Get your teeth into this

The fox skull with those scary teeth that reader John Severs found on the North York Moors

Following my columns about the urban fox, I was sent a fantastic picture from reader John Severs. It is a photograph of a full fox skull that John found on one of his walks on the North York Moors.

He writes: “I enjoyed your recent article on foxes and I thought you might like to see a photo of a fox’s skull. I found this fox caught on a dry stone wall top near Danby in a running snare, well and truly dead and mummified. Those teeth are really vicious, similar to a shark’s tooth, designed for catching, cutting etc. I wouldn’t like a nip!”

Having looked at the image, I certainly agree. There are two pairs of large canines (the ones that look like fangs) and two sets of sharp incisors at the front of the mouth. They look ferocious and have obviously evolved to enable the fox to be ruthlessly efficient at snatching and despatching live prey.

Having a set of teeth is unique to vertebrates, and our earliest relatives, homo habilis who lived two and a half million or so years ago, had some things in common with the fox, in that they had large, sharp canines and angled incisors that could cope well with a meat-heavy diet. As with the fox, special gaps in the appropriate places in the jaw catered for these enormous teeth enabling the owner to close his or her mouth. The teeth were arranged like a three-sided rectangle around a long, protruding jaw, with a row of sharp incisors at the front between the canines, and two parallel rows of premolars and molars down either side. The molars had large cusps, or bumps, on the grinding surface and only a thin layer of enamel.

As time went on and humans evolved, teeth became smaller and less pointy, we think because our diets changed. With the invention of tools and the development of agriculture, humans began to eat more cereal-based foods which needed a flatter-surfaced tooth more suited to chewing. The shape of the face also evolved, the jaw becoming less protruded, and a more defined chin started to form.

Today our teeth are generally vertical rather than angled, are covered in a thick coating of enamel, and instead of being arranged in a rectangular shape, they curve in a smooth arc around the jaw. Our incisors are small, almost blunt, and are more or less level with the rest of our teeth. As our jaws have shrunk back, many of us only have 28 teeth. However, the remaining four do sometimes try to squeeze in. We call these four molars wisdom teeth, and they are the last to appear, usually during our teens and early 20s. For some they cause no problems, but for others, having four extra teeth trying to force their way into the already packed jaw leads to trouble, and hence they are removed.

It has been suggested that this harks back to the days of homo habilis who had that elongated jaw which easily accommodated all 32 teeth. But now, as our diets have changed so dramatically since then, these extra molars are unnecessary. Dental x-rays reveal that many people don’t have any wisdom teeth at all, while others have them hiding within the gum unseen. If your parents don’t have them, then it is unlikely you will either, and vice versa. It is believed that as we continue to evolve, wisdom teeth will eventually disappear altogether.

And so back to foxes. They are not strictly carnivorous, and do consume seeds, nuts, berries and fruit, although their main diet is worms, bugs, rodents and other small animals. But it is a fact that they are opportunistic hunters, and if soft human food is readily available then they are likely to take that rather than go to the effort of chasing a creature that is running away from them.

As more and more foxes migrate into our towns and cities where food waste is plentiful, it will reduce the need for them to rely on their own skills in catching prey and eating the carcass. So their diet is radically going to change to one where their impressive canines and incisors will not be needed in the same way.

So will their teeth, like the humans, evolve into a set that is not quite so scary to look at?

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This column appeared in the Darlington and Stockton Times on 14th and Ryedale Gazette and Herald on 12th October 2022