Hi everyone, so I’m Kyle and I’ve just finished my second year of studying biological natural sciences at Cambridge. I’m making this video today to talk you through one of the interview questions I was asked at my interview a couple of years ago. It is a bit of a bizarre question, it doesn’t really require any hard biological knowledge, but I hope that by talking it through you will come to realize that actually this underpins a lot of biology. So the question is this. Why do we have a heel on our shoe? Now I know it’s a bit of a bizarre question but there are lots of ways to approach it. An artist could say it’s something that’s pleasing to the eyes. A philosopher could argue whether the shoe even exists at all. But as a biologist, I think it is important to argue efficiency, moreover fitness. So according to Darwinian evolution, every trait is optimized to give the maximum lifetime reproductive success. That sounds a little bit jargony but basically means that everything has evolved to be as fit as possible. But how does that apply to shoes? So to consider that we have to think about the walking motion. During stepping, the heel lifts off the floor and to do that the muscles in the leg have to contract. Well, by having a heel on the shoe, the foot is already off the floor slightly so that will minimize the amount of work the muscles have to do to lift the foot up. As a result, over time there’s going to be less strain on the muscles, there’s going to be less need for ATP and altogether you are going to be saving a lot of energy. It might be negligible but over a lifetime that may add up to something a bit more meaningful. The same argument could be used for something like proteins. Why does the protein have 155 amino acids as opposed to 157 if they are both working at the same rate? But it’s efficient for the cell. It’s easier to make a protein of 155 amino acids than of 157. The argument from there could go on. It could talk about how ATP is made or what the implications are of saving so much energy in the muscles. But I’ll be honest, the question confused me at first during my interview and it took me a while to work it out. But the interviewers helped me through. They gave me lots of support and guidance with the question. They are not as scary as you might think. So this really is a question for seeing how you think and how you rationalize your decisions. But I think the main lesson to get from this is what I see as a key interview skill which is to think out loud. They can’t know what’s going on inside your head unless you tell them. And with a question like this there isn’t really a wrong answer. So thank you for watching this video. I really hope it’s been helpful and good luck.