What a Wonderful World

This book came about because I have an exceptional editor – Neil Belton. In fact, I am his stalker. I have pursued him all the way from Jonathan Cape to Faber. Neil has many talents. But one of those talents is that he knows what his authors are good at and what they should be writing better than they do.

My skill is that I can take complex physics and explain it to someone on a number 25 bus (or perhaps I should say someone
unfortunate enough
to be sitting next to me on a number 25 bus). But, in addition to physics, I am also interested in other things. I read a lot of fiction. I am interested in history. I like running. In fact, in 2012, I did the London Marathon (something I rarely fail to mention in the first three minutes of meeting someone).

Neil’s big idea was that I combine these two things: that I use my skill at explaining complex physics in layperson’s terms to explain
everything
in layperson’s terms.

I was daunted. How could I possibly write about everything? Where would I even start? I began thinking about how to
organise
such a wide range of material logically. But I tore up outline after outline. What changed everything, however, was writing
Solar System for iPad
. I had only 9 weeks to write 120 stories about planets, moons, asteroids and comets, so I had no option but simply to dive in and learn to swim on the job. It must have worked because the App won several awards. So that is what I did. I overcame my apprehension and just dived in.

It was a struggle. Usually, when I need to know something about physics, I identify a physicist – it could be a Nobel Prizewinner – and simply phone them. There is a 95 per cent chance they will be able to answer my stupid questions immediately. And, if they cannot, they will at least make an attempt at answering them. But, with subjects I knew nothing about, such as money, sex and the human brain, it was difficult even to identify someone who might be able to answer my incredibly basic questions. And, when I did and phoned them, they were often not able to explain things at the toddler level I needed. Worse, it was sometimes as if we were speaking different languages. Often, I had to go to two, three or four people before I could find someone who could answer all my questions. And, on occasion, I could not find anyone who was able to do that. Instead, I was forced to piece together an explanation from things people I had gone to had said and from things I had read.

But Neil was right. This was the book I should have been writing. It was one that stretched me beyond my comfort zone and that, ultimately, proved to be an exhilarating and a joyful experience. I loved learning about all kinds of things I know nothing about. And I began to appreciate what a wonderful world we live in – one far more incredible than anything we could possibly have invented. Along the way, I learnt many surprising things, such as …

• To understand a single collaterised debt obligation squared – one of the toxic investments that sunk the world economy in 2008 – would require reading
  1 billion pages
  of documentation
  
• Slime moulds have 13 sexes (and you think you have problems finding and keeping a partner)
  
• You could fit the whole human race in the volume of a sugar cube
  
• You are
  ¹
  /
  ₃
  mushroom – that is, you share
  ¹
  /
  ₃
  of your DNA with fungi
  
• You age more slowly on the ground floor of a building than on the top floor
  
• The crucial advantage that humans had over Neanderthals was …
  sewing
  
• IBM once predicted that the global market for computers was …
  five
  
• Today your body will build about 300 billion cells – more than there are stars in our Galaxy (no wonder I get knackered doing nothing)
  
• Believe it or not, the Universe may be a giant hologram.
  You
  may be a hologram
  

If everything in our information-overloaded society has passed you by in a high-speed blur, my book just might bring you quickly and painlessly up to speed on how the world of the twenty-first century works. It is, after all, one man’s attempt to understand everything. No, I cannot really claim that. It’s one man’s attempt to understand everything …
volume one
.

Marcus Chown, London, March 2013

I think I am me. But I am not. I am a galaxy. In fact, I am a thousand galaxies. There are more cells in my body than there are stars in a thousand Milky Ways. And, of all those myriad cells, not a single one knows who I am or cares.
I
am not even writing this. The thought was actually a bunch of brain cells – neurons – sending electrical signals down my spinal cord to another bunch of cells in the muscles of my hand.
1

Everything I do is the result of the coordinated action of untold trillions upon trillions of cells. ‘I like to think my cells work in
my
interest, that each breath they draw for
me
, but perhaps it is
they
who walk through a park in the early morning, sensing my senses, listening to my music, thinking my thoughts,’ wrote American biologist Lewis Thomas.
2

The first step on the road to discovering that each and every one of us is a super-colony of cells was the discovery of the cell itself. Credit for this goes to Dutch linen merchant Antonie van Leeuwenhoek. Aided by a tiny magnifying glass he had adapted from one used to check the fibre density of fabrics, he became the first person in history to
see
a living cell. In a letter published in April 1673 in the
Philosophical Transactions
of the Royal Society of London, van Leeuwenhoek wrote, ‘I have observ’d taking some blood out of my hand that it consists of small round globuls.’

The term ‘cell’ had actually been coined two decades earlier by the English scientist Robert Hooke. In 1655, he had examined
plant tissue and noticed dead compartments stacked together. However, neither he nor van Leeuwenhoek realised that cells are the Lego bricks of life. But that is what they are. A cell is the ‘biological atom’. There is no life – as far as we know –
except cellular life
.

The first evidence of cells comes from fossils about 3.5 billion years old. But there is more tentative evidence, from about 3.8 billion years ago, in the shape of telltale chemical imbalances in rocks that are characteristic of living things. The first cells, known as prokaryotes, were essentially just tiny transparent bags of gloop less than a thousandth of a millimetre across. The bag, by concentrating stuff inside, speeded up key chemical reactions such as those that generate energy. It also protected proteins and other fragile products of those reactions from toxic substances such as acids and salt in the environment. The bag of gloop was an island haven in an ocean of disorder and chaos, a protected micro-universe where order and complexity might safely grow.

The complexity of such cells was in large part due to the proteins – megamolecules assembled from amino-acid building blocks and made of millions of atoms. Depending on their shape and chemical properties, these Swiss-army-knife molecules can carry out a myriad tasks, from speeding up chemical reactions to acting as cellular scaffolding to flexing like coiled springs to power the movement of cells. Even a simple bacterium possesses about four thousand different proteins, though some proteins, such as those needed for reproduction, are assembled, or expressed, only intermittently. The structure of these proteins is encoded by
deoxyribonucleic acid, or DNA, a double-helical molecule floating freely as a loop in the chemical soup, or cytoplasm, inside a cell.

Cellular structure is beautifully intricate. First, there is the bag, or membrane. This is made of fatty acids, molecules that are characterised by having a water-loving end and a water-hating end. When such lipids come together in large numbers – typically a billion – they spontaneously self-assemble into two layers, with their water-hating ends on the interior and their water-loving ends on the outside.

The lipid layers that enclose a cell are not a passive barrier. Far from it. This double skin regulates the molecules coming in and going out of the cell. Imagine the cell as an ancient city surrounded by a wall. In the same way that small creatures such as mice can pass easily back and forth through the city wall, small molecules can pass unhindered in and out of the cell membrane. And, just as bigger creatures such as people are admitted only through gates in a city wall, the passage of big molecules is regulated by ‘gates’ in the cell membrane. For instance, there are proteins shaped like hollow tubes spanning the width of the membrane through which bigger molecules can tunnel into and tunnel out of the cell. And there are transporter proteins whose job is to shuttle bigger molecules physically from one side of the membrane to the other.

The molecules that come in to the cell are those needed for energy and to make proteins and to provide information about the outside world. For instance, an abundance in the surrounding environment of molecules necessary for building new cells might trigger a cell to reproduce.
3
On the other hand, a shortage of water molecules coming across the membrane might warn a cell
that it is in danger of drying out. This might trigger a cascade of chemical reactions inside the cell, ultimately causing a stretch of DNA to be copied repeatedly into molecules called ribonucleic acid, or RNA. These find their way to ribosomes, nanomachines that use the RNA templates to make proteins that might be components of a mucus that will protect the cell from dehydration.
4
Too big to pass through the cell membrane, the proteins flooding out through the cytoplasm in their millions are packaged into membrane sacs, or vesicles, which fuse with the cell membrane. The membrane can then open up, without rupturing and losing its structural integrity, and cast them into the outside world.

But cells, in addition responding to molecules in their environment, also respond to molecules from
other cells
. Even the simplest and most ancient prokaryotes cooperated with each other, which is revealed by fossils of large microbial communities known as stromatolites. Living stromatolites can still be found today – for instance, in shallow tropical waters off the western coast of Australia – but the oldest of these fossil communities is about 3.5 billion years old.

At the same time that a cell makes proteins to protect itself from environmental changes, it might produce proteins that warn others of its kind to do the same. Such chemical signalling is crucial to the survival of simple prokaryotes, which often live in huge colonies known as biofilms, quite possibly the first organised structures to appear on Earth. The cells on the inside of such a biofilm might secrete a sugary protein that sticks their membranes to the membrane of other cells, whereas those on the outside of the film might produce proteins that help protect them from environmental toxins. Some cells will even kill themselves in order to yield up precious nitrogen for the good of their companions.
This kind of cooperation, with cells within a group differentiating to carry out different tasks, is reminiscent of the cells in our bodies. It hints at how such cellular super-cooperation might have got started billions of years ago.

There are limits on the size and complexity of prokaryotes. For one thing, the proteins assembled, or expressed, by their DNA can travel only by drifting slowly, or diffusing, across a cell. Beyond a certain size, a prokaryote is therefore suicidally slow in reacting to environmental dangers. This problem has been solved by rare prokaryotes such as
Thiomargarita namibiensis
, discovered only in 1997. The giant sulphur bacterium, which is about 0.75 millimetres across and easily visible to the naked eye, possesses not one loop of DNA but
thousands
, spread evenly throughout its cytoplasm. This means that proteins expressed by local strands of DNA, even if they diffuse slowly, can still get to all parts of the cell rapidly.

But there is another serious problem that keeps prokaryotes small. The bigger one of them grows the more energy it needs. If it were to use the strategy of
T. namibiensis
, however, an increasing proportion of that energy would be needed for manipulating large quantities of DNA. Since this would be at the expense of any other cellular processes, the road to increased complexity is well and truly blocked.

But there is another way to grow big: take up cannibalism.

About 1.8 billion years ago, a prokaryote swallowed another prokaryote. Prokaryotes actually include bacteria and more exotic archaea bacteria, microorganisms that survive in extreme
environments such as boiling sulphur springs and so were probably among the first life forms on Earth.
5
What actually happened 1.8 billion years ago was that an
archaeobacterium swallowed a bacterium
.

Such an event must have occurred innumerable times before. But, in all cases, the bacterium was either devoured or spat out. This time, for some unknown reason, the bacterium survived. More than that.
It thrived
. There was some mutual benefit for the swallower and swallowee. The latter found a protective environment, safe from the hostile outside world, and the former a new power source.

The evidence that something like this did indeed happen was gathered by the American biologist Lynn Margulis (the first wife of TV astronomer Carl Sagan). And the evidence is still around us today. The energy-generating mitochondria inside the eukaryotic cells of all animals are not only the same size as free-living bacteria but they
look like them too
.
6
Even more striking, they have their own DNA, which is separate and distinct from the DNA of the whole cell, and fashioned into a loop exactly as in prokaryotes.

In fact eukaryotes may have hundreds, or even thousands, of such mitochondria. These are self-contained power stations, furiously reacting hydrogen from food with oxygen to make life’s mobile power packs, adenosine triphosphate, or ATP.
7
‘My mitochondria comprise a very large proportion of me,’ wrote American biologist Lewis Thomas. ‘I suppose there is almost as much of them in sheer dry weight as there is of the rest of me. Looked at this way, I could be taken for a very large, motile colony of respiring bacteria.’
8

With a cell’s mitochondria working semi-autonomously in this way, it is no longer necessary for it to devote so much of its DNA
to the task of generating energy. The DNA is free to encode other things, other protein nanomachinery. Consequently, when cells gained mitochondria 1.8 billion years ago, they were suddenly free to grow a whole lot bigger and more complex.

A large eukaryote compared with a typical prokaryote is like a cat beside a flea. Such a mega-cell might contain hundreds, even thousands, of membrane-enshrouded bags. These organelles divvy up the chores of the cell, functioning as the equivalent of factories, post-office sorting offices and other specialist buildings in a modern-day city.

Lysosomes, for instance, are the garbage-disposal units of the cell. They break down molecules such as proteins into their building blocks so they can be used again. The reason the lettuce in your burger wilts is that heat from the beef breaks down the lysosome membranes of the lettuce cells. This unleashes enzymes, which devour the lettuce. Other organelles include the rough endoplasmic reticulum, which acts like a cellular DHL office. Dotted with ribosomes, it translates RNA arriving from the nucleus into proteins destined for foreign parts beyond the cell. Yet another organelle is the Golgi apparatus, which acts like a packaging centre. It can modify proteins, wrapping them, for instance, in a sugar coating that absorbs water. Such proteins can be used to make the surfaces of blood cells slimy so they can move about more easily.
9

In fact, a eukaryotic cell is less like a single organism than a colony of organisms, each of which long ago lost its ability to survive alone. ‘For the first half of geological time our ancestors were bacteria,’ says Richard Dawkins. ‘Most creatures still are bacteria, and each one of our trillions of cells is a colony of bacteria.’ And all of this has come about by chance. ‘The mitochondrion that
first entered another cell was not thinking about the future benefits of cooperation and integration,’ says Stephen Jay Gould. ‘It was merely trying to make its own living in a tough Darwinian world.’
10

The organelles are subservient to the cell’s nucleus, which contains its DNA and orchestrates pretty much all cellular activity. The English botanist Robert Brown recognised the nucleus as a common feature of complex cells in 1833.
11
Enclosed in a double membrane, the nucleus is reminiscent of a walled castle inside the walled city of the cell. The membrane controls the passage of molecules into the nucleus and the passage of proteins expressed by the DNA out of the nucleus.

The presence of a nucleus is one of the defining features of a eukaryote, along with the presence of a plethora of organelles. A prokaryote has neither a nucleus nor organelles. In fact, the very word
prokaryote
means ‘before kernel, or nucleus’, while
eukaryote
means ‘true nucleus’. Very probably, a nucleus is a necessity in a cell as complex as a eukaryote because of the need to protect the precious DNA from the frenzied activity going on in every corner.
12

In addition to having a nucleus and a large number of organelles, a eukaryote contrasts with a prokaryote in having a cytoskeleton. Proteins such as tubulin form long scaffolding poles that criss-cross the cell. Such microtubules stiffen the soft bag of the cell, giving it a shape. They also anchor organelles to the membrane. This ensures that they are arranged in a similar way in all eukaryotes much as internal organs are arranged in a similar way in all humans. But, in addition to providing internal scaffolding, microtubules act as an internal rail network that can rapidly transport material about the cell. They do this by growing
at one end and disintegrating at the other, so, bizarrely,
it is the track rather than the train that provides the motive power
. Newly made proteins, enclosed in bags, or vesicles, simply hop on a convenient microtubule and are instantly speeded off to a faraway destination within the cell.