You don’t have to be particularly intelligent to use tools – many animals do so, including some insects. But it takes a uniquely intelligent animal to be able to combine different tools to solve a problem. We can do it, the great apes can do it, and now the New Caledonian crow joins our exclusive club.

Animals can use tools using little more than pre-programmed behaviour patterns that require little intelligence. But combining tools, or using one tool on another (a metatool, if you will), is a different matter entirely – that takes reasoning. This type of intelligence has been the engine of human innovation. It allowed us to use simple tools to make advanced ones, or to combine different tools