Evolutionary synthesis 1930s-1940s
aka Neo-Darwinian synthesis
Reconciled natural selection & genetics
-by early 19th century, basic concepts of evolution already
present1 Hutton (geologist) age of earth millions of years2.
extinct fossil species3. systematists, embryologists, anatomist
noticed similarities among different species4. most scientists
believed organisms descended through inheritance from previously
existing organisms-still controversial:1.what natural mechanism
explained why organisms change?2.what hereditary mechanism could
enable organisms to change?-Darwin answered 1st question Mendel
answered 2nd
1809-1882 birthday is Feb 12 (same as Lincoln)born to
wealthfather Robert, grandfather Erasmus, both prosperous
MDsErasmus early popularizer of evolution but judged wildly
speculative in science
At 16 yrs, left Shrewsbury and sent to Edinburgh Univ to study
medicineSurgery turned him off so transferred to Cambridge-studied
theology, minister for Church of England-interests not academic or
ministerial-despised formal education, mediocre student-enjoyed
hunting, collecting, natural history, botany, geology
would walk with Henslow, botany prof-1831 graduated but not
ordained, went on Beagle voyage-ships naturalist for 5 years-Captn
Fitzroy almost rejected Darwin based on his noseBritish naval
vessel mapping s. America-Fitzroy very meticulous, gave Darwin lots
of time to explore
Voyage of the BeagleThe famous 1831-36 voyage of His Majesty's
Ship (HMS) Beagle, with Charles Darwin on board as naturalist, was
a voyage in service of the Creator. Its primary purpose was to
survey the coast of lower South America. In helping secure the
safety of British shipping, the survey fulfilled the Cultural
Mandate of Genesis 1:28 to subdue and rule the earth. Even Darwin's
observations added to man's knowledge of the natural resources in
those lands. Another goal of the Captain, Robert Fitzroy, was to
return three natives to Tierra del Fuego at the tip of South
America. Darwin wrote, "To settle these natives in their own
country, was one chief inducement to Captain Fitzroy to undertake
our present voyage" (1: 222). With the natives was the Rev. Richard
Matthews of the Anglican Church Mission Society. Matthews hoped to
establish a mission to the Fuegians in obedience to the Great
Commission of Matthew 28:19-20. While this initial effort was
rebuffed, it inspired later, fruitful outreach to the Fuegians.
-Darwin collected samples from Brazil rain forests-unearthed
fossils, giant sloth, armadillo, hippo-like organism-observed wide
range of organisms/geological formations-had Lyells Principles of
Geology-1 event deeply affected himearthquake at bay of conception,
coast of Chileraised level of the land from 2-3 feet above sea
level to 10A bad earthquake at once destroys or associations: the
earth, the very emblem of solidity, has moved beneath our feet like
a thin crust over a fluid; one second of time has created in the
mind a strange idea of insecurity, which hours of reflection would
not have produced.-spent a month off the Galapagos Islands-500
miles from Ecuador-strange collection of organisms: giant
tortoises, marine iguanas, birds, plants, shells etc-similar
habitats not occupied by similar species-no warblers/woodpecker in
Galap, but finches assumed their roles-each island had its own
constellation o species-what could account for this distribution?It
is the circumstance that several of the islands possess their own
species of the tortoise, mocking-thrush, finches, and numerous
plants, these species having the same general habits, occupying
analogous situations and obviously filling the same place in the
natural economy of this archipelago, that strikes me with
wonder.-transformation occurred but mechanics not obvious
-transformed from casual amateur to dedicated
geologist/biologist-sent letters to Henslow and collections of
samples-samples created scientific interest even before his return
to England-return to England, substantial income inheritance so he
didnt have to work devoted to biology-married cousin Emma Wedgwood
(famed and wealthy)1842 settled in Down house in Kent-physical
discomfort, possibly weird parasite infection (Chagas
disease)-isolated except by lettersOrigin of species controversial
among clergy & laity as well as some scientists-by 1870s most
scientists accepted historical reality of evolution by common
descent-golden age of evolution in lat 19th early 20th
centuries-paleontology, comparative morphology, embryology amassed
data, established evolution as fact-but no Darwins mechanism,
natural selection-natural selection rejected for 60 years, numerous
other theories proposed
Anti-Darwinian theories-based on dislike for purely
materialistic theory of natural selection-wanted life to be seen as
purposeful, not merely responding passively to environmental
pressures
Neo-Lamarckism-inheritance of modifications acquired during an
organisms lifetime-opposed by Weismann, cut off mice tails-
Weismann very dogmatic, drove others away from natural
selection
Orthogenesis-variation is directed toward a fixed goal-so
species evolve in predetermined direction without aid of
selection-based on trends in paleontology-no mechanism proposed
Mutationism-based on Mendelian genetics-process of mutation
sufficient to account for origin of species, natural selection
superfluous-Mendelian genetics disproved Lamarckism and blending
inheritance-but proposed mutation and natural selection mutually
exclusive-therefore delayed synthesis
Evolutionary synthesis-resolution in 1930s-40s-reconciled
Darwins natural selection with genetics-natural populations have
genetic variation-variations arose by mutation-R Fisher, JBS
Haldane, S Wright proved a newly mutated gene would not
automatically form a new species-nor would it automatically replace
the existing form of the gene-mutation could confer survival
advantage as per Darwinian natural selection-or mutation could be
neutral, random genetic drift replaces one gene by another purely
by chance-genetic drift emphasized less than natural selection for
which evidence was abundant-integrate genetics and Darwinian
evolutionary theory-mutation, natural selection account for major
long-term features of evolution (macro evolution)-purged
neo-Lamarckism, orthogenesis and simple mutation
theories-Dobzhansky demonstrated natural selection in the lab
(fruit flies); lots of genetic variation which affected
survival/reproduction
