Charles Darwin and Selection As a Cause of Adaptive Evolution 1837
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Charles Darwin Carl Jay Bajema is professor and Selection of biology at Grand Valley State College, Allendale, MI 49401. He teaches introducto- ry biology, human ecology, as a Cause of human genetics, and human sexuality in the Department *- x *l of Biology, and a course on / the Darwinian revolution in Adaptive the History of Science program. Bajemaeamed a Ph.D. in zoolo- gy from Michigan State Univ. in 1963. Bajemahas served as Sen- ior Population Council Fellow in demography and population ge- netics at the Uiiiv. of Chicago (1966-1967);as researchassociate in Evolution population studies at HarvardUniv. (1967-1972);as researchasso- ciate in biology at the Univ. of California, Santa Barbara(1974); at Har- and most recently as visiting professor of anthropology Downloaded from http://online.ucpress.edu/abt/article-pdf/47/4/226/86148/4448024.pdf by guest on 27 September 2021 vard Univ. (1974-1975).His research interests have concentrated 1 837-1 859 on estimating the direction and intensity of naturalselection espe- cially in human behavior and on the history of ideas on evolution. He is coauthor of an introductory college biology textbook. Ba- CarlJay Bajema jema has edited four volumes of benchmarkpapers. Charles Darwin triggered a scientific revolution in win (1958 p. 68) wrote that these two books "stirred 1859 when he contended that species have under- up in me a burning zeal to add even the most hum- gone "descent with modification"-evolution, and ble contribution to the noble structure of science." that selection operating on heritable variations in in- Darwin's enthusiasm for science was cultivated by dividuals was the primary cause of adaptive evolu- Professor Henslow who made arrangements for Dar- tion. Valuable knowledge can be gained about the win to accompany the geologist Adam Sedgwick on processes of scientific discovery and the justification a 1831 field trip to Wales. Sedgwick's views on sci- of scientific theories by studying the methodologies ence led Darwin (1958 p. 70) to conclude that "sci- employed by Charles Darwin in his search for the ence consists in grouping facts so that general laws causes of evolution and in his subsequent advocacy or conclusions may be drawn from them." and defense of adaptive evolution by selection theo- ry. Charles Darwin's personal scientific diaries, The Voyage of the H.M.S. Beagle notebooks, correspondence, and publications have enabled scholars to reconstruct much of the logic and the Impactof CharlesLyell Charles Darwin employed to solve scientific prob- Charles Darwin accepted an opportunity to serve lems. as a naturalist aboard the H.M.S. Beagle and took the first volume of Charles Lyell's recently published Darwin'sFormal and InformalEducation Principlesof Geologyalong on the voyage. Lyell used Charles Darwin's interest in natural history dates the uniformity of causes principle-the theory that back to his childhood passion for collecting spec- present causes now in operation are sufficient to ex- imens of rocks, insects, birds, and other species. plain past changes-to scientifically interpret the Darwin learned how to collect, preserve and de- geological history of the earth. Darwin concluded scribe species scientifically while he was a student that Lyell's naturalistic uniformity of causes princi- studying medicine at Edinburgh. While Darwin ple rather than geological catastrophism provided studied for the ministry at Cambridge, he pursued the best theory for interpreting the geological obser- his interest in natural history with John Henslow, vations that Darwin was making on the voyage professor of botany. Darwin also read the works of (Darwin 1958 p. 77). The tremendous impact that Bishop Paley including NaturalTheology which cham- Lyell's uniformity of causes scientific problem solv- pioned the religious argument from design (adapta- ing method had on Darwin's thinking was empha- tion) in nature to the existence and attributes of sized by Darwin in an 1844 letter: God. ... the whole merit of the Principleswas that it al- During his last year at Cambridge, Charles Dar- tered the whole tone of one's mind and, therefore, win read John Herschel's 1830 book on the philoso- that when seeing a thing never seen by Lyell, one yet saw it partially though his eyes [and confessed that] I phy of science, A PreliminaryDiscourse on the Studyof always feel as if my books came half out of Sir Natural Philosophyand Alexander von Humboldt's Charles Lyell's brain . .. (Darwin and Seward 1903, PersonalNarrative of Travels.In his AutobiographyDar- II, p. 117). 226 THE AMERICAN BIOLOGY TEACHER, VOLUME 47, NO. 4, APRIL 1985 The impact of Charles Lyell on the biological ideas including those that led him to construct his theory Charles Darwin explored while on the voyage has of "descent with modification" by natural, sexual, been analyzed by Hodge (1983). and artificialselection. In his Autobiography,Charles Charles Darwin made field observations and col- Darwin (1958 p. 119) contended that when he was lected the fossil remains of extinct animal species in trying to identify the natural processes which gener- addition to capturing and preserving specimens of ated evolution he "worked on true Baconian princi- numerous contemporary species during his many ples [inductive logic], and without any theory col- expeditions in South America and the Galapagos Is- lected facts on a wholesale scale, more especially lands. The geological and biogeographical observa- with respect to domesticated productions . tions which Darwin made while on the voyage con- However, the scholars who have analyzed the con- cerning the distribution of species through time and tents of Darwin's four Notebookson Transmutation space ultimately led young Darwin to seriously have concluded that, contrary to his recollection, question the religious doctrine of separate creations Darwin employed and tested a number of theories and to begin testing the deductions of the theory in his search for the natural processes generating that contemporary species are the products of evolu- evolution (Gruber 1974; Schweber 1977; Kohn 1980). tion. However, Darwin did not begin thinking of Darwin even made an entry in his NotebookD stating species as the products of evolution while he ex- that he was employing deductive logic to test the Downloaded from http://online.ucpress.edu/abt/article-pdf/47/4/226/86148/4448024.pdf by guest on 27 September 2021 plored the Galapagos Islands 150 years ago (Sept 16- theories of evolution he was considering: Oct 20, 1835) (Sulloway 1982a, 1982b; Mayr 1982; The line of argumentoften pursuedthroughout my Gould 1984). theoryis to establisha point as a probabilityby in- Soon after his return to England, Darwin loaned duction,& to apply it as hypothesesto otherpoints, his collections of birds and mammals to other scien- & see whetherit will solve them (Darwin[1838], p. tists to study, and concentrated on writing up the D117). geology of the voyage of the HMS Beagle. The com- Charles Lyell's comprehensive review of the argu- parative anatomist Richard Owen concluded that ments for and against the transmutation of species virtually all of Darwin's fossil mammals were extinct in the first and subsequent editions of ThePrinciples larger versions of the smaller mammals-llamas, of Geologywhich Darwin read for a second time dur- sloths, armadillos-that presently inhabit South ing the Spring of 1837 provided young Darwin with America. The ornithologist John Gould informed numerous theories to test. Darwin's notebooks are Darwin in March 1838 that virtually all the Ga- full of deductions from theories that he tested lapagos Islands land birds in Darwin's collection against observations made by others or by himself. were found only in the Galapagos; their closest rela- Ratherthan working solely by induction Darwin em- tives were found in South America. Gould also told ployed "multiple working hypotheses" in his search Darwin that the Galapagos Islands finches con- for the natural processes that cause adaptive evolu- stituted an unique genus which also included two tion. Darwin tested and rejected such theories as the species-a "wren" and an "oriole" that Darwin had production of adaptations by the "willing" of organ- mistakenly identified as representatives of species isms and the life of a species being fixed and analo- they appeared to mimic (Sulloway 1984). gous to the life cycle of an individual organism. Lyell also made Darwin acutely aware of the Searchingfor the NaturalCauses of Evolution "struggle for existence" as a force in nature by championing its importance as a cause of the extinc- The expert judgments of Gould and Owen con- tion of many species. However, Lyell rejectedevolu- cerning the taxonomic relationships of Darwin's tion primarilybecause he was unable to identify any specimens triggered a revolution in Darwin's think- cause now acting that was powerful enough to have ing leading him to consider seriously the possibility brought about evolution. that species have undergone descent with modifica- tion from common ancestors. This led Darwin to re- Analogy Between ArtificialSelection cord a few ideas concerning speciation in his Red and NaturalSelection Notebook(Darwin 1980), and to open a series of Note- bookson Transmutationof Species(Darwin 1960-67)in Nonetheless it was Charles Lyell who started which he recorded "any facts that might bear on the young Darwin on the pathway to scientific discovery question." of selection as a powerful cause of adaptive evolu- The entries that Charles Darwin made in his trans- tion. Lyell drew Darwin's attention to a possible mutation notebooks between July 1837 and June analogy between the selective breeding of domesti- 1839 have enabled scholars to reconstruct many of cated species and processes operating in nature: the intellectual ideas Darwin explored in his search The best authenticated examples of the extent to for the causes of adaptation and the origin of species which species can be made to vary, may be looked CHARLES DARWIN & SELECTION 227 for in the historyof domesticatedanimals and culti- marized Comte's contention that scientists possess a vated plants...