Chapter II - Variation under Nature
In his introduction to Variation under Nature, Darwin briefly discussed the terms "species" and "varieties". He said that naturalists had various definitions for "species" but that most people believed a species was a type of plant or animal created by God in an individual act. He noted also that "The term 'variety' was almost equally difficult to define" (Page 59).
Darwin supported the idea that when the "conditions of life" changed, the individual changed. The changes that the environment produced in the individual plant or animal made that plant or animal a new variety and the offspring of that plant or animal inherited those changes (page 59). Again Darwin fully embraced the vitalistic theories developed by Jean Baptiste Lamarck in the early 1800s.
Critique
The changes Darwin observed represented physiological and structural variation extant within the genetic boundaries of the species. He did not observe species evolving gradually into new species.
Individual Differences
Darwin defined "individual differences" as the "many slight differences which appear in the offspring" from the same parents in a confined locality. He said that these individual differences "afford materials for natural selection to act on and accumulate..." (Page 60). But he noted:
These facts are very perplexing, for they seem to show that this kind of variability is independent of the conditions of life (Page 61).
However, Darwin believed that a change in environmental conditions and/or in the individual animal's behavior caused adaptive physiological changes in the individual and that these changes could pass to the offspring. Thus, when he encountered different variations in the offspring from the same parent stock in the same geographical area, he was puzzled. He reasoned that such variations existed because they were "of no service or disservice to the species" and were therefore not subject to natural selection. Darwin noted that variation within the offspring of the same parents, which he could not explain, continued because "Natural Selection" had no "Power" to "Change" it.
Critique
Hypotheses to explain the origin of apparently extraneous variation in a gene pool include programming for future environmental conditions and genetic alteration caused solely by random gene mutation, or both. In addition, many behavioral and structural characters first considered extraneous by scientists and other observers, are later found to be beneficial or even necessary for the survival of the species.
Darwin believed that a change in behavior or environment mysteriously produced new variation in an individual's structure and physiology. His belief that such changes were heritable by the offspring was definitely a vitalistic, Lamarckian concept. He generally glossed over mysterious observations/beliefs and filed them under "principles" or "laws" or "rules". These are the same "laws" of determinism that forced Darwin to write On the Origin of Species. As a philosophical materialist, lacking all but the appearance of free will, he apparently had no particular logic nor choice but to do so.
Doubtful Species
In this section, Darwin said: "It should be added that De Candolle no longer believes that species are immutable creations" (Page 67). It appears Darwin believed that if he could show that "species" and "varieties" were interchangeable and arbitrary classifications, he could show that the creation of new forms of plants and animals was a wholly natural process. He noted that the systematists/taxonomists of his day differed a lot in their methodology for classification and in their classifications of the same plants and animals. Thus, Darwin concluded that species of plants and animals were ill-defined and unstable because the individuals and their populations were fluid and always changing. Such changes over long periods of time produced new species.
Darwin stated:
Hence I look at the individual differences, though of small interest to the systematist, as of the highest importance for us, as being the first steps towards such slight varieties as are barely thought worth recording in works of natural history... A well marked variety may therefore be called an incipient species... (Page 68).
Critique
Darwin believed that species were in the process of changing into new species and that there were few cases where change, given great spans of time, was limited. Thus, his purpose in this section was to push the idea that classification of organisms was arbitrary and difficult because populations were constantly changing into new species. Of course, many of his conclusions about the origin of species were based on his observations of varieties of domestic plants and animals. To date, the breeding of domestic plants and animals has allowed none to escape its species boundaries.
Wide-ranging, Much Diffused, and Common Species Vary Most
The title of this subject needs little elaboration. Generally, species that are abundant and widely distributed have a more varied gene pool than species that are localized and small in population size. In Darwin's view, large populations evolved into new species that replaced their progenitor species. Speciation in small, isolated populations seldom occurred because smaller ranges provided more simplistic living conditions that would create less variation in the species for natural selection to act upon.
Smaller populations were also subject to the deleterious effects of inbreeding.
Critique
In this section, Darwin was correct and incorrect. He believed that widely distributed species developed more varieties that were developing into new species. He was correct about widely distributed species generally displaying greater genetic diversity. He was correct thinking that small isolated species with small ranges frequently lose genetic potential through inbreeding. He was generally incorrect, however, to think that wide ranging, large populations of a species are in the process of creating new species.
This fundamental cornerstone of Darwinian gradualism has been dropped, I think I can safely say, by most evolutionists in favor of Gould and Eldridge's (1977) "allopatric speciation" and more recently by "evolutionary developmental biology" ("evo-devo"). See "Definitions/Notes" at the end of this essay for a brief explanation of "evo-devo".
I see "allopatric speciation" as "Darwinian gradualism in a relatively small isolated population where speciation approaches warp speed." According to Gould and Eldridge, the fossil record does not support the evolution of large, well established and widely distributed populations. I will discuss Gould's hypothesis later in this essay.
Species of the Larger Genera in Each Country Vary More Frequently than the Species of the Smaller Genera
Darwin said that species from genera with more species, had more varieties within the species; that is, they had more variation for natural selection to act upon. He stated:
All that we want to show is, that, when many species of a genus have been formed, on average many are still forming; and this certainly holds good (Page 71).
Critique
We could observe that when a species or genus has a lot of genetic potential or produces numerous phenotypes (different body forms), the chances of some offspring successfully responding to environmental changes are better. We cannot say, as Darwin supposed, that the potential of most species to change is without boundary. His statement that "many (species) are still forming" (Page 71) from large genera was a hypothesis and possibly tautological. Genera with many species may rapidly produce new sister species (see epigenetic niche-match under Definitions/Notes) in a nonrandom, non-Darwinian fashion. Or, perhaps genera with many species have a lot of species. Again, Darwin was trying to establish support for the gradual evolution of a large, widely distributed populations into new species, as opposed to rapid speciation in small isolated populations.
Many of the Species Included within the Larger Genera Resemble Varieties in Being Very Closely, but Unequally, Related to Each other, and in Having Restricted Ranges
Within this topic Darwin again attempted to show that life is fluid/plastic and that the classification of species is unfounded and arbitrary:
We have seen that there is no inf
allible criterion by which to distinguish species and well-marked varieties... (Page 71).
He said that there are relatively small differences among species from large genera (those with numerous species) and that those differences are comparable to those found among varieties within some species:
Now Fries has remarked in regard to plants, and Westwood in regard to insects, that in large genera the amount of difference between the species is often exceedingly small (Page 72).
Darwin further noted that "some sagacious and experienced observers" concurred with his view. He failed to identify these prominent and important observers.
Critique
Today DNA sequencing processes distinguish genera, species, and individual differences. Cytochrome c sequence analysis, for example, showed equal distances at the biochemical level between the various classes of organisms (Denton 1986:274-307). That is, each taxonomic class appears distinct from other classes. By contrast, while the hardware (body type) of various species are radically different, the master regulatory genes from insect to human being are the same. That observation questions the power of random mutation to change regulatory genes, suggests common descent, and makes one wonder about the origin of complex gene regulatory programs. I wonder how these kinds of information would have impacted Darwin's need to show connectedness among the classes of organisms.
Summary
Darwin concluded:
...the amount of difference considered necessary to give to any two forms the rank of species cannot be defined (Page 73).
He further noted that species with numerous varieties were analogous to genera with numerous species. He said that the species of large genera and the varieties from species with numerous varieties, were more similar than those species from small genera and those varieties from species with fewer varieties. He hypothesized that species were therefore not created individually by God:
And we can clearly understand these analogies, if species once existed as varieties, and thus originated; whereas, these analogies are utterly inexplicable if species are independent creations. (Page 73)...and, Thus the larger genera tend to become larger...and ...the larger genera also tend to break up into smaller genera (Page 73).
Critique
Darwin's arguments noted above against creation by God is equivalent to saying that God could not have made wild pigeons because intelligent agents developed domestic varieties from wild pigeons. As pointed out previously, Genesis 1 said that God made animals of every "kind". Darwin, as have some theologians, assumed that man's classification "species," which he repeatedly asserted to be arbitrary, was the same classification as God's class "kind". But Darwin was clearly incorrect about the biblical definition for "kind". In Leviticus 11:22, as noted in the Introduction above, the Bible referred to both grasshoppers and crickets as "kinds" of animals. Thus the biblical "kind" obviously refers to a class above the genus level because there are numerous genera and species of grasshoppers and crickets.
If animals breed and plants cross pollinate and produce viable offspring in the wild, they are members of the same species. And, if they do not, they are not members of the same species whether taxonomists can tell them apart or not. That definition is not as arbitrary as Darwin would have us believe, nor does saying so produce supposed connections among distinct/disparate classes of organisms.
In his statement that "...the larger genera also tend to break up into smaller genera," Darwin appeared to embrace a kind of "top-down" adaptive radiation of new genera from a single founder species. Because "genus" is an abstract classification and not an organism, it is unclear how a single species produces other members in the hierarchy above the species level without large evolutionary leaps.