Chapter Three is, in many ways, the beginning of ecology. One of the ecologists in our reading group said that very little in modern community ecology was not laid out there. The concept of organisms interacting with both their environment, other species, and other members of the same species, and indeed the word "competition" in its ecological sense, are if not Darwin's pioneering work alone at least popularised by him (I do not know enough of the history of biology to say which). This chapter was inspired primarily by the work of the economist Thomas Malthus, who analysed the relative birth and death rates in human populations. Darwin's genius was to take this to a mechanical level, without the action of individual intentions. It was one of those ideas which seems obvious in retrospect but which was groundbreaking when first presented. As I read it I kept thinking that this chapter would be an ideal assignment to an introductory ecology class: it really is that comprehensive, that modern. The majority of the work that followed (at least in community ecology) has been merely refinement, primarily through the application of mathematics.
The chapter focuses on what Darwin called the "struggle for existence". The language was meant only partly to be taken literally: while animals must in fact frequently struggle to avoid being eaten, or to subdue rivals, the concept can also be applied to plants (as Darwin did). Those organisms that are able to leave offspring have succeeded in that struggle: they have had to survive long enough to reach reproductive maturity. The struggle goes further for those organisms that must mate in order to reproduce, and still further for those that must nurture their offspring -- but again, the struggle can be metaphorical. Plants which release more pollen, for instance, might win their struggle against others of the same species, in that they would leave more offspring. The struggle to produce viable offspring is implicit in the amount of energy that must be expended to build another organism: pregnant and nursing mothers, for instance, "eat for two", and this intensifies the daily efforts of finding food.
The struggle for existence has its place in the theory of evolution by making explicit the fact that more offspring are produced in each generation than can survive to replace their parents. In a stable population, this means that some offspring will die without having themselves reproduced: they will have lost in Darwin's struggle. Meanwhile, organisms are also individuals, and as such they vary, as was discussed in the previous chapter. Some individuals succeed in the struggle by virtue of inherited characteristics that give them an advantage over their less-endowed kin, and will pass those characteristics on to their own offspring. These advantages may help adapt the organism to its physical environment, or they may help the organism find food or avoid becoming food, or they may help the organism increase its likelihood of reproducing, or the number or health of its offspring.
This leads to the concept of natural selection, which is the topic of the next chapter, but not without offering what must be one of the most obvious attempts at softening the blow in scientific history. Darwin's depiction of Nature is as a brutal and ultimately losing struggle to stay alive, wherein the best that any living thing can hope for is to leave successful offspring before it succumbs to the myriad and overwhelming forces arrayed against it. This must have been appalling to Victorian sensibilities, which Darwin attempts to soothe: "When we reflect on this struggle, we may console ourselves with the full belief, that the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply." I will not deny that there is much joy in life, but fear, sorrow, anger, and pain are also unavoidable. Darwin's empathy for living things is here curiously selective: what of the weak, the sickly, the despondent? Do they really feel no fear? Do they never suffer for long? Of course, the question must here be addressed as to whether other forms of life are capable of feeling fear or suffering pain. It is not my intention to debate that here, except to say that it was this same work of Darwin's that made this question scientifically viable.
But while such a passage fails in any way to support its implication that (in this context) ecological and (ultimately) evolutionary success leads to a more enjoyable life, its greatest failing lies in its assertion that the "struggle for existence" is not constant. Perhaps it is not constant in every aspect of life, but the interactions between living things are so complex that it cannot be assumed that, at one level or another, one is never at loggerheads with something. In finding shelter, we must displace others looking for that same resource. The very act of eating implies that something else had to die: how is that not part of the struggle? Our immune systems are continually fighting off infections -- and doing so the more militantly when we are not aware of it! In winning the hand of one's mate, another must lose the same; what is (one hopes) a happy union for some is necessarily a source of frustration and feelings of loss for others. Nature may not always be red in tooth and claw, but our interactions with one another and with other living things are rarely benign for all.
Thursday, 29 January 2009
Sunday, 25 January 2009
The Origin, Chapter Two
Chapters Two and Three will be discussed this week together. They lay the foundation for the principle of Natural Selection, covering respectively variation in nature and the "struggle for existence", the principle wherein with each generation many more offspring are generated than can survive.
Chapter Two is only twenty pages long in the online facsimile, and alludes to Darwin's never-written follow-up to the Origin, in which he planned on expanding on the Origin to his satisfaction. As it happened, the degree of detail provided in this work proved sufficient, and the "long catalogue of dry facts" that would have constituted much of the successor unnecessary.
The question of variation within species brings up the question of what constitutes a species, which is a contentious issue today. Back in Darwin's day, the question was just as open, although the candidate answers were very different. One of the more popular notions was that each species was created independently, and that "varieties" (sub-species and so on, a term used here with some scientific force, and somewhat interchangeable with "race") had obviously descended from and were members of the same species. At the same time, then as now, "every naturalist knows vaguely what he means when he speaks of a species." It is odd how some things never change!
Again anticipating the study of ecology, Darwin notes that features found to be useful in one individual of a species may not be so useful in another. He alludes to thickness of coat as an example: this is a more important feature to an animal in an extreme environment than to one in a more temperate locale, although the capacity to vary its thickness seasonally may be more important to the resident of the temperate zone. What varies in a species has traditionally not been considered important, but Darwin notes the circularity of the argument in which "important organs never vary", thereby removing such variation from consideration by using it to divide organisms into different species. Yet, substantial variation in unambiguously important organs can be found within otherwise-defined species: what we now know to be developmental variation in insects is noted by Darwin to produce very different morphologies in the paths taken by individual nerves.
The problem is most severe in what Darwin calls "protean" or "polymorphic" species. Such species (or indeed genera), claims Darwin, tend to be highly variable everywhere that they have been found, and in the case of fossils, in every period. This suggests that plasticity in development is itself an inheritable trait, at least inasmuch as that the corrective forces keeping development on a particular path are stronger in less-variable species, and weaker in more-variable ones. Darwin notes that the parts of organisms that vary are likely of less value to their survival than are the parts that do not, which is a necessary observation of any system in which natural selection is in operation.
Darwin next delves into the question of terminology, addressing the question of how much variation can be tolerated within a given species. Essentially, he says, the question cannot easily be settled; every specialist has a different list of valid species. He brushes by the distinction between allopatric and sympatric species, which would become important to evolutionary theorists in years to come. Here he merely notes that geography can be as characteristic as is form to determining species boundaries. Ultimately, the question of dividing individual species must be done using objective criteria, something that still has not been settled today; to do otherwise is "vainly to beat the air." Darwin briefly mentions what are now called "ring species", in which neighbouring forms are obviously continuous species, but members of the extremes of the range are distinct and do not easily interbreed.
The degree of known variation within a group of organisms is in no small part a function of the degree to which it has been studied. This is, of course, obvious, but it has important implications to the distinction of individual species, and Darwin goes from there to point out that it is much easier to learn a new group of organisms by taking their representatives from a particular locale in isolation; to consider initially those from other locations as well tends to confuse things. Once familiarity with a particular flora or fauna is attained, though, extending one's range of observations will challange one's sense of "species", both usefully and otherwise, as what could be diagnostic for a species in one region may ultimately prove highly variable between regions.
Having shown how variable individual species may be, and having suggested almost in passing that varieties within a species may in fact be incipient species, Darwin makes the important point that such varieties need not ultimately become different species. He goes on to point out that larger genera (those with more species) are both more widely distributed and more dominant than smaller genera, a point which I am not sure holds today. There are, at the very least, certainly exceptions, and Darwin points to a few of them himself. In particular, those species adapted to unusual environments (aquatic plants, for instance), tend to be more uniform. The other case that he gives, "plants low in the scale of organisation" being more widely distributed than their "higher" counterparts, I find definitely doubtful, on a similar principle to Darwin's own above. While individual knowledge of variation increases (at the very least) one's capacity to erect species distinctions, the features which vary in "lowly" organisms do so less markedly, and so the important distinctions are all the more subtle. To make a modern point of this, while they may not have evolved as far from the common ancestor as "higher" forms, they have nevertheless been evolving for the same length of time, and often for the same number of generations, and have had every opportunity to vary in ways that we may not appreciate.
An unwritten generalisation follows: Darwin believes nature to be essentially uniformitarian. This was a controversial geological principle when Darwin left on the Beagle, stating that the processes which shaped the Earth in the past are still in effect today. There are too many known exceptions for this to be considered strictly true today, and many of the processes which we now understand to be in effect (plate tectonics, for instance) were unsuspected in the early nineteenth century, but the essential notion is correct. Darwin's application of this to biology is a cornerstone to the science. In other words, evolution has happened, and it is continuing to happen today: it can be made an experimental science. These notions are not explicit in the Origin (at least not at this point in the work), but they are very much implied.
In summary, this chapter appears to make two important main points. First, the larger genera (by which is meant the more speciose genera), the more varieties can be found within each of its species. A related though distinct point is that the threshold of variation characterising each of those species and varieties is lower than that for the smaller genera, within which species and varieties tend to be more distinct from one another. As I said above, I am not sure that this is actually the case, and in any event, I do not see how it is critical to Darwin's argument. Far more important is this chapter's other point, that variation is a continuum: the more closely one looks, the more similarities one finds between different groups, and the more individual differences one sees within individual groups. Species are artificial constructs, conveniences for human classification, and are not always unambiguously delineated. Furthermore, "little groups of species are generally clustered like satellites around certain other species", by which Darwin means that genera may be divided into subgenera, the species of which resemble one another to a greater degree than they do members of other subgenera, and which tend to be found in closer proximity to one another geographically as well as morphologically. This is not an unimportant point: the continuity between species is not evenly distributed, and the fuzziness of the species definition can be extended to higher levels as well.
Chapter Two is only twenty pages long in the online facsimile, and alludes to Darwin's never-written follow-up to the Origin, in which he planned on expanding on the Origin to his satisfaction. As it happened, the degree of detail provided in this work proved sufficient, and the "long catalogue of dry facts" that would have constituted much of the successor unnecessary.
The question of variation within species brings up the question of what constitutes a species, which is a contentious issue today. Back in Darwin's day, the question was just as open, although the candidate answers were very different. One of the more popular notions was that each species was created independently, and that "varieties" (sub-species and so on, a term used here with some scientific force, and somewhat interchangeable with "race") had obviously descended from and were members of the same species. At the same time, then as now, "every naturalist knows vaguely what he means when he speaks of a species." It is odd how some things never change!
Again anticipating the study of ecology, Darwin notes that features found to be useful in one individual of a species may not be so useful in another. He alludes to thickness of coat as an example: this is a more important feature to an animal in an extreme environment than to one in a more temperate locale, although the capacity to vary its thickness seasonally may be more important to the resident of the temperate zone. What varies in a species has traditionally not been considered important, but Darwin notes the circularity of the argument in which "important organs never vary", thereby removing such variation from consideration by using it to divide organisms into different species. Yet, substantial variation in unambiguously important organs can be found within otherwise-defined species: what we now know to be developmental variation in insects is noted by Darwin to produce very different morphologies in the paths taken by individual nerves.
The problem is most severe in what Darwin calls "protean" or "polymorphic" species. Such species (or indeed genera), claims Darwin, tend to be highly variable everywhere that they have been found, and in the case of fossils, in every period. This suggests that plasticity in development is itself an inheritable trait, at least inasmuch as that the corrective forces keeping development on a particular path are stronger in less-variable species, and weaker in more-variable ones. Darwin notes that the parts of organisms that vary are likely of less value to their survival than are the parts that do not, which is a necessary observation of any system in which natural selection is in operation.
Darwin next delves into the question of terminology, addressing the question of how much variation can be tolerated within a given species. Essentially, he says, the question cannot easily be settled; every specialist has a different list of valid species. He brushes by the distinction between allopatric and sympatric species, which would become important to evolutionary theorists in years to come. Here he merely notes that geography can be as characteristic as is form to determining species boundaries. Ultimately, the question of dividing individual species must be done using objective criteria, something that still has not been settled today; to do otherwise is "vainly to beat the air." Darwin briefly mentions what are now called "ring species", in which neighbouring forms are obviously continuous species, but members of the extremes of the range are distinct and do not easily interbreed.
The degree of known variation within a group of organisms is in no small part a function of the degree to which it has been studied. This is, of course, obvious, but it has important implications to the distinction of individual species, and Darwin goes from there to point out that it is much easier to learn a new group of organisms by taking their representatives from a particular locale in isolation; to consider initially those from other locations as well tends to confuse things. Once familiarity with a particular flora or fauna is attained, though, extending one's range of observations will challange one's sense of "species", both usefully and otherwise, as what could be diagnostic for a species in one region may ultimately prove highly variable between regions.
Having shown how variable individual species may be, and having suggested almost in passing that varieties within a species may in fact be incipient species, Darwin makes the important point that such varieties need not ultimately become different species. He goes on to point out that larger genera (those with more species) are both more widely distributed and more dominant than smaller genera, a point which I am not sure holds today. There are, at the very least, certainly exceptions, and Darwin points to a few of them himself. In particular, those species adapted to unusual environments (aquatic plants, for instance), tend to be more uniform. The other case that he gives, "plants low in the scale of organisation" being more widely distributed than their "higher" counterparts, I find definitely doubtful, on a similar principle to Darwin's own above. While individual knowledge of variation increases (at the very least) one's capacity to erect species distinctions, the features which vary in "lowly" organisms do so less markedly, and so the important distinctions are all the more subtle. To make a modern point of this, while they may not have evolved as far from the common ancestor as "higher" forms, they have nevertheless been evolving for the same length of time, and often for the same number of generations, and have had every opportunity to vary in ways that we may not appreciate.
An unwritten generalisation follows: Darwin believes nature to be essentially uniformitarian. This was a controversial geological principle when Darwin left on the Beagle, stating that the processes which shaped the Earth in the past are still in effect today. There are too many known exceptions for this to be considered strictly true today, and many of the processes which we now understand to be in effect (plate tectonics, for instance) were unsuspected in the early nineteenth century, but the essential notion is correct. Darwin's application of this to biology is a cornerstone to the science. In other words, evolution has happened, and it is continuing to happen today: it can be made an experimental science. These notions are not explicit in the Origin (at least not at this point in the work), but they are very much implied.
In summary, this chapter appears to make two important main points. First, the larger genera (by which is meant the more speciose genera), the more varieties can be found within each of its species. A related though distinct point is that the threshold of variation characterising each of those species and varieties is lower than that for the smaller genera, within which species and varieties tend to be more distinct from one another. As I said above, I am not sure that this is actually the case, and in any event, I do not see how it is critical to Darwin's argument. Far more important is this chapter's other point, that variation is a continuum: the more closely one looks, the more similarities one finds between different groups, and the more individual differences one sees within individual groups. Species are artificial constructs, conveniences for human classification, and are not always unambiguously delineated. Furthermore, "little groups of species are generally clustered like satellites around certain other species", by which Darwin means that genera may be divided into subgenera, the species of which resemble one another to a greater degree than they do members of other subgenera, and which tend to be found in closer proximity to one another geographically as well as morphologically. This is not an unimportant point: the continuity between species is not evenly distributed, and the fuzziness of the species definition can be extended to higher levels as well.
Tuesday, 20 January 2009
The Origin, Chapter One
A couple of weeks ago, a friend asked whether there was a group in place to read Darwin's Origin of Species this year, on the 150th anniversary of its initial publication. I replied that I was not aware of any such group, and somehow wound up helping to found one. I had read the sixth and final edition before, and have decided to read the first edition for this group. (All editions are available for free online at Darwin Online.) We are having our initial meeting tomorrow, but I have had enough thoughts about the work that I felt it appropriate to record them here, before being shaped too much by others' interpretations.
The Introduction begins abruptly, so much so that I almost wondered whether there was a page missing in the submitted manuscript. It is written in a comparatively casual tone, almost as a letter to the reader, and nothing like one would expect of one of the most significant works of science ever published. It starts with a summary of the genesis of the work, in what would be a brief account in modern terms, and nothing short of astonishingly so in Darwin's Victorian terms. I should mention that, though I am tempted to cover this history here, it is not my point to summarise the book, so much as to critique it, from both a modern and (so far as I can succeed in placing myself into it) a contemporary context. My prior experience with it was positive enough that I would encourage others to read it for themselves; I flatter myself to think that this account might help in understanding Darwin's work, but I have no intention of replacing it. At the same time, Darwin regarded this 450-page book as an abstract, which only a Victorian could do. He apologises for not citing the work of others (although he does refer to such work frequently, and attributes it accordingly, he does not indicate where one might find it published), appealing to a lack of space -- again, a charmingly (some might say irritatingly) Victorian conceit in so large a work. I think it more reasonable to consider that Darwin was under considerable pressure to get his work published, since he had almost been scooped by Wallace. He gives an acknowledgement to his peers and mentors that (again) would be concise in modern terms, mentioning nobody by name aside from Hooker.
Then the Introduction begins as one might expect it to, setting the stage for the work to follow. Darwin first addresses the complexity not only of living things in and of themselves but as well that of their interactions with their environment and with other living things, which he supposes makes the proposition all the more marvellous that they arrived at their present state exclusively through natural processes. All this, he says, will be explained; and he feels it best to start with a discussion of a process analogous to his favoured mechanism, and so begins an outline of the book itself. The first part of the book (comprising five chapters) takes off from this point to discuss artificial selection, and moves on from there to cover variation in nature; the overproduction and differential survival of members of each successive variation; and the central principle of natural selection. He rounds this part of the book off with a discussion of the laws of variation and of correlation (of which I have more to say shortly). The second part of the book (the next four chapters) discusses possible objections to his theory: the complexity of any living thing and its constituent parts; the matter of instinct and other behavioural traits; the erection of biologically relevant boundaries between species; and the paucity of data from the fossil record. The third part of the book (another four chapters) picks up on this last theme, but move from addressing possible flaws in the theory to demonstrating its strengths: the continuity of living things from one form to another through time; two chapters on biogeography; and finally one on classification and comparative biology. Finally, he summarises the whole work in the last chapter.
Darwin finishes his Introduction with more uncharacteristic brevity, remarking with model honesty that the theory is far from finished, and while it is capable of explaining much, it does not cover everything. His last sentence is worthy of repetition: "Furthermore, I am convinced that Natural Selection has been the main but not exclusive means of modification." This is remarkable especially in that Darwin is often assumed to have been a strict adaptationist -- to have held that everything in life can be explained solely through natural selection acting on existing variation. This misconception has gone to the point of modern scientists claiming exactly that being called "Darwinians". Darwin was ahead of his time in many ways, and one of them was this very conviction.
Chapter One of the book (as mentioned) covers artificial selection. I have comparatively less to say on this; it is at this point that the Victorian locks are opened and the flood of words rushes through. Stylistic considerations aside, the fact that the meat of the book begins here means that the pace must necessarily slow somewhat. My earlier impression is not contradicted, though: Darwin remains quite readable, for all his verbosity.
The first chapter is divided into several sections in the table of contents, but these are lumped together by headings in the text itself, and by the running titles at the top of the page. The first such section deals with what Darwin knew of genetics, which is almost embarrassingly incorrect. It is truly impressive how much he got wrong -- not just wrong, but at times fantastically so -- and yet he managed to draw the right conclusions from such faulty premises. Much has been said of the irony of Darwin and Mendel being contemporaries unaware of one another's work, and of how the combination of their work led to a paradigm shift in biology almost as significant as that generated by each body of work taken by itself. Darwin assumed that inheritance was an analogue matter, that traits from each parent blended together rather than existed as isolatable units, and had no explanation for such phenomena as recessive traits or chromosomal linkage. At the same time, he was quite aware that some traits did seem to be connected, and suggests something suspiciously close to pleiotropy, in which a single gene affects multiple traits -- a situation which can explain the evolution of many seemingly neutral or even deleterious traits, assuming them to be so linked to beneficial traits. Darwin is similarly aware of reversions as significant, but has no appreciation for any mechanisms behind such phenomena. Then again, he is not concerned with the mechanisms of genetics, which is perhaps why is able to be so right in his conclusions while being so wrong in his premises. Another angle that Darwin plays a fair bit on is the origin of domestic animals and plants, on which he speculates somewhat unrestrainedly, but rarely far from what has become accepted today.
The second section of this chapter deals with one particular example of domestication. Having spent five years at sea, Darwin proceeded to invest himself in studies of individual groups of living things -- beetles, barnacles, earthworms, and pigeons. The latter provide the subject of this section. Here he is on much firmer footing. Darwin impresses, perhaps ostentatiously so, with his encyclopaedic knowledge of breeds and characteristics of pigeons, and gives examples of how some of the more extravagant breeds could have come about. This blends into the third section, which expands the discussion to cover other species, and from there to the fourth, which covers the mechanisms of selection -- but from an ecological rather than a genetic point of view. The fifth and sixth sections take this further, positing that much artificial selection is unconscious. There are thus two types of artificial selection at work, one planned and rapid, the other a slow and organic extension of the collective preference of those charged with keeping living things. Throughout these sections, this is where Darwin truly shines (I have read -- though I forget where -- of Darwin being regarded as a pioneer in ecology as well as evolution); he looks best at the big picture, even while supplying a torrent of fine details. At the same time, his arguments here are obvious, which is perhaps why his work made such an impression at the time. It is impossible not to agree with him.
A seventh section concerns the "circumstances of man's selection", in which Darwin refutes the notion that many domesticated varieties arose recently because their variability manifested itself only recently. Not so, claims Darwin: rather, it is only recently that human meticulousness and record-keeping rose to the level of being able to pick out such subtle differences as were always present but insufficiently selected before. At the same time, he falters a little here, in his assessment of the degrees of variability amongst different domesticated plants and animals. It is true that (as he suggests) individual species' behavioural attributes contribute (and this is an important factor which I am not sure others had noted beforehand), but there are many more dimensions to consider. Among other things, some species simply do have a greater tendency toward morphological variation than others. Time is a factor as well: something that has been bred for thousands of years will have had the chance to diverge much further from its original form than something that has only been bred for hundreds of years. Dogs and cats illustrate both of these points: dogs are not merely more tractable animals than cats -- they are in fact more plastic as a species, and they have been domesticated for far longer than cats (or, for that matter, anything else), giving far more time in which to exaggerate that plasticity.
Finally, Darwin gives us a single-page summary of the chapter, and a pithy ending: "Over all these causes of Change I am convinced that the accumulative action of Selection, whether applied methodically and more quickly, or unconsciously and more slowly, but more efficiently, is by far the predominant Power." Thus begins the book that changed biology.
The Introduction begins abruptly, so much so that I almost wondered whether there was a page missing in the submitted manuscript. It is written in a comparatively casual tone, almost as a letter to the reader, and nothing like one would expect of one of the most significant works of science ever published. It starts with a summary of the genesis of the work, in what would be a brief account in modern terms, and nothing short of astonishingly so in Darwin's Victorian terms. I should mention that, though I am tempted to cover this history here, it is not my point to summarise the book, so much as to critique it, from both a modern and (so far as I can succeed in placing myself into it) a contemporary context. My prior experience with it was positive enough that I would encourage others to read it for themselves; I flatter myself to think that this account might help in understanding Darwin's work, but I have no intention of replacing it. At the same time, Darwin regarded this 450-page book as an abstract, which only a Victorian could do. He apologises for not citing the work of others (although he does refer to such work frequently, and attributes it accordingly, he does not indicate where one might find it published), appealing to a lack of space -- again, a charmingly (some might say irritatingly) Victorian conceit in so large a work. I think it more reasonable to consider that Darwin was under considerable pressure to get his work published, since he had almost been scooped by Wallace. He gives an acknowledgement to his peers and mentors that (again) would be concise in modern terms, mentioning nobody by name aside from Hooker.
Then the Introduction begins as one might expect it to, setting the stage for the work to follow. Darwin first addresses the complexity not only of living things in and of themselves but as well that of their interactions with their environment and with other living things, which he supposes makes the proposition all the more marvellous that they arrived at their present state exclusively through natural processes. All this, he says, will be explained; and he feels it best to start with a discussion of a process analogous to his favoured mechanism, and so begins an outline of the book itself. The first part of the book (comprising five chapters) takes off from this point to discuss artificial selection, and moves on from there to cover variation in nature; the overproduction and differential survival of members of each successive variation; and the central principle of natural selection. He rounds this part of the book off with a discussion of the laws of variation and of correlation (of which I have more to say shortly). The second part of the book (the next four chapters) discusses possible objections to his theory: the complexity of any living thing and its constituent parts; the matter of instinct and other behavioural traits; the erection of biologically relevant boundaries between species; and the paucity of data from the fossil record. The third part of the book (another four chapters) picks up on this last theme, but move from addressing possible flaws in the theory to demonstrating its strengths: the continuity of living things from one form to another through time; two chapters on biogeography; and finally one on classification and comparative biology. Finally, he summarises the whole work in the last chapter.
Darwin finishes his Introduction with more uncharacteristic brevity, remarking with model honesty that the theory is far from finished, and while it is capable of explaining much, it does not cover everything. His last sentence is worthy of repetition: "Furthermore, I am convinced that Natural Selection has been the main but not exclusive means of modification." This is remarkable especially in that Darwin is often assumed to have been a strict adaptationist -- to have held that everything in life can be explained solely through natural selection acting on existing variation. This misconception has gone to the point of modern scientists claiming exactly that being called "Darwinians". Darwin was ahead of his time in many ways, and one of them was this very conviction.
Chapter One of the book (as mentioned) covers artificial selection. I have comparatively less to say on this; it is at this point that the Victorian locks are opened and the flood of words rushes through. Stylistic considerations aside, the fact that the meat of the book begins here means that the pace must necessarily slow somewhat. My earlier impression is not contradicted, though: Darwin remains quite readable, for all his verbosity.
The first chapter is divided into several sections in the table of contents, but these are lumped together by headings in the text itself, and by the running titles at the top of the page. The first such section deals with what Darwin knew of genetics, which is almost embarrassingly incorrect. It is truly impressive how much he got wrong -- not just wrong, but at times fantastically so -- and yet he managed to draw the right conclusions from such faulty premises. Much has been said of the irony of Darwin and Mendel being contemporaries unaware of one another's work, and of how the combination of their work led to a paradigm shift in biology almost as significant as that generated by each body of work taken by itself. Darwin assumed that inheritance was an analogue matter, that traits from each parent blended together rather than existed as isolatable units, and had no explanation for such phenomena as recessive traits or chromosomal linkage. At the same time, he was quite aware that some traits did seem to be connected, and suggests something suspiciously close to pleiotropy, in which a single gene affects multiple traits -- a situation which can explain the evolution of many seemingly neutral or even deleterious traits, assuming them to be so linked to beneficial traits. Darwin is similarly aware of reversions as significant, but has no appreciation for any mechanisms behind such phenomena. Then again, he is not concerned with the mechanisms of genetics, which is perhaps why is able to be so right in his conclusions while being so wrong in his premises. Another angle that Darwin plays a fair bit on is the origin of domestic animals and plants, on which he speculates somewhat unrestrainedly, but rarely far from what has become accepted today.
The second section of this chapter deals with one particular example of domestication. Having spent five years at sea, Darwin proceeded to invest himself in studies of individual groups of living things -- beetles, barnacles, earthworms, and pigeons. The latter provide the subject of this section. Here he is on much firmer footing. Darwin impresses, perhaps ostentatiously so, with his encyclopaedic knowledge of breeds and characteristics of pigeons, and gives examples of how some of the more extravagant breeds could have come about. This blends into the third section, which expands the discussion to cover other species, and from there to the fourth, which covers the mechanisms of selection -- but from an ecological rather than a genetic point of view. The fifth and sixth sections take this further, positing that much artificial selection is unconscious. There are thus two types of artificial selection at work, one planned and rapid, the other a slow and organic extension of the collective preference of those charged with keeping living things. Throughout these sections, this is where Darwin truly shines (I have read -- though I forget where -- of Darwin being regarded as a pioneer in ecology as well as evolution); he looks best at the big picture, even while supplying a torrent of fine details. At the same time, his arguments here are obvious, which is perhaps why his work made such an impression at the time. It is impossible not to agree with him.
A seventh section concerns the "circumstances of man's selection", in which Darwin refutes the notion that many domesticated varieties arose recently because their variability manifested itself only recently. Not so, claims Darwin: rather, it is only recently that human meticulousness and record-keeping rose to the level of being able to pick out such subtle differences as were always present but insufficiently selected before. At the same time, he falters a little here, in his assessment of the degrees of variability amongst different domesticated plants and animals. It is true that (as he suggests) individual species' behavioural attributes contribute (and this is an important factor which I am not sure others had noted beforehand), but there are many more dimensions to consider. Among other things, some species simply do have a greater tendency toward morphological variation than others. Time is a factor as well: something that has been bred for thousands of years will have had the chance to diverge much further from its original form than something that has only been bred for hundreds of years. Dogs and cats illustrate both of these points: dogs are not merely more tractable animals than cats -- they are in fact more plastic as a species, and they have been domesticated for far longer than cats (or, for that matter, anything else), giving far more time in which to exaggerate that plasticity.
Finally, Darwin gives us a single-page summary of the chapter, and a pithy ending: "Over all these causes of Change I am convinced that the accumulative action of Selection, whether applied methodically and more quickly, or unconsciously and more slowly, but more efficiently, is by far the predominant Power." Thus begins the book that changed biology.
Thursday, 8 January 2009
One Reason Why We Need Government
The always-excellent Slacktivist has a long but very readable post about the evils of big monopolies. Go read it.
I continue to maintain that any Libertarian whingeing about "big government" fails to take into consideration the fact that, in theory at least, the government is accountable to the people, while international corporations (and especially monopolies) can and will do anything that they can get away with. It is only the government that is capable of defining what they can get away with. The government may not presently be as accountable as it should be, but that is the fault of the voters. So, when the opportunity arises, vote, and vote responsibly. Only that way will we get both fair government and fair businesses.
I continue to maintain that any Libertarian whingeing about "big government" fails to take into consideration the fact that, in theory at least, the government is accountable to the people, while international corporations (and especially monopolies) can and will do anything that they can get away with. It is only the government that is capable of defining what they can get away with. The government may not presently be as accountable as it should be, but that is the fault of the voters. So, when the opportunity arises, vote, and vote responsibly. Only that way will we get both fair government and fair businesses.
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