Notes on the Evolutionary Theory and Charles Darwin

Introduction to Evolution and Darwin's Influence

• Belief in God creating mankind in His image was prevalent until the mid-19th century.
• Most Western scientists believed all creatures were conceived by a divine force until Charles Darwin's arrival.
• Darwin introduced the theory of evolution by natural selection, fundamentally changing biology and our understanding of human origins.
• His journey involved extensive experimentation and 20 years of refining his ideas.

Darwin's Early Life and Voyage

• In 1831, at age 22, Darwin was studying at the University of Cambridge.
• Invited as a naturalist on the HMS Beagle, he traveled for almost five years, starting in South America.
• Collected numerous life specimens, illustrations, and fossils, which provided clues about evolution.

Key Discoveries During the Voyage

• Observed the remains of a milodon, drawing parallels to present-day sloths, suggesting a link between species.
• At the Galapagos Islands, noted giant tortoises with unique physical characteristics on different islands:
  • Humid island tortoises: short neck and dome-shaped shell.
  • Dry island tortoises: saddle-shaped shell and long neck.

Understanding Evolution Through Natural Selection

• After returning, Darwin studied animal crossbreeding, noting artificial selection's role in creating new varieties.
• Inspired by Thomas Robert Malthus' essay on demography:
  • Malthus stated that population growth would outstrip food supply, leading to a struggle for survival.
  • This idea helped Darwin understand natural selection as a survival mechanism.

Mechanism of Natural Selection

• The struggle for survival leads to adaptation:
  • Success in reproduction is tied to adaptability.
  • Traits enhancing survival will be passed down, leading to new species over time.
• Example: Differences in Galapagos tortoises resulted from adaptations to their environments:
  • Longer necks for drier environments vs. shorter necks for humid areas.

Impact of Darwin's Theories

• Darwin proposed that all species, including humans, descended from a common ancestor.
• Life diversified as a result of natural processes, not divine intervention.
• Despite writing thousands of pages over 20 years, Darwin was hesitant to publish due to anticipated controversy.

Catalyst for Publication

• Received a letter from Alfred Russel Wallace, who reached the same conclusions about evolution via natural selection.
• They agreed to present a joint letter; however, Darwin published "On the Origin of Species" a year later, becoming widely recognized.

Legacy of Darwin's Work

• Darwin's theory shook the foundations of Victorian Britain,
  • Comparable to Copernicus's revolution in astronomy.
• Positioned humans within the evolutionary framework alongside other creatures.
• Scientific advances have confirmed his theory, which the Catholic Church later accepted as compatible with faith.

Conclusion

• Over 150 years later, evolution is recognized as a fact.
• Continual changes occur on the planet which influence the evolution of species.