DNA base pairs at the Science Museum

Mechanisms of evolution

The discovery of genes provided a mechanism for heredity and a way to explain how natural selection operated

Darwin’s theory of evolution depends on information being passed from parent to offspring. In Darwin’s day, however, the mechanisms of heredity were a complete mystery.

Curiously, though, at almost exactly the same time Gregor Mendel was carrying out experiments that would lay the foundations of a new discipline – genetics – and provide Darwin’s missing mechanism.

We now know that hereditary information is contained within genes. They carry information in a form that can change – creating variation – and yet still be passed on.

Key moments in genetics and evolutionary biology

  • 1908: Hardy–Weinberg equilibrium principle developed, stating that allele frequencies in a population remain constant over generations in the absence of factors such as selection, mutation or migration.
  • 1910–11: Thomas Hunt Morgan maps a gene for a physical trait (white eyes mutation) to a fruit-fly sex chromosome.
  • 1928: Fred Griffith discovers transformation in bacteria.
  • 1930s: R A Fisher, J B S Haldane, Sewall Wright and others use mathematical techniques to combine genetics and evolutionary biology in the ‘modern synthesis’.
  • 1944: Oswald Avery shows that DNA is the cell’s hereditary material.
  • Late 1940s: Barbara McLintock discovers mobile genetic elements – ‘jumping genes’.
  • 1953: Watson and Crick, supported by a team of researchers, publish the structure of the DNA double helix.
  • 1960s: Three-letter genetic code of DNA worked out.
  • 1968: Motoo Kimura proposes the neutral theory of evolution.
  • 1976: Richard Dawkins publishes ‘The Selfish Gene’, popularising the idea of gene-based evolution.
  • 1977: Fred Sanger invents a method for sequencing DNA.
  • 2001: Human genome sequenced.
  • 2004: Chimpanzee genome sequenced and compared with human genome.
  • 2010: Neanderthal genome sequenced.
  • 2012: Denisovan genome sequenced.
  • 2012: 1,092 human genomes sequenced.

Are genes selfish?

Of course, genes cannot have their own motives. Dawkins’s point was that selection acted on genes; bodies are, in a sense, nothing more than the receptacles by which genes are transmitted to future generations.

Lead image:

John Goode/Flickr CC BY

References

Questions for discussion

  • How did Darwin think inheritance worked? Were his theories on inheritance correct?

About this resource

This resource was first published in ‘Evolution’ in January 2007 and reviewed and updated in December 2014.

Topics:
Genetics and genomics, Statistics and maths, Ecology and environment, History
Issue:
Evolution
Education levels:
16–19, Continuing professional development