In trying to understand what kind of a creature we are, I closely examined our nearest living relatives (the great apes) our nearest extinct relatives (Neanderthals and Homo erectus) looking for clues about how we came to be as we are. I travelled the world to interview all kind of experts, exploring deep dark caves for paintings in Spain and France, archaeological digs in the Republic of Georgia and visited a power couple of paleoanthropologists in North Carolina.

Then I turned my eyes to the future, meeting domestic robots in Berlin and a scientist of ancient DNA a bit further south. I travelled to California to talk with a range of people keen to evolve into the next iteration of human beings, trying to greatly increase our future lifespan. I talked with some science fiction writers with a very long range view of the years ahead. And in each setting with each person I interviewed, they taught me something I had not expected beyond their expertise about humans.

When you take on such a range of scientific subjects you let yourself in for different kind of problem to that of my previous book. You don’t need to worry as much about causing offence (although writing about living people is always tricky) but you have keep up to date on all these topics right up to the moment your book is being printed. Finally you can’t make any more changes and so can stop worrying about getting every fact right.

And despite my initial urge never to write about family again, I didn’t leave that completely behind. Layla, my youngest granddaughter, whose name is in the title of the book, was my companion while I babysat her. From a few-weeks-old tiny  baby, over the five years that it took to do all this traveling and research and interviewing and writing, I watched her grow, and I realised I had in her my own little human laboratory subject, and I took many notes.