Your Body - The Fish That Evolved. Dr. Keith Harrison

where we put our food. With so much information passing to the nerves from these sense organs, the processing of this information also takes place in the head. That’s why the brain evolved there. We owe all these fundamental aspects of our body to our invertebrate past.

      Timing

      This book has hardly begun and already I’m talking casually about evolution without having said anything about it. Before we continue the story and describe our time as fish, let’s pause to explore in simple terms the timescales involved and the ideas of science, evolution and natural selection that underpin our understanding of ourselves. We can begin by putting the evolution of life in perspective.

      The Earth is about 4,550,000,000 years old. If we compress the whole of this time into one year, with the Earth forming on 1 January and today being midnight on 31 December, the first microscopic living cells appeared on 1 March, but the ancestral fish – those earliest vertebrates – did not appear until 21 November. It had taken about 750 million years for life to evolve from simpler chemistry, then more than another 3,000 million years (two-thirds of the age of the Earth) for that life to create the complexity of the fish. After that, things changed quickly but it was December before some fish colonised the land. Amphibians appeared on 2 December, followed by reptiles on the 8th. Mammals appeared on the 13th and the dinosaurs died out just after tea on the 26th. Humans did not arrive until this evening, just a few hours ago.

       Chapter Two

       Science, Religion and Rocks

       I n this book, we are going to explore the history of the human body. As everything we shall meet has been discovered by generations of scientists, it is worth taking a minute or two to consider what exactly this thing science is.

      The word ‘science’ is just Latin for ‘knowledge’ but throughout history the way people have decided what they know about the universe hasn’t always been constant. In medieval Europe, scholars would observe the world around them and theorise about why it was the way it was. They would then gather and debate their theories in an attempt to persuade others of their viewpoint. This convention of arguing the way to an agreed explanation eventually went out of fashion to be replaced in the 17th century by the rise of the scientific method.

      The scientific method is an approach to understanding which we can visualise as a triangle. First, we observe the universe (or more usually the part that interests us). Next, we devise a theory to explain what we are seeing – a hypothesis. So far, this does not differ from the old approach but now a new step was added. Instead of arguing about the strengths and weaknesses of the theory, we test it in some way, usually by carrying out a form of experiment. When we view the result of the experiment, we are back at the beginning of the triangle, again making an observation.

       The Scientific Method

      We can go round this triangle as many times at it takes to convince ourselves that we finally understand what is happening, modifying the theory and devising new tests each time.

      The scientific method now predominates in most cultures but it was not a new invention. It was simply an extension of how we live our everyday lives. For example, imagine you are walking down the street and see a fist-sized fuzzy brown ball on the path ahead of you. This is an observation (Step 1). You wonder what it is and speculate it might be a small coconut from the nearby market. You now have a theory: ‘It’s a coconut’ (Step 2). You bend down to examine the ball and you roll it over with your foot. You are now conducting an experiment to test the theory (Step 3). As you observe the result of the experiment (Step 1 again), you are startled to see the ball spring to life and scamper off towards some bushes. Your theory was wrong so you devise a new theory: ‘It’s a small animal’ (Step 2 again) and follow it to see if you can find out more. Whether you know it or not you are using the scientific method. You are a scientist. We all use this technique virtually every day. We can’t find our keys but think we left them in the pocket of the jacket we were wearing last night, so we go to look – observation, theory, test. We are all scientists and always were. Today, people tend to reserve the word science for particular academic activities to which they give technical names – astronomy, geology, chemistry, genetics and dozens more – and they call people who are paid to use the scientific method in their jobs ‘scientists’, but in reality we are all scientists.

      Since the 17th century, the word science has acquired an aura of mystique but this is a misunderstanding. Science is not at all mysterious; it’s just that triangle. Two things make it seem impenetrable. First, the subjects the professionals study are often very complicated (‘How are stars formed?’ ‘What is inside an atom?’ ‘How can continents drift across the surface of a solid Earth?’) and, second, every branch of science has its own technical jargon which means nothing to us and may leave us feeling excluded and threatened.

      When scientists study complicated subjects like star formation, they break the topic down into hundreds of different observations and hundreds of simple theories then test each theory. Sometimes, they need complicated equipment to test their simple theory but ultimately it’s only the technology and the overall subject that are complicated. As for the jargon, virtually every branch of human activity has its own vocabulary. Who can understand what a motor mechanic is talking about or name all the tools used by a carpenter? At least in those cases, other motor mechanics and carpenters stand some chance. Science is such a broad subject (or in truth many broad subjects) that few scientists understand what other scientists are saying even within their own discipline. A biologist studying bird classification and a biologist studying bird physiology may as well come from different planets. Neither will understand the other’s technical terms, and they are both biologists working with the same group of animals. Science should not be seen as a coherent activity with ‘insiders’ and ‘outsiders’. Most professional scientists find out what is happening in most of science from the newspapers and television, just like the rest of us.

      What is not science?

      Some subjects don’t fall into the category of science because they are impossible to fit into the science triangle. For example, our observations of the world may lead us to theorise that there is a higher spiritual power, a god. We therefore have two limbs of the triangle: an observation and a theory to explain it. The problem arises when we try to devise a test. What experiment would test the theory ‘There is a god’? To date no one has ever thought of one. Religion, therefore, is not science.

      It has been argued by some people that science is antagonistic to religion and promotes atheism. This is not true. The results of scientific activity do not, and could not, imply there is no god. That would also require evidence from an experiment. As the old saying goes, ‘Absence of evidence is not evidence of absence.’ Science simply cannot investigate, and hence has nothing to say about, the existence or non-existence of a god. These are matters of faith. A self-professed atheist is just as much a believer as is a bishop. A bishop believes as an act of faith there is a god; an atheist believes as an act of faith there is no god. Science cannot help either of them. Science is necessarily agnostic (from the Greek, ‘without the power of knowing’). The only scientific approach to a god’s existence is to say, ‘I cannot explore that question using the scientific method with any hope of success, therefore I should not try.’ Many scientists believe in a god as an act of faith. There is no contradiction here. Science is only capable of investigating the physical universe, yet scientists are human, and two of the cornerstones of the human condition are our logic and our intuition – parallel approaches in the way we build our view of the universe. Science and religion reflect these two approaches. They can survive and flourish together.