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Discovering Evolution: IV. The Demise of Darwinism.

“Soapy” (because he was so smooth) Sam Wilberforce (left) and Thomas Henry Huxley (right) “debated” Darwinism at the 30th an-nual meeting of the British Association for the Advancement of Sci-ence. Legend, e.g., Eldredge (2005), has it that the exchange was a turning point in the struggle between science and religion. But this view may say more about the legend-tellers than about what actually transpired – see Lucas (1979) and Brooke (2001).

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Readings. Bartholomew, M. 1975. Huxley's defence of Darwin. Ann. Sci. 32: 525-535. Jenkin, F. 1867. [Review of] The Origin of Species . The North British Review. 46: 277-318. Gould, S. J. and R. C. Lewontin. 1979. The Spandrels of San Marco: A critique of the adaptationist programme. Proc. Roy. Soc. London. Ser. B. 205: 581-598. (Excerpt) Herschel, J. F. W. 1867. Physical Geography of the Globe. Adam and Charles Black, Edinburgh. [Note added in 1861 to page 12 RE Darwin's Law.] Huxley, T. H. 1896. [Excerpt from] The genealogy of animals. Pp. 107-119. In, Huxley, T. H., Collected Essays. Vol. II. Dar-winiana. Appleton, NY. Powell, J. L. 2001. Mysteries of Terra Firma. The Age and Evolution of the World. The Free Press. NY. (Chapter 1). Thomson, W. 1871. On the Origin of Life. [Excerpt from] The Presidential Address to the British Association for the Ad-vancement of Science held at Edinburgh in August, 1871.

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The Origin in Review. Victorian reviews mostly anonymous.

1st round emphasized the deficiencies one might expect.

1. Limited variability in contemporary species. 2. No examples of species in statu nascendi.

3. Absence of transitional forms in the fossil record.

4. What is now called the “Cambrian explosion.”

5. What contemporary anti-evolutionists call “irreducible

complexity”, i.e., structures such as the vertebrate eye that only work when fully formed.

6. Consistency not equivalent to proof – e.g., homology,

development.

7. Conflict with theology and the problem of man and his nature.

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Richard Owen (1860) wrote a blistering review that infuri-ated Darwin and his allies by virtue of its self-promotion.

Sedgwick (now 74) fulminated: “I have read your book with more pain than pleasure. Parts of it I ad-mired greatly; parts I laughed at till my sides were almost sore; other parts I read with absolute sorrow; because I think them utterly false & grievously mischievous—You have deserted … the the [sic] true method of induction—& started up a machinery as wild I think as Bishop Wilkin’s locomotive [1] that was to sail with us to the Moon.

Many of your wide conclusions are based upon assumptions which can neither be proved nor disproved.” There is a moral or metaphysical part of nature as well as a physical … You have ignored this link; &, if I do not mistake your meaning, you have done your best in one or two pregnant cases to break it. Were it possible (which thank God it is not) to break it, humanity in my mind, would suffer a damage that might brutalize it—& sink the human race into a lower grade of degradation than any into which it has fallen since its written records tell us of its history.” [Letter of 24 Nov 1859 to CD (DCP 2548)]

1 Actually “a spaceship powered by wings, springs and gunpowder”. See Con-nor, S. 2012. “Cromwell's moonshot: how one Jacobean scientist tried to kick off the space race”. The Independent 3 July; also, Chapman, A. 1991. “A World in the Moon’. John Wilikins and his lunar voyage of 1640. Quart. J. Royal Astr. Soc. 32: 121-132.

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Herschel Scoffed:

“I have heard by round about channel that Herschel says my Book ‘is the law of higgledy-pigglety’.[2]— What this exactly means I do not know, but it is evidently very contemptuous.— If true this is great blow & discouragement.” [Letter of 10, December, 1859 from CD to C. Lyell, (DCP 2575)]

But later conceded that with allowance for “intelligent direc-tion”, i.e., by a First Cause and “with some demur as to the genesis of man, we are far from disposed to repudiate the view taken of this mysterious subject [temporal succession of species] in Mr. Darwin’s work” [Herschel, 1867, p. 12. Quoted by Schweber (1989)]

Carpenter’s3 review (1859) arguably the most prescient:

“The history of every science shows that the great epochs of its pro-gress are those not so much of new discoveries of facts, as of those new ideas which have served for the colligation of facts previously known into general principles, and which have thenceforward given a new direction to inquiry.”

2 The reference was to the belief (Darwin and Wallace) that the “stuff” of evo-lution is random variation – see Herschel (1867, p. 12). 3 William Benjamin Carpenter (1813-1885), physiologist and supporter of the view that Nature’s Author works through secondary laws.

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Science vs. Religion.

Popular view: Darwin’s opponents motivated by religion.

1. There is much truth to this – e.g., Agassiz, Lyell, Sedg-wick, Whewell, etc.

a. Clerical antipathy, and that of the non-clerical ruling

elite, to evolution had fueled previous generations’ rejec-tion of transmutation – the speculations of Erasmus Dar-win and “Mr. Vestiges” in particular.

b. Of the eight Bridgewater authors, five were divines.

The Bridgewater Treatises

Author Span Degree FRS Publication

Date Title

The Rev. T. Chalmers

1780-1847

D.D. No 1833 The Adaptation of External Nature to the Moral and Intellectual Condition of Man.

The Rev. Dr. J. Kidd

1775-1851

M.D. Yes 1833 On The Adaptation of External Nature to the Physical Condition of Man

The Rev. W. Whewell

1794-1866

D.D. Yes 1833 Astronomy and General Physics Consid-ered with Reference to Natural Theology

Dr. Sir C. Bell 1774-1842

M.D. Yes 1833 The Hand, its Mechanism and Vital Endow-ments as Evincing Design

Dr. P. Roget 1779-1869

M.D. Yes 1834 Animal and Vegetable Physiology Consid-ered with Reference to Natural Theology

The Rev. W. Buckland

1784- 1856

D.D. Yes 1836 Geology and Mineralogy considered with reference to Natural Theology

The Rev. W. Kirby

1759-1850

M.A. Yes 1835 On the History, Habits and Instincts of Ani-mals

Dr. W. Prout 1785-1850

M.D. Yes 1834 Chemistry, Meteorology, and the Function of Digestion Considered with Reference to Natural Theology

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2. But – a. Vestiges had been attacked by the just about everyone

including Huxley (1854), who took palpable delight in bashing the clergy.

b. Contrapuntally, Fleming Jenkin, arguably The Origin’s most effective critic (F. Darwin, 1887, III, 103 ff) was an atheist (Stevenson, 1887).

Moreover, some of Darwin’s stoutest defenders were men of the cloth.

1. Charles Kingsley4

a. Sent CD an approving letter on 18 November, 1859 from

which Darwin (1860, 481) later quoted.

b. Eloquently reworked by Kingsley (1894, p. xxv) in 1871. “Of old it was said by Him without whom nothing is made, ‘My Father worketh hitherto, and I work.’ [John 5:17] Shall we quarrel with Sci-ence, if she should show how those words are true? What, in one word, should we have to say but this?—We knew of old that God was so wise that He could make all things: but, behold, He is so much wiser than even that, that He can make all things make themselves.”

4 Better known for his novels, such as Water Babies, Kingsley was the Vicar of Eversley, Hampshire and Chaplain-in-Ordinary to Queen Victoria.

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2. Essays and Reviews. a. Published by seven Anglican theologians who promoted

the “grand conclusion” (Powell, 1838, 155) that God eve-rywhere worked by secondary laws.

b. Included a chapter by Baden Powell 5 who equated be-lief in miracles with “the anarchy of chaos and the dark-ness of atheism” (ibid).

i. Previously defended Lyellian uniformity & Vestigarian

development. Regarding The Origin, he now wrote:

"… Mr. Darwin's masterly volume … must soon bring about an entire revolution of opinion in favor of the grand principle of the self-evolving powers of nature.”

ii. Quoted approvingly6 by Carpenter in his review.

3. Factual & exegetical difficulties in Darwin’s argument allowed opponents such as Samuel Wilberforce7 to

5 Liberal Anglican cleric and professor of mathematics at Oxford. 6 “… we have no sympathy with those who, to use the admirable language of Professor Powell, … maintain that we behold the Deity more clearly in the dark than in the light’“ [Carpenter, 1860, 194] 7 Bishop of Oxford and the embodiment of ecclesiastic pushback.

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a. Reference scientific opinion against evolution: “… Charles Lyell on the limits of organic variability; Roderick Murchison on evidence that was missing for the Silurian life Darwin was assuming; Richard Owen on the caution that should be exercised before admitting any possible mechanism for the transformation of species.” [Brooke (2001), p. 139. Emphasis added]

b. Characterize The Origin as “unphilosophical”.

“Huxley himself once conceded that if there were a weak point in Darwin’s armour it was that the transformation of one species into another could not be directly observed. For Wilberforce there were many weak points. Darwin had introduced his asser-tions with statements like ‘I do not doubt’, ‘it is not incredible’, ‘it is conceivable’. ‘What new words are these’, Wilberforce asked, ‘for a loyal disciple of the true Baconian philosophy?’ When dealing with difficulties, such as the elaborate structure of the human eye, Darwin had chosen his words carefully: ‘if it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.’ Wilber-force was not impressed. What kind of logic was it that asked leave to advance ‘as true any theory which cannot be demon-strated to be actually impossible’? This was why Wilberforce could say to Lyell that he found Darwin’s book so unphilosoph-ical.” [Brooke (2001, 136]

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c. Defer getting round to Revelation until page 31 of a 40 page review.

“Our readers will not have failed to notice that we have objected to the views with which we have been dealing solely on scientific grounds. We have done so from our fixed conviction that … the truth or false-hood of such arguments should be tried. We have no sympathy with those who object to any facts or alleged facts in nature, or to any infer-ence logically deduced from them, because they believe them to con-tradict what it appears to them is taught by Revelation. We think that all such objections savour of a timidity which is really inconsistent with

a firm and well-instructed faith …" [Wilberforce, 1860, 256]

4. Regarding the famous “debate” precipitated by Wilber-force’s Oxford address to the BAAS. a. The conventional telling, e.g., http://www.ucmp.berke-

ley.edu/history/thuxley.html: “Wilberforce … asked Huxley whether he was descended from an ape on his grandmother's side or his grandfather's. Accounts vary as to exactly what happened next, but according to one telling of the story, Huxley mut-tered ‘The Lord hath delivered him into my hands,’ and then rose to give a brilliant defense of Darwin's theory, concluding with the rejoinder, ‘I would rather be the offspring of two apes than be a man and afraid to face the truth.’ … “All accounts agree that Huxley trounced Wilberforce in the debate, de-fending evolution as the best explanation yet advanced for species diver-sity.”

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b. But, there is no written record – only recollections.

c. Lucas (1979) argues that the traditional telling of the tale is history written by the victors. Regarding the ad-dress itself, he suggests that the good bishop

“may not have told his audience … that it was … possible that Darwin’s theory was true, in which case humanity would have to eat humble pie, but it is clear that he did not argue that Dar-win’s theory must be false because its implications about the nature of man were unacceptable. As he saw it, and as most of his audience saw it, he was showing that it was, as a matter of scientific fact, false, and only having established this did he go on to say in effect ‘and a good thing too’.”

5. Be that as it may, Wilberforce

a. Was unabashed in his opinion that The Origin chal-

lenged Christian belief: “Man’s derived supremacy over the earth; man’s power of absolute speech; man’s gift of reason; man’s free will and responsibility; man’s fall and man’s redemption; the incarnation of the Eternal Son; the indwelling of the Eternal Spirit, – all are equally and utterly irreconcil-able with the degrading notion of the brute origin of him who was created in the image of God, and redeemed by the Eternal Son ...” [Wilberforce, 1860, p. 258]

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b. And he would later lead the delayed reaction (mid-1860s) when “the controversy between ‘science’ and ‘re-ligion’ took fire” (Brock & Macleod, 1984).

6. Contemporary authors who reference

“Darwin’s invocation of the travails of astronomers [who] labored so hard (occasionally relinquishing their lives!) to establish the laws of gravitation …” [Eldredge, 2005], a. Say more about their own beliefs than about history.

b. Ignore CD’s wish to be natural history’s Newton.

7. As emphasized by Robert Young (1985)

“Anyone wishing to continue to take a simple view of the relations between Victorian scientific naturalism and the establishment, as represented by the Victorian Anglican hierarchy, has many appar-ent anomalies to explain. Here are two … Essays and Reviews advocated the treatment of the Bible as a historical text and sup-ported naturalism with respect to the history of life. It was a scandal and was prosecuted in the theological courts. One of the notorious essayists in this book, which caused as great a stir as On the Origin of Species, was Frederick Temple [who] … went on to be-come Archbishop of Canterbury. The second striking fact is: Dar-win is buried in Westminster Abbey.” [p. 22. Emphasis added]

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Scylla and Charybdis. Hutton (1788) concluded his

Theory of the Earth thusly: “… if the succession of worlds is es-tablished in the system of nature, it is in vain to look for … the origin of the earth. The result … is, that we find no vestige of a beginning,--no prospect of an end.” [p. 304. Emphasis added] 1. Lyell followed Hutton, and

Darwin followed Lyell in as-suming plenitudes of time.

2. Recall his letter to Gray: “We have almost unlimited time; … millions on millions of genera-tions.”

3. CD attempted a single cal-culation – “The denudation of the Weald[8],” he wrote

8 The term derives from Old English Weald (forest).

Figure 4.1. Top. Geology of south-eastern England. The High Weald is in lime green (9a); the Low Weald, darker green (9). Chalk Downs, pale green (6). Bottom. Geological section from north to south: High and Low Weald shown as one.

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“has been a mere trifle, in comparison with that which has re-moved masses of our Palaeozoic strata, in parts ten thousand feet in thickness … . Yet it is an admirable lesson to stand on the North Downs and to look at the distant South Downs; … one can safely picture … the great dome of rocks which must have cov-ered up the Weald … since the latter part of the Chalk formation [lower Cretaceous] … [A]ssume that the sea would eat into cliffs … at the rate of one inch in a century. … At this rate … the denudation of the Weald must have required … three hundred million years.” [9] [The Origin, 1st Edition. Pp. 285-287].

Darwin likewise assumed a sufficiency, If not an exuber-ance, of heritable variability – recall his letter to Asa Gray later excerpted in DW58:

“This [environmental change] will tend to cause some of its inhabitants to vary slightly – not but that I believe most beings vary at all times enough for selection to act on them.” [Letter of 5 September, 1857, DCP-2136 ]10

9 Darwin’s geological model of erosion by the sea, is no longer accepted. As the Weald’s antiquity, the most recent Lower Cretaceous dates to ~105 Mya (million years ago), which would make Darwin’s estimate about 3.5 times too long. . 10 Omitted from the material excerpted was the following: “You will, perhaps, think it paltry in me, when I ask you not to mention my doctrine; the reason is, if anyone, like the Author of the Vestiges, were to hear of them, he might easily work them in, & then I shd. have to quote from a work perhaps despised by naturalists & this would greatly injure any chance of my views being received by those alone whose opinion I value.—

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But by 1870, CD was trying to navigate between paucities of both time & variation. Both

1. Fatal to the argument of

The Origin.

2. Contributed to what Julian Huxley11 (1942) and Peter Bowler (1992) called “the eclipse of Darwinism”.

By century’s end, everyone accepted the reality of evolu-tion, but there was skepticism regarding the ability of varia-tion plus selection could ac-count for it.

“Those who were opposed to the selection mechanism had no doubt about the overall trend. Darwinism was on the decline and would soon be eliminated altogether as a major evolutionary theory. This confidence is best illustrated by the title of a German work as translated into English, Eberhard Dennert’s[12]

At the Deathbed of Darwinism (1907).” [Bowler, 1992, 4]

11 The grandson of Thomas Henry Huxley. 12 A German naturalist with a theistic ax to grind. Dennert founded the Kep-lerbund, an organization with Volkish, as well as evangelical, ties.

Figure 4.2. The eclipse.

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Slayers of Time and Variation.

William Thomson (Lord Kelvin).

1. Co-discoverer of Thermo-dynamics’ 2nd Law which is incompatible with a time-less earth.

“To suppose, as Lyell … an end-less cycle, violates the principles of natural philosophy in exactly the same manner, and to the same degree, as to believe that a clock constructed with a self-winding movement may fulfil the expecta-tions of its ingenious inventor by going for ever.” (Thomson, 1862)

2. Like Buffon13, Thomson cal-

culated the age of the hab-itable earth assuming it cooled from a molten state - obtained estimates of 28-100 m.y. (Thomson, 1866).

13 Buffon’s estimates empirical; Kelvin’s theoretical.

Figure 4.3. “Some of the great sci-entists … have arrived at the convic-tion that our world is prodigiously old, and they may be right but Lord Kelvin is not of their opinion. He takes the cautious, conservative view, in order to be on the safe side, and feels sure it is not so old as they think. As Lord Kelvin is the highest authority in sci-ence now living, I think we must yield to him and accept his views.” [Mark

Twain quoted by Burchfield (1990, p. ix)]

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3. Later estimated the age of the sun assuming its heat from gravitational collapse with order of magnitude similar result.

4. Intersection of two inde-pendent “lies”, i.e., approxi-mations.

5. Britain’s most famous sci-entist of the day.

6. Believed “strong proofs of intelligent and benevolent design lie all round us.” (Thomson, 1871) But a. 1st writings on the subject

date to 1852, i.e., before publication of The Origin.

b. At least initially, his quarrel was with Lyell and uniform-itarian geology, not with evolution.

7. Kelvin’s estimates dominated scientific opinion for ~40

years. Only with the discovery of radioactive decay, was the true age of the earth (~4.5 b.y.) determined.

Figure 4.4. Top. Transatlantic cable construction in the 19th century. Bottom. The 1869 cable from Brest to Saint-Pierre was laid by the Great Eastern, with Jenkin and Kel-vin on board.

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a. As Ernest Rutherford later reminisced,

“I came into the room … and presently spotted Lord Kelvin in the audience and realized that I was in trouble at the last part of my speech dealing with the age of the earth, where my views con-flicted with his. To my relief, Kelvin fell fast asleep, but as I came to the important point, I saw the old bird sit up, open an eye and cock a baleful glance at me! Then a sudden inspiration came, and I said Lord Kelvin had limited the age of the earth, provided no new source was discovered.[14] That prophetic utterance refers to what we are considering tonight, radium! Behold, the old boy beamed upon me.” [Powell (2001)] b. Observation had replaced deduction: “Close to the time of his speech to the Royal Society, Rutherford was walking the McGill campus. In his pocket he carried … a specimen of a uranium oxide mineral called pitchblende. Meeting a colleague, Rutherford said, ‘Adams, how old is the earth sup-posed to be?’ The answer came back at Kelvin's earlier figure of 100 million years. ‘I know,’ said Rutherford quietly, ‘that this piece of pitchblende is 700 hundred million years old.’ [Ibid]

14 The reference is to the sun: "It seems … most probable that the sun has not illumi-nated the earth for 100,000,000 years … As for the future … inhabitants of the earth cannot continue to enjoy the light and heat essential to their life, for many million years longer, unless sources now unknown to us are prepared in the great storehouse of creation." [Thomson (1862). Emphasis added]

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Kelvin and the Geologists. 1. Darwin had imagined effectively limitless time.

2. Being unable to follow Kelvin’s mathematics, he had no

response but to a. Forgo future attempts to quantify geological time.

b. Posit mechanisms to speed things up – see below.

3. Privately, CD rejected the physicists’ machinations.

“I cannot think how you can attach so much weight to the physicists, seeing how Hopkins, Hennessey, Haughton, and Thomson have enormously disagreed about the rate of cooling of the crust; remem-bering Herschel's speculations about cold space,[15] & bearing in mind all the recent speculations on change of axis, I will maintain to the death that your case of Fernando Po and Abyssinia[16] is worth ten times more than the belief of a dozen physicists.” [CD to Hooker, 20 February, 1866 DCP 5020]

15 Haughton’s estimate exceeded Kelvin’s by a factor of 10. Herschel imag-ined the temperature of space varied thereby affecting earth’s climate. 16 "Dr. Hooker has … shown that several of the plants living on the upper parts of the lofty island of Fernando Po and on the neighbouring Cameroon Mountains in the Gulf of Guinea, are closely related to those in the mountains of Abyssinia, and likewise to those of temperate Europe." [Darwin, 1876, 337] an observation indicative of past climatic cooling and only tangentially related to the age of the earth.

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4. Kelvin’s calculations deeply disturbing to geologists. In 1895, Archibald Geikie17 observed

“Geologists have not been slow to admit that they were in error in assuming that they had an eternity of past time for the evo-lution of the earth’s history. They have frankly acknowledged the validity of the physical arguments which … place … limits to the antiquity of the earth. They were on the whole, disposed to acquiesce in the allowance of 100 millions18 of years granted … by Lord Kelvin, for the … whole … of geological history. But the physicists have been … inexorable. As remorseless as Lear’s daughters, they have cut down their grant of years by successive slices, until some of them have brought the number to something less than ten millions.” [Emphasis added].

5. Geologists eventually produced their own estimates based on rates of sedimentation, salt accumulation, etc. (Burchfield, 1974; Dalrympal, 1991; Powell, 2001).

a. On average, an order of magnitude greater than Kel-vin’s maximum allowance.

b. And, per Darwin’s letter to Hooker, there was consid-erable scatter (Figure 4.5).

17 Archibald Geikie (1835-1924) was head of the Geological Survey of Great Britain from 1881-1901. 18 The reference is to Kelvin’s (1862) initial estimate of 98 my.

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Estimating the Age of the Earth.

Figure 4.5. Estimates of the earth’s age vs. time. Current estimate in green; Kelvin’s upper limit, in red. Data from Dalrymple (1991, 14-17)

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At the same time, Huxley (1869) questioned Kelvin’s as-sumption that the earth had cooled from a molten state.

“Mathematics may be compared to a mill of exquisite workman-ship, which grinds you stuff of any degree of fineness; but, nev-ertheless, what you get out depends upon what you put in."

This line of argumentation went nowhere at the time, (but see below), and THH forced to fall back on “mother wit”:

“Biology takes her time from geology. The only reason we have for believing in the slow rate of change in living forms is that they persist through a series of deposits which, geology informs us, have taken a long while to make. If the geological clock is wrong, all the naturalist will have to do is to modify his notions of the rapidity of change accordingly.” [Huxley, 1869]

1. Which was pure sophistry – Darwinian gradualism

demanded vast stretches of time, and everyone knew it.

2. Huxley had transitioned from upstart outsider to de-fender of a new establishment to which he now be-longed – i.e., “one man in his time plays many parts”.

3. By this time, Darwinians had founded the journal Na-ture, taken control of BAAS, Royal Society, etc. (Bar-ton, 1998).

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Moving in Herds: 1. The discovery of radioactivity would have made models

like Kelvin’s and sophistry like Huxley’s obsolete.

2. And it would have confirmed previous geological opinion that the earth was ancient, indeed.

3. But, like the dinosaurs of Jurassic Park, geologists trav-eled in herds. “Not all geologists, however, greeted this new evidence for the vastness of geologic time and the antiquity of the Earth with equal enthusiasm. Many had reconciled their thinking to the shorter time scales and were highly skeptical of evidence to the contrary based on radioactivity. George Becker (1901c), for example, after finding that both cooling and sodium accumulation indicated the Earth’s age was 70 Ma or less, concluded that ‘this being granted, it follows that radioactive minerals cannot have the great ages that have been attributed to them.’ Becker was not alone, nor did skepticism end quickly.” [Dalrymple, 1991, 75]

4. Instead, they demanded reconciliation. “In the face of two rival and mutually inconsistent systems of earth chronology … it becomes essential to examine ... the fundamen-tal assumptions underlying each method …” [Holmes, 1913, 19]

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The Problem with Kelvin’s Calculation.

Rutherford’s reference to new sources of heat sug-gests that Kelvin’s calcula-tions might be corrected by including heat generated by decay of crustal deposits of radioactive minerals.

Would steepen tempera-ture gradient near earth’s surface.

Long part of evolution folk lore, e.g., Eiseley (1961).

But – England et al. (2007) calculated that heat from ra-dioactive decay affects the estimated age very little.

Real problem was assum-ing that the earth’s interior is homogeneous. It isn’t. Think plate tectonics!

Figure 4.6. Graphical version of Kelvin’s model. As an ini-tially molten earth cools, the temperature gradient near the surface, e.g., in a coal mine, declines. If conduction be the only means of heat transport, the gradient can be compared with Kelvin’s calculated curve and the age of the earth esti-mated as shown. However, if there are superficial sources of heat transport, the ob-served gradient must be cor-rected by their removal. Like-wise if heat is transported from the interior by convec-tion. Both corrections yield an older age.

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Current models assume a crustal cap that sits atop a viscous interior wherein heat is transmitted by con-vection (England et al., 2007). a. First proposed by Kelvin’s

former assistant, John Perry, in 1895.

b. Writing in Nature, Geikie

observed (1895, 369),

“Prof. Perry … finds that on as-sumption that the earth is not homogeneous as postulated by Lord Kelvin, but possesses a much higher conductivity and thermal capacity in its interior than in its crust, its age may be enormously greater than pre-vious calculations have allowed.”

In short – Kelvin underestimated the age of the earth be-cause he used the wrong model.

Kelvin could not, however, have correctly estimated the age or life expectancy of the sun, thermonuclear fusion in his day being an unknown energy source “prepared in the great storehouse of creation.”

Figure 4.7. Model of earth’s interior with the core shown in orange. Convective heat flow invalidates Kelvin’s calcula-tion. From England et al. (2007).

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Fleeming Jenkin (1867).

1. His review of The Origin published anonymously in The North British Review. a. An engineer & business

associate of Kelvin’s.

b. An atheist until shortly before his death.

“‘The longer I live, my dear Louis,’ he wrote but a few months before his death, ‘the more convinced I become of a direct care by God – which is reasonably impossible – but there it is.’ And in his last year he took the communion.” [Ste-venson (2000) p. 116]

2. Darwin took Jenkins’ criticism very seriously.

a. As evidenced both in correspondence with Wallace, re-

visions to the Origin and later writings.

b. His son, Francis would later editorialize

Figure 4.8. Mr. Jenkin and his telphers.

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It is not a little remarkable that the criticisms, which my father … felt to be the most valuable ever made on his views should have come, not from a professed naturalist but from a Profes-sor of Engineering.” [F. Darwin (1887), Vol. 3, p. 107]

c. And indeed, to Hooker, Darwin had written on 16 Janu-ary, 1869

“It is only about two years since last edition of Origin, and I am fairly disgusted to find how much I have to modify, and how much I ought to add; but I have determined not to add much. Fleeming Jenkins [sic] has given me much trouble, but has been of more real use to me than any other essay or review.”

3. Jenkin’s refutation of Darwin’s argument was one of “cu-

mulative proof”. Among some dozen objections, the fol-lowing may be noted: a. Continuing selection exhausts variability.

b. Blending inheritance eliminates variability by ~ 50%

each generation.

c. DwM works if sports breed true. But – “The appearance of a new specimen capable of perpetuating its peculiarity is precisely what might be termed a creation, the word being used to express our ignorance of how the thing happened.

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The substitution of the new specimens, descendants from the old species, would then be simply an example of strong race sup-planting a weak one, by a process known long before the term 'natural selection' was invented. Perhaps this is the way in which new species are introduced, but it does not express the Darwinian theory of the gradual accumulation of infinitely minute differences of every-day occurrence [CD’s individual differences], and apparently fortuitous in their character.” [Emphasis added]

4. Patterns of similarity do not

necessitate DwM. E.g., a. Chemical elements;

b. Human inventions.

“It is very curious to see how man's contrivances … fall into series, presenting the difficulty complained of by naturalists in classifying birds and beasts ... It is this difficulty which pro-duces litigation under the Pa-tent Laws.”

5. Called attention to Kelvin’s age of the earth calculations in a forum sufficiently public and accessible that the Darwinians had to respond.

Figure 4.9. Phylogenetic tree of musical instruments. Verti-cal lines correspond to differ-ent models; curved lines, to information transfer; triangles, to key innovations. From Tëmko and Eldredge (2007).

29

6. Emphasized correlation of parts and decried “just so” adaptive tales, thereby following Cuvier and anticipating Gould and Lewontin (1979).

7. Justified his right (as an engineer) to an opinion thusly: “The opponents of Darwin … have asserted that animals are not so similar but that specific differences can be detected, and that man can produce no varieties differing from the parent stock, as one species differs from another.” “About the truth and extent of those facts none but men pos-sessing a special knowledge of physiology and natural history have any right to an opinion; but the superstructure based on those facts enters the region of pure reason, and may be dis-cussed apart from all doubt as to the fundamental facts.” [Em-phasis added]

8. For further discussion and (often conflicting) opinions re-

garding Jenkins’ review and its impact, see Eiseley (1959), Vorzimer (1963), Gould (1985), Morris (1994) and Bulmer (2004).

30

Darwin’s Reaction.

Weald calculation 1. Already removed from the 3rd British (1861) edition of The

Origin in response criticism in the Saturday Review.

2. Retained in the 4th American (1860) edition accompanied by the following footnote: “I have left the foregoing passages as they stand in the second edi-tion, but I confess that an able and justly severe article, since pub-lished in the Saturday Review (Dec. 24th, 1859), shows that I have been rash. I have not sufficiently allowed for the softness of the strata underlying the chalk …. Nor have I allowed for the denudation going on both sides of the ancient Weald-Bay; but the circumstance of the denudation having taken place within a protected bay would prolong the process … I always supposed that the reader would double or quadruple or increase in any proportion which seemed to him fair the probable rate of denudation per century.” [p. 252]

3. Important point being that the criticism to which Darwin

responded was geological (rocks / erosion) as opposed to physical (heat transfer). i.e., no reference to Kelvin’s mathematics.

31

In response to Jenkin’s review and the comprehensible and widely circulated summary of Kelvin’s calculations therein, Darwin

1. Gave up on “single” variations i.e., “sports” – acknowl-

edged that they would quickly be blended out.

2. Increasingly emphasized direct environmental induc-tion of concordant “individual” variations en masse, i.e., in multiple individuals.

3. Argued that widespread subdivision of species into local breeding populations would retard loss of variation by blending.

4. Tied rates of evolution to intensity of geological activity – i.e., the young earth was more active geologically, for which reason evolution proceeded faster than it does to-day.

5. Increasingly emphasized use and disuse and the inher-itance of acquired traits, for which his “Provisional Hypoth-esis of Pangenesis” (Darwin, 1868, v2, 357-405] fortui-tously provided a mechanism.19

19 As noted in Lecture III, Pangenesis antedates Jenkins’ review, CD having sent Huxley a draft of the theory in 1865 (Olby, 1963, 251).

32

Additions to the 6th Edition (1872).

Single Variations Rarely Perpetuated.

“… until reading an able and valuable article in the 'North British Re-view' (1867), I did not appreciate how rarely single variations, whether slight or strongly-marked, could be perpetuated.” [p. 71]

“The justice of these [Jenkin’s] remarks cannot, I think, be disputed. If, for instance, a bird of some kind could procure its food more easily by having its beak curved, and if one were born with its beak strongly curved, … nevertheless there would be a very poor chance of this one individual perpetuating its kind … ” [p. 72]

Individual Variations Induced en Masse by the Environ-ment and, if Advantageous, Preserved.

“[I]f the varying individual did not actually transmit to its offspring its newly acquired character, it would undoubtedly transmit to them … a still stronger tendency to vary in the same manner. … [T]he tendency to vary in the same manner has often been so strong that all the indi-viduals of the same species have been similarly modified without the aid of any form of selection. … . [I]f the variation were of a beneficial nature, the original form would soon be supplanted by the modified form … .” [p. 72. Emphasis added.]20

20 Note that this not only responds to swamping, but also to the random loss of infrequent “mutations” no matter how beneficial.

33

Population Structure, i.e., Mating with One’s Neighbor, Retards Homogenization by Blending.

“To the effects of intercrossing in eliminating variations … , I shall have to recur; but … most animals and plants keep to their proper homes, and do not needlessly wander about; … Consequently each newly-formed variety would generally be at first local, …; so that similarly modified individuals would … often breed together. If the new variety were successful in its battle for life, it would slowly spread from a central district, competing with and conquering the unchanged individuals on the margins of an ever-increasing circle.” [p. 72. Emphasis added]

Faster Rates of Evolution Early in Earth’s History.

"It is, however, probable, as Sir William Thompson [sic] insists, that the world at a very early period was subjected to more rapid and violent changes in its physical conditions than those now occurring; and such changes would have tended to induce changes at a cor-responding rate in the organisms which then existed." [p. 286, Emphasis added]

34

“Soft” Inheritance and Variability. Use and disuse: In a letter to Nature, Darwin wrote,

“Can Sir Wyville Thomson [who had criticized NS] name any one [sic] who has said that the evolution of species de-pends only on natural selection? As far as concerns myself, I believe that no one has brought forward so many observa-tions on the effects of the use and disuse … , as I have done in my "Variation of An-imals and Plants under Domestication"; … I have likewise there adduced a con-siderable body of facts, showing the di-rect action of external conditions on or-ganisms;” [Darwin (1880). Empha-sis Added]

Responding to Sir Wyville’s failure to observe excessive variability in his samples, Darwin argued that unfavorable variations are rap-idly eliminated by selection.

Meanwhile Wallace (1889) began quantifying variability in nature.

Figure 4.10. As the cen-tury waned, Wallace be-came the leading expo-nent of natural selection. His book, Darwinism in-cluded figures such as this documenting natural variation.

35

Pangenesis.

Darwin proposed the existence of microscopic gemmules. 1. Circulated through the body and modified by environment

(including somatic activity), when in peripheral tissues.

2. Thereafter returned to the gonads where they and the in-formation acquired were transmitted to offspring.

Gemmules compete within the body as individuals com-pete within populations.

Darwin imagined that pan-genesis could account for

1. Origin of variability.

2. Blending inheritance.

3. Inheritance of acquired

characters (IAC) – gem-mules modifiable by use and disuse.

4. Atavisms – activation of dormant gemmules.

Figure 4.11. Polydactyly in horses. Left. Normal condi-tion. Middle. Duplication of the central toe. Right. En-largement of the splint. Only the latter is an atavism.

36

Variation en masse in response to changed environmental circumstances – gemmules in different individuals respond the same way.

This, plus rapid environmental change in the past the core of Darwin’s response to Kelvin / Jenkin.21

Alas!

1. Pangenesis experimentally invalidated: Galton (trans-fusion expts.); Weismann (mutilation expts.).

2. But stay tuned: Predator-induced polyphenisms in-clude apparent examples of adaptive “transgenerational effects” induced by environ-mental factors – in this case predator produced odor-ants.

21 As noted by Olby (1963) and Vorzimmer (1963), pangenesis was con-ceived, passed to Huxley for comment and sent to the printer prior to publi-cation of Jenkin’s review. In fact, CD’s interest in use and disuse dates to his “notebook days” – see Lecture VI.

Figure 4.12. Electron micro-graphs of Daphnia cucullata. Left. Standard shape. Right. Predator-induced morph with helmet (green) and tail (blue). From Sciencephoto.com.

37

Figure 4.13. Pangenesis (left) imagined that environmental influ-ences were transmitted to the germ via circulating particles that Dar-win called gemmules. Germ plasm theory (right) of August Weis-mann emphasized isolation of the germ line from environmental in-fluences. The Modern Synthesis allows for environmental induction of mutations but holds that they are random with regard to effect.

38

Waiting for Mendel and the Curies.

The next century would bring 1. Particulate inheritance (Mendelism) and the recovery of

variation.

a. Initially taken as evidence for ‘saltation’. b. Linked to Darwin’s “individual differences” by Fisher

(1918) via polygenic inheritance.

2. Radiometric dating and the recovery of time. a. Allowed for absolute dating of geological strata, etc.;

Earth far older than ever imagined.

b. Made Kelvin’s calculations irrelevant.

3. Until then, a. Case for DWM strengthened by advances in em-

bryology, anatomy and especially paleontology.

b. While the “how” remained unclear.

39

Figure 4.14a. Archaeopteryx, the so-called “Urvogel”, was identi-fied by both Owen and Huxley as a bird. The only specimen avail-able at the time lacked the skull, thereby enabling Owen (1863b) to infer the existence of “a beak-like instrument fitted for preening the plumage of Archeopteryx [sic].”

40

Figure 14b. Relationship of Archaeopteryx to birds and other dino-saurs. Current thinking places Archaeopteryx close to, but not on, the line leading to modern birds, i.e., both are contained within the clade of feathered dinosaurs called Maniraptora. As shown here, the genus Archaeopterix is a sister taxon to modern birds (Aves). Modi-fied from Wellnhofer, P. 2010. A short history of research on Archae-opteryx and its relationship with dinosaurs. Pp. 237-250, In, Moody, R. et al. (eds.) Dinosaurs and Other Extinct Saurians. Geol. Soc. London. Spec. Publ. 343.

41

Huxley.

“How extremely stupid not to have thought of that!” [F. Darwin, 1887, II, 197]. But – THH not certain that Darwin had the entire answer. “the explanation … offered by Mr. Darwin is as superior to any preced-ing … as was the hypothesis of Copernicus …. But the planetary orbits turned out to be not quite circular after all, and, grand as was the ser-vice Copernicus rendered to science, Kepler and Newton had to come after him. What if the orbit of Darwinism should be a little too circular? What if species should offer residual phænomena, here and there, not explicable by natural selection?” [Huxley, 1860, 569]

Preferred abrupt to gradual change and continued to en-courage Darwin to experimentally derive new species. “I see you are inclined to advocate the possibility of considerable "saltus" on the part of Dame Nature … I always took the same view, much to Mr. Darwin's disgust, and we used often to debate it.” [Huxley, 1909, 394 (Letter to Wm. Bateson, 20 February, 1894)] “If it can be proved that the process of natural selection … can give rise to varieties of species so different from one another that none of our tests will distinguish them from true species, Mr. Darwin's hypothesis … will take its place among the established theories of science …“ [Huxley, 1859, 147-148]

42

In fact, evolution didn’t show up in Huxley’s research until nearly a decade after The Origin’s publication.

1. Reference not to Darwinian selection, but to Ernst

Haeckel (development) and neo-Platonic archetypes.

2. For Huxley, the key realizations were

a. Inheritance and modification of body plans.

b. Recapitulation – phylogeny reflected development.

3. Bartholomew (1975, 535) quoting Ghiselin (1971): “[He] ‘remained a pre-Darwinian anatomist as long as he lived’ “

4. Di Gregorio (1982, 417):

“…Huxley's own research is not the place to look for evidence of any direct impact … of the publication of the Origin of Species … prior to the late 1860s when systematologists … began to adjust. The same line of thought also dispels the expectation … that … natural selection ought to be featured … in those works of Huxley that deploy the idea of evolution; for that expectation is countered by … [the] irrelevance of natural selection to the [then cur-rent] concerns of systematics. … Both his heavily qualified ac-ceptance of natural selection and the survey of his research show that Huxley became an evolutionist, but not of the Darwin-ian kind.” [p. 417]

43

But Huxley did contribute greatly to the case for DwM.

1. Anatomical similarities among higher primates.

2. Demolished Owen’s claim that

“the brain of the gorilla was more different from that of man than from that of the lowest primate particularly because only man had a posterior lobe, a posterior horn, and a hippocampus minor.” [22]

22 The hippocampus minor, now called the calcar avis, is a ridge in the floor of the posterior horn of the lateral ventricle.

Figure 4.15. Anatomical correspondences among higher primates. From Huxley. T. H. 1883. Evidence as to Man’s Place in Nature.

44

3. Man had always been the elephant in the room, and on that score, Huxley and Owen had been at odds for years. Now Huxley made the fool of his rival – see Gross (1993).

“Then HUXLEY and OWEN With rivalry glowing With pen and ink rush to the scratch. ‘Tis Brain vs. Brain Til one of them’s slain By Jove! It will be a good match.

Says OWEN, you can see The brain of a chimpanzee Is always exceedingly small With the hindermost “horn” Of extremity shorn And no “Hippocampus” at all.

Next HUXLEY replies That OWEN he lies And garbles his Latin quotation; That his facts are not new, His mistakes are not few, Detrimental to his reputation.” [Punch, 1862].

4. 20th century discovery of small-brained hominids (Aus-

tralopithecus, etc.) eventually settled the matter.

Figure 4.16. Human brain with hippocampus minor in

45

Hippocampus aside, Owen and Huxley shared an attach-ment to archetypes and reservations about NS.

1. From his hypothetical vertebrate archetype, Owen de-

rived the structure of real vertebrates by segmental spe-cialization.

2. Archetypes the third heretical wave of continental biol-

ogy to wash the British shore.23

a. Pre-Darwin, these products of German idealism neither necessitated nor were inconsistent with the descent of one species from another.

b. Post-Darwin, archetypes became ancestors.

23 The first two waves were Lamarckian transformism and Geoffroy’s philo-sophical anatomy – see Lecture V.

Figure 4.17. Owen’s (1846) vertebtate archetype imagined that the vertebrate skeleton could be viewed as a series of identical segments, some of which were modified to form the skull, appendages, etc.

46

3. Rupke (2009, p. 229 ff), whose biography attempts a more balanced view of Owen than that perpetuated by Huxley and his intellectual heirs, argues that Owen24 a. Rejected ideas of a force vitale, an immaterial soul, etc.

b. Believed in “a non-miraculous origin of species, includ-

ing Homo sapiens [which] meant a rejection of continu-ing divine intervention in the workings of nature “ [op. cit. p. 232]

c. Rejected Darwinism and “never warmed to the idea of

human evolution” [op. cit., p. 234].

4. Regarding NS, he argued (1860), (shades of Lyell’s as-sessment), that The Origin’s author adduced few facts to support his conjectures; observed variation limited; no ex-amples of species having been created by selection, etc.

5. Likewise, in his monograph (Owen, 1863c) on the aye-aye, a highly modified lemur, while acknowledging the in-direct evidence for DwM, he opined with regard with re-gard to “the how” that

“Darwin seems to be as far from giving a satisfactory explanation of them as Lamarck.” [p. 96]

24 Comparison of Owen vs. Huxley with Cuvier vs. Lamarck not unwarranted, i.e., in both cases the younger of the pair felt slighted by the older.

47

The Aye-aye, Daubentonia (Chiromys) madagascariensis.

1. A lemur with spectacular specializations for detecting and extracting insects from tree bark.

a. Large ears. b. Narrow middle finger. c. Chisel incisors that grow continuously through life.

2. In short, a primate intent on becoming a squirrel.

3. Owen’s (1863c) take in his celebrated monograph on the creature: “The terms in which the anatomist would express the sum of his observations on the structural resemblances traceable from the Aye-aye throughout the Lemuridae would be, that the principle of ‘unity of organization’ prevailed through such group. “And such terms would have a more intelligible meaning on the hy-pothesis that these singularly diversified Lemurs were genetically related by descent from a common ancestral form” “Whilst admitting the general evidence, therefore, on favour of ‘cre-ation by law,’ I am compelled to acknowledge ignorance of how such secondary causes may have operated in the case of Chiormys.

48

“… all the surmises and guesses as to the conditions of such changes , all the attempts to explain how they were brought about – if they have been brought about – by still operative causes, are inadequate and unsatisfactory. [p. 96-97]

Figure 4.18a. The aye-aye, a highly modified lemur specialized for detecting and extracting insects from the bark of trees. Among them large ears; a narrow, elongate middle finger and chisel incisors. Figure continued on following page.

49

Figure 4.18b. (Left. Enlargement of the face and forepaws. Right. Skull and skeleton showing chisel incisors and elongate third fin-ger. From Owen, R. 1863c. “Monograph on the Aye-Aye (Chiromys madagascariensis Cuvier)”. Taylor and Francis, London.

50

Evolution by the Century’s End. Neo-Darwinism.

1. Term coined by George Romanes (Darwin’s friend and

assistant (1874-1882) who argued (Romanes, 1886) that a. Characters that distinguish species generally not adap-

tations and likely to be lost due to blending.

b. Darwin’s theory “explains the origin of useful structures” but not species, which requires barriers to crossing.25

2. Neo-Darwinists emphasized natural selection to the ex-

clusion of other mechanisms.

a. Rejected IAC in particular.

b. Compatible with August Weismann’s germ plasm theory – sequestration of the germ.

c. Specific characters are or have been useful or cor-

related with other useful traits.

25 Romanes’ solution was “physiological selection”: concordant variations in multiple individuals consequent to lability of the reproductive system lead-ing to sympatric speciation. Seventy-five years later, the Synthesis would substitute allopatry and selection for reproductive isolation

51

Biometrical School (Francis Galton). 1. Consequent to interest in “individual” differences.

2. Focused on parent-offspring correlations.

a. “Heritability” of quantitative traits.

b. Reversion to the mean (Figure 4.19) – recall Jenkin’s

“sphere of variation”.

3. Galton argued that reversion would prevent small varia-tions from inducing indefinite deviation from an original type.

4. Possible to overcome this tendency, but to do so would require a large “push”.

5. Illustrated his ideas with the response of an asymmetric stone polygon to gravity and external forces (Figure 4.20).

6. Biometrical approach evolved into “quantitative genetics” – “genes exist, but only in back of the blackboard.”

52

Figure 4.19. The first regression line constructed by Francis Galton in 1877. The slope being less than one, illustrates “reversion to the mean” thereby enabling Galton to conclude that significant departure from an original type can only take place by saltation. A modern statement of quantitative inheritance is

�̅�𝑜 − �̅� = ℎ2(�̅�𝑝 − �̅�),

where �̅�𝑜 is the expected offspring trait value; �̅�𝑝, the parental mean

and �̅�, the population mean and ℎ2, the slope of regression.

53

Figure 4.20. Francis Galton’s “polygonic” reconciliation of saltation and reversion to the mean. Top. A forceful right to left rotation (thick arrows) will shift the stone from a more stable (i) to a less stable orientation (ii). A less forceful rotation (thin arrows) in the opposite direction will restore the stone to its original position. Bottom. A forceful right to left rotation of the less stable state (ii) will result in a new orientation that is again more sta-ble. Galton’s construction is, of course, purely metaphorical. Sewall Wright’s adaptive landscape concept (see below) provided a mechanistic alternative.

54

6. Saltation, which Galton believed the principal evolutionary driver, would have its real renaissance in the 20th century following rediscovery of Mendel and the promotion of the so-called “mutation theory” (below).

7. Galton’s biometrical studies intimately connected to the eugenics movement of which he is often referred to as “father”.

“I also showed that a powerful influence might flow from a public recognition in early life of the true value of the probability of future performance, as based on the past performance of the ancestors of the child. It is an element of forecast, in addition to that of present personal merit, which has yet to be appraised and recognised. Its recognition would attract assistance … to the young families of those who were most likely to stock the world with healthy, moral, intelligent, and fair-natured citizens. The stream of charity is not un-limited, and it is requisite for the speedier evolution of a more perfect humanity that it should be so distributed as to favour the best-adapted races. I have not spoken of the repression of the rest, be-lieving that it would ensue indirectly as a matter of course; but I may add that few would deserve better of their country than those who determine to live celibate lives, through a reasonable conviction that their issue would probably be less fitted than the generality to play their part as citizens.” [Galton, 1883, 219]

55

Neo-Lamarckism.

1. Especially among American paleontologists, Neo-Darwin-ism took a back seat to Neo-Lamarckism.

2. Emphasized both an inherent tendency to evolve in pre-determined, often, but not always, progressive, direction (orthogenesis) and IAC.

3. This view consistent with apparent phylogenetic linearity as evidenced by fossils, e.g., horses, brontotheres.

4. Noteworthy in this regard were Edward Cope (neo-La-marckian) and Othniel Marsh (committed Darwinian who collected fossils in the American West (so-called “bone wars”).

5. Also noteworthy was Herbert Spencer, a prominent Brit-ish neo-Lamarckian, who a. Formulated the phrase “survival of the fittest,” but

b. Nevertheless promoted a law of universal progress

(shades of Chambers’ Law of Development) in which regard he clashed repeatedly with Weismann during the 1890’s.

6. Widely replaced by Mendelian genetics prior to WWII.

56

Figure 4.21. Orthogenetic reconstruction of Brontothere evolution by Henry Fairfield Osborn (1929. The Titanotheres of ancient Wy-oming, Dakota, and Nebraska. USGS Monograph Ser. 55.)

57

Summing Up. Arguments deployed against the selection theory.

1. Immediate responses to The Origin. a. Discontinuities in the fossil record. Cambrian explo-

sion, in particular.

b. Irreducible complexity, e.g., the vertebrate eye. c. Law of higgledy-pigglety – recall Hoyle RE 747. d. Insufficient time – Kelvin’s calculated age of the earth e. Loss of variation due to blending – Jenkin’s argument.

2. Later responses. a. Existence of apparently non-adaptive characters,

e.g., those that distinguish species (Romanes, 1886).

b. Orthogenetic trends suggestive of internal and / or ex-ternal (goal-directed) “guidance”.

c. Evolutionary momentum, mal-adaptive characters; ra-

cial senescence (e.g., Hyatt, 1897).

58

In this regard, Bowler (1992, 12) asked: “Why did the original Darwinian theory gain wide support despite a number of unresolved problems? Why did the level of opposition increase after the first couple of decades? … All the standard ob-jections to natural selection were formulated in its first decade, yet the theory went on to gain wide popularity.” [Emphasis added]

And then proposed several answers (pp. 13 ff): 1. The fact that Darwin converted the scientific community

to evolution gave him a “leg up”.

2. Continuing theistic concerns: dissatisfaction with materi-alism; more conservative theories that accommodated an innate tendency to progress, if not divine purpose, and were consistent with embryology.

3. Emergence of disciplinary specialization promoted rival opinions each reinforced by its ability to account for disci-pline-specific concerns - e.g., paleontology (linear evolu-tion) vs. field biology (scatter shot variation).

4. Emergence of biology as an experimental, laboratory-based, science, particularly with regard to the study of he-redity, i.e., rediscovery of Mendelian genetics.

59

The following also pertinent:

1. Before the rediscovery of particulate inheritance, seem-ingly “orthogenetic” trends in the fossil record viewed as compelling evidence

a. For directed (internal or external) evolution.

b. Against random variation and selection.

2. After the rediscovery of Mendelism, particulate inher-itance viewed as compelling evidence a. Against gradualism.

b. For saltation via “mutations” that effectively resurrected

Darwin’s single differences – see Hubrecht (1904).

c. To which Wallace (1908), of course, took sharp excep-tion.

60

More Generally.

Both the immediate and delayed responses to Darwinism involved ideas that had long been discussed.

1. Nature of change: directional vs. steady state.

2. Agents of change: External environment (IAC and / or

selection) vs. force vitale vs. Author of Nature.

3. Tempo of change: gradual vs. catastrophic.

Author of Nature’s role, of course, pre-eminent and until 1859 unquestioned by the scientific establishment.

In Kuhnian terms (e.g., Nichols, T. 2016. Scientific Revolu-tions. Stanford Encyclopedia of Philosophy), 1. The ultimate concordance of God’s two Books the para-

digm within which respectable naturalists worked.

2. Into the coffin of said concordance, The Origin drove the final nail.

3. What had once been denounced as unphilosophical spec-ulation became acceptable for public discussion, i.e., par-adigm failure loosens the strait jacket of normal science.

61

19th Century Ideas Now Discarded. Orthogenesis.

1. Inherent tendency of line-ages to evolve in a linear fashion – e.g., horses.

2. Compare with Lamarck’s

Power of Life.

Racial senescence.

1. Mal-adaptation as lineages aged – converse of La-marck’s Power.

2. Examples: Gryphaea and

the “Irish Elk”.

Neo-Lamarckism.

1. IAC.

2. Power of Life.

Figure 4.22. Horses then (bottom) and now (top). The linear sequence is a “fig-new-ton” of incomplete sampling. From Marsh (1879).

62

Figure 4.23. A “bushier” representation of horse evolution. From Simpson (1944), i.e., with more fossils came more branches.

63

Figure 4.24. The “Irish Elk” was neither Irish nor an elk. Left. Skel-eton showing the enormous antlers. Right. Allometric comparison of Megaloceros giganteus with 10 other species of deer. The anal-ysis suggests that the antlers of Megaloceros are about the "right" for a cervid of its size. As emphasized by Gould, allometric scaling of the antlers of M. giganteus can be consistent with selection for large body size (the antlers tagged along), for large antlers (the body tagged along) or both. From Gould (1974).

64

Figure 4.25. Gryphaea arcuata – a Jurassic oyster once cited as a paradigmatic example of mal-adaptive evolution.

65

Ideas that Survived. Incorporated into the Modern Synthesis.

1. Descent with modification.

2. Principle of Divergence; Phyletic bushiness; Tree of life. 3. Gradualism.

4. Isolation as speciation facilitator.

Initially De-emphasized / Dismissed by the Synthesis but subsequently Resurrected / Reconsidered.

1. Influence of the conditions of life (mutagenesis, reaction

norms, transgenerational effects, etc.) 2. Limits to variation (developmental constraints / toolkits,

baupläne, “spandrels,” etc.)

3. Saltations (pseudogene resurrection, punctuated equilib-rium; mass extinction).

4. Inherent tendency to progress – positive feedback be-

tween size and complexity.

66

From Darwin to Mendel.

Particulate inheritance rediscov-ered Hugo de Vries and others in 1900. Promoted by Wm. Bateson.

Initially interpreted as evidence for saltation. 1. Due to work of de Vries who

studied color morphs in Oeno-thera (evening primrose).

a. Oenothera Self-fertilizing.

b. Multiple co-occurring races. c. De Vries grew seeds of natural hybrids. d. While most bred true, there were occasional new

forms that also bred true. 2. Inspired so-called “mutation theory”.

a. Speciation by jumps. b. Dominant view RE Mendel vs evolution for ~ 10 years.

Figure 4.26. O. lamarckiana, a naturally occurring, self-fertile hybrid.

67

Figure 4.27. De Vries’ Oenothera experiments. The original plants (top) were naturally occuring hybrids.

Figure 4.19. Recombination results from crossing over dur-ing meiosis.

68

3. Turned out that

a. Stability of original hybrids maintained by systems of balanced lethals.

b. De Vries’ “mutations” produced by recombination events that made formerly inviable chromosome com-binations viable.

Figure 4.28. Left. Maintanence of hterozygosity by a pair of balanced lethals. Homozygosity at either locus (red) results in infertility or inviability. Right. Recombiantion can produce new viable chromosome combinations and the appearance of saltatory change, i.e., Jenkins’ sports that “breed true.”

69

Elementen → Genes.

1. Rediscovery of Mendel’s paper was followed by observa-tion of exceptions to Independent Assortment.

2. Explained by postulating a. Genes on chromosomes; recombination consequent

to crossing over.

b. ⟹ chromosomes can be mapped by computing recom-bination frequencies of alleles on same chromosome.

Figure 4.29. Genetic maps.

70

And Back to Darwin.

Crucial advance was the realization that particulate inher-itance compatible with “continuous” variation of quantitative traits (Darwin’s individual differences). 2. In 1917, Fisher argued that quantitative traits under what

is now called “polygenic inheritance.” “For stature the coefficient of correlation between brothers is about .54, which we may interpret by saying that 54 per cent of their vari-ance is accounted for by ancestry alone, and that about 46 per cent must have some other explanation. “It is not sufficient to ascribe this last residue to the effects of the environment. Numerous investigations by Galton and Pearson have shown that all measurable environmental factors] have much less effect on such measurements as stature. Further, the facts collected by Galton respecting identical twins show that in this case … the variance is far less. The simplest hypothesis … is that such features as stature are determined by a large number of Mendelian factors, and that the large variance among children of the same parents is due to the segregation of those factors in respect to which the par-ents are heterozygous.”

3. There followed ~30 pages of impenetrable math that nonetheless opened the floodgates.

71

Along with Sewall Wright and J. B. S. Haldane, Fisher de-veloped a “Genetical Theory of Natural Selection”. 1. Included Fundamental Theorem of Natural Selection:

𝑑�̅�

𝑑𝑡= 𝑉𝑔

2. Wright’s discrete analog the basis of adaptive land-

scapes.

∆𝑝 =𝑝(1 − 𝑝)

2�̅�

𝑑�̅�

𝑑𝑝

Figure 4.30. Evolution on a 2-D adaptive landscape. Axes are gene frequencies or character states. Dashed lines are contours of equal fitness. Plus signs indi-cate fitness maxima; minus signs, minima. Left. Increased mutation or reduced selection leads to increased variability. Center. Converse. Right. Environmental shift places population on a new peak, which it then climbs.

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3. Fisher emphasized selection in large populations;

4. Wright emphasized evolution in local populations subject to selection and drift - Shifting Balance Theory.

5. The resulting “modern synthesis” was a theory of gene frequencies as determined by a. Selection;

b. Mutation; c. Migration; d. Chance (genetic drift).

6. Subsequently incorporated:

a. Systematics –theory of allopatric speciation (Mayr)

b. Selection in nature (Ford, Dobzhansky). c. Paleontology (Simpson).

7. Development really not included until the advent of “evo-devo” and the discovery of “developmental toolkits” com-mon to distantly related organisms – e.g., orthologous control of limb development in flies and man.

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The Modern Synthesis.

Figure 4.31. The Modern Synthesis (top) compared with Lamarck (bottom left) and Darwin (bottom right). Note progressive simpli-fication (Leigh, 1999) of evolutionary purported mechanisms.