Pesky Details: Essays for "Left Brain" Christians
Chapter V - Laws of Variation
Darwin believed there were two factors that caused variation in the species: 1) the conditions of life (environmental conditions) and 2) the nature of the organism. He stated that the "nature of the organism" was more important in creating variation in the species than was the organism's environmental conditions. He believed this to be the case because it was common knowledge that numerous species occupied highly variable habitats without notable differences within the species class.
According to Darwin, changed conditions of life created plasticity in the individual and the nature of the organism became more flexible and responsive to environmental changes. Darwin was not sure if natural selection acting on small successive changes or changes in the nature of the organism played a bigger part in the production of variation. On the other hand, because individuals within the same species frequently occupy such disparate living conditions, Darwin conceded that species have "a tendency to vary, due to causes of which we are quite ignorant" (Page 134).
Critique
Today we have an improved understanding of the mechanics of random mutations; e.g., insertions, deletions, gene duplication, and mobile DNA transpositions. We understand that random mutation works only with pre-existing machinery (Behe 2014:38, 62) and that all random mutations are diminishments and that they do not have the power to construct new protein-protein interactions (Behe 2014:77). Thus, we cannot account for the mechanics of new adaptations that lead to periodic and explosive speciation events on the planet like the Cambrian explosion. Oddly, Darwin thought natural selection played a role in the production of variation? Perhaps he had forgotten that natural selection can fix or undo variation in a population but has no power to create new variation? See Mutation at the end of this essay under Definitions/Notes.
Effects of the Increased Use and Disuse of Parts, Controlled by Natural Selection
In this section, Darwin discussed the loss and gain of the structural parts of species. He believed that species could modify themselves by their behaviors. For example, if an individual bird flew less often, it would lose some of its ability to fly and would pass that diminished ability on to its offspring. Over time, if individuals of a bird species continued to fly less, the species would evolve to a flightless state. The ostrich is a result and example of this process. To support his belief, he referred again to his observations of domestic species:
...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 (Page 135).
By contrast, if individuals of a bird species flew more frequently, this change in behavior would create variations aimed at producing more powerful flight. In addition to the behavior of a species producing variation, natural selection would act upon and select for variations that were favorable to the species' survival. Darwin also suggested the possibility that offspring could inherit some effects of mutilations suffered by their parents:
...the remarkable cases observed by Brown-Sequard in guinea-pigs, of the inherited effects of operations should make us cautious in denying this tendency (Pages 135, 136).
Critique
Darwin's belief that behavior causes heritable changes in an organism's structure and organs may be in line with the new field of epigenetics. It also reminds one of Jean Baptiste Lamarck's vitalistic theory. Lamarck believed that the individual could strive for and acquire improvements in its lifetime and those improvements would pass on to its offspring. As each generation thereby improved, the species achieved perfection in adaptations to its surroundings. Oddly, Darwin never questioned the mysterious, vitalistic, teleological, programming components of his hypotheses on the "use and disuse of parts." That may be because his goal was to discover the "laws" of variation. Anything inexplicable or too complicated to understand fell into the black hole of "law" or "principles" or "rules" with total acceptance and without further question. Just get up from the obvious questions left on the table and walk away.
Changing the structure and behaviors of organisms would require changes in biological information, a something that has neither mass nor charge (Meyer 2009). The best inference to explain the origin of biological information is that an intelligent agent was responsible. The capability to make that inference should qualify as vitalistic.
Of interest, when I was in college, my professors ignored Darwin's behavior-caused structural and functional changes in the organism that were heritable by the offspring. Also, they failed to mention that offspring could inherit injuries to their parents. Perhaps my professors did not want to tarnish the memory of the icon of biological "science."
Acclimatisation
This discussion addressed the capacity of species to adjust to different climates. Darwin noted that dogs, as do a number of other domestic species, adjust to and live in cold and in hot climates. He accredited this ability of domestic and other species to adjust to changes in climates to "habit" and to "use and disuse of parts," often governed by natural selection (Page 141).
Critique
It appears that Darwin made no distinction between physiological adjustment of the individual to changing weather conditions and microevolutionary changes within the limits of the existing gene pool of a population. An example of microevolution would be the survival of smaller individuals within a species population isolated on an island. Because food resources are often scarce in small, isolated islands of habitat, the smaller individuals within a population are more likely to survive and produce offspring than are larger members of the population. Thus the island population microevolves toward smaller size without the introduction of new heritable characters or additional random mutations. If you take your pet cat to Alaska from Florida and it grows a thicker coat of fur, you will not have observed a recently acquired competitive edge in your pet.
To Darwin, organic beings were "plastic". Their "habit" and "use and disuse of parts" produced unlimited variation for natural selection to act upon. Variation without limit in species was apparently one hypotheses that rose in his mind to the level of established "law." Evolution with limits would cast doubt on his vision of all species evolving gradually from a 1-celled ancestor. Microevolutionary changes and simple, random mutation within a population and physiological adjustments of the individual to seasonal changes, which are empirically obvious, offered no evidence for escape from the species class nor support for the gradual evolution of all species from a single primitive ancestor.
Correlated Variation
I mean by this expression that the whole organization is so tied together during its growth and development, that when slight variations in any one part occur, and are accumulated through natural selection, other parts become modified (Page 141).
Darwin noted several examples to show how the appearance of various physical characters in plants and animals are often linked. He observed, for example, that white cats with blue eyes are often deaf and cats with the tortoise-shell color are female. Thus, a small variation that appears in a species will also produce other coordinated changes in other organs and structures. He referred to another scientist who had interesting observations on the evolution of snakes:
In snakes, according to Schlegel, the form of the body and the manner of swallowing determine the position and form of several of the most important viscera (Page 142).
Thus, alterations in "habit" can produce other fortuitous and linked changes in the species. Darwin said that the associated and heritable changes may provide no survival value to the individual:
Hence modification of structure viewed by systematists as of high value, may be wholly due to the laws of variation and correlation, without being, as far as we can judge, of the slightest service to species (Page 142).
Critique
For Darwin, the "law" of variation explained why species were "plastic" and variation unlimited. This "law" explained why so much coordinated, fine-tuning among complex organs
and structures continued to develop in a mysteriously synchronized manner during the evolution of species into new species. We are expected to assume that because tri-colored cats are observed to be female; blind, random forces synchronized the production of irreducible complexities (Behe 1996) and derived complex information systems in the cell (Meyer 2009).
Contrary to Darwin's simplistic view, we now know that at the molecular and biochemical level, irreducible complexities appear. Cilia, for example, are little whip-like structures found on many cells, including protozoa and some cells in the human esophagus. These are little molecular machines that operate in synchrony to move fluids across the cell (Behe et al. 1999: 120-123). I suppose it was just fortuitous chance that simultaneously developed the two hundred protein parts required for the irreducibly complex cilium to function? Without each part being fully developed and operational, the cilium fails to function. It is therefore difficult to see how all those working parts developed slowly and in synchrony through the innumerable steps required of Darwin's gradualism. And, if such complexity appeared abruptly, intelligent design provides a more acceptable explanation than do chance or chemical/physical necessity. Darwin usually favored necessity; that is, "laws" of nature, whenever his theory hit a brick wall. If it was mysteriously complicated and reeked of intelligent design, it was just some "law," "principle," or "rule" in operation.
And, what are the probabilities of the chance appearance of variation through the production of new proteins and genes? Chemical engineer Douglas Axe investigated the probabilities of the evolution of a single functional protein by chance. He calculated that the probability of producing a functional protein of modest length (150 amino acids) by random selection was 1 in 1074 (Meyer 2013:185-204). The number 1074 is a 1 followed by 74 zeroes. For comparative purposes, there are 1065 atoms in the Milky Way Galaxy and 1080 elementary particles in the known universe.
Natural selection cannot play a role in evolution prior to the appearance of a functional protein. Thus, the neo-Darwinian model of gene evolution by chance is mathematically challenged in the extreme. Insofar as necessity is concerned, neither attraction nor repulsion among the specific nucleotide bases attached to the sugar-phosphate backbone of the DNA molecule can explain the functional sequences that comprise that molecule's specified, digital information (Meyer 2009:232-252). That is, neither chance nor necessity can explain the origin of the functional/specified arrangements of these nucleotide bases. By contrast, intelligent agents in our everyday world generate and receive specified/functional information continuously, providing a steady stream of solid information that verifies the existence, the intents, and the power of intelligent design.
Multiple, Rudimentary, and Lowly-organised Structures Are Variable
Darwin classified numerous, repeated phenomena as "laws" and "rules" or "principles". This subject addressed one of his "rules". He noted that when a part or organ appears in relatively large numbers in an individual, such as the vertebrae in snakes, the organisms tend to have variable numbers of those parts. By contrast, quadrupeds only have and always have four legs, a constant number of parts. Darwin said: ". ...beings which stand low in the scale of nature are more variable than those which are higher" (Page 145). Because natural selection has little chance to act on structures that are not specialized for specific functions, rudimentary and lowly organized organs persist in species. Thus, we have the "rule" concerning multiple, rudimentary, and lowly-organized structures.
Critique
Odd it is that "lowly" organisms changed so little over hundreds of millions of years. Darwin covered all bases by noting that primitive organisms remained unchanged for two reasons: 1) because natural selection had no power to change their less specialized structures into more specialized structures and/or 2) because the "lower" organisms had evolved to a state of evolutionary perfection (see On the Degree to Which Organization Tends to Advance above). Are we to believe that a lack of specialization represents advanced levels of evolutionary perfection? Are we to believe that the "lower" organisms are "simple" at the biochemical level?
Different species of snakes have different numbers of vertebrae to accommodate species differences in size, which represents a form of anatomical specialization. In like fashion, most humans have a specific number of teeth, 16 in the mandible and 16 in the maxilla. These teeth include specialized incisors, canines, premolars, and molars. People born with small mandibles and maxillae sometimes have a single set instead of two sets of molars above and below. Most of these people get along fine with fewer teeth though the teeth are specialized rather than "primitive" structures. On the other hand, a person born without one or more limbs faces considerable adjustments to survive well. These observations, which do not show that teeth are "primitive" and limbs more evolutionary "advanced," provide no support for Darwin's vision of all organisms arising from a 1-celled ancestor through natural selection acting on unlimited variation.
A Part Developed in Any Species in an Extraordinary Degree or Manner, in Comparison with the Same Part in Allied Species, Tends to be Highly Variable
This subject constitutes another "rule of high generality" (Page 146). Darwin believed for example, that if a species had wings that differed a lot from the wings of other species in the same genus, the wings of that species would show a lot of variability. To make his point, he referred to his regular and trust-worthy data source, the domestication of species. He said that in domestic species, the rudimentary organs or those for less specialized purposes are variable. In pigeons he observed this variability in such organs: "the beaks of tumblers, in the beaks and wattle of carriers, in carriage and tail of fantails..." (Page 148). Species tend to revert to their inherited characters and to change due to inherent variability, both in nature governed by natural selection. Because of the changes in character are evident, for example, in domestic varieties, Darwin dismissed God as creator:
On the view that each species has been independently created, with all its parts as we now see them, I can see no explanation (Page 147).
Critique
This discussion was representative of Darwin's repeated argument that microevolutionary changes in populations and/or mutation within the species boundaries, as illustrated in the production of domestic varieties, proved his vision of the gradual, macroevolution of all species from a common 1-celled ancestor. It would seem a bit of a leap to conclude that God had nothing to do with the appearance of the rock dove because man derived numerous varieties of domestic pigeons within the species.
Specific Characters More Variable Than Generic Characters
A specific character is a character that differentiates a species within a genus from other species in that genus. A generic character is a character that links a species to other species in the same genus. Darwin provided an example of how specific characters are more variable than generic ones. If all the plants in a genus had blue flowers, the color blue would be a generic character. If some species in the same genus had blue flowers and some species had red flowers, the color of each species would be a specific character (Page 149). And, when a genus has species with red and other species with blue flowers, both colors are more likely to appear in a single species. Darwin said:
... that specific characters are more variable than generic, because they are taken from parts of less physiological importance than those commonly used for classing genera (Page 149).
Darwin believed that the greater variation in specific than in generic characters indicated evolutionary derivation from a common ancestor:
On the ordinary view of each species having been independently created, why should that part of the structure, which differs from the same part in other independently-created species of the same genus, be more variable than those parts which are closely alike in the several species? (Page 150).
Critique
Darwin's argument that greater variation occurs in specific than in generic characters is tautological. This is true because a genus is not a
n existing organism. Genus is simply an abstract category showing the anatomical similarities between/among sister species. Because taxonomists place species in the same genus class because of characters they have in common, it stands to reason that those relationships are based on characters species have in common. Thus, it is tautological to say that generic characters shared by sister species show small variability. They are not supposed to. If they did, the taxonomist would not place two discordant species into the same genus.
Darwin noted high variability within the species category? If one observes all the varieties of domestic breeds, one would conclude that gene pools at the species level (species are real organisms), show a lot of inherent variation. Darwin felt he was logical in saying that species belong to genera because they are similar in some characters and God did not make species because variation exists within the species. Not convincing.
Again, Darwin's question:
On the ordinary view of each species having been independently created, why should that part of the structure, which differs from the same part in other independently-created species of the same genus, be more variable than those parts which are closely alike in the several species? (Page 150).
That is: why would some parts shared by species of the same genus be more alike and other parts shared by the species of the same genus be more variable? Darwin apparently ignored the survival value of variation within the species boundary. Extensive variation in a wild population enables that population to adjust to radical and rapid changes in environment. Thus, the population can adjust to new or recurrent external pressures much as the immune system adjusts to invasions of decimating and variable microbes. Adaptability within the species does not mean God did not program species to be adaptable nor that God did not program species to produce sister species.
Secondary Sexual Characters Variable
Darwin said that the differences in secondary sexual characteristics between male and female gallinaceous (chicken family) birds illustrated that those characteristics are more variable than other species characters (Page 150). Darwin explained that the secondary sexual characters tend to be highly variable because sexual selection is more forgiving than natural selection. Rejection of a suitor is not final because the individual may find another mate and reproduce at a reduced rate but death through natural selection is final.
Generic similarities in the genus showed that natural selection had preserved those features that aided survival and variation in the secondary sexual characters showed that the species in the same genus derived from a common ancestor.
Critique
More variation in the secondary sexual characters among species in the same genus indicated a common ancestor and less variation at the genus level of classification showed that natural selection had preserved characters that are necessary for survival. I question that.
How odd it is that over millions of years, sexual selection failed to "perfect" the secondary sexual characters of species. I suppose that if every man was a gentleman there would be more blonds? Rather, I suggest that there is a lot of selection for variety in mates and that it is the fixed variation itself that has survival value for the species. Within a species, individuals show considerable variation because variation within the gene pool enables the species to make microevolutionary adjustments to new or changing environmental conditions. Sexual selection has survival value because it helps to retain variation in the species.
As noted above, basic characters at the genus level are the product of an abstract classification system. Taxonomists place white-tailed deer into the same genus as mule deer because both species have certain characters in common. It is a bit of a jump to say that, because taxonomists place some species into the same genus, bacteria mechanistically evolved into human beings.
Concerning the power of natural selection and the total plasticity of species, Stanley (1979) and Eldredge and Gould (1972) would remind us that species do not change, except in size, in their morphology (bone structure) over the life of the species. Thus, the species, during the existence of the species, does not change structure natural selection has repeatedly demonstrated no power to change the morphology of established species.
Distinct Species Present Analogous Variations, so that a Variety of One Species often Assumes a Character Proper to an Allied Species, or Reverts to some of the Characters of an Early Progenitor
Darwin defined "analogy" as:
That resemblance of structures which depends upon similarity of function, as the wings of insects and birds. Such structures are said to be analogous, and to be analogues of each other (Page 161).
Darwin relied on his observations of domestic species to explain the appearance of analogous variations among species and the reappearance of characters from an early progenitor. He repeatedly referred to microevolution in domestic species because "...we do not know the common ancestors of any natural group..." (Page 154). In this section, he discussed characters in domestic pigeons, Swedish turnips, and domestic varieties of horses and asses.
In the case of domestic pigeons, Darwin observed that different varieties will, for example, grow feathers on their feet, a character that wild stock did not display. He also noted that different varieties commonly produce evidences of the same parental stock; i.e., slate-blue contour feathers with two black bars on the wings, white loins, and a bar at the end of the tail:
...are characteristic of the parent rock-pigeon...I presume that no one will doubt that this is a case of reversion... (Page 153).
Darwin concluded that the varieties of domestic pigeons came from a common ancestor and were therefore not "closely related acts of creation" (Page 153). Darwin further talked about the spinal stripes and transverse bars on the legs of horses and asses to show that varieties of each of these species descend from a common ancestor and were not individually created.
Critique
We observe that domestication of species has not produced new species. I also suggest that today it is unreasonable to confuse the ultimate cause of "bird" with the proximate production of "fantail pigeon" by intelligent (human) selection. Darwin's reasoning that God could not have created the wild pigeon because man's intelligence selectively bred varieties of domestic pigeons was logically fallacious. Darwin would have us believe that God could not have been the ultimate creator of mankind because different races of man cross and produce mixed races of human beings.