The Book of Humans Read online

  In 2015, a wandering team of researchers from Stony Brook University in New York took a wrong turn in Lomekwi and stumbled into a site scattered on the surface with lithic detritus indicative of intentional tool-making. After excavating further, they found many other fragments and tools themselves. The dirt in which they were found could be accurately dated, which is not always easy, but in this case, was dependent on layers of volcanic ash, and the geological phenomenon of magnetic pole reversal.4 The tools found are not quite as sophisticated as the Oldowan set, but are much older, probably 3.3 million years. In one case a lithic flake could be matched to the stone from which it was chipped. It is viscerally powerful: imagine an ape-like person sat right there, intentionally chipping at a rock with purpose in mind. Maybe he or she wasn’t happy with how it split, discarded both halves, and moved onto something else. Or maybe it was chased away by a ravenous predator. There, the pieces lay undisturbed for more than three million years.

  We don’t know who it was who sat and carved those tools, though we do know that it was a creature that pre-dates the origin of the genus Homo – the humans – by maybe 700,000 years, and may well be the flat-faced Kenyans. The Oldowan tool set has now been found in key sites all over Africa where other significant evidence of human presence is known, including Koobi Fora on the east side of Lake Turkana in Kenya, and Swartkrans and Sterkfontein in South Africa. Further afield, these tools have been discovered in France, Bulgaria, Russia and Spain, and in July 2018, in south China – the oldest yet found outside Africa. The timescale over which this technology was used is huge, covering maybe more than a million years.

  An Oldowan chopper

  In our reading of the history of technology in humans, Oldowan tools in time are replaced with a new set consisting of more complicated kit. Thousands of miles from east Africa, St Acheul is a suburb of the northern French city of Amiens where, in 1859, a major haul of axe heads would come to define the most common industry in the whole of human history. They weren’t the first of these discovered – in the late eighteenth century, similar examples were found in a Suffolk village near to the pleasant market town of Diss – but they are the type of specimens of what is now known as the Acheulian tool set.

  Acheulian hand axes have been worked more precisely than their Oldowan ancestors. Typically, they are teardrop-shaped, chiselled into sharp points, and crafted into flattened blades, often on both sides. They are also larger, with a roughly 20cm cutting edge, compared to just 5cm in a typical Oldowan blade. They represent the fruit of a concerted cognitive ability to truly craft a tool, or a weapon, and require skilled hand–eye coordination and an even greater degree of foresight and planning. The flaking of a stone occurs in multiple stages, as the initial shape is crafted, and then the blade thinned and sharpened with a second round of delicate lithic reduction. Try it next time you’re on a rocky beach, with a flint. It’s a difficult, skilled process; an indelicate or badly placed blow will lethally crack the stone, and maybe your fingers.

  We see an increase in symmetry in these blades as brains get bigger over evolutionary time. The instruments are found distributed around the world, and across species. The oldest Acheulian tools, as of 2015, have in fact been found in Olduvai Gorge, home (at least in name) of the technology it replaced, but they are also found all over Europe and Asia. Homo erectus chiselled these blades, as did other early humans such as Homo ergaster, and Neanderthals and the first Homo sapiens. They used them to hunt, to butcher animals, to strip meat from skins and bones, and to carve those bones. They were used as spearheads, and some researchers have suggested that sometimes they were not used as originally intended but were ceremonial or even traded as currency.

  Acheulian tools are the dominant form of technology in human history. Though there are minor refinements over time, it is truly fascinating how stable these blades are. Many more people today use telephones or drive cars, have reading glasses or use cups, but in terms of longevity, Acheulian tools win hands down. We define this period by the technology. The Palaeolithic period ranges from 2.6 million years ago until 10,000 years ago. Palaeolithic means ‘old stone’, which might be slightly ironic, because much of what was being engineered by those worked stones was probably wood and bone.

  So, a few decades ago, the genus Homo was defined by tools. But we now know that earlier apes who we don’t call humans were also using stone tools. Therefore, we have to conclude that, historically, tool use has not been limited to humans. This is borne out by examples of tool use in living non-human animals, as we will see later. For these animals, the technological material is frequently not stone, but harvested from trees, and there is no reason to suppose that early humans were not tooling wood as well. Of course, wood biodegrades, and we have scant physical remains of prehistoric tooled wood. There is a beautiful site in Tuscany in northern Italy that has revealed some of the best examples of ancient carpentry. They’re boxwood fragments, around 170,000 years old, scattered in the ground alongside Acheulian stones and bones from an extinct straight-tusked elephant, Palaeoloxodon antiquus. A couple of spears have been found in other sites, including in the seaside town of Clacton in Essex, but these Tuscan remains are probably multipurpose sticks, and show evidence of having been tooled, partially using fire. Boxwood is hard and stiff, and the sticks show evidence of having had their bark worn away with a stone scraper, and possibly charred to remove extra fibres or knots. Who carved these spears and digging sticks? The time and place squarely put this carpentry in the hands of Neanderthals.

  These wooden tools are few and far between, especially at that age. So when it comes to naming conventions, we work with the evidence available, and what follows the age of old stone is the middle age of stone, a 5,000-year period we call the Mesolithic, and then the Neolithic and into the present.

  The Palaeolithic covers both the Oldowan and Acheulian tool sets, and combined, these periods represent more than 95 per cent of the history of human technology. There’s a measurable shift between the two types, but otherwise the toolbox of humans changes very little for two periods of more than a million years each. There are no great leaps forward in development. Humans migrated around the world during this period, reaching all the way to Indonesia, and all over Europe and Asia. We see them slowly change in their anatomy, in species and in their global distribution, but the technology remains recognisable.

  With the Lomekwi tools dated at 3.3 million years old, it’s worth noting that these first technological people were already maybe four million years distant from the separation of our evolutionary branches and that of chimps, bonobos and other great apes. All of them also use tools today, which we will come to in a few pages. What we are unsure of is the continuity of cultural tool use. Humans accumulate knowledge and skills and transmit them through time, mostly without losing those acquired abilities. Generally, we don’t have to invent the same technology over and over again. Have all the great apes used tools continuously since that divergence, or has tool use been forgotten and reinvented many times? This is unclear, and possibly unknowable, as there is little evidence of other great apes crafting stones, even if they did use wooden tools, which are not preserved well in the fossil record. With the advent of the basic Oldowan technology in ancestors that pre-date humans, but came after the split between those apes that would evolve to become us and those that would become gorillas, chimps and orangutans, we are witnessing an ability to deliberately manipulate external objects for specific purpose that exceeds any other animal – including all the other great apes – by a significant margin.

  1 Animal Tool Behavior: The Use and Manufacture of Tools by Animals by Robert W. Shumaker, Kristina R. Walkup and Benjamin B. Beck (Johns Hopkins University Press, 2011).

  2 Geologists have all the best names: obsidian is a rock formed when felsic lava rapidly cools on the edges of rhyolitic flows; that means it’s rich in the silicate compounds feldspar and quartz.

  3 Historically, the word ‘man’ has been used to describ
e these species in common parlance, as in Neanderthal man, Cro Magnon Man, etc. It’s a casual usage that is annoying in that it fails to recognise 50 per cent of our species but it can be easily corrected by generally using ‘human’, as in humankind, which is an easy and inclusive fit. In this case though, ‘human’ specifically refers to the genus Homo, which Kenyanthropus platyops is not in, but anthropus implies human-ness, though in Greek it literally means ‘man’, so I’m not quite sure how to represent it here. It is a hominin, which includes both Homo – the humans – and Australopithecines, whose name roughly translates as ‘southern ape-like things’.

  4 The magnetic poles are constantly moving and have flipped many times in our planet’s history. We’re not sure why and cannot predict when they will flip. The change happens over thousands of years, and no pattern has yet been discovered for the known times that magnetic north and south have reversed. But these reversals are recorded in microscopic fragments in rocks, and thus are useful for dating when the rocks were formed. The North Pole is currently moving south at a rate of about a few miles a year, though this is nothing to be worried about – it is too slow to have any noticeable effect on us, or the many migratory animals that have magnetoception and navigate using the Earth’s natural polarity.

  What it Takes to Be a Maker

  The scale of difference between us and the other great apes is important if our technological skills are to be considered as part of a great leap forward for us. Crafting a tool requires foresight and imagination, which needs to be translated into fine motor control actions. That is a lot of brain power to contemplate. But we must also consider the dexterity that is being enabled. When thinking about technology, we have to talk about the physicality of both brains and bodies. Our hands are awesomely complex. Roboticists try to model the number of degrees of freedom that a normal human hand has, upwards of twenty, maybe thirty, in trying to emulate what you can do without much thought. Consider the bewitching precision in dexterity that Kyung Wha Chung displays when she plays the Bruch Violin Concerto. Or when Shane Warne would spin a cricket ball so outrageously that it would turn almost ninety degrees upon hitting the ground, and utterly hoodwink the best batsmen in the world. Conjuring such magic into the muscles in our fingers and thumbs, hands and wrists requires a great deal of neurological processing, not just in the motor control, but with intention too.

  We have unusually large brains. They are also unusually folded and crenellated, meaning that the density of connections between cells is extremely high, and increases the surface area of our cerebral cortex, with which modern behaviour is most commonly associated. There are many metrics that can be applied to brains, and we come out near – but not at – the top of most.

  We don’t have the biggest brains as, in general, they increase in size as bodies do. Blue whales are probably the largest animal to have ever existed, but sperm whales have the heaviest brains, weighing in at around a monstrous eighteen pounds. On land, the heavyweight brain champion is the African elephant. In terms of the absolute number of neurons, African elephants come out on top too, with an absurd 250 billion, around three times more than ours, in second place with around 86 billion. For comparison, the nematode Caenorhabditis elegans is beloved of biologists for many reasons, one of which is that we have mapped the pathway of every single cell in its body as it matures from a single fertilised egg to a fully grown worm. Its whole nervous system is made up of precisely 302 cells. Don’t let this apparent paucity fuel complacency: they have around the same number of genes as us, but outweigh us, outnumber us and, in terms of evolutionary longevity, will outlast us by hundreds of millions of years.

  The cerebral cortex in mammals is of particular interest because of its place as the seat of thought and complex behaviours, but we’re second on that chart too, this time to the long-finned pilot whale; they have more than twice the number of cells in their cortex. At this scale, African elephants have dropped down below all the great apes, four species of whale, a seal and a porpoise.

  We try to compare like with like in these sorts of scientific parlour games. After all, women are smaller on average than men, and women’s brains are proportionally smaller too, though – and this cannot be stressed enough – that conveys categorically no measurable difference in cognitive capabilities or behaviour. So, perhaps comparing brain-to-body mass is a more useful metric in trying to establish a neurological basis for brain power.

  Aristotle thought that we were the top dogs by this measure, saying in his clearly titled book On the Parts of Animals that ‘Of all the animals, man has the brain largest in proportion to his size.’ Aristotle was a tremendous scientist as well as being better known as a philosopher, but he wasn’t quite right about that. Again, we’re close but not at the top; ants and shrews beat us hands down. It was a better scientist than Aristotle who in 1871 worked this out. Again, it was Charles Darwin in The Descent of Man:

  It is certain that there may be extraordinary mental activity with an extremely small absolute mass of nervous matter: thus the wonderfully diversified instincts, mental powers, and affections of ants are notorious, yet their cerebral ganglia are not so large as the quarter of a small pin’s head. Under this point of view, the brain of an ant is one of the most marvellous atoms of matter in the world, perhaps more so than the brain of a man.

  Only about one pound in forty of our total body mass is brain. That ratio is about the same as mice, much higher than in elephants, where it’s more like 1:560. The record for the lowest brain-to-body mass ratio is held by an eel-like fish called Acanthonus armatus. If this ignominy wasn’t enough, its colloquial name is the bony-eared ass-fish.

  In the 1960s we invented a more complex method of brainpower calculation. The encephalisation quotient (or EQ) effectively registers the ratio between the actual brain mass compared to its predicted mass based on the size of the creature. It allows us to rank animals with a better fit that relates to observed complexity of behaviours, and in this way, we hope to get a better handle on the amount of brain involved in cognitive tasks – brains don’t scale perfectly with body size or behavioural complexity. The method only really works for mammals, and lo and behold, humans come out on top. Different types of dolphin are next, then orcas, chimps and macaques.

  The trouble is that bigger brains don’t necessarily mean more brain cells. Density of cells is one aspect of the physiology of cognition, but there are myriad types of cells in our heads, and they’re all important. It is often said that we only use 10 per cent of our brains at any one time (and therefore the implication being ‘imagine what we could achieve if we used the whole lot!’).1 Alas, that is a tremendous nonsense, an appealing urban legend. All parts of our brains are used, though not all with the same ferocity at all times. There isn’t a great chunk of unused hard-drive sitting there lazily awaiting stimulation. The complexities of thought and action are predicated on having multiple cell types functionally connected in ways that we don’t yet understand, and cellular density is not the only or defining factor in determining cognitive processing power. A study in 2007 undermined the sensitivity of EQ as well, showing that if you leave humans out of the picture, absolute brain size was a better predictor of cognitive ability, and the relative size of the cortex made little difference.

  Just as with so many areas of biology, there is no simple answer to the question of how brains, tools and intelligence are related. We’re dealing with some of the trickiest research areas here: neuroscience is a relatively new field, at least when it comes to gaining a precise understanding of what and how specific brain cells relate to thought or deed; behavioural psychology and ethology are difficult sciences because experiments are hard to do – there are ethical constraints to consider when experimenting on people – and observations in nature are inherently limited.

  Brain size, density, size relative to body mass, number of neurons – all of these factors are important, and none of them appears to be the mythical one thing that sets us apart as intellec
tual maestros. If it sounds like I’m being cynical about these metrics, it’s more that I am critical of an over-reliance on any of them as a smoking gun. Big brains are clearly crucial to behavioural sophistication. But it’s not all down to brains, whichever way we measure them. Evolution occurs according to one’s environmental pressures, and is not in any way a predestined pathway towards the type of complexity that we have developed. Big-brained finned pilot whales, with their densely packed neocortex, will never invent violins, because they don’t have fingers.

  In that sense, part of the answer to the question of how we developed such artisan tool-making skills is luck. Our environment and our evolution meant that manual dexterity and brains in which the sophistication required to make and play a fiddle (a long way down the line) were things that natural selection would favour, nurture and develop. It turns out that there are tools and technology used by dozens of animals, as we shall soon see, but to arrive at the level of dextrous sophistication that is so natural to us was our path alone. It was the co-evolution of minds, brains and hands that drove us to use sticks, knap stones, refine those flakes, and eventually, after long periods of stasis, develop our technological prowess so that we could carve statues, and musical instruments, and weapons that made resources ever-more available. Despite a few animals having similarly complex brains, none has come close to our tool skills for many millions of years.

  1 ‘Imagine if we could access 100 per cent’ is a surfeit-of-gravitas line spoken by a typically august Morgan Freeman in the 2014 film Lucy. Scarlett Johansson is the titular protagonist who pharmacologically gains access to the other 90 per cent, and acquires telepathy, telekinesis, the ability to somehow encounter her Australopithecine namesake, and even witness the Big Bang. It’s dumb-as-bricks scientifically illiterate hooey, and highly recommended for that precise reason.