Emergence of Evolutionary
All cultures throughout history have come to contemplate "the
big picture": where we came from and where are we going. Belief systems of all
types have evolved to explain the unexplainable, but one unique system has
recently accumulated an unprecedented paradigm of theories that stand up to
rigorous logic and experimental testing. Science will never replace other
religions, but the ground it is covering is often seen as an unholy encroachment
to time honored traditions.
Darwin’s Theory Takes Form
- Early Beliefs, Confounding Discoveries
- The Great Chain of Being
- The Greeks began a systematics of classification that led to a formal
dendrogram (dirt to angels!).
- Questions from Biogeography
- Technological developments led to further and faster travel.
Naturalists observed incredible diversity of life in their travels. How
could such variety, which was endemic in
many areas, have spread to corners of the earth without a trace?
- Questions from Comparative Anatomy
- The variation of homologous and
analogous structures puzzled anatomists.
Some said they were variations from the moment of creation, but what about
vestigial structures (pelvic girdle in snakes, tailbones in humans)?
- Questions About Fossils
- Studies of sedimentary beds revealed that deposits had been laid down
slowly, one above the other.
- The layers held recognizable remains or impressions of
organisms–fossils. The arrangement of the layers suggested that
different organisms had lived at different times.
- De Buffon’s explanation: Perhaps species originated in more
than one place, and perhaps species became modified over time–evolution!
- A Flurry of New Theories
- Squeezing New Evidence Into Old Beliefs
- Georges Cuvier believed in an original creation of all species.
He further suggested that the abrupt changes in the fossil record in
different rock strata reflected the concept of catastrophism.
- After each catastrophe, fewer species remained.
- The survivors were not new species; it was just that their
ancestors’ fossils had not been found.
- Lamarck formulated a theory of inheritance of acquired characteristics which
the idea that simple forms had changed into more complex ones by a
built-in drive for perfection up the Chain of Being. For instance, a
giraffe stretching its neck to reach higher branches would result in
longer necks in the offspring.
- Voyage of the Beagle
- As a child (early 1800s), Darwin was curious about nature, but in
college he first pursued premedicine and finally received a degree in
- Darwin, age 20, sailed around the world as the ship’s naturalist.
- He was reading Lyell’s Principles of
Geology, which proposed a theory of uniformity–the notion of a
gradual, lengthy molding of the earth’s geologic structure.
- Thus, the earth was not thousands, but possibly millions of years
old – enough time for evolution.
- Old Bones and Armadillos
- In Argentina, Darwin had observed extinct glyptodonts that bore suspicious resemblance
to living armadillos; Darwin wondered if the present species had evolved
from the extinct one.
- A Key Insight–Variation in Traits
- Thomas Malthus had suggested that as a population outgrows its
resources, its members must compete for what is available; some will not
- Darwin felt that if some normally variant members of a population bore
traits that increased their survival, then nature would select those same
individuals to survive, reproduce, and possibly change future populations’
- On the Galapagos Islands, the dozen or so species of finches all
varied from one another to some extent but resembled the mainland
finches to some degree also; perhaps they had descended from common
- Darwin reasoned that a population is evolving when its heritable
traits are changing through successive generations.
- In 1858, Darwin received a paper from Alfred
Wallace, who had developed the same theory of natural selection
independently of Darwin. Wallace had been travelling throughout present
- Darwin and Wallace presented a joint paper but Darwin published
(alone) his ideas in book form in 1859.
- The book was entitled: On the Origin of Species or the Preservation
of Favoured Races in the Struggle for Survival.
- "Origin" went through several revisions, each omitting
critically shortsighted elaborations.
- Darwin saw evolution of one kind into another as happening gradually, in
small increments, over hundreds or thousands of generations.
- It is crucial to note that Darwin had no knowledge of either Mendelian
or molecular genetics to support or guide his theory. Some say that this is
direct evidence of the weakness of evolutionary theory, but Darwinists have
considered this the greatest strength.
- Today, we have expanded and modified the theory to include recent
evidence: The Modern Synthesis.
- "Evolution" is now separated into two semantic divisions: microevolution (change within a species) and
macroevolution (change from one species to
another). This seems to have been done to divide religious opposition. Now
another division "human evolution" seeks to again divide the shrinking
religious opposition from what seems undeniable by even the most uniformed.
- The possibility of transitional forms was illustrated when, in 1861,
fossil evidence of Archaeopteryx was
- This animal appears to be a transitional form between reptiles and
birds. Like birds, it was covered with feathers; but like reptiles, it had
teeth and a long, bony tail.