Chapter IV - Natural Selection; or the Survival of the Fittest
In his usual rambling way, Darwin asked his readers to focus on the obvious struggle for existence in the natural world and on the power of selection by man to produce domestic varieties of plants and animals from wild stock. He further noted that the relations of "all organic beings" are "infinitely complex and close fitting" to each other and to the "physical conditions of life" (Page 88). His conclusion from his observations was that nature provided a strong power of selection to fine tune and produce new species of plants and animals. The process by which nature produced the slow changes in plants and animals to produce new species, he called "Natural Selection or Survival of the Fittest" (Page 88):
...natural selection is daily and hourly scrutinizing, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life (Pages 91-92).
He defined "nature" as the "aggregate action and product of many natural laws," and "laws" were "the sequence of events as ascertained by us" (Page 88).
Critique
It is redundant for me to state that according to the fossil record, species appear and disappear abruptly without the evidence of change required to support Darwinian gradualism. In addition, the power of selection man has used to acquire domestic plants and animals from wild stock has failed to create new species.
Darwin's concept of his "natural law" was virtually anything that he believed happened or appeared repeatedly without a natural explanation. It simply was; e.g., the appearance of the fully functioning, replicating, living cell from the primordial soup. He believed in the application of "Occam's razor;" that the simplest explanation for phenomena is more likely to be accurate than more complicated explanations with more assumptions. Thus, anything that happened or was assumed to happen repeatedly, was the result of a "law of nature" and required no further elucidation. One is prone to wonder if Darwin would have written On the Origin of Species had he known of the complex machinery and digital information required for the operation of a 1-celled bacterium.
Sexual Selection
Darwin noted that sexes of animals within a species were different. He hypothesized that often females selected specific males because they were more physically fit or more melodious or more beautiful than other males. Those males selected therefore had a greater chance of breeding and passing on their sexually preferred characteristics to their offspring. And those males rejected produced few or no offspring. This process, Darwin called "selection". He further noted that some sexual dimorphism was not related to sexual selection:
The tuft of hair on the breast of the wild turkey-cock cannot be of any use, and it is doubtful whether it can be ornamental in the eyes of the female bird... (Page 96).
Critique
Darwin made numerous statements without any knowledge of their validity. A case in point was his conclusion that a turkey beard on a gobbler has no survival value and likely no sexual appeal to the hen. Such statements provided no real support for his cause and had no scientific merit. The question as to the origin of female bird preferences for "beautiful" males apparently never entered Darwin's mind? If an observation provided a mystery, it was deemed irrelevant and fell into the abbess of "laws," "rules," and "principals" of nature.
The concept of sexual selection does provide a bit of a conundrum. Why does all-powerful natural selection allow a female bird to select for bright colors and outlandish courting behaviors in the male bird, open displays that can subject the male to higher rates of predation? Why do not female birds fall in love with reclusive males, well-camouflaged? Of course, there are numerous possible answers/hypotheses. Perhaps there is an absolute concept of beauty, often shared among different species? For example, humans find the colors in flowers that attract pollinators or the colors in birds and fish that attract suitors, pretty. The concept of beauty as an absolute, though repeatedly experienced in the worlds of many organisms, does not fit Darwin's philosophical materialism.
Illustrations of the Action of Natural Selection, or the Survival of the Fittest
Darwin provided several examples of how natural selection/survival of the fittest produced new varieties and subsequently new species of plants and animals. All of the examples were hypothetical because he had no real data to use. He said of wolves preying on deer:
...the swiftest and slimmest wolves would have the best chance of surviving and so be preserved or selected... (Page 97).
The stocky and fat, slower wolves would catch fewer deer, I suppose, and would therefore be subject to starvation. Darwin noted:
...according to Mr. Pierce, there are two varieties of wolf inhabiting the Catskill Mountains, in the United States, one with a light greyhound-like form, which pursues deer, and the other more bulky, with shorter legs, which more frequently attacks the shepherd's flocks (Page 97).
Darwin imagined a kind of bird that "could procure its food more easily by having its beak curved" and if nature produced an individual or individuals with curved beaks, those birds would have higher survival rates and would pass on the curved beak to more offspring. Over a span of time the entire species would change and prosper because of the development of the curved beak. He described his vision of the gradual evolution of a large continuous population:
...each newly-formed variety would generally be at first local, as seems to be the common rule with varieties in a state of nature; so that similarly modified individuals would soon exist in a small body together, and would often breed together. If the new variety were successful in its battle for life, it would slowly spread from a central district, competing with and conquering the unchanged individuals on the margins of an ever-increasing circle (Page 98).
From his imagination, Darwin described relationships between pollen-devouring insects and flowering plants evolving together, tree species evolving from having female and male flowers on the same individual trees into male and female trees ...to "be advantageous on the principle of the division of labour..." (Page 100). He provided other hypothetical examples to illustrate how natural selection or survival of the fittest worked to produce new species. These examples illustrated how:
...Natural selection acts only by the preservation and accumulation of 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 diluvia wave, so will natural selection banish the belief of the continued creation of new organic beings, or of any great and sudden modification in their structure (Page 102).
Critique
Imagination produces non-evidence - long-legged wolves chasing deer and short-legged wolves catching sheep? Try submitting that observation today for publication in the Journal of Mammalogy. Darwin said that evolution was a slow process and that species do not change rapidly. It is common knowledge now that the fossil record supports the pattern of the abrupt appearance and abrupt disappearance of species and the persistence of species' morphologies unchanged during the lives of the species (Stanley 1979; Eldridge and Gould 1972). The purpose of Darwin's imaginary examples of the evolution of whole populations from a core area within the extensive range of a large population was to support his concept of the gradual evolution of a species population. The abrupt appearance of new species and physiological and structural complexities pointed to programming and was too vitalistic and mysterious to accept.
On the Intercrossing of Individuals
In this relatively short discussion, Darwin talked about sexual reproduction by plants and animals that possess both male and female parts. He also discussed hybrid vigor that results from crossing varieties within a species and the detrimental effects of inbreeding within small populations of plants and animals.
Critique
Inbreeding in sma
ll isolated populations can reduce gene frequency/available variation. Thus, Darwin speculated that speciation occurred through the gradual evolution of whole, large populations with extensive ranges.
Circumstances Favourable for the Production of New Forms through Natural Selection
In this section, Darwin described the best conditions for the production of new species. As noted above, he believed large, continuous populations provided the best conditions for the production of new species. For example, large land masses provide room for large populations of plants or animals. Species with access to large ranges also must contend with varying environments that expose the species to differing selective forces. Competition, Darwin believed, was more intense for species that had large ranges than for species in isolation:
Although isolation is of great importance in the production of new species, on the whole I am inclined to believe that largeness of area is still more important, especially for the production of species which shall prove capable of enduring for a long period, and of spreading widely (Page 108).
Darwin believed species in isolation were less subject to modification than species in large, continuous habitats because smaller populations provided less variation for natural selection to act upon. Also, he said that the inorganic conditions of a smaller areas were more uniform and natural selection would therefore modify all the individuals of the same species in the same manner (Page 107).
Regarding the production of new species, Darwin ended this section:
That natural selection generally acts with extreme slowness I fully admit (Page 110)...I can see no limit to the amount of change, to the beauty and complexity of the co-adaptations between all organic beings, one with another and effected in the long course of time through nature's power of selection, that is by the survival of the fittest (Page 111).
Critique
Notwithstanding my obvious redundancy, the paleontological record supports the pattern of species appearing abruptly, living out their lives without substantial changes in their morphology, and disappearing abruptly (Stanley, 1979). Stephen Jay Gould and Niles Eldredge (1972) reviewed the fossil record in the 1970s and determined that the process of evolution happens in spurts and then stays unchanged for the life of the species. Gould and Eldredge called their new model of evolution "Punctuated Equilibrium". Of course, "Punctuated Equilibrium" is primarily a snapshot of species history in the fossil record and not an explanation of process.
Gould and Eldredge provided a hypothetical model for the process of speciation that they called "allopatric speciation". This model might be described as Darwinian gradualism in the parent population, followed by speciation conducted with apparent lightning speed (geologically speaking) once a small segment of the population is isolated, peripheral to the parent species' range. Gould believed natural selection occurred between species rather than between individuals within the species. The competition between species occurred once the isolated, new offspring species regained access to the parent species' or to a sibling species' range (Meyer 2013: 144).
One of the chinks in the theory of "allopatric speciation" concerns the step-wise development of beneficial mutations in genes housed by but not expressed in the parent population. How did the parent population develop superior genes ever so gradually in the Darwinian fashion but fail to make any use of those superior traits? How did the parent population develop multiple add-on, beneficial traits that failed to benefit the parent population?
According to the "allopatric speciation" model, relatively small populations of offspring, isolated from the parent population, extract beneficial changes in organs and structures inherited from the parent population. These beneficial mutations were originally stored by the parent population in "junk" DNA or non-coding portions of the DNA.
With greater chances for inbreeding in a small population, favorable traits have a greater statistical chance of appearing and being "fixed" or expressed and retained in a relatively small population. Of course, inbreeding within a small population virtually always leads to deleterious losses of genetic diversity. But, for the sake of the "allopatric speciation" argument, let us ignore that recurrent negative effect.
Thus, the offspring species in isolation, through inbreeding and random selection, finds and fixes the superior traits, formally stored in the junk DNA of the parent population, and then evolves rapidly by random chance into a superior species. Natural barriers over time diminish and the offspring species gains access to the large range of its parent species. Subsequently, the superior offspring species replaces the parent species through inter-species competition. Not surprisingly, the "allopatric speciation" hypothesis depends upon mutation of extant genes and offers no explanation whatsoever for the origin of the highly specified information those genes provide. For a formidable critique of neo-Darwinian hypotheses on the mechanisms underlying "allopatric speciation," see Meyer (2013: Chapters 7-14) and Behe and Snoke (2004) and Behe (2014).
Darwin was aware of the dangers of rapid speciation to his materialist model. Structures and organs were too complex and functionally fine-tuned to undergo coordinated changes unless developed step-wise ever so gradually. Rapid speciation in isolation offered no support for Darwin's vision of gradual evolution by wholly natural causes.
Meyer (2013:37-38) explained Darwin's obsession with gradualism:
...In the Origin, he (Darwin) sought to counter the famous watch-to-watchmaker design argument offered by theologian William Paley. Paley had argued that just as complex structures such as watches necessarily issue from intelligent watchmakers, the complex structures in living organisms must likewise owe their origin to a designing intelligence. With natural selection, Darwin proposed a purely natural mechanism for constructing the complex organs and structures (such as eyes) present in many forms of life. His mechanism of natural selection worked by constructing such systems one tiny step at a time, discarding the harmful variations and seizing upon the rare improvement. If evolution progressed by "whole watches" - that is, by entire anatomical systems like the trilobite's eye - then biology would have fallen back to the old absurdity of imagining that a watch could fall together purely at random and all at once. Thus, unless Darwin's evolutionary mechanism worked gradually by preserving the tiniest of random changes over many millions of years, it didn't work at all.
The fossil evidence asks: What is left of the Darwinian model for evolution? The answer - nothing except the assumptions that all species evolved from a common primitive (1-celled) ancestor and that intelligence was not involved in the creation of biological life in its myriad forms. Nothing is left but hope and faith...hope and faith in metaphysical materialism.
Extinction Caused by Natural Selection
Darwin repeated his gradualist model for evolution of species. He noted that because biological organisms tend to increase geometrically, each area will be fully stocked (Page 111). Thus, because of competition for limited resources, the "favored forms" will increase in number and the "less favored forms" will decline in number. Species with the largest number of individuals will have the greatest chances of producing favorable variations within a given time period. As new species in the course of time are formed through natural selection, others will become rarer and rarer, and finally extinct (Page 112). Extinction, like evolution, by the necessity of competition, must also occur ever so slowly.
Critique: It is apparent that Darwin believed that species developed gradually over time and that those species and varieties of species that were less adapted to their environments, in like fashion, slowly faded into extinction. He failed to recognize the role played by the abrupt appearance of new predators in the extinction of species. For example, the introduction of foxes, house cats, and rats into Australia in the last century caused the extinction of numerous native species within fifty years. A virulent strain or introduced microbe can exterminate a population of plants or animals in a short period of time in an obviously non-Darwinian fashion.
Dive
rgence of Character
The principle, which I have designated by this term (divergence of character), is of high importance, and explains, as I believe, several important facts (Page 112).
Darwin's wordy statement appears to apply, though vaguely so, to rather simple concepts in this section. He referred to an observation that varieties within a species have more in common than they do with other species. He also restated his belief that varieties within a species are incipient species. He then continued to explain how a variety becomes a new species with his usual reference to the microevolutionary and simple mutation processes involved in the process of domestication:
As has always been my practice, I have sought light on this head from our domestic productions (Page 113).
Darwin used several examples, including selection for swifter horses. Horse breeders tested their horses and kept the fastest horses to breed and they eliminated the slower individuals from their breeding stock. Over time, this selection process produced the fastest horses. Darwin used this illustration to show how natural selection produces new species in natural settings:
Here, then, we see in man's productions the action of what may be called the principle of divergence, causing differences, at first barely appreciable, steadily to increase, and the breeds to diverge in character, both from each other and from their common parent.
This change in character in the animal through selective breeding appears to be what Darwin called "the principle ...of high importance"...that "explains several important facts" (Page 112).
Darwin further explained that the more diversified the members of a species become, the more often they will successfully fit into varied environments within their range. For example, a theoretical species of carnivore might have numerous varieties slightly modified to climb trees better, or use water better, or eat and utilize different food sources more efficiently than competing varieties or other competing species (Pages 113-114).
Additional observations convinced Darwin that:
The truth of the principle that the greatest amount of life can be supported by great diversification of structure, is seen under many natural circumstances (Page 114).
He believed that complex environments produced high species diversities because competition was most intense in complex environments:
In an extremely small area, especially if freely open to immigration, and where the contest between individual and individual must be very severe, we always find great diversity in its inhabitants (Page 114).
Critique
Darwin referred to "the principle" and then talked about his "principle" of how selection works on variation to produce new species and then talked about "the principle" that a varied environment has more species because competition (selective pressure) is more intense in more complex environments. This principle or these principles, for Darwin, "explained several important facts" (Page 112). Because Darwin's model was theoretical and the organization of his ideas loose and rambling, it is difficult to determine where in his mind existed the line between "fact" and speculation. He did not appear to distinguish between the two.
I do, of course appreciate the observation that, generally more species occur in more complex environments, but whether competition within and between species is more intense in simple or more complex environments is a matter of speculation. How does one measure such relationships and their intensities? Again, as noted above, it is odd to me that Darwin made such bold statements with little or no justification, aside from the need to support his case for the macroevolution of species within the acceptable framework of his philosophical materialist beliefs.
Darwin's statements about severe competition between individuals "in an extremely small area" (Page 114) appeared to support evolution within small, isolated populations and contradicted his usual emphasis on evolution of whole populations widely distributed over large areas.
The Probable Effects of the Action of Natural Selection through Divergence of Character and Extinction, on the Descendants of a Common Ancestor
In this section, Darwin provided a theoretical diagram, his evolutionary tree of life, to represent his view that new species, new genera, and new sub-families derive from a common ancestor. He noted that natural selection acts on new variations that appear in a large genus with numerous species and the fit survive to reproduce and pass on their advantages to their offspring. These offspring do the same thing and over a thousand or a million or more generations of this repeated occurrence, new species and new genera develop by wholly natural means. These new genera and species successfully fill all the new and changing living situations that the world offers (Pages 116-124). That the tree of life diagram represented a gradual process of evolution, Darwin fully admitted:
In the diagram, each horizontal line has hitherto been supposed to represent a thousand generations, but each may represent a million or more generations... (Page 122).
Critique
Darwin's evolutionary tree of life graphically presented his speculations on the gradual evolution of species once again, just with a different theoretical format. By contrast, Gingerich (l977) showed that the major orders of placental mammals appeared over a relatively short time period during the Paleocene and Early Eocene. Orders as diverse as rodents, primates, bats, whales, carnivores, and hoofed mammals appeared fully formed over a period of about ten million years. That explosion of mammalian orders must be considered rapid in light of the observation that the average life span of a mammalian genus is about 8 million years (Stanley 1998:83). That burst of evolution left little time for the many intermediate forms required under Darwin's gradualist model.
At this point, Darwin had created a problem. His tree of life icon conflicted with his model for the gradual evolution of a whole population, widely distributed over a large land area, into a new species. His evolutionary tree of life could only develop if single parent species gave rise to two or more new offspring species at the same time; particularly if, as Darwin insisted, the improved offspring are always in the business of replacing the inferior parent species. If the parent species always evolved into a new species, Darwinian gradualism would have only produced a single species on the planet. Thus, the tree of life model brings to mind the question of how multiple species derive from the same parent species without some form of physical isolation.
In Darwin's gradualist model, the offspring variety with superior modification spreads throughout the area occupied by the parent species and through competition, replaces the parent species. In this phyletic model, how do multiple varieties compete with each other and with the parent species to from two or more different species...without physical isolation and with continual crossbreeding? Under On the Absence or Rarity of Transitional Varieties below, Darwin answered this question; albeit, with obvious awkwardness and rather comic effect.
He made an attempt to reign in his two disparate icons - the gradual evolution of a population and the evolutionary tree of life in light of the absence of transitional forms in the fossil record. He decided that there must be a "neutral zone" within the parent population. From this part of the parent species range, new modifications travel outward in different directions and modify different parts of the same population. Somehow, the offspring varieties evolve into separate species ever so gradually and without physical isolation.
At the same time, the various transitional forms that spread from the same "neutral zone" and are superior to the parent species, do not last as long as the various offspring species they eventually evolve into. This explains why the intermediate forms are not in the fossil record? Let's see...the superior and different varieties spread across different parts of the landscape and gradually replace the inferior parent population without replacing each other. And though they are superior offspring, they do not persist long because their own improved offspring ever so gradually but quickly replace them in order to explain their absence from the fossil record? Sounds like inexplicable twaddle to me.
&n
bsp; Another problem. Darwin's tree of life (page 117) shows opposite stems branching from the parent stem. That is, each parent stem terminates with a fan-shaped diversion of sister species continuing on after replacing the parent species. Subsequent renditions of the evolutionary tree of life have offered trees with alternate branching of species while the main branch, representing the parent species, continues to coexist with its offspring. I suppose Darwin was happy enough with the apparent support and felt no need to correct his followers. As noted earlier in this essay, neo-Darwinists now ignore Darwin's insistence on replacement of the parent species by improved offspring species.
On the Degree to Which Organisation Tends to Advance
Darwin's opening statement:
Natural Selection acts exclusively by the preservation and accumulation of variations, which are beneficial under the organic and inorganic conditions to which each creature is exposed at all periods of life.
Thus, Darwin encapsulated in a single sentence his hypothesis to explain the origin of species. The question remained, however, as to the ultimate goals of his gradualist model? He said that the goals of his model for evolution among the Vertebrata was toward the development of intellect and the "structure to man clearly..." (Page 124). Other criteria for the goals of gradual evolution included the differentiation of parts and specialization of function and "the standard of high organization..." (Page 125).
Of course, the question of why numerous primitive species still exist and often remained unchanged through time required a ready answer. Darwin said that such species live under relatively simple conditions where competition is reduced and natural selection has little opportunity to modify them. Also, he said that some of these primitive species live in small, confined spaces where the number of individuals is relatively small and therefore less variation is available for natural selection to act upon (Pages 125-126).
Another argument to explain why some "primitive" species have remained unchanged by evolution was that they are more complex than thought, showing that they had evolved to a relatively complex, static state:
...for every naturalist who has dissected some of the beings now ranked as very low in the scale, just have been struck with their really wondrous and beautiful organization" (Page 126).
Critique
Darwin had a lucid moment when he considered the initial origin of apparently complex but "primitive" beings:
But as we have no facts to guide us, speculation on the subject is almost useless (Page 127).
It seemed odd that the vitalistic goal of natural selection was the perfection of intellect in man. That made me feel good, special, and almost loved by natural selection. Quite oddly, natural selection anticipated Shakespeare, Mozart, and calculus through the process of selecting for the most aggressive bacteria. And, we see that the "primitive species" that remained unchanged for several hundred millions of years were unchanged because their simple systems functioned in areas of low competition and secondly, because they were actually very complex organisms that had reached evolutionary perfection. That was the really great thing about Darwin's materialist model of evolution...it explained everything, albeit in contradictory terms if necessary.
Convergence of Character
Darwin doubted that two species from "widely distinct" genera in the same living conditions would converge to form a single genus. However, in like environments, species from related genera would develop the same "organization" and eventually produce a single genus:
...and thus the descendants of two distinct genera would converge into one (Page 127).
Complex environments would have numerous species but there would be smaller populations of those species. With smaller populations, these species would be more subject to extinction by environmental extremes and predators. Dominant, better adapted species would spread over wide areas and would cause the extinction of many species; this being the primary cause for extinction of rare species. He noted that invaders in the southeast corner of Australia had reduced the number of endemic species there and such processes limited the creation of new forms/species (Page 129).
Critique
To date, there is no evidence that different species from different genera in like environments evolved together to produce a new genus. Again, Darwin ignored the obvious impact of new predators on endemic species. It is likely that many marsupials in Australia disappeared and thereby failed to produce new varieties of themselves simply because introduced foxes, domestic cats, and rats killed and ate them. The introduction of the European hare into Australia fit into Darwin's view of loss of endemics by displacement. Such displacement provided as much support for gradualism as did the development of varieties of domestic pigeons from the rock dove.
Summary
Because of the apparent relatedness of groups of species, Darwin concluded that species were not independently created. He produced a theoretical "tree of life" or "diagram" to illustrate how he believed species gave rise to numerous other species and genera.
Critique
Denton (1986:125) noted:
...today zoologists find it impossible to relate the major groups of organisms in any sort of lineal or sequential arrangement.
The relatively rapid diversification of complex organisms; e.g., whole phyla of animals extant today, during the Cambrian explosion/radiation left no evidences for family tree linkages to previous organisms. Up to the time of the Cambrian radiation, there is no support for common descent. After the Cambrian, the fossil evidence supports a pattern of rapid, adaptive radiation of groups of organisms. Insofar as the Darwinian model of gradualism is concerned, evidence trumps materialist theories.