Your first choice is Armand Leroi’s Mutants, which is about a biologist who recounts the lives of people with extreme deformities.

That’s right. Armand Leroi is a biologist at Imperial College, London. And this is a really wonderful book because Leroi takes what could have just been a freak show and turns it into a really amazing experience. He writes about these people as people. He finds wonderful portraits of individuals – for example, some of them are covered in hair and look like wolves – and he tells the story of their lives in quite beautiful prose. He also uses their conditions to talk about the rules of development.

And what does he reveal about those rules?

What is important is that mutants are not random. You don’t get a random range of deformities; they have certain patterns. So you don’t see people developing an eye on their hands, for example. That just doesn’t happen. But it is possible for two eyes to become one. So, why is it that you don’t see eyes developing on hands but you do see two eyes becoming one? And why do Siamese twins form in particular patterns and not others? You don’t see twins joined at the toe.

The reason is that our development follows a pretty tight path. When the genes that are governing our development are mutated, they don’t get disrupted in all that many different ways.

These regularities in disruptions can reveal to you what is going on underneath. This is a tried-and-true method in biology. When people are trying to understand how the brain works, one of the most important things they can do is to study people who have different kinds of psychological disorders. People can lose their ability to use language but not their ability to perceive music, and that starts to show that, actually, there are networks for these different kinds of cognition.

The same thing goes with development. Three biologists won the Nobel Prize in 1995 for studying how fruit flies sometimes develop extra wings or sprout legs on their heads. Those kinds of deformities let them zero in on genes that define a body from head to tail. They studied it in fruit flies – and then, lo and behold, it turns out that we actually have the same genes. They govern our anatomy. When those genes mutate in us, we can end up with extra fingers.  And so again there is a hidden unity under there.

Which he is exploring.

Yes. And he does such a beautiful job of showing that and doing it with poetry. He is able to show the beauty in a birth deformity.

Your next choice is Rebecca Skloot’s Immortal Life of Henrietta Lacks. This is almost a detective story – it’s about the woman who unknowingly helped create the polio vaccine and uncover the secrets of cancer.

Yes. This is a fascinating book on so many different levels. It is really compelling as the story of the author trying to uncover the history of the woman from whom all these cells came.

Who was known as ‘HeLa’.

She had cervical cancer, and samples were taken from her body. Scientists who were trying to culture human cells discovered that her cells could just grow and grow and grow. It had never been seen before.

Why do you think that was?

That is one of the things that I find particularly fascinating. What happened to Henrietta Lacks is that she was infected with human papillomavirus. Now lots of people get infected with this virus. It is very common on people’s skin, for example. A lot of people carry it and don’t even know it; in some cases, it causes a small wart. But if it is spread sexually, women can develop cervical cancer from it. 

And it is amazing what this virus does. We usually think of viruses as infecting cells and making new copies of themselves until the cells explode and die. All the new viruses then go off and kill other cells. But that’s not what all viruses do. I am obsessed with viruses.

I know you have just written a book about them.

For me, part of the fascination with Rebecca’s book is that it is the story about what viruses can do. The papillomavirus infects a cell in the skin or other kinds of lining in the body. But it doesn’t try to kill the cell; it actually does the opposite. It actually produces proteins that link onto the proteins in the cell and speed up its growth and division. Basically, its strategy is: If there are more host cells that are infected with the virus, that means there are more viruses.

The reason most of us can have this type of virus and not be harmed by it is that we are constantly shedding the top layer of our skin.