On Darwin's blunder?

Darwin’s Category Errors and Their Consequences

Neil Thomas 

After his return from the Beagle expedition in the later 1830s Charles Darwin spent some time putting together thoughts about evolution which were to result in a provisional, unpublished pencil sketch of 1842 and in another, informal essay of 1844 both of which, in expanded form, were to form the basis of his Origin of Species of 1859. It was because his eventual magnum opus was to remain under wraps for the best part of two decades that Darwin in this period might have appeared to be more active in the field of geological debate than he was in the biological sphere. Yet behind the scenes he was working on both fronts at the same time and his modus operandi in his geological work may be usefully compared with his methods in the biological sphere, all the more so since his approach to biological matters was so heavily influenced by methods used by Sir Charles Lyell, Britain’s premier geologist of the earlier Victorian era. 

Thinking in Analogies

Darwin’s first public communication in this pre-Origin of Species period was on the subject of whether a Scottish loch had been of marine or fresh water provenance. The geological puzzle concerned some physical features in the Glen Roy area of the Highlands of Scotland, some twenty miles from Loch Ness, an area noted for the geological phenomenon of its three “roads,” as local folklore terms them. It is now known that the so-called parallel roads on a hillside in Glen Roy are in reality loch terraces or strand lines that formed along the shorelines of an ancient ice-dammed loch at the time of the last Ice Age. The ice had repeatedly melted and refrozen over geological time with the water levels coming to rest at slightly different set points each time. In 1839, in a paper read before the Royal Society, Darwin unwisely chanced his arm by seeking to explain these roads as having resulted from ancient, marine beaches; but premier Harvard academic Louis Agassiz and Scots geologists soon showed that this must have been an ancient freshwater lake once dammed up by ice (the Swiss-American Agassiz had ample experience of glaciers in the country of his birth).

What is instructive about Darwin’s swiftly disproved conjecture is that it was based on a misleading analogy he had come across in his voyaging years in South America. This he freely confessed in his autobiography when he wrote,

This paper was a great failure, and I am ashamed of it. Having been deeply impressed with what I had seen of elevation of the land in S. America, I attributed the parallel lines to the action of the sea; but I had to give up this view when Agassiz propounded his glacier-like theory.1

As Robert Shedinger has observed, Darwin advanced his theory despite the telling absence of any ancient marine residues such as seashells, adding that “when Darwin developed what he thought he felt was a compelling idea, he doggedly held to it even when faced with a lack of clear evidence.”2 This was a tendency readily observable in the biological sphere when he notoriously declined to recognize the true import of the absence of fossilized transitional forms as being detrimental to his theory of natural selection with its (claimed) capacity to leap-frog over the species barrier — that physiological barrier whose importance had been repeatedly underscored by such authorities as Cuvier and Richard Owen.

Argument from an inappropriate analogy was also to bedevil a second geological theory Darwin developed in 1842, this time in relation to the formation of coral reefs. During his travels in South America he had once observed what he took to be evidence that coral reefs emerged with the subsidence of surrounding land: as the land subsided, a coral reef or atoll would come to the fore. However, work by other geologists suggested that as often as not the reverse could be the case. That is, land underneath the sea would rise and bring towards the surface small organic forms congregating in reefs. Darwin’s theory could not then be one of general validity and his would-be universal theory could not in the end be substantiated. Crossing over to the biological sphere again one is reminded of Darwin’s wholly theoretical postulation of those hereditary entities he termed “gemmules,” a theory which failed to find acceptance since the postulation had no empirical back-up, as even Darwin conceded (it was definitively disproved by Mendelian genetics at the beginning of the 20th century).

A Major Category Error

In addition to resistance to such questionable analogies in Darwin’s thinking, there also arose the profounder objection lodged by Sir Charles Lyell to the effect that biology and geology ought not properly to be even mentioned in the same breath. In Lyell’s view the implicit analogy invoked by Darwin between the two domains was impermissible. It was of course only natural, given that Darwin’s earliest publications were in the field of geology, that he took Sir Charles Lyell, the leading geologist of the mid-Victorian era, as guide. Lyell’s three-volume Principles of Geology (1830-3), which worked on and developed geological principles first enunciated by James Hutton in his Theory of the Earth (1788), was to furnish an important intellectual springboard for the Origin of Species, as Darwin himself readily acknowledged. Lyell had described the crust of the earth by reference to natural forces alone without reference to such phenomena as the Biblical Flood (which he dismissed as “Mosaic geology”). Since Lyell had removed the hand of God from geological history, why then retain it to explain natural history in terms of separate special creations? If there was a story of natural evolution in the geological record, so too surely there must be a similar story to tell in the study of sentient beings, Darwin reasoned.

Yet although biological gradualism-cum-natural selection inspired by the idea of geological “uniformitarianism”3 seemed an uncontroversial form of intellectual progression to Darwin, Lyell thought that Darwin carried over his early formation as a geologist into the biological realm too indiscriminately and without attending to the appropriate modifications of analysis required. In short, Darwin’s ambition to apply Lyell’s uniformitarian approach to biology represented for Lyell a wrong-headed determination to postulate an ontological equivalence between organic and inorganic spheres. Discounting Darwin’s implied equivalence between geology and biology, Lyell as late as 1872 (and despite numerous appeals by Darwin himself) declared the basic problem of creation/evolution to be as inscrutable as it had been in the earlier Victorian period when it was candidly termed “the mystery of mysteries.” In Lyell’s opinion, Darwin’s intervention had solved nothing since it had been flawed from the start by some fundamentally misconceived philosophical reasoning. 

One can easily see the force of Lyell’s objection. There seem to be limited grounds for comparing the wholly material and inorganic substratum of Earth with its living superstructure. One would not, for instance, think it appropriate to compare rocks and cliffs with human consciousness and view those entities as lying only slightly distant from each other on the same sliding scale. There is a great difference between planet Earth as a geological formation, which shares its history and mode of formation with the rest of the outer cosmos, and the later, superposed realm of terrestrial life and sentience, that superstructure of life forms of unknown etiology thought to have developed on our once barren planet only some five million years ago — which in geological terms of course counts as fairly recently. That ancient geological segment of our planet is self-evidently different in kind to the animate sphere, being quite simple in texture when compared with the quite unsearchable complexities and subtleties of the organic world.4 As Barry Gale once pointed out, 

Mountains might decay and new mountains be thrust up again, but these new mountains were not considered to be more complex or very different from previous ones. For Lyell, there were no basic changes in the forms of natural phenomena.5

Lyell denied any development in non-organic phenomena which simply underwent slow, non-directional change over the eons. Although the earth was in a state of constant flux, it was not moving in any particular direction. Darwin on the other hand claimed that, in the organic world, there was a progression of forms with movement over time from the very simple to the exceptionally complex. Such was the grand narrative of evolution which Darwin inherited and extended from the work of his grandfather, Erasmus Darwin. Yet since nothing of this sort was observable in Lyell’s inorganic world of arbitrary forces it is hardly surprising that Lyell thought the two domains incommensurable. 

A Category Error Repeated?

The living part of our planet then has no identifiable counterpart in the external universe — despite unceasing attempts by space explorers to somehow conjure life from what appears to be the irredeemable barrenness found on Mars and other bodies in the external universe. There are now conspicuously fewer alien-hunters about than there were in the era of Frank Drake and Carl Sagan in the 1970s and ’80s6 since modern space science tends to confirm Lyell’s view of the radical dissimilarity of organic and inorganic worlds. The sheer exceptionalism of the terrestrial biosphere stands in sharp contrast both to the life-denying deadness of the outer cosmos and even to 90 percent of the world we inhabit. Viewed quantitatively, the areas of our planet amenable to human habitation represent a relatively small area of the earth for, as Michael Marshall has recently noted, our ambient atmosphere above a certain height will kill us (a fact all too well-known to mountain climbers, let alone astronauts) and so would the ever-burning furnace at the earth’s core were we to descend so far. Only about 10 percent of our world is human friendly (to this degree or that) with many terrestrial extremities remaining “egregiously hostile to life.”7 Our much-bruited “Goldilocks zone” is all the more to be treasured for being such a very narrow band of habitability. Life on earth represents an absolute cosmic singularity (pace the alien-hunters) and, being such a singularity, is by definition not amenable to comparison with anything else at all.

It is the way in which critical parts of our planet represent an albeit flawed paradise whereas some terrestrial extremities together with all known outer parts of the universe remain a life-averse hellscape which requires pondering, comments Marshall. This decidedly nontrivial distinction has indeed been pondered, particularly in the last half century in debates stemming from our somewhat belated recognition of the exceptionalism of Planet Earth. This has led to a considerable shift in what might be termed many persons’ cosmographic imagination. In no few cases it has resulted in a very sharp reversal of the once very influential cosmological Weltanschauung typical of philosopher Bertrand Russell’s generation in the first half of the 20th century.

The Cosmographic Paradigm Shift 

Where once Russell (to whom Richard Dawkins likes to acknowledge his philosophic debt) famously described Planet Earth as an accident in a cosmic backwater, the recently revealed bio-friendliness of our planet would appear to stand in implicit opposition to that older conception of Earth as an unconsidered cosmic orphan. Crucially, Russell was writing in the first decades of the 20th century, well before the discovery of what astrophysicist Brandon Carter in 1973 dubbed the “anthropic principle” — meaning the way in which planet Earth appears to be fine-tuned to generate and sustain animal and human life.8 Indeed, so complete is the discontinuity between Earth and the extraterrestrial dead zone revealed by modern findings that it seems to make nonsense of the centuries-old “Copernican principle” whose general acceptance ousted the earth from the centrality it had enjoyed in the medieval world picture. Michael Denton has even gone so far as to suggest that the openly anthropocentric view held by our medieval forbears — that our world represented the geographic center of the universe — should now be rehabilitated under revision. To be sure, planet Earth is clearly not central in the spatial sense but it certainly is so in the far more important symbolic and moral sense that we are the unique beneficiaries of a planet on which all available meaning centers — a recognition that has proved little less than revolutionary in changing hearts and minds. 

It is not insignificant that, five years after the promulgation of the anthropic principle, eminent biologist William H. Thorpe encouraged a return to ideas of intelligent design first proposed by William Paley in his famous Natural Theology (1802):

The Argument from Design has been brought back to a central position in our thought from which it was banished by the theory of evolution by natural selection more than a century ago. There seems now to be justification for assuming that from its first moment the universe was “ordered” or programmed — was in fact Cosmos not Chaos.9

Leading astronomers such as Paul Davies have endorsed that sentiment by stressing how such benign cosmic arrangements as we enjoy could hardly have arisen by chance. Davies points out that it is a merely semantic point as to whether you conceive of the shaping force behind this providential arrangement as the Christian God or some other unseen power.10 The essential point remains that it is logically impossible to conceive of our planet as an arbitrary and accidental collocation of atoms, objects, and life-forms (as both ancient Lucretianism11 and Lucretianism’s modern legatee, present-day evolutionary orthodoxy, insist in the teeth of universal evidence to the contrary). 

And even if we are obliged to concede that the ultimate seat of authority cannot be apprehended by our common, anthropomorphic categories of understanding, a basic respect for the balance of probabilities should dictate that the existence of such an agent be taken seriously in our current conversations. It is of course well enough known that some cosmologists have, for purely doctrinaire reasons, tried to evade the theistic implications of the available evidence by appealing to a wholly imaginary “multiverse.” They have wished to conclude that planet Earth’s unique good fortune is due to a kind of cosmic roulette wheel which decreed that somewhere had to be the winner from an infinity of parallel universes. Lyell’s fine distinctions have apparently been lost sight of in the rather wholesale views of those who, like Darwin, would indiscriminately lump together organic and inorganic spheres — a grand category error whose origin Lyell would have diagnosed as a lack of clarity in philosophic reasoning — the same kind of contra-logical reasoning that is determined to believe that human consciousness will have arisen as an accidental “epiphenomenon” of purely material factors.