Title: Life Ascending: The Ten Great Inventions of Evolution
Author: Nick Lane
Scope: 4 stars
Readability: 4 stars
My personal rating: 5 stars
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Topic of Book
Comparing evolutionary evolution to technological innovation, Lane identifies the ten most significant “inventions” of evolution by natural selection.
- The process of humans inventing new technologies is not that different from how biological organisms evolve due to natural selection.
- Just as there are a few key technologies that have played transcendent roles in human history can be identified (for example, the domestication of grain, the printing press and the railroad), so can we identify key “inventions” of evolution.
Important Quotes from Book
“This book is about the greatest inventions of evolution, how each one transformed the living world, and how we humans have learned to read this past with an ingenuity that rivals nature herself. It is a celebration of life’s marvellous inventiveness, and of our own. It is, indeed, the long story of how we came to be here”
“The first criterion is that the invention had to revolutionise the living world, and so the planet as a whole.”
“My second criterion is that the invention had to be of surpassing importance today. The best examples are sex and death. ”
“The third criterion is that each invention had to be a direct outcome of evolution by natural selection, rather than, for example, cultural evolution.”
“My final criterion is that the invention had to be iconic in some way.”
Origins of Life:
“by 3,400 million years ago, the signs of life are unequivocal… Bacteria dominated our planet for another 2,500 million years before the first truly complex organisms appeared in the fossil record. ”
“My point is that thermodynamics makes the world go round. If two molecules don’t want to react together, then they won’t be easily persuaded; if they do want to react they will, even if it takes some time to overcome their shyness.”
“Conversely, all life on earth shares common properties: all living things are composed of cells (excluding viruses, which can only operate within cells); all have genes made of DNA; all encode proteins by way of a universal code for particular amino acids. And all living things share a common energy currency, known as ATP”
“This paints an extraordinary portrait of the last common ancestor of all life on earth. If Martin and Russell are right–and I think they are–she was not a free-living cell but a rocky labyrinth of mineral cells, lined with catalytic walls composed of iron, sulphur and nickel, and energised by natural proton gradients. The first life was a porous rock that generated complex molecules and energy, right up to the formation of proteins and DNA itself.”
“DNA, of course, is the stuff of genes, the hereditary material. It codes for human being and amoeba, mushroom and bacterium, everything on this earth bar a few viruses.”
“Prise the strands apart and each acts as a template to reform the other, forging two identical double helices where once there was one. Every time an organism reproduces, it passes a copy of its DNA to its offspring. All it needs to do is pull the two strands apart to produce two identical copies of the original.
While the detailed molecular mechanics could give anybody a headache, the principle itself is beautifully, breathtakingly, simple. The genetic code is a succession of letters (more technically ‘bases’). There are only four letters in the DNA alphabet–A, T, G and C. ”
“Constrained by their shape and bond structure, A can only ever pair with T, and C with G (see Fig. 2.1). Prise the double helix apart, and each strand bristles with unpaired letters. For every exposed A, only a T can bind; for every C, a G; and so on. These base pairs don’t just complement each other, they really want to bind to each other. ”
“This is true chemistry: an authentic ‘basic attraction’. So DNA is not merely a passive template; each strand exerts a sort of magnetism for its alter ego. Pull the strands apart and they will spontaneously coalesce together again, or, if they’re kept apart, each strand is a template with an urgent tug for its perfect partner.”
“Even in DNA, though, errors build up, if only because the genome is so very big. Such errors are called point mutations, in which one letter is substituted for another by mistake.”
“Natural selection, by casting away all but the least of these monsters, is actually a force for stability. DNA morphs and twists, selection straightens.”
“Oxygen is the key to planetary life. No more than a waste product of photosynthesis, oxygen really is the molecule that makes a world. It is let loose by photosynthesis so fast that it finally overwhelms the capacity of a planet to swallow it up. In the end, all the dust and all the iron in the rocks, all the sulphur in the seas and methane in the air, anything that can be oxidised is oxidised, and free oxygen pours into the air and the oceans. Once there, oxygen puts a stop to the loss of water from the planet. Hydrogen, when released from water, inevitably bumps into more oxygen before it finds its way out into space. Swiftly it reacts to form water again”
“Oxygen doesn’t just rescue a planet’s life: it energises all life, and makes it big. Bacteria can do perfectly well without oxygen: they have an unparalleled skill at electrochemistry, they are able to react together virtually all molecules to glean a little energy. But the sum total of energy that can be derived from fermentation, or by reacting two molecules like methane and sulphate together, is negligible in comparison with the power of oxygen respiration–literally the burning up of food with oxygen, oxidising it fully to carbon dioxide and water vapour. Nothing else can provide the energy needed to fuel the demands of multicellular life.”
“So oxygen makes large organisms not just feasible but also probable.”
“So without oxygen there would be no large animals or plants, no predation, no blue sky, perhaps no oceans, probably nothing but dust and bacteria. Oxygen is without a doubt the most precious waste imaginable. Yet not only is it a waste product, it is also an unlikely one. It is quite feasible that photosynthesis could have evolved here on earth, or Mars, or anywhere else in the universe, without ever producing any free oxygen at all. That would almost certainly consign any life to a bacterial level of complexity, leaving us alone as sentient beings in a universe of bacteria.
One reason why oxygen might never have accumulated in the air is respiration. Photosynthesis and respiration are equal and opposite processes. In a nutshell, photosynthesis makes organic molecules from two simple molecules, carbon dioxide and water, using sunlight to provide the energy needed. Respiration does exactly the opposite. When we burn organic molecules (food) we release carbon dioxide and water back into the air; and the energy released is what powers our lives. All our energy is a beam of sunlight set free from its captive state in food.”
“Respiration burns all the organic molecules put away by plants: on a geological timeframe, plants disappear in a puff of smoke. This has one profound consequence. All the oxygen put in the air by photosynthesis is taken out again by respiration. There is a long-term, unchanging, never-ending equilibrium, the kiss of death for any planet. The only way that a planet can gain an oxygen atmosphere–the only way it can escape the dusty red fate of Mars–is if a little plant matter is preserved intact, immune to the elements and to life’s ingenuity in finding ways of breaking it down for energy. It must be buried.
And so it is. Preserved plant matter is buried as coal, oil, natural gas, soot, charcoal or dust, in rocks deep in the bowels of the earth. According to the ground-breaking geochemist Robert Berner, recently retired from Yale, there is around 26,000 times more ‘dead’ organic carbon trapped in the earth’s crust than in the entire living biosphere.”
“Once misnamed, poetically, the ‘blue-green algae’, the cyanobacteria are the only known group of bacteria that can split water via the ‘oxygenic’ form of photosynthesis. Exactly how some of their number came to live within a larger host cell is a mystery wrapped in the shrouds of deep geological time. It undoubtedly happened more than 1,000 million years ago, but presumably they were simply engulfed one day, survived digestion (not uncommon), and ultimately proved useful to their host cell. The host, impregnated with cyanobacteria, went on to found two great empires, the algae and the plants”
“In the beginning there was a single photosystem, which probably used sunlight to extract electrons from hydrogen sulphide, and thrust them on to carbon dioxide to form sugars. At some point the gene became duplicated, perhaps in an ancestor of cyanobacteria. The two photosystems diverged under different usage. Photosystem I carried on doing exactly what it had done before, while Photosystem II became specialised to generate ATP from sunlight by way of an electron circuit. The two photosystems were switched on and off according to the environment, but the pair were never switched on at the same time. Over time, however, Photosystem II has a problem, resulting from the properties of a circuit of electrons–any extra input of electrons from the environment jams up the circuit. It’s likely there was a constant slow input of electrons from manganese atoms, used by bacteria to protect against ultraviolet radiation. One solution was to inactivate the switch, enabling both photosystems at once. Electrons would then flow from manganese, through both photosystems, to carbon dioxide, via a complex pathway that foreshadows the convoluted Z scheme in every eccentric detail.”
“This little cluster of manganese atoms opened up a new world, not only for the bacteria that first trapped it, but for all life on our planet. Once it formed, this little cluster of atoms started to split water, the four oxidised manganese atoms combining their natural avidity to yank electrons from water, thereby releasing oxygen as waste. Stimulated by the steady oxidation of manganese by ultraviolet radiation, the splitting of water would have been slow at first. But as soon as the cluster became coupled to chlorophyll, electrons would have started to flow. Getting faster as chlorophyll became adapted to its task, water was sucked in, split open, its electrons drawn out, oxygen discarded. Once a trickle, ultimately a flood, this life-giving flow of electrons from water is behind all the exuberance of life on earth. We must thank it twice–once for being the ultimate source of all our food, and then again for all the oxygen we need to burn up that food to stay alive.”
The Complex Cell:
“On just one occasion a complex cell arose from bacteria, and the progeny of this cell went on to found all the great kingdoms of complex life: the plants, animals, fungi and algae. And that progenitor cell, the ancestor of all complex life, is very different from a bacterium.”
“The gulf between bacteria and everything else is a matter of organisation at the level of cells. In terms of their morphology at least–their shape, size and contents–bacteria are simple. Their shape is usually plain, spheres or rods being most common. This shape is supported by a rigid cell wall around the outside of the cell. Inside there is little else to see,”
“In behaviour, eukaryotic cells are equally arresting, and again utterly different from bacteria. With a few fiddling exceptions, so to speak, practically all eukaryotes have sex: they generate sex cells like the sperm and egg, which fuse together to form a hybrid cell with half the genes of the father, and half of the mother”
“The difference is illustrated forcibly by history. For the first 3,000 million years or so of life on earth (from 4,000 to 1,000 million years ago), bacteria dominated. They changed their world utterly, yet barely changed themselves. The environmental changes brought about by bacteria were awesome, on a scale that even we humans find hard to conceive. All the oxygen in the air, for example, derives from photosynthesis, and early on from cyanobacteria alone. The ‘great oxidation event’, when the air and sunlit surface oceans became flooded with oxygen, around 2,200 million years ago, transfigured our planet forever; but the shift didn’t make much of an impression on bacteria. There was merely a shift in ecology, towards the kind of bacteria that like oxygen”
“Nothing is more conservative than a bacterium.”
[Cambrian Explosion] “The technical term for such an explosion is a ‘radiation’, in which one particular form suddenly takes off, for whatever reason, and embarks on a short period of unbridled evolution. Inventive new forms radiate out from the ancestral form like the spokes on a wheel. While the Cambrian explosion is the best known, there are many other examples: the colonisation of the land, the rise of flowering plants, the spread of grasses, or the diversification of mammals, to mention but a few. These events tend to occur when genetic promise comes face to face with environmental opportunity, as in the wake of a mass extinction. But regardless of the reason, such magnificent radiations are uniquely eukaryotic. Each time, only eukaryotic organisms flourished; bacteria, as ever, remained bacteria. One is forced to conclude that human intelligence, consciousness, all the properties that we hold so dear and seek elsewhere in the universe, simply could not arise in bacteria: on earth, at least, they are uniquely eukaryotic traits.”
“So much for the inevitability of complex life on earth or of human consciousness. The world is split in two. There are the eternal prokaryotes and the kaleidoscopic eukaryotes. The transition from one to the other seems not to have been a gradual evolution.”
“Only a rare and fortuitous event, a collaboration between two prokaryotes, one somehow getting inside the other, broke the deadlock. An accident. The new chimeric cell faced a host of problems, but one great freedom: the liberty to expand in size without incurring a crippling energetic penalty, the freedom to become a phagocyte and break out of the bacterial loop.”
“All in all, the odds seem massively loaded against sex as a mode of reproduction. An inventive biologist may conceive of peculiar circumstances in which sex could prove beneficial, but most of us, on the face of it, would feel compelled to dismiss sex as an outlandish curiosity. It suffers a notorious twofold cost compared with virgin birth; it propagates selfish genetic parasites that can cripple whole genomes; it places a burden on finding a mate; it transmits the most horrible venereal diseases; and it systematically demolishes all the most successful gene combinations.
And yet despite all that, sex is tantalisingly close to universal among all forms of complex life. Virtually all eukaryotic organisms indulge in sex at some point in their lifecycle, and the large majority of plants and animals are obligately sexual, which is to say that we can only reproduce ourselves by sex.”
“If sex is an occupational folly, an existential absurdity, then not having sex is even worse, for it leads in most cases to extinction, a non-existential absurdity.”
“Recombination is the real heart of sex. ”
“It’s plain, then, what sex does: it juggles genes into new combinations, combinations that may never have existed before. It does so systematically, across the entire genome. ”
“Let’s assume that two beneficial mutations arise in a population reproducing clonally. How would they spread?… Crucially, no individual could benefit from both mutations at once”
“Sexual reproduction, in contrast, is able to bring together both mutations in a single moment of transcendence. The benefit of sex, then, said Fisher, is that new mutations can be brought together in the same individual almost immediately, giving natural selection the chance to test their combined fitness.”
“Sex, then, benefits populations by bringing together favourable combinations of genes, and by eliminating unfavourable combinations.”
“The great advantage of sex is that it allows good genes to recombine away from the junk residing in their genetic backgrounds, while at once preserving a great deal of the hidden genetic variability in populations.”
“Sex works out better than cloning (despite the twofold cost) under almost any circumstances. The difference is greatest when the population is highly variable, the mutation rate is high, and the selection pressure strong–an unholy trinity that makes the theory conspicuously relevant to the origin of sex itself.”
“The only way to forge a chromosome that doesn’t kill you, the only way to bring the best innovations and genes together in a single cell, is by sex. Total sex. Not a little half-hearted gene swapping. Only sex can bring together a nuclear membrane from one cell with a dynamic cell skeleton from another, or a protein-targeting mechanism from yet another, and at the same time eliminate all the failures. The randomising power of meiosis might throw up only one winner in a thousand (survivor is a more fitting term) but it’s far, far better than cloning.”
“Without sex, we eukaryotes would never have existed at all.”
“Natural selection isn’t about ‘the survival of the fittest’, for survival counts for nothing if the fit fail to reproduce. Sex grants a huge head start to cloning, but has prevailed among almost all eukaryotes. The advantage that sex offered at the beginning was probably no different from today–the ability to bring together the best combinations of genes in the same individual, to purge detrimental mutations, and to incorporate any valuable innovations.”
“Rather than a gradual accrual of complexity over time, it seems there was a sudden gearshift after the great Permian extinction. Before the extinction, for some 300 million years, marine ecosystems had been split roughly fifty-fifty between the simple and complex; afterwards, complex systems outweighed simple ones by three to one, a stable and persistent change that has lasted another 250 million years to this day. ”
“The answer is the spread of motile organisms. The shift took the oceans from a world that was largely anchored to the spot–lampshells, sea lilies, and so on, filtering food for a meagre low-energy living–to a new, more active world, dominated by animals that move around, even if as inchingly as snails, urchins and crabs. Plenty of animals moved around before the extinction, of course, but only afterwards did they become dominant.”
“So motility brings with it a need to deal with rapidly changing environments, more interactions between plants and other animals, new lifestyles like predation, and more complex ecosystems. All these factors encouraged the development of better senses (better ways of ‘sampling’ the surrounding world) and a faster pace of evolution, simply to keep up, not just among animals, but among many plants too. At the heart of all this innovation is a single invention, which made it all possible: muscle. ”
“We find that 95 per cent of all animal species have eyes: the handful of phyla that did invent eyes utterly dominates animal life today.”
“The evolution of proper eyes, capable of spatial vision rather than simply detecting the presence or absence of light, gives every appearance of having transformed evolution. The first true eyes appeared somewhat abruptly in the fossil record around 540 million years ago, close to the beginning of that ‘big bang’ of evolution, the so-called Cambrian explosion”
“The close correspondence in time between the explosion of animal life in the fossil record and the invention of eyes was almost certainly no coincidence, for spatial vision must have placed predators and prey on an entirely different footing; this alone could, and perhaps did, account for the predilection for heavy armour among Cambrian animals, and the much greater likelihood of fossilisation. ”
“The immediate impetus for the evolution of large animals was most likely rising levels of oxygen in the air and sea. Large size and predation are only possible in high oxygen levels (nothing else can provide the energy necessary; see Chapter 3) and oxygen rose swiftly to modern levels shortly before the Cambrian, in the aftermath of a series of global glaciations known as the ‘Snowball Earth’. In this electrifying new environment, supercharged by oxygen, large animals living by predation became possible for the first time in the history of the planet.”
“Mammals and birds generate up to ten or fifteen times as much internal heat as a similarly sized lizard. They do so regardless of circumstances. Place a lizard and a mammal in suffocating heat and the mammal will continue to generate ten times as much internal heat, to its own detriment. The lizard will just enjoy it. It’s not surprising that lizards, and reptiles in general, fare much better in the desert.”
“Now try placing the lizard and the mammal in cold conditions, let’s say close to freezing, and the lizard will bury itself in leaves, curl up and go to sleep… Under such conditions, we just burn up even more food. The cost of living for a mammal in the cold is a hundred times that of a lizard. Even in temperate conditions, say around 20°C, a pleasant spring day in much of Europe, the gap is huge, around thirtyfold. To support such a prodigious metabolic rate, the mammal must burn up thirty times more food than a reptile. It must eat as much in a single day, every single day, as a lizard eats in a whole month. Given that there’s no such thing as a free lunch, that’s a pretty serious cost.”
“So if lizards and mammals both earmark, say, 3 per cent of their resources to the brain, but mammals have at their disposal ten times the resources, they can afford ten times more brain, and usually have exactly that. Having said that, primates, and especially humans, allocate a far greater proportion of their resources to brainpower. Humans, for example, dedicate around 20 per cent of resources to the brain, even though it takes up only a few per cent of our body. I suspect, then, that brainpower is little more than an added extra, thrown in at no extra cost, for a hot-blooded lifestyle. There are far cheaper ways of building bigger brains.”
“As a rule of thumb metabolic rate governs population size, and reptiles often outnumber mammals by ten to one. By the same token, mammals have fewer offspring ”
“What exactly is it that we have but the reptiles don’t? It had better be good.
The single most compelling answer is ‘stamina’. Lizards can match mammals easily for speed or muscle power, and indeed over short distances outpace them; but they exhaust very quickly. Grab at a lizard and it will disappear in a flash, streaking to the nearest cover as fast as the eyes can see. But then it rests, often for hours, recuperating painfully slowly from the exertion. The problem is that reptiles ain’t built for comfort–they’re built for speed. As in the case of human sprinters, they rely on anaerobic respiration”
“There’s no doubt that hot-blooded animals have far more stamina than cold-bloods, typically ten times the aerobic capacity. In both mammals and birds, this soaring aerobic capacity is coupled to a turbocharged resting metabolism–large visceral organs, with high mitochondrial power–but little deliberate attempt to generate heat.”
“In essence, genes specify the general circuitry of the brain, whereas experience specifies the exact wiring and all the idiosyncratic detail that entails. Meaning comes mostly with experience, which is written directly into the brain. As Edelman puts it, ‘neurons that fire together wire together’. In other words, neurons that fire at the same time strengthen their connections (synapses) and form more connections that bind them together physically.”
“Edelman refers to the process of brain development as neural darwinism, which emphasises the idea that experience selects successful neural combinations. All the basic tenets of natural selection are present: we start out with a massive population of neurons, which can be wired up in millions of different ways to achieve the same ends. The neurons vary among themselves and can either grow more robust or wither away; there is competition between neurons to form synaptic connections and differential survival on the basis of success, the ‘fittest’ neuron combinations forming the most synaptic connections.”
“The difference between a colony and true multicellularity is best seen in terms of commitment to differentiation. Algae like Volvox benefit from community living, but also ‘opt out’ and live as single cells. Retaining the possibility of independence curtails the degree of specialisation that can be attained”
“True multicellular life can only be achieved by cells ‘prepared’ to subsume themselves entirely to the cause. Their commitment must be policed, and any attempted reversions to independence are punishable by death. Nothing else works. Just think about the devastation caused by cancer, even today, after a billion years of multicellular living, to appreciate the impossibility of multicellular life when cells do their own thing. Only death makes multicellular life possible. And, of course, without death there could be no evolution; without differential survival, natural selection comes to nothing.”
“True multicellularity evolved independently no less than five times in the eukaryotes–in the red algae, green algae, plants, animals and fungi. In their organization these disparate forms of life have little in common, but all of them police their cells and punish transgressions with death using remarkably similar caspase enzymes. Interestingly, in almost all cases the mitochondria are still the principal brokers of death, the hubs inside cells that integrate conflicting signals, eliminate noise, and trigger the death apparatus when necessary. ”
“A single mutation in just one gene can double lifespan and at once put ‘on hold’ the diseases of old age.”
“The significance of these findings to ourselves can’t be overstressed. All the diseases of old age, from cancer to heart disease to Alzheimer’s disease, can in principle be delayed, even avoided, by simple permutations of a single pathway. It’s a shocking conclusion, yet it’s staring us in the face: it should prove easier to ‘cure’ ageing and all age-related diseases with a single panacea than it will ever be to cure any one age-related disease like Alzheimer’s in people who are otherwise ‘old’. ”
“Age-related diseases depend on biological age, not chronological time. Cure ageing, and we cure the diseases of old age–all of them. And the overriding lesson from these genetic studies is that ageing is curable.”
“I don’t know any other fact as shocking in all of medicine: a tiny change in the mitochondria halves our risk of being hospitalised for any age-related disease and doubles our prospects of living to 100. If we are serious about tackling the distressing and cripplingly expensive health problems of old age on our greying planet, this, surely, is the place to start. Shout it from the rooftops!”
“Evolutionary theory suggests that we can eradicate the diseases of old age with a single well-judged panacea. The anti-ageing pill is not a myth.
But I suspect that a ‘cure’ for Alzheimer’s disease is a myth. ”