Pesky Details: Essays for "Left Brain" Christians
Chapter XIII - Geographical Distribution - Continued: Fresh-Water Productions
Darwin discussed his speculations on methods of the distribution of freshwater plants and animals among sources of fresh water. The speculations were several; e.g., movement of plants and animals by tornados, movement of tiny seed and eggs on the feet, bills, and bodies of waterfowl and wading birds, and adjustment of marine species to freshwater habitats.
Critique
Darwin conducted some interesting experiments and provided observations and speculations on the dispersal and geographic distribution of organisms; however, the discussion had no particular relevance to his general theory of macroevolution.
On the Inhabitants of Oceanic Islands
Darwin's statement in the opening paragraph of this section:
In the following remarks I shall not confine myself to the mere question of dispersal, but shall consider some other cases bearing on the truth of the two theories of independent creation and of descent with modification (Page 378).
Darwin said that the lack of biodiversity on oceanic islands and the fact that introduced species often prosper on those locations indicated that God did not create enough life forms to fill all the living situations in isolated islands.
When species found their way to an isolated island, natural selection acting on available variation often modified the species, which explained the presence of endemic organisms restricted to specific islands. Insular species that were not different from species on adjacent, large land masses had remained unchanged because repeated immigration and interbreeding prevented expression of variation. In some cases, groups of competing/interacting species arrived at an island at the same time and the continued interactions among species prevented modification.
To explain the presence of some endemic trees on specific islands, Darwin speculated that a plant in herbaceous form might arrive on an island and grow into a taller plant and gain an advantage -
...by growing taller and taller and overtopping them. In this case natural selection would tend to add to the stature of the plant, to whatever order it belonged, and thus first convert it into a bush and then into a tree (Page 381).
In this section, Darwin again speculated on possible ways plants and animals could cross hundreds of miles of ocean to inhabit island habitats.
Critique
Perhaps God used islands for the specific isolation and production of unusual organisms? Darwin would have us assume that God would have done a better job on the island of New Zealand if he had introduced to the island more advanced organisms such as foxes, rabbits, rats, and house cats. God's statement that creation was "good" before the appearance of man (Genesis 1:24), the story of Noah's ark, and the prohibition of interbreeding animal "kinds" (Leviticus 19:19) showed that biodiversity and its preservation are important to God.
Absence of Batrachians and Terrestrial Mammals on Oceanic Islands
Darwin observed that amphibians and terrestrial mammals were typically absent from oceanic islands, particularly those islands separated by 300 miles or more from a continent or other large land mass. He further observed that imported amphibians commonly thrived on such island habitats and therefore asked: "But why, on the theory of creation, they should not have been created there, it would be very difficult to explain" (page 381). And how odd it was that God did not create terrestrial animals on oceanic islands but he did create volant species on a number of them: "Why, it may be asked, has the supposed creative force produced bats and not other mammals on remote islands?" (Page 382).
Where relatively shallow seas separated continents or other land masses, both land masses often shared the same species, which showed that successful migration, not creation, accounted for the distribution of species.
Critique
As I stated previously, migration of species to favorable habitats does not conflict with the biblical account of species dispersal. In the biblical story of Noah and the ark, God told Noah:
Bring out with you every living thing that is with you of all flesh - birds and animals and every creeping thing that creeps on the earth - so they may abound on the earth, and be fruitful and multiply on the earth (Genesis 8: 17).
Inherent in God's command was the assumption that organisms would "abound on the earth" only if they moved to locations some distance from their point of release.
Darwin asked why God did not create amphibians and terrestrial mammals on oceanic islands. It is just as reasonable to ask why the power of natural selection acting on virtually inexhaustible variation among all those marsupial mammals isolated in Australia failed to give rise to advanced placental mammals.
On the Relations of the Inhabitants of Islands to Those of the Nearest Mainland
Darwin asked:
...why should the species which are supposed to have been created in the Galapagos Archipelago, and nowhere else, bear so plainly the stamp of affinity to those created in America?" (Page 385)...Facts such as these admit of no sort of explanation on the ordinary view of independent creation; whereas on the view here maintained, it is obvious that the Galapagos Islands would be likely to receive colonists from America... (Page 385).
On island groups like the Galapagos, Darwin maintained that the close affinity among species on the different islands was because "...natural selection would probably favour different varieties in the different islands" (Pages 386-387). This section was largely an iteration of Darwin's contention that God did not create species now found in isolated habitats but that species migrated there from nearby populations and then natural selection acting on variation modified them in varying degrees.
Critique
Darwin was redundant. The last three sections in Chapter XIII addressed his protestation that God did not create species on oceanic islands. Apparently he believed he provided additional information if he repeated his basic concepts often enough.
I critiqued Darwin's oceanic island examples in the last two sections. Furthermore, the process of microevolution and genetic drift explained the affinities and differences among species on isolated islands compared with those on the nearest mainland. But what is the difference between microevolution within the limits of a gene pool and Darwin's macroevolutionary concept that all species derive from a common 1-celled ancestor through wholly natural means?
Here is the difference. As discussed previously, protein sequence (DNA) analyses showed that distinct gaps exist among classes of organisms and that species within those classes are equally distant from species members of other classes. Thus, no species at the molecular level is "primitive" or "advanced" in an evolutionary sense. For example, at the molecular level, cytochrome c sequence analysis, showed that the horse (mammal), the rabbit, the chicken (bird), the turtle (reptile), and the bullfrog (amphibian) are equally distant from the carp (fish) (Denton 1986:276-307). Microevolution and random mutation certainly occur within a species and might have occurred within classes such as mammals, birds, reptiles, amphibians, and fish but comparative biochemistry indicated unbridgeable gaps exist between those classes.
But, was Denton correct?
Matthew Landau (1989) provided an interesting critique of Denton's use of protein sequence analysis to illustrate the biochemical gaps among classes of organisms. As stated above, Denton said that cytochrome c percent sequence differences showed that, for example, horses, pigeons, tuna fish, silk moths, wheat, and yeast were equally distant from bacteria. According to Denton, this lack of relatedness between the bacteria and the other organisms provided no evidence for intermediates between bacteria and the higher organisms. Furthermore, according to Denton (1986:285), at the molecular level, the protein sequence analyses provided no evidence for evolutionary transition from fish to amphibian to reptile to mammal or bird.
Landau agreed with Denton by saying that the cytochrome c studies showed that mammals, birds, insects, vascular plants, and yeast were equally distant from existing bacteria. However, he said the reason that the evolutio
nary advanced organisms were related equally to modern bacteria was that all those higher organisms and extant bacteria were equally distant in evolutionary time from an ancient archetype ancestor. That is, for example, the cytochrome c in the modern bird or mammal, as in the modern bacterium, have evolved for equivalent periods of time through different life forms to reach their present adapted state, from one common ancestor species. They all had equal amounts of time to evolve their specific forms of cytochrome c and remained through all those millions of years equidistant from the early bacteria. If so, then protein sequence analysis has no value in depicting primitive nor highly evolved extant species. All individual organisms would be equally distant from a common ancestor. However, if that is true, differences between groups reveal equal distances from a common ancestor and therefore reveal no relative evolutionary distances among them.
When protein sequences showed percentages differences, for example, between the horse and pigeon or between the pigeon and the tuna, Landau said the data showed that the horse was more recently evolved than the pigeon and the pigeon more recently evolved than the tuna and all three more recently evolved than the bacterium. Thus, according to Landau, distinct protein sequence differences indicated the measurable, relative amount of time since a class of organisms evolved from a common ancestor but at the same time, all classes are equally distant from out-of-class ancestors. Apparently one's interpretation of the protein sequence data depends on what one wants to "prove".
Landau failed to offer any explanations for how the higher classes of fungi, plants and animals developed their specific cytochrome c proteins and managed at the same time over millions of years to arrive at a point of equidistance from that protein's make-up as it appears in modern bacteria. Also, the obvious gaps between classes at the molecular level was not an anomaly but a pattern:
The classification system that is derived from these comparative molecular studies is a highly ordered non-overlapping system composed entirely of groups within groups, of classes which are inclusive or exclusive of other classes. There is a total absence of partially inclusive or intermediate classes, and therefore none of the groups traditionally cited by evolutionary biologists as intermediate gives even the slightest hint of a supposedly transitional character (Denton, 1986:286).
Because cytochrome c performs complex, necessary functions in the cells of living organisms, we cannot assume that all cytochrome c differences among species represent random ticks on a molecular clock. Among its functions, this protein is involved in mitochondria regulation and apoptosis (programmed cell death) in plants and animals. For example, apoptosis is the process that separates the fingers and toes in the human fetus and divides the hooves of ungulates. Apparently the complex operations of cytochrome c are as individually specific as species are different in their physiology and morphology. Thus, what hypothesis could explain the cytochrome c percent sequence differences among eukaryotic organisms (organisms with nucleated cells) and their molecular equidistance from bacteria? Saltation. Punctuated bursts of speciation, as demonstrated repeatedly in the fossil record, could explain the persistent and prevailing gaps among classes of organisms and the concomitant appearance of specialized protein sequences.
Anomalous to the anomaly above, but perhaps correctly, Wells (2000:49-53) questioned the use of protein sequences to show relationships among groups of organisms:
A 1996 study using 88 protein sequences grouped rabbits with primates instead of rodents; a 1998 analysis of 13 genes in 19 animal species placed sea urchins among the chordates; and another 1998 study based on 12 proteins put cows closer to whales than to horses.
Various investigators have used molecular studies of extant Cambrian phyla to date their emergence from a common ancestor in the Precambrian, notwithstanding the absence of fossil evidence. The molecular clock studies varied, depending upon the molecules sequenced. Meyer (2013:106) noted that the studies placed the time of emergence:
anywhere between 100 million and 1.5 billion years before the Cambrian explosion (some molecular clock studies, oddly, even place the common ancestor of the animals after the Cambrian explosion).
Protein/molecular sequencing and the ticking of the molecular clock, in the absence of fossil data, have provided rough estimates. As the querulous professor Norm Smith at the University of Arizona once quipped to me: "The key to 'good science' is knowing when to stop collecting data."