CHARLES DARWIN’S EPIPHANY ON THE ROAD TO GALAPAGOS
Have you read the preceding page "Evolution - the basic concept"?
Have you read the preceding page "Evolution - the basic concept"?
Darwin’s ideas were shaped by his five year voyage working as a naturalist on the Beagle which circumnavigated the globe between 1831 and 1836. He visited a variety of countries, observing and taking specimens in the jungles of Brazil, the pampas of the Argentine and the mountains of Chile, and was staggered by the variety of species he encountered, and by the extremely subtle variations he noted between species. He saw clear fossil evidence of evolution in creatures like armadillos, and fossil animals that were similar to living animals, but with slight differences. As a result, the conviction slowly began to form that the separate species had not been individually created - the mainstream view at the time - but had evolved out of simpler life forms. But it was what he saw on the Galapagos Islands which ultimately shaped his world view of the origins of life and how the different species came into being.
The Galapagos Islands comprise a volcanic archipelago of recently formed (in archaeological terms) islands about 600 miles off the coast of South America (Ecuador). Here Darwin observed that different islands housed species similar to each other, but distinct from their counterparts he had observed on the South American continent. Yet, although endemic to the archipelago, from island to island they differed from each other in their individual characteristics to the extent that they comprised separate species. “[T]he most remarkable feature in the natural history of this archipelago … is that the different islands to a considerable extent are inhabited by a different set of beings. My attention was first called to this fact by the vice-governor, Mr Lawson, declaring that the tortoises differed from the different islands, and that he could with certainty tell from which island any one was brought. I did not for some time pay sufficient to this statement … I never dreamed that islands about 50 or 60 miles apart, and most of them in sight of each other, formed of precisely the same rocks, placed under a quite similar climate, rising to a nearly equal height, would have been differently tenanted ; but .. this is the case”[1].
The giant tortoises from the different islands differed not only in their size, but in other characteristics as well. Those from Charles Island had their shells in front thick and turned up like a Spanish saddle, whilst the tortoises from James Island were rounder, blacker, and had a better taste when cooked[2]. Yet they each bore similarities to those on the mainland. The Galapagos also has its own land iguanas and the Galapagos marine iguanas, the latter being unique to the Galapagos archipelago. The land iguana came from the mainland, and speciated on the archipelago to give rise to the marine iguana.
Darwin also observed that the varied types of finches that inhabited the different islands of the Galapagos were similar to those of South America, but differed slightly from island to island because each species was adapted to a slightly different way of life: one, for example, fed on tree insects, and another picked seeds from the ground. Hence, their beaks were different. “Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends”[3].
Darwin reasoned that the birds, reptiles, insects and plants of the Gapalagos had evolved from ancestors that had come over from the continent[4], hence their similarity. But although the separate islands of the archipelago were relatively close to each other, the very strong currents of the sea separated the southern islands from the northern ones, and a strong current was also observed running between the northern islands themselves, these being sufficient to prevent migration from one island to the other. And “(a)s the archipelago is free to a most remarkable degree from gales of wind, neither the birds, insects, nor lighter seeds, would be blown from island to island. And lastly, the profound depth of the ocean between the islands, and their apparently recent (in a geological sense) volcanic origin, render it highly unlikely that they were ever united; and this, probably, is a far more important consideration than any other, with respect to the geographical distribution of their inhabitants”[5] So the result was speciation: the separate islands comparatively isolated from each other each spawned their own species of birds, animals and plants, each of which had originally evolved from a common ancestor on the continent.
Clearly the separate species had changed by adapting to their surroundings. But how had this occurred? Darwin had been fascinated by animals from his childhood. By his twenties he was an expert naturalist, and he knew that humans were quite capable of altering species through artificial selection. This is the means by which dog breeders and pigeon fanciers breed different breeds to enhance particular aspects of their selected species to have longer or shorter beaks or snouts, bigger or smaller stature, tameness or aggression etc by judicious cross-breeding. In Darwin’s time, one breeder, Sir John Selbright, used to say with respect to pigeons, that “he would produce any given feather in three years, but it would take him six years to obtain head and beak”[6]
A recent study has discovered that selective breeding has altered the shape and position of certain dogs’ brains. Using MRI scans, researchers have discovered that the brains of small, pug-like dogs have rotated forward in their skulls compared with larger, long-nosed dogs such as Dalmations and German shepherds, and the olfactory lobe, responsible for smelling, is lower in the brain cavity. The ancestor of all domestic dogs from the Great Dane to the Chihuahua is the wolf, and selective breeding techniques have resulted in the proliferation of shapes, sizes and individual characteristics in the multiplicity of breeds we now see before us. Brain rotation in the smaller pug-like dogs may be an evolutionary trade-off because the length of their skulls had decreased in proportion to the width, and if the brain hadn’t rotated, there would be less space for the frontal lobe, which is responsible for intelligence and problem solving, to develop[7].
Darwin was also aware of sexual selection: the avenue by which peahens choose the most attractive peacocks to mate with, or female canaries who choose to mate with males whose songs are especially appealing. The females are selectively breeding males to become more beautiful or better at singing, as the case may be. On a lighter note, a recent study has suggested that women may unconsciously purchase sexier attire during the hormonal changes associated with ovulation to make them more attractive when competing with same-sex rivals for males[8].
But why did some individuals survive and others not, and what did the selecting in the natural world, or in Darwin’s words, “Who can explain why one species ranges widely and is very numerous, and why another allied species has a narrow range and is rare?”[9] Before Darwin’s time, the general view, even among distinguished scientists was that each species had been created separately by God as a finished work as described in Genesis[10], but for some time many informed observers and thinkers had been querying the biblical account of creation, which did not appear to coincide with fossil finds which revealed the presence of creatures never mentioned in the Bible.
In 1796, the palaeontologist Georges Cuvier (1769-1832)[11] demonstrated that the bones of many large elephant-like creatures found throughout Europe and America were not Asian or Indian Elephants but some other creatures - different species in fact - that nobody had ever seen or heard of before. What were they and where had they come from? (They were in fact woolly mammoths and mastodons). Where were they in the ark? If they came from God, why was it necessary to create so many unnecessary animals in the first place, and why had he suffered them to become extinct? Were they in some way imperfect? As Europeans travelled more widely in the centuries after Columbus, they also became aware of the existence of many more species not mentioned in the Bible, distributed in apparent haphazard fashion across the globe, kangaroos in Australia, pandas in China. So by the late eighteenth century, the concept of the ‘Perfection of Creation’ as a finished work as described in Genesis began to disintegrate as some biologists began considering the possibility that living organisms changed and disappeared over time by natural mechanisms of some kind. Otherwise it seemed that God was continually tinkering with his creation.
Prior to Darwin, it had been suggested (notably by Jean-Baptiste Lamarck) that an individual’s acquired characteristics could be passed on from one generation to the next (eg being a good athlete), but the reality was and is that only inherited characteristics can be passed on in this way. So, if the genetic makeup of organisms is determined by their past, how was it possible for them to adapt to present-day conditions? It was Darwin who solved this riddle with his theory of Natural Selection.
By definition, a species is a group of animals or plants possessing common characteristics. The individuals within a species resemble each other more closely than they resemble members of other species, and during its lifetime, each species may undergo minor changes of many different kinds and regional variations may appear, but biologists will continue to classify the individuals as members of a single species so long as they can continue to interbreed and produce fertile offspring and they are capable of breeding with each other (eg all breeds of the domestic dog constitute a species), but not with members of other species [12].
Most new species in nature appear when a population becomes geographically isolated from other populations. It then adapts to the local environment and, sooner or later, acquire traits that prevent it from successfully mating with the original species or that would make the original species sterile[13], or both[14].
It was Darwin who first argued that species are not fixed entities. They evolve from other species; they exist, sometimes for millions of years; then they either become extinct or evolve into one or more other species. While they exist, they are constantly changing and the way they change is governed by some simple rules. However, over long periods of time, random variations in the feature of individuals may eventually transform the average features of the entire species, as for example in the case of the Galapagos tortoises, iguanas and finches. So, how and why do the features of some individuals become more common and those of others dwindle and disappear?
Darwin knew from Malthus that in most populations only a small minority of individuals survive to adulthood and produce offspring. Yet the future of the species can be shaped only by those individuals that do survive and reproduce, so later generations of life are the offspring only of the survivors. But what determines which individuals reproduce and which do not? Pure chance perhaps, but in the long run, Darwin argued, the individuals most likely to survive and reproduce are those that have had the good luck to inherit from their parents features that will make them slightly better adapted to their environment. They will then pass these same features on to most of their offspring. Over time, these features will become more and more common because those individuals that do not possess them will produce fewer healthy offspring and their lineages die out. Over thousands of generations, many small changes of this kind will ensure that the species as a whole appears to change or evolve in ways that make it better adapted to its environment. In this metaphorical sense, we can say that the environment naturally selects certain features and discards others, just as animal breeders artificially select some individuals to breed and not others, and it is this metaphorical sense that species appear over time to adapt to their natural environments[15].
As many more individuals of each species are born than can possibly survive, it follows that in the struggle for existence, “any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual or any species in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring. The offspring also will thus have a better chance of surviving, for of the many individuals of any species which are perpetually born, but a small number can survive. I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection”[16]. And “[a]s natural selection acts solely by accumulating slight, successive, favourable, variations, it can produce no great or sudden modification; it can act only by very short and slow steps”[17]. “[N]atural selection can act only by the preservation and accumulation of (these) infinitesimally small inherited modifications, each profitable to the preserved being; and as modern geology has almost banished such views as the excavation of a great valley by a single diluvial wave, so will natural selection, if it be a true principle, banish the belief of the continued creation of new organic beings, or of any great and sudden modification in their structure”[18].
So why did some individuals survive and others not, and what did the selecting in the natural world? The answer Darwin came up with was that it was those individuals who were the “fittest”, those who were more appropriately adapted to their environment by pure chance, who were the ones most likely to survive and shape future generations of species: In the struggle for survival, the fittest win out at the expense of their rivals because they succeed in adapting themselves best to their environment, but they do not in any sense “try” to adapt[19]: “Natural Selection acts solely through the preservation of variations in some way advantageous, which consequently endure. [And] … as each selected and favoured form increases in number, so will the less favoured forms decrease and become rare. Rarity, as geology tells us, is the precursor to extinction”[20].
As David Christian points out, Darwin understood that this random statistical process of sorting, which occurs in all forms of life generation after generation, could alter species as effectively as any human breeder if repeated with sufficient frequency. Over and over again, millions of times in each generation, the environment eliminated some individuals while allowing others to survive. Later generations inherited only the qualities of the survivors; as a result over time the entire species began to resemble the survivors rather than the nonsurvivors. Metaphorically, the environment was acting like a human animal breeder, and this is why Darwin called the mechanism ‘natural selection’ in contrast to the 'artificial selection’ performed by those who bred animals[21].
Darwin thus showed that "purely statistical and totally mindless processes repeated over and over again, could explain how species changed in ways that seemed to make them constantly adapt to changing environments, but it was not the individuals who evolved, but the average features of the species". He went on to argue that these mechanisms, repeated over long periods of time, can also explain how distinct species arose, for it is clear that populations of a single species scattered over a large area and shaped by slightly different environments, are likely to evolve in slightly different ways, and the Galapagos finches were a prime example. Over time, such processes could explain all the variety of living organisms to be found on earth. "In other words, all the beautiful and complex organisms on Earth, from amoebae to elephants to hummingbirds to human beings can be created by blind, repetitive processes, and unconscious processes can create not just stars and galaxies, it seemed, but even life itself. Such reasoning seemed to deprive God himself of any reason for existence!" [22] Richard Dawkins expresses the same idea in contemporary molecular terminology when he describes Natural Selection as being the successful survival of genes in gene pools consequent upon hundreds of thousands of small, local interactions, with no overall design linking them together: no overall plan of development, no blueprint, no architect’s plan and no architect.[23]
Dawkins had expressed the same idea in somewhat different conceptual terminology some years earlier when he described natural selection as a "blind watchmaker", consisting of a continuum of slow, gradual, cumulative, step by step evolutionary transformations from simpler things - originally from primordial objects sufficiently simple to have come into being by chance - to the essentially non-random cumulative organised complexity we see about us today [24]:
The Galapagos Islands comprise a volcanic archipelago of recently formed (in archaeological terms) islands about 600 miles off the coast of South America (Ecuador). Here Darwin observed that different islands housed species similar to each other, but distinct from their counterparts he had observed on the South American continent. Yet, although endemic to the archipelago, from island to island they differed from each other in their individual characteristics to the extent that they comprised separate species. “[T]he most remarkable feature in the natural history of this archipelago … is that the different islands to a considerable extent are inhabited by a different set of beings. My attention was first called to this fact by the vice-governor, Mr Lawson, declaring that the tortoises differed from the different islands, and that he could with certainty tell from which island any one was brought. I did not for some time pay sufficient to this statement … I never dreamed that islands about 50 or 60 miles apart, and most of them in sight of each other, formed of precisely the same rocks, placed under a quite similar climate, rising to a nearly equal height, would have been differently tenanted ; but .. this is the case”[1].
The giant tortoises from the different islands differed not only in their size, but in other characteristics as well. Those from Charles Island had their shells in front thick and turned up like a Spanish saddle, whilst the tortoises from James Island were rounder, blacker, and had a better taste when cooked[2]. Yet they each bore similarities to those on the mainland. The Galapagos also has its own land iguanas and the Galapagos marine iguanas, the latter being unique to the Galapagos archipelago. The land iguana came from the mainland, and speciated on the archipelago to give rise to the marine iguana.
Darwin also observed that the varied types of finches that inhabited the different islands of the Galapagos were similar to those of South America, but differed slightly from island to island because each species was adapted to a slightly different way of life: one, for example, fed on tree insects, and another picked seeds from the ground. Hence, their beaks were different. “Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends”[3].
Darwin reasoned that the birds, reptiles, insects and plants of the Gapalagos had evolved from ancestors that had come over from the continent[4], hence their similarity. But although the separate islands of the archipelago were relatively close to each other, the very strong currents of the sea separated the southern islands from the northern ones, and a strong current was also observed running between the northern islands themselves, these being sufficient to prevent migration from one island to the other. And “(a)s the archipelago is free to a most remarkable degree from gales of wind, neither the birds, insects, nor lighter seeds, would be blown from island to island. And lastly, the profound depth of the ocean between the islands, and their apparently recent (in a geological sense) volcanic origin, render it highly unlikely that they were ever united; and this, probably, is a far more important consideration than any other, with respect to the geographical distribution of their inhabitants”[5] So the result was speciation: the separate islands comparatively isolated from each other each spawned their own species of birds, animals and plants, each of which had originally evolved from a common ancestor on the continent.
Clearly the separate species had changed by adapting to their surroundings. But how had this occurred? Darwin had been fascinated by animals from his childhood. By his twenties he was an expert naturalist, and he knew that humans were quite capable of altering species through artificial selection. This is the means by which dog breeders and pigeon fanciers breed different breeds to enhance particular aspects of their selected species to have longer or shorter beaks or snouts, bigger or smaller stature, tameness or aggression etc by judicious cross-breeding. In Darwin’s time, one breeder, Sir John Selbright, used to say with respect to pigeons, that “he would produce any given feather in three years, but it would take him six years to obtain head and beak”[6]
A recent study has discovered that selective breeding has altered the shape and position of certain dogs’ brains. Using MRI scans, researchers have discovered that the brains of small, pug-like dogs have rotated forward in their skulls compared with larger, long-nosed dogs such as Dalmations and German shepherds, and the olfactory lobe, responsible for smelling, is lower in the brain cavity. The ancestor of all domestic dogs from the Great Dane to the Chihuahua is the wolf, and selective breeding techniques have resulted in the proliferation of shapes, sizes and individual characteristics in the multiplicity of breeds we now see before us. Brain rotation in the smaller pug-like dogs may be an evolutionary trade-off because the length of their skulls had decreased in proportion to the width, and if the brain hadn’t rotated, there would be less space for the frontal lobe, which is responsible for intelligence and problem solving, to develop[7].
Darwin was also aware of sexual selection: the avenue by which peahens choose the most attractive peacocks to mate with, or female canaries who choose to mate with males whose songs are especially appealing. The females are selectively breeding males to become more beautiful or better at singing, as the case may be. On a lighter note, a recent study has suggested that women may unconsciously purchase sexier attire during the hormonal changes associated with ovulation to make them more attractive when competing with same-sex rivals for males[8].
But why did some individuals survive and others not, and what did the selecting in the natural world, or in Darwin’s words, “Who can explain why one species ranges widely and is very numerous, and why another allied species has a narrow range and is rare?”[9] Before Darwin’s time, the general view, even among distinguished scientists was that each species had been created separately by God as a finished work as described in Genesis[10], but for some time many informed observers and thinkers had been querying the biblical account of creation, which did not appear to coincide with fossil finds which revealed the presence of creatures never mentioned in the Bible.
In 1796, the palaeontologist Georges Cuvier (1769-1832)[11] demonstrated that the bones of many large elephant-like creatures found throughout Europe and America were not Asian or Indian Elephants but some other creatures - different species in fact - that nobody had ever seen or heard of before. What were they and where had they come from? (They were in fact woolly mammoths and mastodons). Where were they in the ark? If they came from God, why was it necessary to create so many unnecessary animals in the first place, and why had he suffered them to become extinct? Were they in some way imperfect? As Europeans travelled more widely in the centuries after Columbus, they also became aware of the existence of many more species not mentioned in the Bible, distributed in apparent haphazard fashion across the globe, kangaroos in Australia, pandas in China. So by the late eighteenth century, the concept of the ‘Perfection of Creation’ as a finished work as described in Genesis began to disintegrate as some biologists began considering the possibility that living organisms changed and disappeared over time by natural mechanisms of some kind. Otherwise it seemed that God was continually tinkering with his creation.
Prior to Darwin, it had been suggested (notably by Jean-Baptiste Lamarck) that an individual’s acquired characteristics could be passed on from one generation to the next (eg being a good athlete), but the reality was and is that only inherited characteristics can be passed on in this way. So, if the genetic makeup of organisms is determined by their past, how was it possible for them to adapt to present-day conditions? It was Darwin who solved this riddle with his theory of Natural Selection.
By definition, a species is a group of animals or plants possessing common characteristics. The individuals within a species resemble each other more closely than they resemble members of other species, and during its lifetime, each species may undergo minor changes of many different kinds and regional variations may appear, but biologists will continue to classify the individuals as members of a single species so long as they can continue to interbreed and produce fertile offspring and they are capable of breeding with each other (eg all breeds of the domestic dog constitute a species), but not with members of other species [12].
Most new species in nature appear when a population becomes geographically isolated from other populations. It then adapts to the local environment and, sooner or later, acquire traits that prevent it from successfully mating with the original species or that would make the original species sterile[13], or both[14].
It was Darwin who first argued that species are not fixed entities. They evolve from other species; they exist, sometimes for millions of years; then they either become extinct or evolve into one or more other species. While they exist, they are constantly changing and the way they change is governed by some simple rules. However, over long periods of time, random variations in the feature of individuals may eventually transform the average features of the entire species, as for example in the case of the Galapagos tortoises, iguanas and finches. So, how and why do the features of some individuals become more common and those of others dwindle and disappear?
Darwin knew from Malthus that in most populations only a small minority of individuals survive to adulthood and produce offspring. Yet the future of the species can be shaped only by those individuals that do survive and reproduce, so later generations of life are the offspring only of the survivors. But what determines which individuals reproduce and which do not? Pure chance perhaps, but in the long run, Darwin argued, the individuals most likely to survive and reproduce are those that have had the good luck to inherit from their parents features that will make them slightly better adapted to their environment. They will then pass these same features on to most of their offspring. Over time, these features will become more and more common because those individuals that do not possess them will produce fewer healthy offspring and their lineages die out. Over thousands of generations, many small changes of this kind will ensure that the species as a whole appears to change or evolve in ways that make it better adapted to its environment. In this metaphorical sense, we can say that the environment naturally selects certain features and discards others, just as animal breeders artificially select some individuals to breed and not others, and it is this metaphorical sense that species appear over time to adapt to their natural environments[15].
As many more individuals of each species are born than can possibly survive, it follows that in the struggle for existence, “any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual or any species in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring. The offspring also will thus have a better chance of surviving, for of the many individuals of any species which are perpetually born, but a small number can survive. I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection”[16]. And “[a]s natural selection acts solely by accumulating slight, successive, favourable, variations, it can produce no great or sudden modification; it can act only by very short and slow steps”[17]. “[N]atural selection can act only by the preservation and accumulation of (these) infinitesimally small inherited modifications, each profitable to the preserved being; and as modern geology has almost banished such views as the excavation of a great valley by a single diluvial wave, so will natural selection, if it be a true principle, banish the belief of the continued creation of new organic beings, or of any great and sudden modification in their structure”[18].
So why did some individuals survive and others not, and what did the selecting in the natural world? The answer Darwin came up with was that it was those individuals who were the “fittest”, those who were more appropriately adapted to their environment by pure chance, who were the ones most likely to survive and shape future generations of species: In the struggle for survival, the fittest win out at the expense of their rivals because they succeed in adapting themselves best to their environment, but they do not in any sense “try” to adapt[19]: “Natural Selection acts solely through the preservation of variations in some way advantageous, which consequently endure. [And] … as each selected and favoured form increases in number, so will the less favoured forms decrease and become rare. Rarity, as geology tells us, is the precursor to extinction”[20].
As David Christian points out, Darwin understood that this random statistical process of sorting, which occurs in all forms of life generation after generation, could alter species as effectively as any human breeder if repeated with sufficient frequency. Over and over again, millions of times in each generation, the environment eliminated some individuals while allowing others to survive. Later generations inherited only the qualities of the survivors; as a result over time the entire species began to resemble the survivors rather than the nonsurvivors. Metaphorically, the environment was acting like a human animal breeder, and this is why Darwin called the mechanism ‘natural selection’ in contrast to the 'artificial selection’ performed by those who bred animals[21].
Darwin thus showed that "purely statistical and totally mindless processes repeated over and over again, could explain how species changed in ways that seemed to make them constantly adapt to changing environments, but it was not the individuals who evolved, but the average features of the species". He went on to argue that these mechanisms, repeated over long periods of time, can also explain how distinct species arose, for it is clear that populations of a single species scattered over a large area and shaped by slightly different environments, are likely to evolve in slightly different ways, and the Galapagos finches were a prime example. Over time, such processes could explain all the variety of living organisms to be found on earth. "In other words, all the beautiful and complex organisms on Earth, from amoebae to elephants to hummingbirds to human beings can be created by blind, repetitive processes, and unconscious processes can create not just stars and galaxies, it seemed, but even life itself. Such reasoning seemed to deprive God himself of any reason for existence!" [22] Richard Dawkins expresses the same idea in contemporary molecular terminology when he describes Natural Selection as being the successful survival of genes in gene pools consequent upon hundreds of thousands of small, local interactions, with no overall design linking them together: no overall plan of development, no blueprint, no architect’s plan and no architect.[23]
Dawkins had expressed the same idea in somewhat different conceptual terminology some years earlier when he described natural selection as a "blind watchmaker", consisting of a continuum of slow, gradual, cumulative, step by step evolutionary transformations from simpler things - originally from primordial objects sufficiently simple to have come into being by chance - to the essentially non-random cumulative organised complexity we see about us today [24]:
All appearances to the contrary, the only watchmaker in nature is the blind forces of physics, albeit deployed in a very special way. A true watchmaker has foresight: he designs his cogs and springs, and plans their interconnections, with a future purpose in his mind’s eye Natural selection, the blind, unconscious, automatic process which Darwin discovered, and which we now know is the existence and apparently purposeful form of all life, has no purpose in mind. It has no mind and no mind’s eye. It does not plan for the future. It has no vision, no foresight. No sight at all. If it can be said to play the role of a watchmaker in nature, it is the blind watchmaker. [25]
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An ancient dynamic planet
The process by which random variations in the features of individuals eventually transform the average features of the entire species takes huge periods of time, and the conventional wisdom in Darwin’s time was that the earth was very young. In the seventeenth century, the Archbishop of Armagh in Ireland, James Ussher, came to the view that the earth was only some 6,000 years old by totalling up the number of generations recorded in the Bible. By refining his methods, some of his colleagues had pinpointed the very moment of creation: 23 October 4004 BC at 9 am. Fossils were generally believed to be the remains of animals that had perished during the Biblical flood.
The Archbishop’s chronology came under severe attack in the eighteenth century when the geologists James Hutton (1726-1797) and William Smith (1769-1839) offered evidence that the earth was not thousands but millions of years old. Hutton, whose ideas and approach to studying the Earth established geology as a proper science and who is known as the Founder of Geology, came to believe that the Earth was perpetually being formed; for example, molten material is forced up into mountains, eroded, and then eroded sediments are washed away. He recognized that the history of the Earth could be determined by understanding how processes such as erosion and sedimentation work in the present day. Hutton perceived that this sedimentation takes place so slowly that even the oldest rocks are made up of, in his words, “materials furnished from the ruins of former continents.” The reverse process occurs when rock exposed to the atmosphere erodes and decays. He called this coupling of destruction and renewal the “great geological cycle,” and realized that it had been completed innumerable times[26].
Hutton’s portrait of an ancient, dynamic planet had a profound effect on Darwin. He was also a close friend of and collaborator with Sir Charles Lyell (1797-1875)[27] whose Principles of Geology popularised Hutton's concepts of uniformitarianism: the idea that the earth was shaped by slow-moving forces still in operation today. Here lay at least a framework for the eons required by the biological evolution Darwin observed in the fossil record, but there was much farther to go. In the ensuing hundred years and more, radiometric dating techniques have pushed back the age of the earth from a few million years to something like 4.570 billion years – more than enough time for Darwinian processes to evolve within. This has enabled geologists, paleontologists and other earth scientists to describe the timing and the relationships between events that have occurred during the history of the Earth and to identify with accuracy the age of rocks, their various strata and the fossils found within and between them.
[1] Darwin’s Journal, 29 September 1835, The Voyage, 141-2, cited in Christopher Ralling, The Voyage of Charles Darwin, His autobiographical writings, BBC, London, 1978.
[2] Ibid, 142
[3] Cited in Richard Dawkins, The Greatest Show on Earth – The Evidence for Evolution, Bantam Press, London, 2009, 270. At least that is the conventional view. Actually, Darwin's conclusions were not in fact inspired by his noticing a diversity in the beaks of the finches. It was his friend the ornithologist John Gould who later drew his attention to the significance of what he had found. In his inexperience he had not noted which birds came from which islands. He made a similar error with the tortoises: Bill Bryson, A Short History of Nearly Everything, Broadway Books, 2003, 384, citing Desmond A and Moore J, Darwin, London, Penguin Books, 1992, 197.
[4] Arthur T Gregor, Charles Darwin, Angus & Robertson, London, 1967, 84.
[5] Darwin’s Journal, 143, cited in Ralling, above.
[6] Cited in Christian, Maps of Time, 87.
[7] “It’s enough to make young Fido’s brain go into a spin”, SMH, 28 July 2010.
[8] “It’s not a shoe fetish, it’s natural selection”, SMH, 10 August 2010.
[9] Darwin, On the Origin of Species, Introduction, Penguin (2009),15.
[10] “And God saw everything that he had made and behold it was very good”: Gen 1:31.
[11] It was Cuvier who came up with the idea of extinction. He did not agree with evolutionary ideas involving the gradual transmutation of one form into another
[12] Gregor, Charles Darwin, 6; Christian, Maps of Time, 120, 133.
[13] Thus, a horse can mate with a donkey but the product of their union, a mule, will be infertile.
[14] Jerry Coyne, “What makes a new species”, Scientific American, September 2012, 62.
[15] Source for these paragraphs: Christian, Maps of Time, 83-84.
[16] Darwin, On the Origin of Species, 441-2; 115. See also in the Penguin Books (2009) edition, Charles Darwin’s Introduction, 14.
[17] Darwin, On the Origin of Species, Penguin (2009), Recapitulation and Conclusion, 411.
[18] Darwin, On the Origin of Species, Penguin (2009), Chapter on Natural Selection, 93.
[19] Christian, Maps of Time, 87- 88.
[20] Darwin, Origin of Species, Chapter on Natural Selection, Penguin (2009), Chapter on Natural Selection, 104.
[21] Maps of Time, 88
[22] Ibid, 89.
[23] Richard Dawkins, The Greatest Show on Earth, op cit Ch 8, p 250.
[24] Richard Dawkins, The Blind Watchmaker, Norton, New York, 1987, 1986, 2006, pp 32, 62, 71, 452, 453. The reference to the blind watchmaker is a riposte to an analogy drawn by the eighteenth century theologian, William Paley between a watch and living things: both must have been manufactured by a greater intelligence, he hypothesised. They were both just too complex and functional to have sprung into existence accidentally; ibid, 8.
[25] Ibid 9.
[26] http://www.amnh.org/education/resources/rfl/web/essaybooks/earth/p_hutton.html
[27] On Lyell, see http://en.wikipedia.org/wiki/Charles_Lyell
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