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
- Gregor Mendel and the principles of inheritance (2008)
- History of genetics timeline
- Hardy-Weinberg Principle
- Thomas Hunt Morgan and sex linkage (2008)
- The transforming principle – Griffith’s experiment about genetics
- Sparknotes: a synthesis of Darwin and modern genetics
- Barbara McClintock and the discovery of jumping genes (2011)
- Molecular structure of nucleic acids: a structure for deoxyribose nucleic acid (1953)
- Reading the genetic code (2008)
- Neutral theory: The null hypothesis of molecular evolution (2008)
- Wikipedia: ‘The Selfish Gene’
- Wikipedia: Sanger sequencing
- Press release: International Human Genome Sequencing Consortium publishes sequence and analysis of the human genome
- Nature’ web focus: the chimpanzee genome (2005)
- Neanderthal genomics and the evolution of modern humans (2010)
- Nature News: New DNA analysis shows ancient humans interbred with Denisovans (2012)
- An integrated map of genetic variation from 1,092 human genomes (2012)
Questions for discussion
- How did Darwin think inheritance worked? Were his theories on inheritance correct?