This morning as I raised the blinds covering our living room windows, I noticed that a spider had built a web that spanned the entirety of the central pane. “Wow, I’ll need to clear that off before this evening so none of the moths that frequent that window will get caught.” As soon as that thought went through my head, I immediately became aware of my faulty reasoning. The fact that the window is such a popular place for moths to come to rest in the evening is quite likely the reason the spider built the web there in the first place.

However even beyond that, what caused me to immediately leap to the defense of the moths? I could just as well have thought to myself “Now there’s one smart spider that will be feasting well this evening; good hunting lad!” Perhaps it was because I have a tendency to cheer for the underdog. Perhaps it was because I have dedicated more of my life to watching moths than to watching spiders. Yet I think at its core, the reason was that just for a moment, my consciousness lept back into the deep ancestral part of my brain – the basal ganglia, the contents of which were formed millennia ago on the African savanna, where the equation “spiders = bad” is inscribed.

When our species was still in its infancy on the plains of Africa, the dangers we faced were quite different than they are today. Spiders, snakes, and the other beasties that could bring sickness or death were deeply imprinted on our minds as things to be feared and hated. Such imprinting runs deep; deep enough that although today when most of us who live in industrialized societies face very little danger from these ancestral enemies they still elicit an instantaneous reaction of revulsion and avoidance in us. Were we more correctly to be afraid of the things that could truly more readily harm us today, spiders would exist alongside us as little noticed as the rest of the myriad other ever-present arthropods that inhabit the world. True instinctive fear would be reserved for those dangerous things all but invisible to us – viruses, diseases, chemicals in our food, water, and air, and the avarice resident in the human heart which has unleashed horror after horror upon the world.

Fortunately, the higher functions of my cerebral cortex quickly took over and I found myself no longer wishing to remove the spider on our window from the web it had taken so long to create. I was able to contemplate its beauty, to examine the spider itself closely and marvel in its intricate structure and marvelous colors, some of which appeared to be translucent under the rays of the morning sun. Finally, I wished it good hunting and went on with my own day.