Closer to home, chemists are working to understand how the first replicators arose, and how they joined with membranes and metabolism to form the first cells. Such work, coupled with computer simulations of complex molecules, is revealing possible routes to how life began. In the coming decades there is a possibility, though perhaps only a small one, that we will create primitive life in the laboratory.
The science of the spread of life, and of the eventual rise of humans, and the development of civilizations is based on less evidence than most of the other scientific endeavours described in this book. Fossils of our ancestors are rare, and piecing together narratives based on partial skeletons or fragments of ancient DNA is challenging. Technologies that chemically analyse fossils and the surrounding rock and soil have helped date key events, but the scarcity of evidence means the field is subject to change. Human evolution, and early hominin evolution, is a fascinating subject, but it currently involves a lot of speculation. More important archaeological sites will be found, and each will help us understand how our ancestors lived in a little more detail. We are a remarkable species, and understanding of our technological and artistic history will continue to grow. Studies of Neanderthals and other now-extinct hominins will likely provide stronger evidence that two intelligent species have walked the Earth in the last few tens of thousands of years.
In the previous chapter, I considered why we turn out as we do. Understanding how patterns emerge at the level of the population is what scientists tend to do, but robustly explaining why a particular individual turned out as they did requires an understanding of developmental mechanisms that is currently beyond us. We do know that at the level of the population, people who smoke are, on average, more likely to die at an earlier age than those who do not smoke, but that does not mean we can predict when any individual will die. I have occasionally heard people say things like ‘My Uncle Harry smoked all his adult life, and he lived well into his nineties, so smoking can’t be that bad.’ Uncle Harry got lucky. On average, smokers do have shorter lives, but that doesn’t mean they will all die before all non-smokers. Much as we can say that, on average, smokers will die at a younger age than non-smokers, and we can also make statements that extremely traumatic events early in life can impact personalities, it does not mean that all individuals are impacted in the same way or to the same extent. It feels to me as if there were some key events in my life, but I may be simply imposing a subsequent narrative to account for my past behaviour and the decisions I made. Not all twenty-one-year-olds who thought they might die of malaria decided to write an overly ambitious book, so I cannot prove this is what inspired me to take the task on.
At the start of this book, I described a universe rerun experiment to explore whether our existence was inevitable or down to chance. No one other than me really cares whether I would exist in another universe, and you are the only person who will be fascinated by your existence. The question was a little narcissistic, but if you’re still reading, it was a successful hook. The question I was really asking is whether the universe is deterministic or stochastic, and I have concluded it is stochastic. Our existence is down to luck, and that makes us special. Nonetheless, our feeling of being special is probably an evolutionary feature of all sentient life. Two questions naturally arise: is sentient life inevitable in all universes, and how common is it in ours? We know the answer to the first of these questions: if the four fundamental forces had different strengths, then protons, neutrons, atoms, stars and planets could not form, and life as we know it could not evolve. The answer to the second question has not been answered as we are yet to find intelligent life elsewhere. There are billions of galaxies and trillions of stars. Many of these stars will have orbiting planets, and some of these planets will be suitable for life. My conclusion is that life will have emerged on a proportion of these planets, and on some it will have thrived, while on others it will have been killed off by some cosmic catastrophe or other. On those where life persisted for long enough, life would have become complex and sentient beings will have arisen. Some of these sentient beings may have been able to harness energy to build civilizations, and in some of these perhaps an alien author has written a popular science book on their existence. I can’t be certain that has happened, but if it has, they will have uncovered the same forces and principles that I have described. Science finds universal truths, and it will be those truths that unite intelligent life in the cosmos. The universe is sometimes strange, but science has shown it does not work in mysterious ways.
I finish with a plea: for you to embrace science if you have not done so already. Our universe is governed by rules, with science being humanity’s invention to uncover them. The way that science coaxes these rules to show themselves is profound, beautiful and inventive, and through applying scientific approaches to a whole host of problems scientists have come a long way in explaining our existence. There are still many questions that science has not yet answered, and as our understanding increases, new questions will doubtless be posed. Some of the workings of physics, chemistry, earth sciences and biology are still shrouded in mystery, but the progress that has been made over the last three centuries is staggering, and in the coming years much of the mysterious will be explained. The peculiarity of our existence is humanity’s ultimate puzzle to solve, and science has completed quite a bit of the jigsaw of what had to happen for us to be here, but there are many pieces that are yet to be put in place.
I am extraordinarily privileged to be a scientist whose work on investigating how evolution operates has contributed ever so slightly to our understanding of why we exist. I am sure I would have had an enjoyable life if I had become a builder, plumber, electrician, hairdresser or professional cricketer, but if I had my time again, I would still choose to be a scientist. Each day I gaze on our universe with a mix of shock and awe, and revel in being conscious and having an admittedly incomplete and in places blurred simulation playing in my mind as to how I came to be.
In writing this book I did have moments when my lack of faith was tested. I personally don’t think we will ever know why there is something instead of nothing, and that is frustrating, and at times while researching the chapters on life the chasm between relatively simple replicating molecules and the life cycle of humans seemed almost too vast for natural processes to cross, even in 4 billion years. Rationality won the day, and I kept a belief in a deity at bay, but I did conclude that if a god did exist, it would be a scientist. I use ‘it’ because I do not wish to assign form or gender to a deity. It wouldn’t care about me or what I did, but it would want to identify the set of rules required for a universe to produce beings like it. I don’t say this intending to be derogatory or disrespectful of anyone’s personal belief, and I do not wish to raise scientists to an elevated status. I say this because if I could, I would run the replicated universe experiment I detailed at the start of this book, and in creating new universes I would presumably become some sort of deity in those universes that evolved intelligent life. My desire to create universes comes from a thirst for knowledge and a desire to learn more. If a deity was omnipotent and understood everything, why bother creating a universe when the outcome would be known with certainty?