As human beings, we’re all mammals. Most of us appreciate that at some level. But what does it mean for us to have more in common with a horse and an elephant than we do with a parrot, snake or frog? That’s exactly the question Liam Drew sets out to answer in I, Mammal, one of the latest titles to be released by our friends at Bloomsbury Sigma.

We were delighted to speak to Liam about his own mammalian-ness, and what inspired him to write his book...

It says on the cover of your book that to write I, Mammal you considered yourself “a mammal first, a human second” – how was that?

I’m not sure it was as peculiar as it sounds. It’s funny that it naturally evokes the idea of me sniffing around like a badger or imitating an elephant, but ultimately neither a badger nor an elephant is any more mammalian than I am. 

Focusing on my mammalian-ness was about looking at my human brain, body and behaviour – the whole biological shebang – and asking what do I owe to being a mammal? 

Why did you want to think about being a mammal?

I don’t think people who write about “What makes us human?” get asked this – it’s accepted that that is an intrinsically interesting question.  But nearly all attempts to answer it focus on understanding what makes our species unique, leaving aside all the things that we have in common with other animals.  

For most of my life I’d always been quite happy with that – in terms of personal biological identity, my stream of consciousness had always been the most interesting thing about being me – human language and ingenuity, big brains and nimble hands I saw as definitional.

The mammalian focus began with a painful encounter with a football – struck, very firmly, just below the waist while goalkeeping. This inspired me to write an essay about the strange phenomenon that is the scrotum.  Testicle externalisation is something only mammals have evolved (probably twice) and so writing about this introduced me to mammalian history.  And it also caught the attention of Bloomsbury.

When Bloomsbury got in touch I was in the throes of early parenthood and for me becoming a father had been a kind of biological awakening!  I was mesmerised by the primacy of parenthood – by the psychological hijacking that had transformed me from some guy in his mid-thirties worrying about losing his social life to an incredibly focused care-giver transfixed by his offspring.  I was absolutely enthralled by the intricacy of the biological systems that made a new person: wombs, placentas, mammary glands…

Mammalian things…

Exactly! That seemed to be the theme linking my fascinations. Mammals are named after the mammary gland, but mammalian evolution was associated with many reproductive innovations. And as these characteristics took centre stage in my life, I became very interested in how and why they’d evolved. 

With mammalian-ness being the link between these traits, I wondered if I might produce a book by writing a series of connected essays about all the traits that made a mammal a mammal. A book that would make the case that our mammalian heritage is central to how we live.

I suggested this to Bloomsbury, and they said do it.

And what exactly are these traits that we share with all our mammalian cousins?

To start the project, I wrote out a list of the main distinguishing features of mammals – those mammary glands; hair and warm blood; our particular cerebral cortex; three bones in our middle ears and unique jaw joint; the diaphragm, and so on…. Those were basically my chapter headings, and the exact things that we have in common with other mammals. 

Initially, I just listed the traits and set to writing a chapter about each. But as soon as I started writing, it was clear that these weren’t at-all stand-alone entities. Types of animals don’t evolve by older versions acquiring new traits the way we download apps onto our phones – all these traits were intimately linked in interesting and often surprising ways, so I had to consider the overall animal and make that creature run through the book.  In the last chapter, I try to think about what exactly defines a mammal.

Were there many surprises in researching and writing this book?

There were many. Some small, some large. I loved learning about animals I’d never heard of and their many idiosyncrasies. Also, in trying to grasp why and how traits evolved, I took a pretty historical approach to looking at how current theories arose, and that was often intriguing: the way a single fossil can change everything (like looking at changes in capillary diameters 250 million years ago); learning that Erasmus Darwin, Charles’s grandfather, had made a key contribution to understanding placenta function; and reading about eccentric but insightful experiments, like those that involved dressing lizards in fur coats.

I was also surprised – and very pleased, given the book’s origins – by the way that parenting was a recurring theme. There are various approaches to reproduction.  Put crudely, you can either produce lots and lots of cheap offspring, put very little effort into parental care, and hope that a small fraction of the many make it.  Or you can have far fewer offspring and invest very heavily in each.  Mammals have taken the latter route – even mammals that breed like rabbits, aren’t producing that many young offspring – and so maternal care was elemental to the way mammals evolved.  The effects of this span the emergence of mammalian wombs through to young mammals learning key skills from their parents.  This really resonated with my experience of parenthood.

So, I, Mammal is a book about being human?

Ha! Well, yes and no. No, in the sense that it really is about all that we humans share with the other five-and-a-half thousand species of mammals kicking about this globe. It’s about saying, Wow, you too, Mr Badger, Miss Elephant! This is your history as well. We’ve got a lot in common!

That was a really nice process, and now when I walk through a field, I feel a stronger kinship with the rabbits hopping about its margins.

But, yes, it very much is about being human too, in the sense that I think to fully appreciate who or what we are as a species, it’s essential to grasp this mammalian inheritance. It very much rounds out this conversation about “What is it that makes us human?”

I, Mammal is available to buy now from Bloomsbury Sigma, priced at £15.29.