It is notable that almost all of the examples given above are mammals, and most of them primates. Mammalian brains are generally larger than those of other vertebrates, and also differ by having large forebrains, crammed with structures that relate very specifically to the complex behaviours associated with mammals. As we’ve discussed earlier, size really isn’t everything. I’ve dissected a lot of pig’s brains in my time – a creature that is often considered intelligent and social. Their brains are relatively small, the size of a plum, but encased in inches-thick cranium. If you spend much of your life butting your head up against things, a robust skull is recommended.
A macaw’s brain is about the size of a small walnut, which for a bird is quite big. Birds are a large group of animals, descended directly from theropod dinosaurs, which includes the T. rex, the even more fearsome Giganotosaurus, and the much more birdlike archaeopteryx (researchers consider birds to be avian dinosaurs). We know that like the small mammals, birds massively diversified after the meteorite that landed sixty-six million years ago off the coast of what is now Mexico, and called time on the big dinosaurs. There are maybe 9,000 bird species living today, which is not quite double the number of mammal species. With a group that big, there is an enormous range of diversity: the smallest is the bee hummingbird, which weighs about the same as half a teaspoonful of sugar, and the largest the ostrich (the Madagascan elephant bird was even bigger, a towering ten feet tall and half a tonne in weight, but it went extinct around 1,000 years ago, mostly because we ate them). All birds today are feathered, toothless and lay hard-shelled eggs.
When it comes to cognitive behaviour, our gaze has historically focused on the beasts closest to us, and the ones we are most attracted to. That means we study primates and cetaceans and elephants more than anything else. Recently though, we have turned to the corvids and parrots, and with good reason. Crows, rooks and ravens seem to be leagues ahead of most of their bird brethren when it comes to social skills and tools (raptors seem to have their own very fiery skills, and we’ll come to that below).
New Caledonian crows are the kings and queens of avian technology. They are known to not only use sticks to wheedle grubs out of logs and rotting bark, but to craft these tools themselves. In lab conditions and in the wild, crows will strip a twig, typically four or five inches long, until it is straight and true, and use it to root around to find food. This is an instinctive behaviour – a murder of crows raised in captivity who had never seen it in another group were observed crafting and using these sticks. We also know that hooks are better than spikes. These crows manufacture and use hooked tools to fish out fat grubs, and carry them away on the hooks. In experiments where one tool was placed out of reach but visible, they used a shorter stick to retrieve the grub-fishing stick. Using a tool to carry a second object is almost unheard of in non-human animals, as is using one tool on another (a ‘metatool’). That shows an astonishing level of analogical reasoning which allows them to think a few steps ahead: I know that the long stick can be used to get food; can the short stick be used to get the long one?
Though I mentioned above that there is currently a lack of quantitative assessment of the evolutionary benefits of tool use across the board, a study in 2018 put some useful numbers onto the Caledonian crows. Crows with hooked tools were timed to see how quickly they could retrieve either worms or grubs from a tight hole, or spiders from a wide hole. When they used hooked sticks, they retrieved the bugs up to nine times quicker than when using straight ones. This is not a metric of reproductive success directly, but an efficiency in foraging or hunting for food is just the type of thing which has a very positive effect on mating: you can spend more time foraging, and get more food, all of which make you a healthier and more attractive potential mate.
Hooks are an important technological innovation. Ask any fisherman. Orangutans may fish with their hands, or even with simple straight spears, but a hook captures prey much better than a spike. Maybe this was how Palaeolithic humans first started to hunt fish rather than just forage them. We know of rich early human culture using the fruits of the seashore from the Blombos Cave in south Africa at least 70,000 years ago, which include dozens of remains of the tick-shell sea snail carefully punctured to become beads, possibly for a necklace – probably the earliest examples of jewellery. The coast provides an abundance of edible life, and we were certainly eating sessile sea-foods at that time – that is, ones that are immobile, such as molluscs that can’t swim away. That’s a different buffet from hunting. The very first hooks, at least that we know of, were carved from molluscs in Japan. They’ve been found in the island of Okinawa, carefully ground out of the flat bases of shells from a different sea snail, the trochus, around 23,000 years ago. Of the two examples we have, one is an almost perfectly preserved crescent, with a ground edge that could still slice flesh. Though these are the earliest, and they probably represent a mature technology, they are a significant discovery in charting the development of us: the fish hooks, among other things, show our successful colonisation into island chains, and an ability to hunt from the bounty of the oceans, rather than merely gathering from it.
No one would imagine that the ability to carve a hook from a conical snail shell was encoded in DNA. This is a skill that has to be taught, or learnt, or passed on in a subculture of the broader sweep of the lives of our ancestors. Again, cultural transmission of an idea emerges as a thing that we need in order to explore our evolution. This mode of transmission of ideas isn’t limited to us – as in the case of the sponging dolphins of Shark Bay. Nor is it limited to technology.
The crow’s social cognitive behaviour is even more intriguing. They seem to be capable of not just recognising human faces but being able to distinguish between people who are looking at them, or looking into the distance. It’s a simple experiment: scientists merely approached a murder of crows in Seattle in 2013, either looking straight at them, or not. Like punters in a fighty Saturday night pub, the birds scattered far more quickly if they were being eyeballed. Perhaps this is a recent adaptation to living in cities, in close proximity to humans, who are not always a threat. Fleeing is a costly business – it takes time and effort, energy that could be better used foraging. Pigeons and other birds with lesser cognitive abilities than corvids will just scarper in response to proximity without adjudging the intention of the person approaching. The follow-up experiment with the crows was bizarre. The researchers approached the birds wearing one of two masks. People wearing the first mask walked on by, but those with the second trapped the birds. They were conditioning the crows to recognise one face as a threat and the other as benign. Five years later, they returned to the same locations, still occupied by the same birds, and now younger ones including their offspring. The response to both masks was the same. They appeared to have remembered the threat, and somehow, they may have passed this information on to the younger birds. If these results are correct, we are yet to understand how this transmission of knowledge may work.
Despite these skills, ‘birdbrain’ remains an insult. The origin of this cuss is not known, but we do know it was being used in the US in the first half of the twentieth century, so pre-dates our newfound interest in corvid intellect. It might simply be because birds literally have small brains, or that they’re flighty and twitchy, and chickens can operate for a while after decapitation. Either way, this affront cannot fly any more. The number of neurons required for the complex vocalisations of any songbird, or even the entertaining mimicry of cockatoos or parrots was known to be high, and this posed a conundrum given the overall size of their brains. In 2016, twenty-eight species of birds had their brains anatomised at a scale never before undertaken. A neurological basis for the cognitive abilities of birds was surprisingly straightforward: what the researchers found was that the neurons are just much more densely packed. Corvids and parrots have forebrains that are comparatively the same size as the great apes, and they are crammed with neurons at a density that in some cases is higher than primates. This result may yet account for the curious case of these smart avian dinosaurs. As for the insult birdbrain, quoth the raven, ‘nevermore’.
Now we know that many animals do in fact use tools, the key question has mutated. When thinking about our extreme abilities in technology, so extreme that it has defined our existence from chipping stones to a laptop computer, we should think less about what the tool is, and more about how that skill was acquired. Dolphins will not acquire dexterity, nor will the raven rapping at my chamber door do it with a tool much more sophisticated than a worked stick.
Perhaps it is not the use itself that distinguishes us from them. It is more that we pass on this knowledge and these abilities to craft tools.