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Biology 30: Natural Selection

Circumnavigation of the World

The voyage of the Beagle included a significant journey across the Pacific Ocean, with stopovers in various important locations such as Australia, Madagascar, South Africa, and again in Brazil. The journey concluded with the return to England on October 2, 1836.

Darwin after the Voyage

Post-voyage, Charles Darwin quickly authored a book detailing his adventures, titled "Voyage of the Beagle". In 1839, he married his second cousin, Emma Wedgewood. Throughout much of his life following the voyage, he experienced several unexplained health issues, which affected him significantly.

The Idea Grows

Darwin's observations during his travels led him to contemplate the "transmutation of the species problem". He started gathering data on variations among a wide range of organisms, from bats to barnacles. These efforts culminated in the formulation of his theory, leading to the writing of his seminal work, "On the Origin of the Species".

The Delicate Problem

Upon returning from his journey in 1836, Darwin dedicated himself to the development of his theory until 1858. However, in June of that year, he encountered a dilemma that prompted him to seek counsel: he received a letter from Alfred Russel Wallace, a fellow naturalist.

Alfred Russel Wallace

Alfred Russel Wallace was conducting research in Indonesia and had been corresponding with Darwin regarding the concept of the "transmutation of the species". In May 1858, Wallace sent Darwin a letter proposing a theory that closely mirrored Darwin's ideas on evolution.

The Solution?

In scientific discourse, the individual who first publishes a new theory often receives the recognition and acclaim. Darwin, feeling unprepared to publish, faced the potential of being overshadowed by Wallace’s work. To resolve this, he consulted several trusted friends for advice.

The Solution?

Charles Lyell, a geologist, facilitated a compromise that allowed both Darwin’s and Wallace’s papers to be presented at the Linnaean Society on July 1, 1858. This collaboration pressured Darwin to expedite the completion of his manuscript, which resulted in the publication of "The Origin of the Species" in 1859. The book became an immediate bestseller and gained substantial acclaim.

The Origin of the Species

Currently, "The Origin of the Species" is in its 42nd printing and remains a widely read and influential text. The book has been translated into all major languages. Initially, only 1000 copies of the original edition were published, with each copy now valued at around $200,000. Notably, it was the first significant book published in English focused on evolution.

Natural Selection

Darwin's theory of natural selection rests on four major concepts:

  1. Variation: Individuals within a population exhibit differences.
  2. Inheritance: Traits can be passed from parents to offspring.
  3. Differential Adaptedness: Some individuals are better suited to their environment than others.
  4. Differential Reproduction: Those better adapted are more likely to reproduce, thereby passing traits to the next generation.
Explanation of Natural Selection

In fundamental terms, natural selection can be simplified to the following observations:

  • More organisms are born than can survive, leading to competition for resources.
  • Each organism has unique traits.
  • Some traits provide better adaptation for survival than others.
  • Those individuals that survive are able to pass on their advantageous traits.
  • Fitness is defined in biological terms as the number of fertile offspring produced by an individual.

Through natural selection, populations of organisms evolve over time to better suit their constantly changing environments.