The Greatest Show on Earth

The Greatest Show On Earth, The Evidence For Evolution, is a non-fiction science book authored by Richard Dawkins and published by First Free Press in 2009. Richard Dawkins explains evolution in simple words, understandable by everyone who is seeking proof of evolution, or would like to add to his or her knowledge. For those who are not able to read this 470 page book (hard cover), some interesting and valuable excerpts which can be understood independently, are quoted here, beginning with the page reference:

Cover Page- In 2008, a Gallup poll showed that 44 percent of Americans believed God had created man in his present form within the last 10,000 years. In a Pew Forum poll in the same year, 42 percent believed that all life on earth has existed in its present form since the beginning of time.

Pages 24, 25- Take a rabbit, any female rabbit (arbitrarily stick to females, for convenience: it makes no difference to the argument). Place her mother next to her. Now place the grandmother next to the mother and so on back in time, back, back through the megayears, a seemingly endless line of female rabbits, each one sandwiched between her daughter and her mother. We walk along the line of rabbits, backwards in time, examining them carefully like an inspecting general. As we pace the line, we’ll eventually notice that the ancient rabbits we are passing are just a little bit different from the modern rabbits we are used to. But the rate of change will be so slow that we shan’t notice the trend from generation to generation, just as we can’t see the motion of the hour hand on our watches- and just as we can’t see a child growing, we can only see later that she has become a teenager, and later still an adult. An additional reason why is that, in any one century, the variation within the current population will normally be greater than the variation between mothers and daughters. So if we try to discern the movement of the “hour hand” by comparing mothers with daughters, or indeed grandmothers with granddaughters, such differences as we may see will be swamped by the differences among the rabbits’ friends and relations gamboling in the meadows round about.

Page 66- experimental interference is of enormous importance, because without it you can never be sure that a correlation you observe has any causal significance. This can be illustrated by the so-called ‘church clocks fallacy’. The clocks in the towers of two neighbouring churches chime the hours, but St A’s a little before St B’s. A Martian visitor, noting this, might infer that St A’s chime caused St B’s to chime. We, of course, know better, but the only real test of the hypothesis would be experimentally to ring the St A’s chime at random times rather than once per hour. The Martian’s prediction (which would of course be disproved in this case) is that St B’s clock will still chime immediately after St A’s. It is only experimental manipulation that can determine whether an observed correlation truly indicates causation.

Page 81- Let me draw this chapter, and the previous one, to a conclusion. Selection- in the form of artificial selection by human breeders- can turn a pye-dog into a Pekinese, or a wild cabbage into a cauliflower, in a few centuries. The difference between any two breeds of dog gives us a rough idea of the quantity of evolutionary change that can be achieved in less than a millennium. The next question we should ask is, how many millennia do we have available to us in accounting for the whole history of life? If we imagine the sheer quantity of difference that separates a pye-dog from a peke, which took only a few centuries of evolution, how much longer is the time that separates us from the beginning of evolution or, say, from the beginning of the mammals? Or from the time when fish emerged on to the land? The answer is that life began not just centuries ago but tens of millions of centuries ago. The measured age of our planet is about 4.6 billion years, or about 46 million centuries. The time that has elapsed since the common ancestor of all today’s mammals walked the Earth is about two million centuries. A century seems a pretty long time to us. Can you imagine two million centuries, laid end to end? The time that has elapsed since our fish ancestors crawled out of the water on to the land is about three and a half million centuries: that is to say, about twenty thousand times as long as it took to make all the different- really very different- breeds of dogs from the common ancestor that they all share.

Page 92- When we look at a solid lump of iron or rock, we are ‘really’ looking at what is almost entirely empty space. It looks and feels solid and opaque because our sensory systems and brains find it convenient to treat it as solid and opaque. It is convenient for the brain to represent a rock as solid because we can’t walk through it. ‘Solid’ is our way of experiencing things that we can’t walk through or fall through, because of the electromagnetic forces between atoms. ‘Opaque’ is the experience we have when light bounces off the surface of an object, and none of it goes through.

Pages 102, 103- Among all the elements that occur on Earth are 150 stable isotopes and 158 unstable ones, making 308 in all. Of the 158 unstable ones, 121 are either extinct or exist only because they are constantly renewed, like carbon-14 (as we shall see). Now, if we consider the 37 that have not gone extinct, we notice something significant. Every single one of them has a half-life greater than 70 million years. And if we look at the 121 that have gone extinct, every single one of them has a half-life less than 200 million years. Don’t be misled, by the way. Remember we are talking half-life here, not life! [the favoured measure of decay rate is the ‘half-life’- page 95] Think of the fate of an isotope with a half-life of 100 million years. Isotopes whose half-life is less than a tenth or so of the age of the Earth are, for practical purposes, extinct, and don’t exist except under special circumstances. With exceptions that are there for a special reason that we understand, the only isotopes that we find on Earth are those that have a half-life long enough to have survived on a very old planet. Carbon-14 is one of these exceptions, and it is exceptional for an interesting reason, namely that it is being continuously replenished. Carbon-14’s role as a clock therefore needs to be understood in a different way from that of longer-lived isotopes. In particular, what does it mean to zero the clock?

Pages 169,170- the move from water to land launched a major redesign of every aspect of life, from breathing to reproduction: it was a great trek through biological space. Nevertheless, with what seems almost wanton perversity, a good number of thoroughgoing land animals later turned around, abandoned their hard-earned terrestrial retooling, and trooped back into the water again. Seals and sea lions have only gone part-way back. They show us what the intermediates might have been like, on the way to extreme cases such as whales and dugongs. Whales (including the small whales we call dolphins), and dugongs with their close cousins the manatees, ceased to be land creatures altogether and reverted to the full marine habits of their remote ancestors. They don’t even come ashore to breed. They do, however, still breathe air, having never developed anything equivalent to the gills of their earlier marine progenitors. Other animals that have returned from land to water, at least some of the time, are pond snails, water spiders, water beetles, crocodiles, otters, sea snakes, water shrews, Galapagos flightless cormorants, Galapagos marine iguanas, yapoks (aquatic marsupials from South America), platypuses, penguins and turtles.

Page 173- I now want to turn to another group of animals that returned from the land to the water: a particularly intriguing example because some of them later reversed the process and returned to the land a second time! Sea turtles are, in one important respect, less fully given back to the water than whales or dugongs, for they still lay their eggs on beaches. Like all vertebrate returners to the water, turtles haven’t given up breathing air, but in this department some of them go one better than whales. These turtles extract additional oxygen from the water through a pair of chambers at their rear end that are richly supplied with blood vessels. One Australian river turtle, indeed, gets the majority of its oxygen by breathing (as an Australian would not hesitate to say) through its arse.

Page 325,326- If molecular genetic technology continues to expand at its present exponential rate, by the year 2050 deriving the complete sequence of an animal’s genome will be cheap and quick, scarcely any more trouble than taking it s temperature or its blood pressure. Why do I say that genetic technology is expanding exponentially? Could we even measure it? There is a parallel in computer technology called Moore’s Law. Named after Gordon Moore, one of the founders of the Intel computer chip company, it can be expressed in various ways because several measures of computer power are linked to each other. One version of the law states that the number of units that can be packed into an integrated circuit of a given size doubles every eighteen months to two years or so. It is an empirical law, measuring that rather than deriving from some piece of theory, it just turns out to be true when you measure that data. It has held good over a period of about fifty years so far, and many experts think it will do so for at least a few more decades. Other exponential trends, with a similar doubling time, which can be regarded as versions of Moore’s Law, include the increase in speed of computation, and size of memory, per unit cost. Exponential trends always lead to startling results, as Darwin demonstrated when, with the aid of his mathematician son George, he took the elephant as an example of a slow-breeding animal and showed that, in just a few centuries of unrestricted exponential growth, the descendants of just one pair of elephants would carpet the earth. Needless to say population growth of elephants is mot, in practice, exponential. It is limited by competition for food and space, by disease, and by many other things. That, indeed, was Darwin’s whole point, for that is where natural selection steps in.

Page 382- Darwin was well aware of evolutionary arms races, although he didn’t use the phrase. My colleague John Krebs and I published a paper on the subject in 1979, in which we attributed the phrase ‘armament race’ to the British biologist Hugh Cott. Perhaps significantly, Cott published his book, Adaptive Coloration in Animals, in 1940, in the depth of the Second World War:

Before asserting that the deceptive appearance of a grasshopper or butterfly is unnecessarily detailed, we must first ascertain what are the powers of perception and discrimination of the insects’ natural enemies. Not to do so is like asserting that the armour of a battle-cruiser is too heavy, or the range of her guns too great, without inquiring into the nature and effectiveness of the enemy’s armament. The fact is that in the primeval struggle of the jungle, as in the refinements of civilized warfare [footnote: an oxymoron if ever there was one], we see in progress a great evolutionary armament race- whose alertness, armour, spinescence, burrowing habits, nocturnal habits, poisonous secretions, nauseous taste, and procryptic, aposematic, and mimetic coloration; and for offence, in such counter-attributes as speed, surprise, ambush, allurement, visual acuity, claws, teeth, stings, poison fangs, and anticryptic and alluring and alluring coloration. Just as greater speed in the pursued has developed in relation to increased speed in the pursuer; or defensive armour in relation to aggressive weapons; so the perfection of concealing devices has evolved in response to increased powers of perception.

Page 394- As a matter of interest, there are aberrant individuals who cannot feel pain, and they usually come to a bad end. ‘congenital insensitivity to pain with anhidrosis’ (CIPA) is a rare genetic abnormality in which the patient lacks pain receptor cells in the skin (and also – that’s the ‘anhidrosis’ – doesn’t sweat). Admittedly, CIPA patients don’t have a built-in ‘red flag’ system to compensate for the breakdown of the pain system, but you’d think they could be taught to be cognitively aware of the need to avoid bodily damage – a learned red flag system. At all events, CIPA patients succumb to a variety of unpleasant consequences of their inability to feel pain, including burns, breakages, multiple scars, infections, untreated appendicitis and scratches to the eyeballs. More unexpectedly, they also suffer serious damage to their joints because, unlike the rest of us, they don’t shift their posture when they have been sitting or lying in one position for a long time. Some patients set timers to remind themselves to change position frequently during the day.

Page 410 [about genetic signature; DNA]- Of course we cannot rule out the possibility that other machine languages may have arisen in yet other creatures that are now extinct – the equivalent of my harumscaryotes [made up organism]. And the physicist Paul Davies has made the reasonable point that we haven’t actually looked very hard to see if there are any harumscaryotes (he doesn’t use the word, of course) that are not extinct but still lurking in some extreme redoubt of our planet. He admits that it is not very likely, but argues – somewhat along the lines of the man who searches for his keys under a street lamp rather than where he lost them – that it is a lot easier and cheaper to look thoroughly on our planet than to travel to other planets and look there. Meanwhile, I don’t mind recording my private expectation that professor Davies won’t find anything, and that all surviving life forms on this planet use the same machine code and are all descended from a single ancestor.