VECTORS
Anyone with a veggie patch or a fruit tree knows that insects can be a pest. They can also transmit diseases – mosquitoes, for instance, can carry malaria and encephalitis, among many others. These diabolical disease-carriers are called vectors.
But this story is about a different kind of vector – a happier one that carries not disease but a line from point to point. (The word vector comes from the Latin vehere: to convey.) Surprisingly, insects play a role in this story, too. For insects aren’t just pests. They’re a vital part of the ecological food chain, and they pollinate many of our food crops. Their populations are declining around the world, and in the hope that we can reverse this before it’s too late, these little creatures are finally being recognised for how environmentally important they are. But they’ve also become famous for their brains, and it’s in those tiny brains that this vector story begins.
In carrying out its precious pollinating, an insect buzzes about from flower to flower on a twisting journey in search of food. Yet it always finds its way home again – and remarkably, by the most direct route. In other words, no matter how tortuous its foraging path, it knows how to make a beeline for home. This extraordinary behaviour has been found in a variety of insects – notably bees and ants – and in various birds, animals and even shrimps. But how do they do it?
Astonishingly, they use a neurological form of mathematical vector arithmetic. As they meander along, these navigating creatures keep track of their course by adding vectors of the happier kind – the kind mathematics students learn to represent as an arrow, because mathematical vectors can encode both distance and direction. The arrow points in the required direction, and its length gives the distance.
Humans can do innate navigational maths too, of course. We can even do it in advance, by instinctively visualising the shortest distance between two nearby landmarks – for example, when deciding to take a shortcut across a paddock from point A directly
