1.4 The Big Theory: Natural Common Descent
Stepping back a bit, the context before Darwin came along.
Before launching into the grisly details of the evidence for evolution and the manifest failure of antievolutionists to get a grip on any of it, or even before outlining more clearly what it means to do sound reasoning in a general sense—outlined in Chapter 1 of Downard (2004), it is useful to step back a ways and trace how science and popular culture got so disconnected in the first place.
The major lights of early to mid-19th century science, from paleontologist Georges Cuvier (1769-1832) to geologist Louis Agassiz (1807-1873) on down, might all be regarded today as “creationists” of a sort (where discontinuities or origins were attributed to some manner of external divine activity), though their religious opinions were seldom close to those of modern creationists—Cuvier was raised a Protestant, for example, but ended up as a minimal deist, Crosland (1992, 200-201). They did not subscribe to any evolutionary explanations for life in the sense scientists do now, as a natural process of descent with modification, but then neither did they accept the simplistic Flood Geology favored by easily a half of today’s Biblical creationists. Although there were hot debates about what might have caused certain deposits, Cuvier’s catastrophism or Agassiz’s glaciation theories were set against the recognition that the earth was nowhere near as young as Genesis chronology had thought. Indeed, the Englishman James Hutton (1726-1797) had got that ball rolling back in the 18th century when his pioneering geology work helped establish the great antiquity of the earth, Baxter (2003) or Repcheck (2003).
As the uniformitarian approach of Charles Lyell (1797-1875)—at that time another non-evolutionist, by the way—came to dominate geological thinking, catastrophic explanations fell by the wayside in geology. The full story of how geological processes and dating get mangled by Young Earth Creationists these days are covered in Chapter 3 of Downard (2004), but the main lesson here was how natural processes observable in the present came to be seen as the key to the past, so by the time Darwin (1809-1882) came on the scene give the study of living things his particular evolutionary spin, the essential outlines of the geological sequence and its temporal implications had been solidly established. Simpson (1983, 59-62) supplies a compact survey of the development of the 19th century geological system, as do Strahler (1987, 296) or Eldredge (1982, 98-101; 2000, 103-107) from the standpoint of the creation/evolution debate. Gohau (1990) and Rudwick (2008) provide fuller technical and historical discussion.
The latest absolute chronology for the various periods may be found in any good encyclopedia or geology source, as well as online resources obtained by googling “age of the earth,” reflected in the scale for my own Figure 1 in Downard (2003b, 15). Viewing things from the early 21st century, though, what is most clear about this process is how the advent of radiometric dating in the 1950s greatly expanded the time frame of the Precambrian era, while only fine-tuning the values worked out over the preceding century for the more recent life-bearing deposits by studying the animal and plant turnover in the rock sequences themselves.
The other big change from 19th century uniformitarian geology relates to plate tectonics, which in the 1960s overturned the view that the continents were fixed blocks of real estate. Douglas Palmer (1999) from the Discovery Channel effectively illustrates this, relating the geological ages to changing global continental configurations. For a grand overview of the whole current view of what has happened on earth up to now, Hartmann & Miller (1991) is still an exhilarating hoot.
The digest version: the Earth was formed during a period of unbelievably intense bombardment, as chunky debris coalesced under gravity. This process continued for two billion years, through the Late Heavy Bombardment (LHB) phase, traceable today in the remains of ancient impact events surveyed by Kyte (2012) and H. Thompson (2012) on Bottke et al. (2012) and B. Johnson & Melosh (2012). Once the asteroid and cometary rain dropped to the point where our developing atmosphere and oceans could avoid being vaporized by incoming, though, life originated (very possibly around some of the very hydrothermal vents generated by the previous waves of impacts). Whether this occurred solely by brute chemical processes or involved some divine fiat is the hotly contested issue, of course. But whatever the cause, this still took place very early in earth’s history, by around 3.5 Ga (using the standard science abbreviation for “giga-years ago”—giga standing in for billions, as mega does for millions, and kilo for thousands).
Life then spent the next three billion years in a bacterial rut, though with a major development along the way being the appearance (by around 2.5 Ga) of the plucky cyanobacteria, whose toxic excretion (oxygen) so many later life forms would grow positively addicted to, and later the nucleated eukaryotic cells (around 2 Ga) from which more complex life would develop. Once animal life worked out first how to be multicellular (around 1 Ga) and then how to devour one another more expeditiously, around 540 million years ago there commenced the “Paleozoic Age,” launched by the Cambrian Explosion that current antievolutionists have grown so enamored of as supposedly undermining the credibility of “Darwinism”. The subsequent proliferation of fish, land plants, insects, amphibians, and primitive reptiles had all developed by the time the Permian stumble took place about 245 Ma, which ushered in the “Mesozoic Age” that the dinosaurs, early mammals and first birds called home. The lesser K-T gearshift 65 Ma that we covered in the section on mass extinctions brought on the present “Cenozoic Age” of Henry Morris and Phillip Johnson.
Seeing the big picture in this way makes one wonder just how the eminent 19th century creationist scientists might have amended their attitudes toward “evolution” in light of subsequent discoveries. Baron Cuvier, for example, never had a crack at explaining the weird Cambrian fauna of the Burgess Shale in British Columbia, because they were only discovered at the turn of the 20th century, and their full evolutionary implications were not recognized until modern paleontologists began to reexamine them in the 1970s.
But given how the Cambrian Explosion figures in modern thinking (scientific as well as creationist) it is likely that whatever religious convictions the older scientists had would have been just as decisive in their response to it as it is for people today. For those inclined to think there is a Grand Plan to it all (especially one laid out authoritatively in a certain revealed scripture) it is an unattractive option indeed to accept the implication that things only turned out the way they did by mere happenstance. This philosophical difference is manifested in the paleontological venue by secularist Stephen Jay Gould (1989; 1998c) readily open to the possibly contingent nature of the past (that had the tape of life’s history been rewound any replay would have been unlikely to have run out along anything like the same track) and the opposing view of the more theistically inclined Simon Conway Morris (1998a-b; 2010) seeing deep developmental trends toward complexity that would have resulted in similar types of winners and losers no matter how often the tape were rerun. The topic remains an active one in the scientific literature, with Vermeij (2006), Dick et al. (2009) and Conway Morris (2010) offering some recent middle ground perspectives.
The reluctance to come to terms with the specter of happenstance naturally runs even more intensely among the overtly antievolutionist, of course, such as Phillip Johnson (1991, 167) finding this “tape of life” contingency issue the “least interesting” feature of Gould’s 1989 book Wonderful Life. For Johnson the only thing that mattered was the anatomical disparity of the new forms that Gould highlighted, as though a proliferation of unexpected arthropods somehow ruled out their common descent from earlier models, or how a penchant for gilled appendages would made an Intelligent Designer any more plausible an explanation for them.
Johnson’s cavalier disinterest is not the most peculiar riff off Gould’s contingency argument, though. C. Stephen Layman (2007, 211-212) tried to use Gould’s assertion of natural contingent evolution as somehow precluding the accommodation of evil in a naturalistic framework. More will be said of Layman’s convoluted arguments in the discussion of religious apologetics.
In his zeal for pigeonholing data Johnson was ironically reversing the stance of the Burgess Shale’s own discoverer, Charles Walcott (1850-1927), who (as Gould had fully noted in that same Wonderful Life Johnson had relied on) downplayed that same anatomical disparity of the Cambrian fauna because it did not fit into his narrow Belle époque brand of theistic evolution whereby God had been creating limited forms prior to his beeline for people as the pinnacle of evolved creation. One may be tempted to see the theistic commonality of Johnson and Walcott as being the stumbling block here, religiously over-primed minds refusing to just let the facts inform the result.
What can be all too easily overlooked in this either-or seesaw is the realization that that these polarities of chance and necessity are by no means mutually exclusive. There could be both naturally evolving developmental constraints that nonetheless play out in many unpredictable and undirected ways depending on inevitably contingent conditions. We’ll be seeing this idea surfacing a lot concerning the issue of evolutionary convergence, where similar anatomical shapes or biological systems evolve independently (from repeated appearances of specialized sabertooth predators all the way down to deep metabolic processes, such as endothermic metabolism in birds and mammals with the same genes applying to the disparate feathers and hair that festoon them).
What Cuvier and others did have to face in the nineteenth century (and modern antievolutionists have had to step around so much more gingerly today) was the reality of something which only became apparent once the great span of Deep Time was recognized: change and extinction. This realization ultimately upended the very foundation of the creationist view of things, for if all life had been perfectly static since some initial starting point, no matter how far back that may have been, evolutionary theorizing would never have entered the picture because there would not have been any change to explain, and Charles Darwin might well have ended up but a scientific footnote for his methodical taxonomy of barnacles.
But instead of nice familiar lions and tigers and bears (oh my) with nothing else appearing on the stage since, the paleontological facts kept accumulating that this picture of fixed creation was utterly and irremediably wrong. The past was nothing but change, new forms appearing and eventually going extinct, century on millennia on eon, all the way back as far as they could see, until the strangest and least familiar of ancient life seemingly dropped off the Precambrian cliff (which we now know was the long pre-multicellular bacterial rut mentioned above).
And something else: there appeared to be a relationship between the strangeness and all that change. The farther back you went, the less those extinct forms seemed like modern ones. Indeed, this principle applied no matter where or when you started. Pick any spot in the parade and you can do the same trick: go backward or forward and the forms you see start diverging from whatever you began with. This looked enough like some sort of evolutionary process might be at work that many thinkers by 1800 had taken a stab at explaining it, surveyed by Corsi (2005), including Darwin’s famous philosopher grandfather, Erasmus Darwin (1731-1802). Though national linguistic limitations slowed the interchange of ideas (bouncing around via haphazard translations, authors in French had an advantage over English, German or Italian writers), in the end the main snag for pre-Darwinian evolutionary thinking involved mechanism. Modern science isn’t very comfortable with just isolated observation. If you don’t end up discovering some coherent system of natural causation for it all, from the scientific perspective there isn’t much point in bothering.
This attitude, by the way, is one that modern antievolutionists rather pointedly do not adhere to, as shall be explored in due course. The “testable model for Creation” proposed by OEC proponent Hugh Ross (2009b) might seem a counterexample here until you start teasing apart the fiddly bit details. Leaving aside the far from quibbling methodological point that Ross is trying to establish the effect of supernatural (not natural) agency here, that Ross thinks his argument actually constitutes a genuinely “testable model” (in that he has standards for being proven wrong and would change his mind based on such “testing”) testifies to the ingenious lengths tortucans can go to in pursuit of a foreordained conclusion.