Humanology E-Book

Luke O'Neill

• Herausgeber: Gill Books
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch
• Veröffentlichungsjahr: 2018

Seitenzahl: 432

Beschreibung

Discover the answers to 20 burning questions about life and our amazing existence with Ireland's most exciting scientist, Professor Luke O'Neill.Taking us on an incredible journey across centuries and galaxies, accompanied by his characteristic wit, Professor Luke O'Neill explains how it all began, how it all will end and everything in between. Readers will benefit from Luke's insatiable curiosity for life when they dive into this ultimate journey through life and death.Among many fascinating facts, you'll discover the science behind how we got to be so smart, why sex with a caveman was a good idea, the science of finding love, why we follow religions, and how robots will become part of everyday life. Humanology is a humbling reminder that we're just a small speck in a big universe – so sit back and embrace the adventure.'A man who can explain 4.2 billion years of life on Earth and make me laugh at the same time – sheer genius.' Pat Kenny, Newstalk

Leseprobe

For Marg, Stevie and Sam, who are the answer ... and I don’t even know what the question is.

CONTENTS

Cover

Title Page

Dedication

Introduction

Chapter 1: Welcome O Life! How life got started

Chapter 2: How we got to be so smart and why sex with a caveman was a good idea

Chapter 3: I want you, I want you so bad: the science of finding love

Chapter 4: Sperm meets egg: the science of fertility

Chapter 5: Irish mammies got it right

Chapter 6: I am what I am: the science of gender and sexual orientation

Chapter 7: The God invention

Chapter 8: Here’s a good one: why do we laugh?

Chapter 9: I got the music in me: why do we listen to music?

Chapter 10: Sleep and the daily rhythms of life

Chapter 11: Our desperate relationship with food

Chapter 12: Superhumans real and imagined

Chapter 13: Are the robots coming to save us or enslave us?

Chapter 14: The biggest and most expensive machines ever built

Chapter 15: Will we stop all diseases?

Chapter 16: Why you shouldn’t worry about getting old

Chapter 17: Don’t fear the Reaper: death and beyond

Chapter 18: Defying death

Chapter 19: Will we become extinct?

Chapter 20: Things will only get better

Endnotes

Acknowledgements

Copyright

About the Author

About Gill Books

INTRODUCTION

THE ARTS AND SCIENCES are often seen as different activities, with different kinds of people engaged in them. The arty-farty type has floppy hair, a cool, detached look, and in the good old days before science ruined it, smoked French cigarettes. The science nerd has buckteeth and glasses and is great at hard sums. They often run in different cliques and hold mutual disregard.

And yet, if we look more closely, both artists and scientists are actually at the same game. Why would someone pick up a paintbrush and daub colours onto paper? Equally, why would someone try to understand the inner workings of our brains or immune systems? Well, first off, it might be fun! But more important, these are all attempts to answer the very question that unites the arts and the sciences: What does it mean to be human?

Erwin Schrödinger was someone who spanned the divide. He won the Nobel Prize for physics in 1933 for his work on quantum mechanics, but he also wrote poetry. On a cold February night in 1943 in Dublin, as World War II raged, he gave a public lecture in Trinity College Dublin entitled ‘What is Life?’ – and changed the world for the better. What was he doing there and why was he asking that particular question? He was obliged to give this public lecture in his capacity as Professor in the Dublin Institute for Advanced Studies. The then Taoiseach, Éamon de Valera, had coaxed him to come to Dublin in what was effectively Ireland’s first attempt since independence to engage in scientific research. Schrödinger was curious about the basis for life and what it is to be human (being all too human himself), and brought a physicist’s mind to bear on the topic. When he gave his lecture, our knowledge of what life is was very limited. For example, his lectures predated the discovery of DNA as the material that genes are made of. And we humans, like all life on Earth (that we know of – scientists must always be open-minded), have DNA as the key ingredient. A recipe and ingredient in one. The book that resulted from Schrödinger’s lectures was hugely influential and directly inspired many scientists to embrace the big scientific questions in life, not least Watson and Crick, the co-discoverers of the structure of DNA. This is widely felt to be the biggest scientific advancement of the 20th century, since it helped explain the basis of life itself – the passing of information to the next generation in the form of the double helix. This was mind-blowing when it was discovered and still mind-blowing today.

If we fast forward 75 years to today, our understanding of what life is has advanced hugely, and, given our narcissism as a species, we can also better comprehend what humans are. Schrödinger lit the touch-paper to launch a rocket that continues to soar. That understanding is a testament to the commitment of scientists, whose restless curiosity has driven all this fabulous knowledge forward.

In this book I will tell you all about these advances, starting with the origin of life (we’re coming close to understanding this event that occurred at least 4.2 billion years ago); how we as a species evolved on the plains of Africa some 200,000 years ago, and how we populated the planet; how we find a mate, and how sperm and egg get it on; what makes us straight or gay; what and why we believe; what makes us interesting as a species (our love of humour and music); why we sleep and have a roughly 24-hour rhythm; our unending efforts to find new ways to stop disease; whether we will create superhumans and the huge machines we’ve already built; how and why we age; how we die and possibly can escape death; and our eventual extinction as a species (which, cheerily enough, is inevitable). I will also discuss how the process of discovery is now being enhanced and accelerated by our own inventions – computing, robotics and artificial intelligence, which are bringing many benefits but also concerns.

My goal is to introduce you to how great science can be as a way of understanding life and what it is to be human. This pursuit is the pinnacle of evolution, involving individual and collective analysis and action by humans working for the greater good. Whether you’re arty-farty, nerdy or a mixture of both, embrace your inner scientist and join me on this exciting journey into the origin of life to us and beyond, the biggest mystery of all – humanology.

CHAPTER 1

WELCOME O LIFE! HOW LIFE GOT STARTED

FOR SOME PEOPLE it began with two hippies and a talking snake. For others a giant cosmic egg – or a rainbow serpent shaking the world into life. Some of these might be true, and certainly many millions of people still believe in some of these so-called creation myths. But if you’re scientifically inclined you are compelled to follow the motto of the world’s oldest scientific society, the Royal Society in London, founded by Isaac Newton, Robert Boyle and other scientific luminaries in 1660: ‘Nullius in Verba’, or ‘Take Nobody’s Word for it’. In other words, show me the evidence; otherwise, stop talking. At scientific gatherings, you’re only truly listened to if you have the data to back up what you’re saying. So what does science tell us about that most narcissistic and fundamental of questions – the selfie of all questions: How did life begin on Earth?

To try to answer that question we need everything that science has to throw at a problem – from chemistry to biology to geology and even astrophysics. But we also need modesty. It is a devilishly difficult question to answer. It’s a great puzzle, and science at its best is about solving puzzles. And the truth is there’s an awful lot of science still to be done about everything. We know a lot about a lot of things, but there’s an awful lot still to be found out.

As to how life began, scientists still have no definitive answer to the puzzle of how inanimate matter, effectively rocks and minerals, somehow formed a living organism. How could a lump of clay turn into a living organism? And don’t mention God; that’s for a different kind of book. But there has been great progress and we now have a reasonable understanding of how life began, and of how that life led to us.

A RAINBOW SERPENT, PART OF THE CREATION STORY OF SOME ABORIGINAL PEOPLE OF AUSTRALIA.

Careful dating of rocks tells us that the Earth formed around 4.54 billion years ago1, and the evidence for the first living creature on Earth is from 4.28 billion years ago2. So a vast amount of time separates us from the first cell to arise on Earth: our most important ancestor. Imagine that amount of time for a moment. Imagine how we perceive one year passing. We can grasp 10 years passing. But how about 1,000 years? A hundred thousand years? A million years? Or 4.28 thousand million years? Such time spans are well beyond our comprehension. If humans had appeared at that time (and they didn’t) there would have been around 140,000,000 generations of us since then. This gives us an indication of how long ago it was – there have been 34 generations of humans since the year 1000 AD. This is probably why we were more comfortable with the notion that the Earth is only 6,000 or so years old.

BISHOP JAMES USSHER (1581–1656), ARCHBISHOP OF ARMAGH AND PRIMATE OF ALL IRELAND. USING MAINLY THE BIBLE FOR EVIDENCE, HE ESTABLISHED THE TIME AND DATE OF CREATION AS 6 P.M. ON 22 OCTOBER 4004 BC. NOT A BAD ATTEMPT FOR THE TIME – BUT WRONG.

An Irish bishop, James Ussher, gets credit for the first systematic attempt to age the Earth. In 1650 he went to the library (in those far-off days people used to go to places called libraries to read books), and using the main book he found there, the Bible, figured out that creation began at 6pm on 22 October 4004 BC, and was completed by midnight3. Remarkably fast, and for most people scarcely enough time to eat dinner and binge watch the latest season of Game of Thrones. This date for the creation of the Earth was put into the King James Bible and held to be true until well into the 1800s, because someone clever had figured it out using a book which people believed contained by definition only truth. This seems ludicrous now, but in 1650 this was a good attempt, given what he had at his disposal, his systematic approach to the question at hand, and the fact that science hadn’t really been invented then.

When the idea was first suggested that the Earth was more than a few thousand years old, people were understandably confused and worried. In 1899, the Irish physicist John Joly, who was a pioneer in the effort to age the Earth, calculated that it was 80–100 million years old, based on how salty the oceans are, and assuming that the salt was caused by rocks being dissolved by rain at a certain rate4. Again, this was a reasonable attempt, and probably caused consternation in some circles. Finally, using a method called radiometry, the formation of the Earth was dated to 4.567 billion years ago. Radiometry involves measuring the radioactive state of elements such as lead, calcium and aluminium in minerals containing uranium. These are known to decay at a particular rate, and so how much they have decayed can be used to date rocks. So although impossible for us to grasp we can state with confidence that the Earth formed 4.567 billion years ago.

JOHN JOLY (1857–1933), PROFESSOR OF GEOLOGY AT TRINITY COLLEGE DUBLIN, CALCULATED THAT THE OCEANS WERE 80–100 MILLION YEARS OLD, SUBSTANTIALLY PUSHING BACK THE AGE OF THE EARTH FROM WHAT WAS THEN KNOWN, CAUSING CONSTERNATION IN SOME CIRCLES.

We can also tell from looking at the rocks that date from then that it was a very inhospitable place, where no life could exist. The atmosphere was full of toxic chemicals like hydrogen cyanide. We have to wait hundreds of millions of years for the first agreed evidence of a living organism to appear. No life on Earth for millions of years, just a vast bubbling cauldron, with random chemicals forming and being destroyed and reacting with other chemicals. And then, somehow, all these random chemical reactions, with energy in the form of heat, coming most probably from warm vents at the bottom of the sea, lead us to the first living creature. What has been observed is not the actual creature, however, but a series of tube-like structures that scientists believe is good evidence for living creatures. These have been observed in rocks from Quebec in Canada. It’s as if the Earth was like a giant test tube full of chemicals and gases, with a Bunsen burner in the form of heat coming from the sea floor. There was also electricity sparking in the form of lightning strikes. The lightning strikes and heat in the Earth provided the energy for the water in the ‘tube’ to boil and simmer and allowed the chemicals to hit off each other and react.

What with all the lightning, life therefore effectively began in bad weather, and we get to the first cell. Was the first cell Canadian or Australian, however? The matter isn’t fully resolved, as there is a competing claim that the oldest evidence for life on Earth is seen in rocks in Western Australia which date from the more recent 4.1 billion years ago5. This evidence is in the form of what one of the scientists involved (Mark Harrison) called ‘the gooey remains of biotic life’6. This whole area of science is very much a work in progress, and typifies the scientific process – produce evidence, evaluate and come to a conclusion. Whatever the outcome, the first cell was likely to have been not American (thankfully), but Canadian (who must love that) or Australian.

Whatever it was, it changed everything. If you had gone back in time to look at it you would need a microscope. It is in fact what we now call a bacterium, a single-celled creature. Not like us at all, as we are made up of lots of different types of cells, all of them working together. When looked at down a microscope our cells are quite different from a bacterium, which is actually pretty boring-looking. But 4 billion years ago, boring was good. The bacterium thrived, sucking up nutrients and dividing to make baby bacteria. This was the start of us. The first cell ever. There should have been some great blast of trumpets, or perhaps as Shakespeare wrote when describing the birth of the Welsh wizard Glendower, ‘The front of heaven was full of fiery shapes … The frame and huge foundation of the Earth shaked like a coward … the goats ran from the mountains’. No goats ran from the mountains when the first cell arose, because goats (and possibly mountains) hadn’t been invented.

We define a cell as the unit of life because all living things are made of cells, but another definition is a bag with chemicals inside it that can make copies of itself. So the ‘origin of life’ question then becomes, How did this first cell arise? A microscopic bag had to form, and in that bag there had to be a molecule that could copy itself to make more bags. How on Earth (literally) could this first bag have arisen?

We’re not completely sure of the answer to this question, but we know it must lie in the realm of chemistry and must obey the laws of physics. What happened was that chemistry and physics gave us biology. There must have been chemicals around that would react with each other to form more complex chemicals that in turn would go on to form the first cell, which is after all composed of sets of biochemicals all contained within a bag we call a cell. The formation of the actual bag itself was probably an early event, as that allowed the chemicals to become concentrated inside, which in turn would allow them to react with each other. The bag must have been made of molecules that were insoluble in water, just like the bags that make our cells today are made of fat molecules (also called lipids).

Chemical reactions need proximity – the chemicals that react have to hit off each other and form a product, and this happens when each constituent chemical reaches a certain concentration and is near another chemical. They then react with each other to form a new chemical, usually with the help of catalysts. In the case of the first cell this would have meant a chemical being able to make a copy of itself, which, as we will see, is what DNA can do. Once that happened the new chemical that formed would become sealed inside its own fatty bag and we now have two bags – the first bag having copied itself. And so, off we go, life begins, with each bag dividing to make a new bag. One definition of life therefore is ‘bags of chemicals that can make new bags of highly similar chemicals’. Or perhaps ‘Papa’s Got a Brand New Bag’?

To answer this question in more detail we need to know a little about the chemistry of life. What are living things made of? In the early days of biology, this was a straightforward question to answer, as biologists could break open cells and tissues from living things and, using chemical analysis, find out what they were made of. It starts out quite simply. There are four main types of chemicals that make up all living things. All are equally important for life because they work together and depend on each other, but we usually start with nucleic acids. These are the information molecules of life – DNA is the chemical recipe to make a cell. It can be copied and has the information that tells cells how to make proteins.

Proteins are the second class of life molecule. They are highly sophisticated biochemicals and are the grunts of life; they extract energy from food, catalyse the chemical reactions of life and copy the information in DNA to make another cell. It’s as if life began with a photocopier that could copy documents (the DNA), and then office workers come along in the form of proteins to help this process along.

ONION CELLS. EACH IS A BAG MADE OF FAT THAT CONTAINS CHEMICALS AND HAS THE AMAZING FEATURE OF BEING ABLE TO COPY ITSELF.

The third family is called carbohydrates. Glucose is a typical carbohydrate. We burn these for energy (critical for any machine to do work), and they also go into structures like the collagen that holds our joints together. In our office analogy, the carbs are the lunch the workers eat.

Finally there are the fats – also known as lipids. These turn out to be absolutely crucial for life. They are insoluble in water, and make the membranes that form the little bags that contain everything else. Without these membranes, everything would be too dilute and nothing would happen. This is what defines the room that has the photocopier. The office workers can go there instead of wandering off in all directions – a much more efficient process. And so we get to our definition of life as being a bag full of complex chemicals that can make copies of itself. Or a room with a photocopier in it.

The photocopier for life has been running for at least 3.567 billion years, and has kept going relentlessly until it got to you and me – a very long string of DNA stretching back 3.567 billion years. The only rational purpose we can give to life therefore is the copying of DNA. Cells are the vessel in which this happens, and all of life that we see on Earth is still doing it. By this definition, then, it turns out that we humans are insignificant. We most likely contain only a tiny bit of the total DNA on Earth. And remember, all life on Earth is descended from that single Canadian (or Australian) cell that first copied its DNA. A recent study has shown that humans make up about 0.01% of all life on Earth7. Most of the rest is in plants with the next prominent group being bacteria, which are abundant and occur everywhere. So if that first cell that arose said to all subsequent cells of which it is the ancestor, ‘Go forth and multiply’, meaning ‘Keep copying your DNA’, we are making a tiny contribution. Even worse, we have caused the loss of 83% of wild animals and nearly half of all plants. We therefore shouldn’t be so full of ourselves. This is especially the case when we consider how many other organisms we carry with us in the form of abundant bacteria in our bodies.

The first problem we run into in trying to explain how the first cell arose is that all these chemicals are very fragile. They don’t like things like acid, or heat, or even oxygen. That last one will come as a surprise, as we normally think of oxygen as being essential for life. It is for us, as we use it to extract energy from food. But it’s also very toxic, and cells had to come up with a way to use it. As for heat, look what happens when you boil an egg, which is mainly made of protein. Conditions to make these chemicals therefore had to be just right – not too hot, not too cold. Life had to be like the tale of Goldilocks, except we’re not talking porridge here, we’re talking nucleic acids, proteins, carbohydrates and fats.

A mere 3.567 billion years afterwards, humans performed the first experiment to try and recreate this Goldilocks world8. In the early 1950s, two scientists (Stanley Miller and Harold Urey), using the knowledge of what the early Earth might have been like, set up a piece of apparatus with a glass vessel that held water. They provided an atmosphere that contained ammonia, methane and hydrogen (which are all simple chemicals and would have been in the Earth’s atmosphere at that time), and set up a storm by sending sparks through it with an electrode. They put the vessel over a flame for heat and let the vapour form and recirculate through a condenser to allow it to form water droplets and made sure the whole thing circulated. Their lab must have looked something like Dr Frankenstein’s lab, all sparks and bubbling noises. They let this run for a few days and then came into the lab one morning and, to their amazement, saw a tiny creature crawl out of the vessel. Life had formed! Well, not quite – but what they did observe was almost as astonishing.

They took a sample and found in it amino acids, the building blocks that make up proteins. This said that those early chemical conditions on Earth, although seemingly unpromising, did indeed have the capacity to make organic building blocks for life. The experiment, dubbed the Miller–Urey experiment, became famous, and it was published in the same year as the more famous Watson and Crick paper on DNA being a double helix. The year 1953 can therefore be seen as something of an Annus mirabilis for explaining life. The Miller–Urey experiment established the principle that applying bad weather to a pond with simple gases dissolved in the water could make at least one life molecule. And it’s been repeated using different combinations of chemicals and has become even more impressive.

THE ORIGIN OF LIFE. MILLER AND UREY RECREATED CONDITIONS ON THE PRIMITIVE EARTH IN THE LAB. A SIMPLE MIXTURE OF GAS AND WATER COMBINED WITH HEAT AND ELECTRICAL DISCHARGE (BAD WEATHER) GAVE RISE TO AMINO ACIDS, KEY BUILDING BLOCKS FOR LIFE.

Another important information molecule for life is called RNA. There is evidence that RNA might have come first, ahead of DNA, and this is because RNA holds information like DNA, but can also act like an enzyme to help everything along (think of a robotic office worker who is a photocopier). Researchers set up an experiment similar to that carried out by Miller and Urey9, but this time all they had was hydrogen cyanide, hydrogen sulphide and UV light. That’s it – two gases that were in the early atmosphere, and some sunlight, which was more than abundant. And this was enough. They saw building blocks for RNA molecules. And it got better. These conditions also led to the production of starting materials for proteins. Finally it got better again – they saw building blocks for lipids, the fats that can form the membranous bags to make a cell.

This suggests that a single set of reactions could give rise to most of life’s building blocks simultaneously. So now even in good weather, and with fewer gases, a lot of life’s basic units come together. Mother Earth has made the flour, sugar and eggs. Hydrogen cyanide might be especially important, as the evidence suggests that this was raining down on the Earth for millions of years. We can therefore now envisage that, over the course of millions of years, the conditions on Earth eventually give rise to the ingredients which then self-assemble into the first cell. This then copies DNA, and we now have the first offspring from that cell – thus life on Earth, which leads to us, begins.

This cell even has a name – we call it LUCA. This stands for Last Universal Common Ancestor. Sadly, given the name, LUCA isn’t Italian (unless we find it in rocks in Italy and they predate the Canadian rocks). We need to put statues up to LUCA all over the world. LUCA and the cells that arise from LUCA are single – they didn’t associate with other cells, and were happy to live alone. We still see that today in the form of bacteria. Sometimes, though, they form colonies, and clump together into filaments or mats, but each cell in the colony is identical and hasn’t specialised.

The next big step towards us is for organisms to form that are colonies of cells but with cells showing specialisms. That is the type of organism we are: multicellular, but with cells having special roles. In your body you have cells called neurons in your brain, cells called macrophages in your blood that fight infection and cells in your liver called hepatocytes that help you detoxify alcohol. And remember, all these come from the cell made when a sperm fertilises an egg, which therefore has all the information needed to make all the cell types in your body. How did we get from single-celled life to complex multicellular life?

Well, again science has the answer. For it to happen, however, we need to be very patient. It takes another 2.5 billion years before we see complex multicellular life on Earth. Life that you don’t need a microscope to see. This means it took a lot longer to arise than the time it took for the first cell to arise. The reason for this seems to be due to its being very unlikely. The chemical reactions that gave rise to LUCA are a bit like monkeys typing Shakespeare (also known as the ‘infinite monkey theorem’). It is theoretically possible to put a huge numbers of monkeys in a room each with a typewriter for a certain amount of time and eventually one will type a line of Shakespeare. This appears to be the case with the random chemical reactions needed for the first cell to arise. For multicellular life to arise something very unusual happened: one bacteria went inside another and stayed there. When the host bacteria divided, it too divided. They formed a mutually beneficial alliance. The term for this is ‘endosymbiosis’, a symbiotic relationship that happens because one cell goes inside (hence ‘endo’) another10. This event, however, is likely to fail, because the cell that goes inside is likely to be eaten.

It turns out that a possible reason for this event was oxygen. Bacteria eventually evolved a way to capture the energy in sunlight. These became the first plants, which arose around 3 billion years ago. This in itself is a remarkable achievement. It meant that life on Earth could directly connect with the cosmos, harnessing sunlight, as opposed to depending on chemicals on Earth for energy. Plants also use the sunlight to make sugars, which can be further burned for energy. Life had come up with a way to make a battery. A way to store energy in the form of sugars which could be burnt when needed. A by-product of this process, however, is oxygen, and this is highly toxic, oxidising molecules it encounters and effectively turning Earth into a rust bucket.

However, what if you can use the oxygen to burn food and get even more energy from it? That is what happened, and one of the cells that could perform this clever piece of biochemistry climbed inside one that couldn’t, forming an alliance. This new host cell had a way of creating an environment where oxygen levels are low, because the invader is utilising the oxygen to burn glucose. This provides the organism with energy. The host meanwhile provides a safe haven and nutrients. It’s almost as if the photocopying room that we’ve used as our analogy of a cell is invaded by the generator for the whole factory, providing an abundant source of energy. This gives rise to a very successful arrangement.

We know it’s successful because from then on, a huge number of species evolve that all have this arrangement. These cells are called eukaryotic cells, and we now call the cells that went inside ‘mitochondria’. From this moment on, cell specialisation evolves. Different cells in the colony develop different roles, with some, say, absorbing food, and others digesting it. This division of labour makes for a very efficient creature indeed, which survives and evolves further. The office/factory analogy can again be used here. There are now different departments, each with their own photocopying room (the nucleus), which has the instructions to make a new department (which happens when a cell divides), with each department having a different function. Some are involved in packaging, others in receiving goods and so on. Evolution then continues to have its effect.

It’s important to remember that evolution is a random process, driven by the fact that every time DNA is copied there are minor errors, giving you slightly different cells. The ones that are better suited to the prevailing environment survive – survival of the fittest in Darwinian terms, although the term was coined by Herbert Spencer after reading Darwin’s book On the Origin of Species. In this way, different species begin to form, and we get the abundance of life on Earth emerging relatively quickly. In one remarkable period, only 541 million years ago, most types of animals on Earth appeared over the course of 20–25 million years, in what is called the Cambrian explosion (after the period in which it happened).

ENDOSYMBIOSIS: A KEY EVENT IN THE EVOLUTION OF COMPLEX LIFE ON EARTH, WHEN ONE BACTERIUM CLIMBED INSIDE ANOTHER MORE THAN 1.45 BILLION YEARS AGO AND STAYED THERE.

What all of this means is that the explanation of how life went from LUCA to us involved energy. The generator climbed inside the photocopying room. It was the ability to use oxygen to burn food that allowed for lots of energy to be captured. As Nick Lane said in his book The Vital Question, ‘it is high time energy joined DNA as the driver of evolution’11. In our case, efficient energy production stemming from endosymbiosis resulting from the presence of oxygen was needed for complex multicellular life to evolve, including us. All of this allows for a very pithy definition of life for us – we’re here because of the copying of DNA and oxygen being used for energy. All of this was driven by the random chemical reactions on the early Earth that gave rise to the first cell, and then the bumping of a cell that could use oxygen to burn food into one that couldn’t. The alliance allowed for highly efficient production and use of energy, and this new eukaryotic machine needed the energy to go on to form multicellular organisms that evolve and thrive and give rise to us.

A well-known way to illustrate this is to describe it in terms of a 24-hour day. If all this happened over the course of a single day, then we humans appear at 17 seconds to midnight. Multicellular organisms might have a high energy demand because they have to coordinate the activity of all the cells in the organism, which requires communication, which in most organisms comes in the form of neurons, which are big energy-users. It’s a very far cry from two hippies and a talking snake. But the science behind this narrative is so well supported that it is almost universally accepted as the most likely answer to the question of how life arose on Earth and then got as far as us.

From all of these findings two important questions arise in the minds of scientists. First, Will we find life on other planets, or are we unique in the universe? The former is becoming more and more likely. The amino acid glycine has been found in the cloud of gas surrounding the comet 67P/Churyumov-Gerasimenko, along with other precursor organic molecules and phosphorus12. Planets are being found that are in the Goldilocks zone. At the last count there may be as many as 40 billion of these, all the right size and distance from their suns to allow for the chemistry of life to occur. Forty billion. Like monkeys and Shakespeare.

ENCELADUS: ONE OF SATURN’S MOONS. DID ANOTHER GENESIS HAPPEN HERE?

It is now almost certain that we are not alone. One recent candidate as a place where life might exist or have existed is the moon Enceladus, which orbits Saturn. In a combined NASA/European Space Agency mission, the probe Cassini went there. This spaceship left Earth in 1997 and travelled the 1.272 billion miles to Enceladus, arriving on 1 July 2004. This was a huge achievement. Enceladus is so far away that if you were to get into your car one night and drive upwards at 50 km per hour it would take 3,000 years to get there. You’d better bring a flask of coffee and some sandwiches. To get there as quickly as possible Cassini had to do four slingshots: two around Venus, one around Earth and one around Jupiter.

Astronomers had observed jets of steam breaking through the ice that covers Enceladus and wondered what was in them. Cassini found out, and, strikingly, detected free hydrogen. This is a great source of energy. The kind of energy plants make from sunlight in photosynthesis. The kind of energy mitochondria use to make the energy currency of all cells, a molecule called ATP. This caused a huge amount of excitement, as not only would the building blocks of life be possible, but free energy would also be present to drive everything forward. Free hydrogen is the missing piece to allow the sugar, flour and eggs to form together into a cake – energy. It is the heat for the oven to bake life.

Scientists are therefore more confident than ever that there may have been more than one Genesis, more than one situation where life arose. Yet again we humans are shown to be not particularly special, not the centre of the solar system or the universe, and not even special for being alive as opposed to being inanimate. We don’t know whether we will find intelligent life, but scientists are confident that other living systems will be found which, who knows, might evolve into complex living systems like us, provided the conditions for endosymbiosis prevail.

The second question that arises is, What will happen next? Life will keep evolving on Earth as it has done since it started. That is, unless we destroy life on Earth, which sadly is not as unlikely as it sounds. If we wreck the Earth because of global warming or another kind of catastrophe, some life might survive and keep on evolving. For all life to be destroyed a cosmic event, like a huge asteroid or burst of gamma rays, would probably have to happen. But even then life in some nook or cranny might survive. We ourselves might evolve further if selective pressure for certain traits is evident. If, after all this struggling from the origin of life, life on Earth becomes extinct, it is likely to continue on some other planet in a galaxy far far away.

After all, life is just a bag of chemicals that can copy itself time after time, and if not on Earth then why not somewhere else?

CHAPTER 2

HOW WE GOT TO BE SO SMART AND WHY SEX WITH A CAVEMAN WAS A GOOD IDEA

AS YOU SIT THERE reading this sentence you are living in a body and with a mind very similar to an ancestor that lived some 200,000 years ago. Our species, Homo sapiens sapiens (or ‘wise wise human’ – so wise they named us twice), then lived on the plains of Africa with no smartphones, no obesity, no nuclear weapons, no spaceships or large hadron colliders and no knowledge of DNA. If we took someone from that time to today, we could, with education, make them exactly like you and be well capable of all the things you can do. We could turn them into airline pilots or doctors or politicians. All that’s happened since then is that we’ve used the cleverness that we evolved way back then in all kinds of interesting ways1.

To begin with, we used our special intelligence to anticipate drought, protect our children from dangers, work together to kill a large animal, try to deal with the death of a loved one, and figure out where we were in the pecking order with our fellow tribe members. The key scientific question is: How did we evolve from an ancestral ape akin to a chimpanzee, who couldn’t do lots of the things I’ve listed (or at least not as well as we can) into us?

Of course if you’re a scientologist you might believe that the alien Xenu brought humans to Earth 75 million years ago and put us in volcanoes to emerge later. But science tells us the ancestor of modern humans arose in Africa at least 200,000 years ago and came to Europe 45,000 years ago, and finally to Ireland around 10,000 years ago. How did a species that would have been classified as a third species of chimp (the other two being chimpanzees themselves and the bonobo – the most closely related apes to us) some time before 200,000 years ago, go beyond their ape identity and become us? From bonobo to Bono in 200,000 years.

As ever with this kind of question we must start with DNA. Remember, DNA is the recipe to make all living things. It provides the instructions to make proteins, the grunts of every cell in your body that do all the heavy lifting, from digesting food to making your brain work to defending you from infection. This recipe is written in a chemical code that is made up of building blocks called nucleotides. These are akin to very tiny beads on a string, each nucleotide being a different bead. Somewhat mercifully, there are only four nucleotides, which go by their letter: A, T, C and G. These are strung together to make up your chromosomes – the structures that contain DNA.

WITH JAMES WATSON OUTSIDE THE EAGLE PUB, WHERE HE AND FRANCES CRICK ANNOUNCED THEY HAD DISCOVERED THE SECRET OF LIFE IN 1953.

Incredibly, the total number of beads strung out along the chromosomes in you is 3 billion. That’s an awful lot of beads, and an awful lot of threading, and yet it’s real. But it’s even more wonderful, because DNA is actually made of two separate strings that wrap around each other, twisting into the iconic double helix. This arrangement makes it stable, a bit like a ladder, though twisted around its centre. When Watson and Crick first inferred that 3D shape, from a picture taken of DNA by Rosalind Franklin using something called X-ray crystallography, they couldn’t believe it. Watson said they ran to their local pub (The Eagle in Cambridge) that lunchtime and exclaimed ‘We’ve found the secret of life!’ Why did they exclaim that? Well, if we look at the two strings that wrap around one another we see something quite remarkable. We see that if there is an A bead on one string, it is always pairs with a T bead on the other. They click together a bit like Lego blocks. If there is a C bead on one string there is always a G bead on the other string. These are a bit like the rungs on the ladder that connect the two sides.

AN X-RAY DIFFRACTION IMAGE OF CRYSTALLISED DNA WHICH WAS TAKEN BY RAYMOND GOSLING, A PHD STUDENT WORKING UNDER THE SUPERVISION OF ROSALIND FRANKLIN AT KING’S COLLEGE LONDON. THIS IMAGE LED TO THE ELUCIDATION OF THE DOUBLE HELICAL STRUCTURE OF DNA, CREATING MODERN MOLECULAR BIOLOGY.

ROSALIND FRANKLIN, INSTRUMENTAL IN DISCOVERING THE MOLECULAR STRUCTURE OF DNA.

This suggested to Crick that the way we pass on information to make a new cell involves the two strings unravelling from each other and then a new string being made one bead at a time, each bead clicking into place by bonding with its corresponding bead on the single string. This process is termed DNA replication. Two strands link together into a double helix, then separate when a cell divides. Each separate strand then gets copied – A bringing in T and C bringing in G – to form a new double helix. In a moment they had found the secret of life – how information is passed on to the next generation. The rule of A clicking into T and G clicking into C applies in all forms of life on Earth, and initially arose in the first cell, from which all other cells are descended.

DNA REPLICATION: TWO STRANDS LINK TOGETHER INTO A DOUBLE HELIX, THEN SEPARATE WHEN A CELL DIVIDES. EACH SEPARATE STRAND THEN GETS COPIED – A BRINGING IN T AND C BRINGING IN G – TO FORM A NEW DOUBLE HELIX.

Now once you have the sequence of the beads on the string – the DNA sequence that tells us the order of the A, T, C and G – you have the recipe for life. The sequence instructs the cell to make proteins in a very complex process called translation. Runs of nucleotides make specific proteins – we call these runs genes. The proteins then make you the living creature that you are. The proteins might give you horns on your head or determine whether you’re hairy or make you tall or short.

We can therefore compare different species for how similar they are to each other in terms of their DNA sequence. An Irish molecular biologist called Des Higgins and colleagues came up with a computer program to do just that: to align DNA sequences and compare how similar they are2. His publication on this is the world’s most cited paper in computer science, which means it has been referred to by more scientists than any other publication in that field – no mean feat. It turns out that half of the beads on the string from a banana are in roughly the same sequence as half of the beads on the string from a human. We share half our recipe with bananas. Sadly some of my friends are probably slightly more banana than human. This makes overall sense as bananas have many of the same features we do: they have cells broadly made of the same things, and use similar enzymes to do lots of ‘housekeeping’, like taking out the trash or extracting energy from food.

When we compare ourselves to chimpanzees and bonobos, we are around 95 per cent identical in our DNA recipe, confirming our close shared ancestry3. We had a common ancestor some 2 million years ago, a creature that looked a lot like a chimpanzee. It had offspring and one of those became our ancestor and another became the ancestor of chimps or bonobos4. Gradually over time, a 5 per cent difference in the DNA sequence became apparent. The trouble is we don’t know what is in that 5 per cent that makes us smartphone-using creatures and the chimp not. It might be a recipe for a special brain protein that makes our neurons work better. It might be a recipe to make our vocal cords better at speaking and for a wiring protein in the brain that allows us to process sounds better. We just don’t know.

An interesting experiment (which could actually be done today because of a gene-editing technique called CRISPR) would be to replace the 5 per cent of DNA in a chimp with the 5 per cent of our DNA and see what happens. Would we make a human? Probably not, as what is also important is the amount of ingredients specified by the recipe (which is also built into the DNA sequence), not just the name of the ingredients, and that is also different between chimps and humans. If you make two cakes from the same recipe but put in different amounts of flour, you will end up with two cakes but they will be slightly different, a bit like how we are broadly like chimps but with clear differences. But still, it might give interesting insights. That 5 per cent difference is certainly a part of what makes us human.

It’s easier to describe the actual differences between us and chimps. This is the work of anthropologists, who have studied other apes and compared their behaviour and abilities to ours. What is thought to have happened is that a trait called inventiveness arose in us humans, or at least we became much more inventive than chimps. We began to use tools in all kinds of interesting ways. We also used this inventiveness and capacity for observing and learning to make fire, which gave us a huge advantage, as we could use it to cook food. Cooking means partial digestion, which means more efficient extraction of energy from the food. It was also a way to preserve food (e.g. by smoking it), which would have been useful in times of food scarcity. A human who could do these things was more likely to survive and pass on that trait to his or her offspring, and that trait would then begin to dominate5.

We also learnt to make elaborate tools for cutting or killing animals or defending ourselves. At some point we began to walk upright, and again that gave us an advantage, as it freed our hands to do other things, such as hunt efficiently, and allowed us to observe our environment more effectively6. We also became very social. Again this provided advantages (as it does in other organisms), but in our case it meant we had to figure out where we stood in the pecking order. We became status obsessed, because to get this wrong could be lethal. If you think you’re the alpha male or female and you’re not, the true alpha might kill you or harm you or exclude you. Equally, you had to lord it over a lesser mortal to get more resources. And so status anxiety became a feature which afflicts us to this very day, and explains much of our behaviour, from the type of car we drive to where we live and to the clothes we wear.

All of this happened on the savannahs of Africa. We then begin to move around, most likely in search of food or other resources. We evolve a hungry heart and a curiosity which drives us to move on in search of adventure. This trait of curiosity is why we eventually become so successful and dominant as a species on Earth. It’s why we become scientists. And our inventiveness allows us to use what science discovers to make things that are useful to us, be it to provide power beyond muscle power to make machines to help us, or to find new medicines to treat diseases that ail us. The curiosity probably evolved to make sure we would move to a new place if resources became scarce, or perhaps to help us find a mate and pass on our DNA. Or it could be a consequence of our ability to anticipate what might happen next and to be curious about that, which would give a clear survival advantage.

Other animals display these traits too, but not to the same extent. Other animals will use tools elaborately, but nowhere near as elaborately as us. Chimpanzees, for example, will strip a twig of its leaves and use it as a tool to catch insects. They also use twigs to fish honey from beehives or to extract marrow from the bones of animals they have caught. Or they use bunches of leaves to soak up water for drinking. Gorillas use walking sticks to help them cross deep rivers. So we’re not alone in using tools – it’s just that we have taken their use to a much higher level, giving us a killer advantage over other species.

We’re so clever that we eventually learn to paint pictures on cave walls. This may have first been a way to pass information on to others (‘hunt these animals’) but it was also the beginning of art, which is a way to express ourselves and give us satisfaction. Our smartness might have had artistic ability as a by-product. We paint the animals we hunt. We must see them and then notice that we can put marks on a wall that resemble them and perhaps that makes us feel we can control them. Or perhaps it just made us smile, our smart brains enjoying the pleasure of it.

We certainly begin to wonder about death. We see our children die, or friends die in a fight, or our old relative dies and we don’t like it because we are so attached to them. Other animals grieve when a loved one dies. A male gorilla will wail beside the dead body of his mate. Dolphins will make keening noises after losing a baby dolphin. But we go one step further. We carefully look after our dead, probably for reasons of hygiene, but also because death disturbs us, and we try to control it somehow. Again, this might be a by-product of us being smart.

So the two traits that emerge that begin to define us – artistic activities and ritualistic burial of our dead – become evident. No other animal is as artistic as us, spending as much time as we do in creating or appreciating art. And no other animal goes to the trouble that we do to look after our dead loved ones, burying them with such ritual, marking where we bury them and visiting where their remains lie.

We take these traits with us as we move around the world. This begins around 90,000 years ago. We begin to get restless and we start to move out of Africa7. The evidence of this is very compelling, based on the dating of fossils from human bones. Maybe it happened because of overcrowding. Maybe it happened because of an accident – a tribe wandered over into the Middle East and couldn’t get back. Evidence suggests that only a small number of our ancestors made this journey, and that all Europeans, Asians and Americans are descended from this intrepid group. And when we leave Africa, two interesting things happen. We move into a part of the world where plants are easy to grow: the so-called Fertile Crescent in the Middle East. We notice this initially perhaps when we drop seeds from a plant and see that the same plant grows there. And so we discover agriculture.