— A Pilgrimage to the Dawn of Evolution
Select Quotes
The Conceit Of Hindsight
‘History doesn’t repeat itself, but it rhymes.’ MARK TWAIN ‘History repeats itself; that’s one of the things that’s wrong with history.’ CLARENCE DARROW History has been described as one damn thing after another. The remark can be seen as a warning against a pair of temptations but, duly warned, I shall cautiously flirt with both. First, the historian is tempted to scour the past for patterns that repeat themselves; or at least, following Mark Twain, to seek reason and rhyme for everything. This appetite for pattern affronts those who insist that, as Mark Twain will also be found to have said, ‘History is usually a random, messy affair’, going nowhere and following no rules. The second connected temptation is the vanity of the present: of seeing the past as aimed at our own time, as though the characters in history’s play had nothing better to do with their lives than foreshadow us. – Page 11
Perhaps, argue some physicists such as the Nobel Prize-winning theorist Steven Weinberg, the fundamental constants of the universe, which at present we treat as independent of one another, will in some Grand Unified fullness of time be understood to have fewer degrees of freedom than we now imagine. Maybe there is only one way for a universe to be. – Page 13
As we wander in imagination through some long-dead epoch, it is humanly natural to reserve a special warmth and curiosity for whichever otherwise ordinary species in that ancient landscape is our ancestor (it is an intriguingly unfamiliar thought that there is always one such species). – Page 18
We can be very sure there really is a single concestor of all surviving life forms on this planet. The evidence is that all that have ever been examined share (exactly in most cases, almost exactly in the rest) the same genetic code; and the genetic code is too detailed, in arbitrary aspects of its complexity, to have been invented twice. – Page 20
If we now were to discover a life form sufficiently alien to have a completely different genetic code, it would be the most exciting biological discovery in my adult lifetime, whether it lives on this planet or another. – Page 20
It is a rather surprising fact that we human pilgrims pass only about 40 rendezvous points in all, before we hit the origin of life itself. – Page 22
The General Prologue
In spite of the fascination of fossils, it is surprising how much we would still know about our evolutionary past without them. If every fossil were magicked away, the comparative study of modern organisms, of how their patterns of resemblances, especially of their genetic sequences, are distributed among species, and of how species are distributed among continents and islands, would still demonstrate, beyond all sane doubt, that our history is evolutionary, and that all living creatures are cousins. – Page 28
If we had fewer or more than ten fingers, we’d recognise a different set of numbers as round.* – Page 29
The Farmer’S Tale
To begin with, hunters of wild animals in open and unowned country might have guarded hunting territories against rival hunters, or guarded the herds themselves while following them about. From there it was a natural progression to herding them; then feeding them, and finally corralling and housing them. I dare say none of these changes would have seemed revolutionary when they happened. – Page 50
Unlike oranges and strawberries, cereal seeds do not ‘want’ to be eaten. Passing through an animal’s digestive tract is no part of their dispersal strategy, as it is of plum and tomato seeds. – Page 57
All Humankind
We seek to prove that if Henry is my ancestor he must be yours too. Imagine, for a moment, the contrary: I am descended from Henry and you are not. For this to be so, your lineage and mine would have to have marched, side by side yet never touching, through 100 million years of evolution to the present, never interbreeding yet ending up at the same evolutionary destination—so alike that your relatives are still capable of interbreeding with mine. This reductio is clearly absurd. – Page 65
Eve’S Tale
All human males have Adam’s Y chromosome (creationists please refrain from deliberate misquotation). – Page 89
Third, Adam and Eve are shifting honorific titles, not names of particular individuals. If, tomorrow, the last member of some outlying tribe were to die, the baton of Adam, or of Eve, could abruptly be thrown forward several thousand years. – Page 90
If their other genes had been traced, they could have had equally emotional ‘reunions’ in hundreds of different sites, all over Africa, Europe and very probably Asia too. – Page 92
Little Foot’S Tale
did our ancestors benefit from the skill of walking on two legs because it freed their hands for carrying food—perhaps back to a mate or children, or to trade favours with other companions, or to keep in a larder for future needs? Incidentally the latter two possibilities may be closer to each other than they appear. The idea (I attribute this inspired way of expressing it to Steven Pinker) is that before the invention of the freezer the best larder for meat was a companion’s belly. How so? The meat itself is no longer available, of course, but the goodwill it buys is safe in long-term storage in a companion’s brain. – Page 148
So, a male who can bring lots of food home might gain a direct reproductive advantage over a rival male who just eats where he finds. Hence the evolution of bipedalism to free the hands for carrying. – Page 149
The Gibbon’S Tale
Different genes are inherited through different routes. The population ancestral to all three species will have been diverse—each gene having many different lineages. It is quite possible for a gene in humans and gorillas to be descended from one lineage, while in chimps it is descended from a more distantly related one. – Page 211
The Howler Monkey’S Tale
All eyes on our planet are set up in such a way as to exploit the wavelengths of electromagnetic radiation in which our local star shines brightest, and which pass through the window of our atmosphere. – Page 227
Rodents And Rabbitkind
Given enough time, will a species of intelligent, cultivated rats emerge? Will rodent historians and scientists eventually organise careful archaeological digs (gnaws?) through the strata of our long-compacted cities, and reconstruct the peculiar and temporarily tragic circumstances that gave ratkind its big break? – Page 279
The Mouse’S Tale
This is the kind of reason why all mammal genomes are approximately the same size as each other—they all need the same toolbox. – Page 283
The Beaver’S Tale
My first book, The Selfish Gene, could equally have been called The Co-operative Gene without a word of the book itself needing to be changed. Indeed, this might have saved some misunderstanding (some of a book’s most vocal critics are content to read the book by title only). Selfishness and cooperation are two sides of a Darwinian coin. Each gene promotes its own selfish welfare, by co-operating with the other genes in the sexually stirred gene pool which is that gene’s environment, to build shared bodies. – Page 285
Anatomical structures have no special status over behavioural ones, where ‘direct’ effects of genes are concerned. Genes are ‘really’ or ‘directly’ responsible only for proteins or other immediate biochemical effects. All other effects, whether on anatomical or behavioural phenotypes, are indirect. But the distinction between direct and indirect is vacuous. What matters in the Darwinian sense is that differences between genes are rendered as differences in phenotypes. It is only differences that natural selection cares about. – Page 287
All intermediate links along the chain are true phenotypes, and any one of them could constitute the phenotypic effect by which a gene is selected: it only has to be ‘visible’ to natural selection, nobody cares whether it is visible to us. There is no such thing as the ‘ultimate’ link in the chain: no final, definitive phenotype. Any consequence of a change in alleles, anywhere in the world, however indirect and however long the chain of causation, is fair game for natural selection, so long as it impinges on the survival of the responsible allele, relative to its rivals. – Page 289
Differences between lakes are influenced by differences between dams, just as differences between dams are influenced by differences between behaviour patterns, which in turn are consequences of differences between genes. – Page 290
After Man: A Zoology of the Future. – Page 293
The Seal’S Tale
The point I am moving towards is that even if australopithecines were much more dimorphic in size than us, our evolution from them may not, after all, have been a move away from polygyny itself. It may just have been a shift in the weapons used for male competition: from sheer size and brute force to economic power and political intimidation. – Page 316
The Duckbill’S Tale
Since Concestor 15, platypuses have had exactly the same time to evolve as the rest of the mammals. There is no reason why either group should be more primitive than the other (primitive, remember, precisely means ‘resembling the ancestor’). – Page 353
sinusoidal – Page 363
But the more important moral of the tale is that even an animal that is genuinely primitive in all respects is primitive for a reason. The ancestral characteristics are good for its way of life, so there is no reason to change. As Professor Arthur Cain of Liverpool University liked to say, an animal is the way it is because it needs to be. – Page 364
Mammal-Like Reptiles
if you measure its direction of movement during any one minute, buffeted by waves and eddies and whirlpools, it will seem to drift west as often as east. You won’t notice any eastward bias unless you sample its position over much longer periods. Yet the eastward bias is real, it is there, and it too deserves an explanation. – Page 388
What picked out this one species and sent it hurtling at high speed in new and strange evolutionary directions: first to become bipedal, then to become brainy, and at some point to lose most of its body hair? Rapid, apparently arbitrary spurts of evolution in quirky directions say one thing to me: sexual selection. – Page 394
For Darwin, peahens choose peacocks simply because, in their eyes, they are pretty. Fisher’s later mathematics put that Darwinian theory on a sounder mathematical footing. For Wallaceans,* peahens choose peacocks not because they are pretty but because their bright feathers are a token of their underlying health and fitness. – Page 397
A fashion for walking bipedally arose, and it arose as suddenly and capriciously as fashions do. It was a gimmick. – Page 402
Those who were especially good at the fashionable new walk would be most likely to attract mates and sire children. But this would be of evolutionary significance only if there was a genetic component to the variation in ability to do ‘the walk’. And this is entirely plausible. We are talking, remember, about a quantitative shift in the amount of time spent doing an existing activity. It is unusual for a quantitative shift in an existing variable not to have a genetic component. – Page 403
And, following the theory that males should make it easy by advertising their quality, males will not hide their mental light under a bony bushel but bring it out into the open. They will dance, sing, sweet-talk, tell jokes, compose music or poetry, play it or recite it, paint cave walls or Sistine chapel ceilings. – Page 405
The human mind, on this view, is a mental peacock’s tail. – Page 405
At every stage around the ring, the birds are sufficiently similar to their immediate neighbours in the ring to interbreed with them. Until, that is, the ends of the continuum are reached, and the ring bites itself in the tail. – Page 455
Yet it is the merest accident that the intermediates all happen to be dead. It is only because of this accident that we can comfortably and easily imagine a huge gulf between our two species—or between any two species, for that matter. – Page 456
Absolutist minds can be a menace. They cause real misery, human misery. This is what I call the tyranny of the discontinuous mind, and it leads me to develop the moral of the Salamander’s Tale. For certain purposes names, and discontinuous categories, are exactly what we need. Indeed, lawyers need them all the time. Children are not allowed to drive; adults are. The law needs to impose a threshold, – Page 457
When we are talking history, even apparently discontinuous modern species like sheep and dogs are linked, via their common ancestor, in unbroken lines of smooth continuity. – Page 463
Plato might find it ironic to learn that it is actually an imperfection—the sporadic ill-fortune of death—that makes the separation of any one species from another possible. – Page 464
The legal mind may find it necessary to impose a barrier between childhood and majority—the stroke of midnight on the eighteenth birthday, or whenever it is. But anyone can see that it is a (necessary for some purposes) fiction. If only more people could see that the same applies to when, say, a developing embryo becomes ‘human’. – Page 466
Nevertheless, perhaps because our brains evolved in a world where most things do fall into discrete categories, and in particular where most of the intermediates between living species are dead, we often feel more comfortable if we can use separate names for things when we talk about them. – Page 467
The diagram illustrates an important fact. The rate of DNA evolution is not always constant, but neither is it obviously correlated with morphological change. – Page 487
The overall rate of genetic change is independent of morphological evolution.* – Page 487
But if survival is a matter of hanging motionless in beds of gently swaying kelp, the standard fish shape can be twisted and kneaded, pulled out in fantastically branched projections whose resemblance to the fronds of brown seaweed is so great that a botanist might be tempted to narrow it down to species (perhaps of the genus Fucus). – Page 495
On the timescale of thousands of years, the lake level may rise and fall like a yo-yo. Now, hold that thought in mind, together with the theory of speciation by geographical isolation. When the Victoria basin dries up from time to time, what will be left? It could be a desert if the drying up were complete. But a partial drying up would leave a scattering of little lakes and pools, representing the deeper depressions in the basin. Any fish trapped in these little lakes would have the perfect opportunity to evolve away from their colleagues in other little lakes and become separate species. – Page 511
There is no drive towards a state of high entropy. – Page 519
Dorsocords have a ventral heart, whereas ventricords have a dorsal heart, pumping blood forward along a main dorsal artery. These and other details suggested in 1820 to the great French zoologist Geoffroy St Hilaire that a vertebrate could be thought of as an arthropod, or an earthworm, turned upside down. After Darwin and the acceptance of evolution, zoologists from time to time suggested that the vertebrate body plan had actually evolved through a worm-like ancestor literally turning upside down. – Page 576
My bet is that Concestor 26 had its main trunk nerve running along the ventral side of the body like any protostome. We are modified worms swimming on our backs, descended from an early equivalent of a brine shrimp which, for some long-forgotten reason, turned over. – Page 583
Second, we tend not to describe people as of mixed race. Instead, we plump for one race or the other. – Page 594
Blackness is not a true genetic dominant like smoothness in peas. But social perception of blackness behaves like a dominant. It is a cultural or memetic dominant. That insightful anthropologist Lionel Tiger has attributed this to a racist ‘contamination metaphor’ within white culture. – Page 595
The fact that the inter-observer correlation remains high, even over a huge spectrum of inter-races, is impressive testimony to something fairly deep-seated in human psychology. If it holds up cross-culturally, it will be reminiscent of the anthropologists’ finding about perception of hue. – Page 596
If all humans were wiped out except for one local race, the great majority of the genetic variation in the human species would be preserved. – Page 598
Positive discrimination in favour of ‘minority’ students on American campuses can fairly, in my opinion, be attacked on the same grounds as apartheid. Both treat people as representative of groups rather than as individuals in their own right. – Page 605
Inter-observer agreement suggests that racial classification is not totally uninformative, but what does it inform about? About no more than the characteristics used by the observers when they agree: things like eye shape and hair curliness—nothing more unless we are given further reasons to believe it. – Page 606
It is plausible that the different conditions have exerted strong selection pressures, particularly on externally visible parts, such as the skin, which bear the brunt of the sun and the cold. It is hard to think of any other species that thrives so well from the tropics to the Arctic, from sea level to the high Andes, from parched deserts to dripping jungles, and through everything in between. – Page 607
All cells in the embryo contain the same genes, so it can’t be their genes that distinguish one cell’s behaviour from another’s. What does distinguish a cell is which of the genes are turned on, which usually is reflected in the gene products—proteins—that it contains. – Page 614
The Hox story shows that animals are not a highly varied, unconnected miscellany of phyla, each with its own fundamental body plan acquired and maintained in lonely isolation. If you forget morphology and look only at the genes, it emerges that all animals are minor variations on a very particular theme. – Page 628
Food caught by one polyp may be used by others, since their gastric cavities are all continuous. – Page 694
The surface layers of the sea are unbroken green prairies, with microscopic single-celled algae in the role of waving grass. The surface is where the food ultimately is, and that is where the grazers, and those that feed on the grazers, and those that in turn feed on them, must be. – Page 696
Selection doesn’t favour a harmonious whole. Instead, harmonious parts nourish in the presence of each other, and the illusion of a harmonious whole emerges. – Page 706
Every cell in the body, after all, is descended from an unbroken line of billions of generations of germ-line cells that have not stopped dividing. – Page 720
Plants import energy from the sun into the biosphere. Animals and fungi, in their different ways, are parasites on the plant world. – Page 737
Deep Green, – Page 750
There are other methods of absolute dating, and new ones are being invented all the time. The beauty of having so many methods is partly that they collectively span such an enormous range of timescales. It is also that they can be used as a cross-check on each other. – Page 771
There is much that we are unsure about in science. Where science scores over alternative world views is that we know our uncertainty, we can often measure its magnitude, and we work optimistically to reduce it. – Page 775
A termite mound has many of the attributes of a single large and voracious organism, with its own anatomy, its own physiology and its own mud-fashioned organs, including an ingenious ventilation and cooling system. The mound itself stays in one place, but it has a myriad mouths and six myriad legs, and these range over a foraging area the size of a football pitch. – Page 781
It becomes quite tricky to draw the line between ‘own’ body and ‘alien’ body in such cases. – Page 786
But it has to be remembered that, owing to the odd circumstances of the Great Historic Rendezvous, bits of our cells are closer to the eubacteria, even if our nuclei are closer to the archaeans. – Page 799
In an imaginative piece of lateral thinking, Philip Pullman, in his epic of childhood fiction His Dark Materials, solves the problem for big animals in a completely unexpected but very biological way. – Page 809
Could there be genuinely persuasive examples of irreducible complexity in nature: complex organisation made of many parts, the loss of any one of which would be fatal to the whole? If so, might this suggest genuine design by a superior intelligence, say from an older and more highly evolved civilisation on another planet? It is possible that an example of such a thing might eventually be discovered. But the bacterial flagellar motor, alas, is not it. – Page 812
Chemically, we are more similar to some bacteria than some bacteria are to other bacteria. At least as a chemist would see it, if you wiped out all life except bacteria, you’d still be left with the greater part of life’s range. – Page 816
Why, the very cells that build you are themselves colonies of bacteria, replaying the same old tricks we bacteria discovered a billion years ago. – Page 824
The origin of life was the origin of true heredity; we might even say the origin of the first gene. By first gene, I hasten to insist, I don’t mean first DNA molecule. Nobody knows whether the first gene was made of DNA, and I bet it wasn’t. By first gene I mean first replicator. A replicator is an entity, for example a molecule, that forms lineages of copies of itself. There will always be errors in copying, so the population will acquire variety. The key to true heredity is that each replicator resembles the one from which it was copied more than it resembles a random member of the population. The origin of the first such replicator was not a probable event, but it only had to happen once. Thereafter, its consequences were automatically self-sustaining and they eventually gave rise, by Darwinian evolution, to all of life. – Page 831
But when a plant dies, its decay, in chemical reactions equivalent to burning all its carbonaceous materials, would use up an amount of oxygen equal to all the oxygen released by that plant during its lifetime. There would therefore be no net gain in atmospheric oxygen, but for one thing. Not all dead plants decay. Some of them are laid down as coal (or equivalents), where they are removed from circulation. – Page 834
What if Z itself is its own abzase? I mean, what if the Z molecule happens to have just the right shape and chemical properties to seize one A and one B, bring them together in the correct orientation, and combine them to make a new Z, just like itself? – Page 844
Each variant catalysed the synthesis of itself, using its preferred variant of one of the ingredients. This raised the possibility of true competition in a population of entities showing true heredity, and an instructively rudimentary form of Darwinian selection. – Page 845
The coded information is subdivided into sub-units small enough to lie below the threshold for an error catastrophe. Each sub-unit is a mini replicator in its own right, and it is small enough for at least one copy to survive in each generation. All the sub-units co-operate in some important larger function, large enough to suffer an error catastrophe if catalysed by a single large chemical rather than being subdivided. – Page 846
You cannot, in detail, forecast the future evolution of any species, except to say that statistically the great majority of species have gone extinct. – Page 866
There are only so many ways to make an eye, and life as we know it may well have found them all. – Page 871
Evolution repeatedly races down the easy corridors, and just occasionally, and unexpectedly, leaps one of the hard barriers. – Page 874
starting situation, there is only a limited number of ways out of the box. So if two reruns of a Kauffman experiment encounter anything like similar selection pressures, developmental constraints will enhance the tendency to arrive at the same solution. You can see how a skilled advocate could deploy these two witnesses in defence of the daring belief that a rerun of evolution would be positively likely to converge on a large-brained biped with two skilled hands, forward-pointing camera eyes and other human features. – Page 881
If nature finds it so easy to evolve the component parts of insecthood separately, it is not all that implausible that the whole collection should evolve twice. – Page 882
The development of weapons, from the stone to the spear through the longbow, the flintlock, musket, rifle, machine gun, shell, atomic bomb, through hydrogen bombs of ever increasing megatonnage, represents progress according to somebody’s value system, even if not yours or mine—otherwise the research and development to produce them would not have been done. – Page 885
We pointed out that the improvements to be seen in an animal arms race are improvements in equipment to survive, not generally improvements in survival itself—and for an interesting reason. – Page 887
Both sides would benefit if such a trades union agreement could be reached. Unfortunately, Darwinian theory knows no route by which this could happen. – Page 887
Arms races, in animal evolution and human technology alike, show themselves not in improved performance but in increased shifting of economic investment away from alternative aspects of life and into servicing the arms race itself. – Page 888
Ultimately, natural selection explains microphones and everything designed too because the designers of microphones are themselves evolved engineers generated by natural selection. Ultimately, design cannot explain anything because there is an inevitable regression to the problem of the origin of the designer. – Page 890
The Wright brothers did not have a blinding flash of inspiration and promptly build a Concorde or a Stealth bomber. They built a creaking, rickety crate that barely lifted off the ground and lurched into a neighbouring field. From Kitty Hawk to Cape Canaveral, every step of the way was built on its predecessors. – Page 890
So, is macrogrowth the sum of lots of small episodes of microgrowth? Yes. But it is also true that the different timescales impose completely different methods of study and habits of thought. Microscopes looking at cells are not appropriate for the study of child development at the whole-body level. And weighing machines and measuring tapes are not suitable for the study of cell multiplication. The two timescales in practice demand radically different methods of study and habits of thought. – Page 893
The language of voltage fluctuations is not useful for discussing how a large computer program, such as Microsoft Excel, works. No sensible person denies that computer programs, however complicated, are entirely executed by temporal and spatial patterns of changes between two voltages. But no sensible person attends to that fact while writing, debugging, or using a large computer program. – Page 895
The universe could so easily have remained lifeless and simple—just physics and chemistry, just the scattered dust of the cosmic explosion that gave birth to time and space. The fact that it did not—the fact that life evolved out of nearly nothing, some 10 billion years after the universe evolved out of literally nothing—is a fact so staggering that I would be mad to attempt words to do it justice. And even that is not the end of the matter. Not only did evolution happen: it eventually led to beings capable of comprehending the process, and even of comprehending the process by which they comprehend it. – Page 906
My objection to supernatural beliefs is precisely that they miserably fail to do justice to the sublime grandeur of the real world. They represent a narrowing-down from reality, an impoverishment of what the real world has to offer. – Page 907