All reviews copyright 2014 Evelyn C. Leeper.
THE ORIGIN OF SPECIES by Charles Darwin:
[From "This Week's Reading", MT VOID, 12/26/2014]
Well, I finally got around to reading THE ORIGIN OF SPECIES by Charles Darwin (ISBN 978-0-451-52906-0). What follows are just random comments.
- "It is, therefore, of the highest importance to gain a clear insight into the means of modification and coadaptation. At the commencement of my observations it seemed to me probable that a careful study of domesticated animals and of cultivated plants would offer the best chance of making out this obscure problem."
Of course, this is only half the problem. We see modification all the time, but there needs to be an explanation of why some modifications are retained and others lost in the ocean of change. Natural selection is Darwin's answer, and to the extent that there are modifications deemed favorable by the breeder/farmer, these survive while other, less desirable modifications do not.
- "efficient cause"
An Aristotelian term, meaning something separate from the object being changed that interacts with it to cause the change. In most of THE ORIGIN OF SPECIES, this would be something in the environment.
- "Not one of our domestic animals can be named which has not in some country drooping ears; and the view which has been suggested that the drooping is due to disuse of the muscles of the ear, from the animals being seldom much alarmed, seems probable."
However, this would be inheritance of acquired characteristics. As we will see, Darwin seemed to believe in this, mostly because the knowledge of how characteristics are passed on to the next generation (genes, chromosomes, etc.) was unknown to him. (Darwin published THE ORIGIN OF SPECIES in 1859. Mendel first published in 1866, but his ideas about inheritance did not take hold until 1900, and DNA as the material was not established until the 1940s.) Could it be that when breeders select for "domesticity" they have an unconscious bias for drooping ears, which look more "relaxed"? (See the Russian experiments on domesticating foxes.)
- "the mysterious laws of correlation." Some of these can be explained by the location of genes--genes located on the same chromosome will tend to be correlated, and even more so the closer together they are.
- "I do not believe, as we shall presently see, that the whole amount of difference between the several breeds of the dog has been produced under domestication; I believe that a small part of the difference is due to their being descended from distinct species."
Actually, the current belief is that they all are descended from one species. (If one believes that species divisions are based in large part on mutual fertility, then Darwin's belief makes no sense, since all dog "varieties" can breed with all other varieties, and it seems unlikely that two or more species could merge into one.)
- "Man can hardly select, or only with much difficulty, any deviation of structure excepting such as is externally visible; and indeed he rarely cares for what is internal."
This is less true now, of course, with X-rays and other diagnostic tools, but in Darwin's day, by the time they had opened up an animal to see what was inside, it was extremely unlikely that they would survive to reproduce.
- "Certainly no clear line of demarcation has as yet been drawn between species and sub-species--that is, the forms which in the opinion of some naturalists come very near to, but do not quite arrive at, the rank of species; or, again, between sub-species and well-marked varieties, or between lesser varieties and individual differences." This is still true, though the "inter-breeding rule" seems to be what most people use for most species.
- "WIDE-RANGING, MUCH DIFFUSED, AND COMMON SPECIES VARY MOST."
- "SPECIES OF THE LARGER GENERA IN EACH COUNTRY VARY MORE FREQUENTLY THAN THE SPECIES OF THE SMALLER GENERA."
These are so important that Darwin puts them in all capital letters.
- "Where many species of a genus have been formed through variation, circumstances have been favourable for variation; and hence we might expect that the circumstances would generally still be favourable to variation. On the other hand, if we look at each species as a special act of creation, there is no apparent reason why more varieties should occur in a group having many species,"
And this is why the previous observations are important. If speciation is randomly generated by a higher being, there is no reason for this to be true. But if it follows rules, then there is an explanation.
- "Owing to this struggle, variations, however slight and from whatever cause proceeding, if they be in any degree profitable to the individuals of a species, in their infinitely complex relations to other organic beings and to their physical conditions of life, will tend to the preservation of such individuals, and will generally be inherited by the offspring."
This is the key point, but again, Darwin seems to be including inheritance of acquired characteristics ("from whatever cause proceeding").
- "It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for in this case there can be no artificial increase of food, and no prudential restraint from marriage. Although some species may be now increasing, more or less rapidly, in numbers, all cannot do so, for the world would not hold them."
Darwin recognizes that humans can increase their food production and consciously limit their reproduction, so strict Malthusian rules do not apply. (See "agriculture", "The Green Revolution", etc.) But what is interesting is that Darwin refers to it applying to the "whole animal ... kingdom", while clearly excluding humans from that group.
- "What natural selection cannot do, is to modify the structure of one species, without giving it any advantage, for the good of another species;"
Even without genetics, Darwin got this one right. Exceptions (symbiotic relationships, for example) evolve because there is an advantage to both sides.
- "with animals and plants a cross between different varieties, or between individuals of the same variety but of another strain, gives vigour and fertility to the offspring; and on the other hand, that CLOSE interbreeding diminishes vigour and fertility;"
It is fascinating that this is considered true for plants and animals, but often not for people, where "purity of blood" seems to be many people's belief.
- "These anomalous forms may be called living fossils; they have endured to the present day, from having inhabited a confined area, and from having been exposed to less varied, and therefore less severe, competition."
Darwin later explains why we find no intermediate forms: the intermediate forms would be the common ancestors from millions of years ago. Yet he needs to explain why some ancient forms are still around.
- "naturalists have not defined to each other's satisfaction what is meant by an advance in organisation. Among the vertebrata the degree of intellect and an approach in structure to man clearly come into play."
This may have been the method then, but not any more. The closest relatives (genetically speaking) to primates are bats, yet in intelligence it would seem that crows are smarter. (Of course, this assumes we know what we mean by "smarter.") The use of structure is important. For example, mammals are defined by structure, whether it is the "has hair", "secretes milk", or "has three bones in the inner ear" rule.
- "the continued existence of lowly organisms offers no difficulty; for natural selection, or the survival of the fittest, does not necessarily include progressive development--it only takes advantage of such variations as arise and are beneficial to each creature under its complex relations of life."
This is something most people do not understand. There is a belief that the most elaborate or complex organisms represent the peak of evolution, the apex of the "tree." But everything that still exists is at the end (the apex) of its branch. It has evolved enough to survive, which is the goal.
- "the advancement of the whole class of mammals, or of certain members in this class, to the highest grade would not lead to their taking the place of fishes." This seems an argument as to why "progressive development" is not required. Fishes are arguably "less developed" than humans, yet humans cannot take the place of fishes. However, the greater development of humans has resulted in them being able to wipe out whole species of fishes, so one can argue that the greater development has led humans to be more adapted to survival than the fishes--or just about any other species.
(Of course, this is only in the short term. If we kill off enough species, we will create an unstable situation that kills us off as well.)
- "I think there can be no doubt that use in our domestic animals has strengthened and enlarged certain parts, and disuse diminished them; and that such modifications are inherited."
Here is where Darwin explicitly endorses the theory of the inheritance of acquired characteristics. His phrasing regarding use and disuse, however, is a clue that he is endorsing the Lamarckian theory which involves the use or disuse of characteristics in response to the environment. Lamarck's theory specifically excluded such commonly offered "counter-examples" as male circumcision and docking boxers' tails. Those are caused by external forces, not use or disuse. And indeed Darwin later says:
- "The evidence that accidental mutilations can be inherited is at present not decisive; but the remarkable cases observed by [Charles-Edouard] Brown-Sequard in guinea-pigs, of the inherited effects of operations, should make us cautious in denying this tendency."
Brown-Sequard is perhaps best known (though not by name) for the claim that extracts of monkey glands "rejuvenated sexual prowess." This is because Sir Arthur Conan Doyle wrote "The Adventure of the Creeping Man" in which a character hopes to rejuvenate himself by injecting himself with monkey glands. (Okay, it's a bit of a spoiler, but the story is over a hundred years old and a classic.)
However, Brown-Sequard also claimed that he had induced a form of epilepsy in guinea pigs by operating on their spinal cords, and that this was inherited by their offspring. The current belief is that this was possibly due to a transmitted disease, or just anomalous results.
- "According to the ordinary view of each species having been independently created, we should have to attribute this similarity in the enlarged stems of these three plants, not to the vera causa of community of descent, and a consequent tendency to vary in a like manner, but to three separate yet closely related acts of creation."
Again Darwin points out the illogicality of the orderliness and structure of the natural world if everything was created in a "separate act of creation."
- "He who believes that each equine species was independently created, will, I presume, assert that each species has been created with a tendency to vary, both under nature and under domestication, in this particular manner, so as often to become striped like the other species of the genus; and that each has been created with a strong tendency, when crossed with species inhabiting distant quarters of the world, to produce hybrids resembling in their stripes, not their own parents, but other species of the genus."
Again, Darwin points out the underlying structure to nature is not consistent with independent acts of creation for all species.
- "animals displaying early transitional grades of the structure will seldom have survived to the present day, for they will have been supplanted by their successors, which were gradually rendered more perfect through natural selection."
Here is Darwin's explanation of the lack of transitional forms.
- "When it was first said that the sun stood still and the world turned round, the common sense of mankind declared the doctrine false; but the old saying of Vox populi, vox Dei, as every philosopher knows, cannot be trusted in science."
Mark compares taking polls about scientific facts to a kindergarten class voting on whether their pet hamster is a boy or a girl.
- "natural selection would have had different materials or variations to work on, in order to arrive at the same functional result; and the structures thus acquired would almost necessarily have differed. On the hypothesis of separate acts of creation the whole case remains unintelligible."
Again, the result of species applying different adaptations to achieve the same result makes a lot of sense in an evolving world, but none in a created one. Why create (for example) several different organs which all are organs of sight rather than just one?
- "if on the whole the power of stinging be useful to the social community, it will fulfil all the requirements of natural selection, though it may cause the death of some few members."
That is, if it is useful to the community overall, those communities which have members who tend to produce stinging insects will survive to produce more, while those communities who do not produce stinging insects will die off.
- "On the other hand, the transportal of the lower eye of a flat- fish to the upper side of the head, and the formation of a prehensile tail, may be attributed almost wholly to continued use, together with inheritance." Another Lamarckian claim.
- "The foregoing rules and facts, on the other hand, appear to me clearly to indicate that the sterility, both of first crosses and of hybrids, is simply incidental or dependent on unknown differences in their reproductive systems;"
Here Darwin indicates that the cross-breeding rule for determining species will not work in all cases.
Why then is not every geological formation and every stratum full of such intermediate links? Geology assuredly does not reveal any such finely graduated organic chain; and this, perhaps, is the most obvious and serious objection which can be urged against my theory. The explanation lies, as I believe, in the extreme imperfection of the geological record.
It may seem like we find all sorts of thing, but the ratio of number of finds to number of animals (or plants) is microscopic.
- "Sir W. Thompson concludes that the consolidation of the crust can hardly have occurred less than twenty or more than four hundred million years ago, but probably not less than ninety-eight or more than two hundred million years. These very wide limits show how doubtful the data are; and other elements may have hereafter to be introduced into the problem."
Thompson is in the ballpark for *oceanic* crust, but the continental crust is between 3.7 and 4.28 *billion* years old, making him off by a factor of 2000 or so.
- "Mr. Croll estimates that about sixty million years have elapsed since the Cambrian period, but this, judging from the small amount of organic change since the commencement of the Glacial epoch, appears a very short time for the many and great mutations of life, which have certainly occurred since the Cambrian formation; and the previous one hundred and forty million years can hardly be considered as sufficient for the development of the varied forms of life which already existed during the Cambrian period."
Croll's estimate is slightly better: the Cambrian was from about 541 million years ago to about 485 million years ago, making him off by a factor of "only" 16.
- "Even the wide interval between birds and reptiles has been shown by the naturalist just quoted to be partially bridged over in the most unexpected manner, on the one hand, by the ostrich and extinct Archeopteryx, and on the other hand by the Compsognathus, one of the Dinosaurians--that group which includes the most gigantic of all terrestrial reptiles."
Darwin cites the interval between birds and reptiles as wider than that between various genera of mammals, yet it is no longer clear than this is so. We have now declared birds to be dinosaurs, and consigned the category "reptiles" to the dust bin, at least in modern cladistic taxonomy. (Reptiles have no common ancestor that does not also include birds among its descendents.)
- "To attempt to compare members of distinct types in the scale of highness seems hopeless; who will decide whether a cuttle-fish be higher than a bee--that insect which the great Von Baer believed to be 'in fact more highly organised than a fish, although upon another type?'"
The problem, as Darwin notes, is that some things are not commensurate. Which is better, a good steak or a dish of good ice cream? Which is more beautiful, a sunset or a flower?
- "Notwithstanding this general parallelism in the conditions of Old and New Worlds, how widely different are their living productions!"
If species were created for their environments, why make two entirely different sets of plants and animals for basically identical environments?
- "there would be great difficulty in their transportal across the sea, and therefore we can see why they do not exist on strictly oceanic islands. But why, on the theory of creation, they should not have been created there, it would be very difficult to explain."
If everything was created, why not create broad populations on oceanic islands, instead of having just a few species (particularly of land mammals?
As for populating islands with plants and animals, Surtsey (an island off the coast of Iceland formed by a volcanic eruption from November 1963 through June 1967) is a perfect laboratory. According to Wikipedia:
Plants began growing even before the eruption ended. By 2008, 69 species of plant had been found on Surtsey, of which about 30 had become established. More species continue to arrive, at a typical rate of roughly 2-5 new species per year.
Birds began nesting on Surtsey three years after the eruptions ended, and twelve species are now regularly found on the island. Marine life is abundant, both mammalian and invertebrate. Insects arrived very early: wind-borne, flying, and floating in on driftwood. A large, grass-covered tussock that arrived in 1974 had 663 land invertebrates on it, mostly alive. There are also slugs, earthworms, spiders, and beetles. As yet, there are apparently no land mammals, but since the island is only a half square mile it is not clear there is enough space.
- "if we had a real pedigree, a genealogical classification would be universally preferred"
Of course, now with DNA analysis, we pretty much have this.
- "Maupertuis' philosophical axiom 'of least action' leads the mind more willingly to admit the smaller number; and certainly we ought not to believe that innumerable beings within each great class have been created with plain, but deceptive, marks of descent from a single parent."
This is another version of "God created the Earth 6000 years ago, along with all the fossils and geological evidence to make us think it was billions of years old." As has been noted, there is nothing that makes this any more believable than "God created the Earth last Tuesday, along with all the memories and fossils and geological evidence to make us think it was billions of years old."
- "I believe that animals are descended from at most only four or five progenitors, and plants from an equal or lesser number."
Later, Darwin actually seems to indicate he thinks there is really only one point of origin, but that may have seemed too radical even for him.
- "In short, we shall have to treat species in the same manner as those naturalists treat genera, who admit that genera are merely artificial combinations made for convenience. This may not be a cheering prospect; but we shall at least be freed from the vain search for the undiscovered and undiscoverable essence of the term species."
I am not sure why naturalists were so willing to consider the larger divisions more artificial than the smaller ones, unless it was that to many the species seemed the final dividing line across which fertile cross-breeding could not take place (although Darwin gave several counter-examples).