Friday, October 28, 2016

Lyell, Darwin and Wallace (2)

Charles Darwin grew up in a Victorian upper-middle class family.  Dad was a doctor.  Mother was often sick, and died when he was eight.  His older sisters looked after him.  Young Charles loved to collect beetles, shells, birds' eggs and the like.   Going to university for a medical education (Dad wanting him to follow in footsteps) was derailed by Charles' dislike of blood, and positive horror at seeing surgery in the days before anesthesia.  Instead, he joined the dedicated amateur scientist Robert Edmond Grant in his study of sea sponges.  Grant was an atheist and "transmutationist" (both of these very troubling and heretical beliefs) and thought the sponge might be a kind of bridge between the animal and plant worlds.  Darwin also learned geology from the lectures of Professors Robert Jameson and Thomas Charles Hope, who sparred over whether igneous rocks like granite and basalt were precipitated out of water (Jameson) or cooled from a melt (Hope).  Museum and field trips taught him to interpret sedimentary rock layers.

After a year and a half at Edinburgh, Darwin's rather frustrated father moved him to Cambridge University and changed his program of studies to prepare for the ministry--another appropriate career track for one of his station.  He continued to be a mediocre student at best--preferring riding, shooting, and competitive beetle-collecting.  But Charles also found he had some doubts about the beliefs he would have had to subscribe to to become a an Anglican cleric, and put off a decision for the Church.  At the same time, though, he studied and came to love the work of William Paley, who had made an eloquent case for the existence of a Creator by pointing out the unmistakable signs of creation all around, and particularly in the incredible complexity and clear "design" of living creatures -- each one intricately adapted to its place in the economy of nature.  Paley it was who extolled the sophistication of the eye in all its permutations, discussing those of mammals and birds in detail.  (Explaining the evolution of the eye would later become one of Darwin's touchstones when he developed his theory.)  Paley it was who made a generation of minister/naturalists: what better pairing of vocations for appreciating the Creator and His creation?  Meanwhile, true to form, Charles learned botany from Professor John Stevens Henslow and became acquainted with geologist Rev'd Adam Sedgewick and mineralogist Rev'd William Whewell.  At about that time Charles realized that, given his father's wealth, he needn't pursue a lucrative career.

Watercolor of Charles in the 30's, after his return to England aboard Beagle.  He will first make his name by writing a readable and insightful account of the voyage, published as an appendix to the captain's report until its popularity justifies its separate publication.

After graduating with his BA, Charles was persuaded to look into signing on for a voyage aboard the little ten-gun brig, Beagle (Robert Fitz Roy, RN), which would be charting parts of South American waters.  A naval captain in the rigid British society of that time led a lonely life, and Fitz Roy wanted someone of the same social class he could talk to.  With a little persuasion from Charles' uncle, Dad agreed to fund Charles' voyage.

Darwin had come to think of himself as a geologist.  And stepping aboard the Beagle, Charles' captain--an amateur geologist in his own right--presented him with the first volume of Charles Lyell's Principles of Geology.  This, along with the two remaining volumes that Darwin had sent to him during his adventures--was to be Darwin's geology theory textbook for the next five years.

Darwin turned out to suffer debilitating seasickness, and apparently never got over it.  His journal, full of tales of new cultures, dangers, adventures, and exploration as he rides or tramps in South America for weeks and months at a time, falls altogether silent when the Beagle weighs anchor, and takes up the story again only in the new port--silence on weeks, sometimes months, at sea.

Filled by Lyell with the vision of lands constantly eroding into the sea and shoreline and ocean floor just as constantly being raised up into plateaus and mountain ranges, Darwin ever interprets the landscapes he sees in these terms.  He finds flood plains raised far above the sea, abandoned by their former rivers; he collects shells from deposits only a few yards above sea level, and also high in the mountains, judging each deposit by the degree to which the species reflect those still present in the ocean nearby.  (He cannot "date" these deposits as we can today, but concludes that, if the species in a deposit are largely extinct, that deposit is very old.)  He experiences the severe earthquake in Concepcion, Chile on Feb 20, 1835; soon after he notices with satisfaction that large stretches of the coast were concurrently uplifted by many feet.

Though primarily a geologist in his own mind, Darwin does not neglect flora and fauna.  He collects specimens constantly: some he shoots, others--tame from limited exposure to man--he simply knocks on the head with a stick.  He is keenly aware of the distribution of plants in the various islands visited.  He notes the changes in that distribution--even extinctions--caused by alien plants and animals introduced by Europeans, and by the land-use decisions the colonists have made.

Returning at last to England, Darwin fills notebooks with ideas that lean more and more toward the theory of evolution by natural selection he will eventually arrive at.  He marries his first cousin, Emma Wedgewood, and settles into domestic life at Down House in Kent.  He is fond of his children and welcomes them into his study.  He writes, he researches, he does many experiments, he raises fancy pigeons to study variation first-hand, but for decades it seems he will never finish the multi-volume work on "my theory."  Probably he worries about the reception it will receive.  Probably he knows he will need overwhelmingly convincing evidence.  And the whole idea that the appearance of new species can be explained by physical causes always in action pains his devoted and devout wife; she fears he may not accompany her to heaven.  In 1846, a two-hundred-plus page essay on his theory is sealed up with specific instructions for publication in the event of his death, and there Darwin would leave it as he considered the fallout from the publication of an anonymously-written book: Vestiges of the Natural History of Creation.  This author had proposed an evolutionary hypothesis that had all the people talking, but scientists treated it with contempt, as the work of one with an inadequate science background, and little evidence, and Darwin finds it riddled with errors.

Instead of continuing work on the theory, Darwin turns his attention to a strange barnacle he had collected years before in South America.  In the end, he spends eight years developing expertise in the classification of barnacles--a large and difficult group of arthropods--and becomes renowned for this work.  "No one," his good friend the botanist Thomas Hooker observes, "has the right to talk about species who has not minutely observed and classified many."  His final, exhaustive, multi-volume barnacle monograph wins Darwin the Royal Society Medal, and establishes him as a bona fide scientist with a world-wide web of correspondents with whom he has consulted or who have provided the thousands of specimens that had arrived at Down House. 

In 1857 Darwin was 48 and had finished his barnacle work as having become the foremost expert on them; the following year he would open the fateful letter from the younger Alfred Russel Wallace.

Finished at last with barnacles, Darwin resumes work on his theory beginning with biogeography: conducting experiments to see how different species could survive passage to distant islands so as to colonize them.

Just two years later in 1858, Darwin receives an essay from the young naturalist Alfred Russel Wallace, who wants Darwin's help in recommending it to his friend Lyell.  They were already acquainted: Wallace had consulted the elder and established scientist before.  The essay was a bombshell: Wallace has arrived at the same conclusions as Darwin on the origin of species by descent with modification, and the same mechanism: the survival of those endowed with favorable variations in the struggle for existence.  Lyell and others pressed Darwin to present a chapter of his own together with Wallace's essay at a scientific meeting.  Then Darwin gets to work at last on a "brief summary" of his argument, and publishes it the next year: The Origin of Species.

He will do more science, showing that, in temperate regions at least, earthworms are the engineers of the soil.  He will extend his curiosity about human origins (cautiously only hinted at in the Origin) into another whole book along with his novel theory about sexual selection.  (Which posits that an important element of adaptation involves being able to attract a mate--leading to all sorts of "decorative" features in the "chosen" sex that lead in turn to reproductive success.)  Some elements of Darwin's theories are still being tested: only quite recently did researchers show that peacocks shorn of the irredescent "eyes" on the tail feathers do not father as many chicks.

And he will, in his own antisocial and retiring way, continue to battle against those who deny his theories.  (Wallace himself eventually decides that the evolution of humans cannot be explained by natural selection, and supports a supernatural "exception to the rule.")  Indeed, although "common descent" catches on pretty quickly due partly to ground prepared by others and partly due to the evidence he marshals, Darwin's most important contribution--evolution by natural selection--will battle all the way into the 20th century (long after Charles' death) before the dust has finally settled and Natural Selection stands alone in triumph: the only theory ever to successfully explain the amazing adaptations that give living things that "designed" look.

Although Darwin was wrong about many details (he had no real notion of genetics or population biology, for examples) it is remarkable that he got so much right; researchers continue to mine some of his more neglected ideas for new insights.

Darwin will die in April 1882 at home, after telling Emma, 
"I am not the least afraid of death – Remember what a good wife you have been to me
 – Tell all my children to remember how good they have been to me." 

The Origin of Species ends with some of Darwin's most famous lines.  "There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved."  

I've learned much from these books: Darwin: Discovering the Tree of Life by Niles Eldridge, and Darwin and the Barnacle byRebecca Stott; The Voyage of the Beagle, The Origin of Species, and The Autobiography of Charles Darwin, all by Himself.
Wikipedia has great articles for pursuing aspects of Darwin's life, among them Charles Darwin's Education.

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