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 intellectual 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.