Over those millions of years, the dinosaurs discovered how to uproot the biggest trees, strip away the branches and leaves, and tie massive boulders to their ends with rattan. If the boulder was round or square, the tree became a hammer so humongous that it could have flattened one of our cars with a single blow. If the stone was flat, the dinosaurs used it as a megalithic axe. If the stone was pointed, they left intact some of the tree’s upper branches and crafted the trunk into a spear tens of metres long. The branches stabilised the spear during flight, and it flew like a dud missile.

The dinosaurs formed primitive tribes and dwelt in enormous caves they excavated themselves. They learnt to use fire, preserving the embers left by lightning strikes to illuminate their cavernous abodes and to cook food. For candles they co-opted entire pine trees several arm-spans around. They even wrote on the walls of their caves with the charred tree-trunks, recording in simple strokes how many eggs were laid yesterday and how many baby dinosaurs hatched today. More importantly, the dinosaurs already possessed a rudimentary language. To our ears, their conversations would have sounded like the whistling of trains.

At the same time, another species on Earth was showing signs of budding intelligence. Ants. They too had undergone a long process of evolution; in fact, by this point, the scale of ant society far outstripped that of dinosaur society. Ants had raised cities on every continent – some of these took the form of towering ant-hills, others were subterranean labyrinths – and many of their kingdoms had populations exceeding 100 million. These vast societies developed ingenious, tightly organised structures and hummed along to an efficient, systematic rhythm. The ants communicated with each other using pheromones – extremely sophisticated odour molecules that could convey the most detailed information – and this endowed them with a more advanced language than that of the dinosaurs.

However, although the first glimmers of intelligence had appeared in two species on Earth – one great and one small – both species were beset with fatal flaws, and their respective paths to civilisation were strewn with insurmountable obstacles.

The dinosaurs’ biggest disadvantage was that they lacked dexterous hands. Their huge, clumsy claws were matchless in a fight (one type of dinosaur, Deinonychus, had claws as sharp as sabres, which it used to disembowel its rivals) and could fashion crude tools, but they were incapable of performing fiddly tasks, manufacturing sophisticated implements or writing anything complicated. This was problematic because manual dexterity is a prerequisite for the development of civilisation. Only when a species has versatile hands can a virtuous circle form between brain evolution and survival activities.