest and therefore portions of cooked meat deliver higher nutrition than they would direct from the carcase. Likewise, cooking some vegetables, especially various tubers, breaks down their chemistry to more easily digested and more palatable materials: think ‘potato’ in this context. In fact many potentially nutritious tubers are positively toxic if not processed and cooked, classic examples being cassava and wild yams.
While some anthropologists consider a change in hominin habits to eating meat per se, probably originally as carrion, as the necessary step to a leap in nutrition from which an enlarged brain developed, others favour the harnessing of fire and the invention of cooking that released greater proportions of proteins and carbohydrates from available foodstuffs. Since hominins evolved in distinctly seasonal savannas and open woodland, the shortage of game and directly edible above-ground plant parts in the dry season suggests indirectly that our early ancestors had two possible survival paths open to them: powerful jaws and complex digestive tracts to survive on woody stems or digging up tubers. Respectively, the anatomy and tooth-wear patterns of paranthropoids and early Homo to some extent support such a dichotomy that arose from the australopithecines after about 2 Ma ago. Both succeeded and cohabited roughly the same ranges in eastern Africa for as long as a million years.
So pinning down the origin of controlled use of fire is a major goal of Pleistocene archaeology to settle the issue of nutrition and brain growth. Also, it would help explain how hominins were able to diffuse far beyond their home ranges to northern latitudes sufficiently high to place fire as an essential source of warmth at night and in winters. Yet, evidence for habitual use of fire is younger than 400 thousand years among H. heidelbergensis, H. neanderthalensis and H. sapiens, literally leaving the wide roaming H. erectus to shiver as far as scientific proof of hearth and home is concerned. There have been claims of early charring, burnt bones and ashes but until recently such evidence has been ambiguous, largely because fire can start easily and naturally in tinder-rich conditions. There are now, however, advanced microscopic, chemical and physical techniques for estimating temperatures to which bones have been subjected and detecting changes in materials caused by fire, which can be applied to minute samples from sites once occupied by earlier people. One test site for the methods has been the Wonderwerk Cave in South Africa that is known from Acheulean tools and cut bone to have been occupied as long ago as 1.1 Ma. They gave a positive result for the use of fire by the earliest cave occupants (Berna, F, et al. 2012. Microstratigraphic evidence of in situ fire in the Acheulean strata of Wonderwerk Cave, Northern Cape province, South Africa. Proceedings of the National Academy of Science USA, www.pnas.org/cgi/doi/10.1073/pnas.1117620109 – open access). The same methods had previously been used to establish controlled human use of fire around 400 ka in once occupied caves in Israel, but at Wonderwerk almost triple the age of earliest known use. But they have refuted similar claims from the famous Zhoukoudian site of ‘Peking Man’ (Asian H. erectus) (http://www.unesco.org/ext/field/beijing/whc/pkm-site.htm).
A useful adage is that ‘the absence of evidence is not evidence of absence’, and it is early days for the routine archaological use of micromorphology, Fourier transform infrared (FTIR) spectroscopy in the search for human embers. In drylands naturally started fires, either as a result of lightning or spontaneous combustion, are so common that hominins would have been well aware of them, their dangers and perhaps their advantages as regards a free barbecue. Possibly Bo-bo’s salivating at the aroma of roast pig from the wreckage of his father house that he had razed to the ground though sheer stupidity would have struck some early hominins as a useful connection between a lucky feast and the still glowing embers of a bush fire. With care, embers can survive for long enough to be carried and used to start controlled fire; a fact not lost on many surviving fully human foragers, and also kids on a South Yorkshire council estate eager for the delights of roasting some ‘borrowed’ potatoes.