See something you'd like to change or add, but you've never edited an open encyclopædia before? This overview was written to help absolute beginners get started.

History of evolution

From A Storehouse of Knowledge
Jump to: navigation, search

Evolution is an ancient idea, but has been developed as a "scientific" study from the 19th century onwards, going through several different versions as evidence has falsified aspects of each previous version.

Contents

Greek evolution

Thales (640–546 B.C.), his student Anaximander (611–547 B.C.), and Empedocles (493–435 B.C.) all taught forms of evolution, with Anaximander believing that humans evolved from fish or similar, and Empedocles teaching that the fitter would pass on their traits.[1] It is even possible that the Greeks were influenced by Hindu ideas of the people having previously been animals.[1]

Lamarckian evolution

Jean-Baptiste Lamarck was the first to present a concrete scientific theory, in his Philosophie Zoologique in 1809. Lamarckian evolution is known for teaching that acquired characteristics are passed on. A well-known example is that of the giraffe, in which it is said that by continually stretching its neck to reach higher branches, it passed on a slightly longer neck to offspring, which repeated the process.

The science of genetics, unknown in Lamarck's time, later showed that this form of evolution is wrong, as inherited characteristics are acquired from the DNA, which was unaffected by what happens to creatures during their lifetime. However, Lamarck's ideas have seen a small revival since genetics has shown that in some cases the environment can affect the DNA which is passed on to offspring.[2]

Robert Chambers popularized the scientific debate, creating great controversy in Victorian England with his 1844 Vestiges of the Natural History of Creation.

Darwinian evolution

In 1859 Charles Darwin published his On the Origin of Species, which popularised evolution. In it, Darwin proposed Natural selection as the key component of evolution, although he also accepted Lamarck's view of the inheritance of acquired characteristics to some extent.

Darwin sought to apply Charles Lyell's uniformitarianism to explain species. A key part of Darwin's evolution was that living things changed gradually, with almost imperceptible changes from generation to generation. He said that a "finely graduated organic chain" must have formerly existed and led to the species we currently find.

Though a Bible-believer in his youth, Darwin grew convinced studying Lyell while voyaging on the Beagle, that "the Old Testament was incompatible with science, particularly uniformitarian geology."[3]

Neo-Darwinian evolution

In 1865 Gregor Mendel, a creationist, studied varieties of pea plants, and discovered genetic inheritance.[4] His work went unnoticed for a long time, but in the 1920s and 1930s[5] it was incorporated into evolution as a mechanism of how variety arose to select from. This new form of evolution was known as Neo-Darwinian evolution, or the Modern Evolutionary Synthesis.[6]

Neo-Darwinism is an attempt to reconcile Mendelian genetics, which says that organisms do not change with time, with Darwinism, which claims they do.Lynn Margulis[7]

Punctuated Equilibrium

In 1972 Stephen Jay Gould and Niles Eldridge realised that the fossil record didn't show evolution as proposed by Darwin, with the transitional forms systematically missing.

The absence of fossil evidence for intermediary stages between major transitions in organic design, indeed our inability, even in our imagination, to construct functional intermediates in many cases, has been a persistent and nagging problem for gradualistic accounts of evolution.[8]

So they proposed that living things remained unchanged for long periods of time, then rapidly changed into new forms, leaving little fossil trace because of the brevity of the change.[9]

Although there was considerable debate about the merits of Punctuated Equilibrium, it has largely become accepted as one of the ways that evolution works. So it has not so much replaced neo-Darwinian evolution as modified it.

However, Darwin is still highly respected by evolutionists for his seminal work, and is still closely associated with current models of evolution. The journal Nature Cell Biology referred to evolution as "a theory that has survived essentially unchanged for 150 years"[10], and although acknowledging that Darwin knew nothing about genetics, Richard Dawkins said that "Everything we know about life, Darwin essentially explained." and that Darwin "got it astonishingly right. So you could almost say he nearly forecast digital genetics ..."[11]

Post-synthesis evolution

By the start of the 21st century, evolutionists were realising that natural selection didn't adequately explain evolution. In part, this was prompted by the discovery of epigenetics, genetic control codes.

From a paper by David J. Depew and Bruce H. Weber:

We trace the history of the Modern Evolutionary Synthesis, and of genetic Darwinism generally, with a view to showing why, even in its current versions, it can no longer serve as a general framework for evolutionary theory. The main reason is empirical. Genetical Darwinism cannot accommodate the role of development (and of genes in development) in many evolutionary processes.[12]

Eugene V. Koonin writes:

So, not to mince words, the Modern Synthesis is gone.

The discovery of pervasive HGT [horizontal gene transfer] and the overall dynamics of the genetic universe destroys not only the Tree of Life as we knew it but also another central tenet of the Modern Synthesis inherited from Darwin, gradualism. In a world dominated by HGT, gene duplication, gene loss, and such momentous events as endosymbiosis, the idea of evolution being driven primarily by infinitesimal heritable changes in the Darwinian tradition has become untenable.

Equally outdated is the (neo)Darwinian notion of the adaptive nature of evolution: clearly, genomes show very little if any signs of optimal design, and random drift constrained by purifying in all likelihood contributes (much) more to genome evolution than Darwinian selection[refs]. And, with pan-adaptationism, gone forever is the notion of evolutionary progress that undoubtedly is central to the traditional evolutionary thinking, even if this is not always made explicit. The summary of the state of affairs on the 150th anniversary of the Origin is somewhat shocking: in the post-genomic era, all major tenets of the Modern Synthesis are, if not outright overturned, replaced by a new and incomparably more complex vision of the key aspects of evolution ... So, not to mince words, the Modern Synthesis is gone.[13]

References

  1. 1.0 1.1 Bergman, Jerry, Evolutionary Naturalism: An Ancient Idea, Journal of Creation 15(2):77–80, August 2001.
  2. Carter, Robert W., Darwin’s Lamarckism Vindicated?, 1 March 2011.
  3. Ruse, Michael, The Darwinian Revolution: Science Red in Tooth and Claw, p.180.
  4. Sean D. Pitman, The Father of Genetics, May 2002.
  5. Brig Klyce, Neo-darwinism: the Current Paradigm.
  6. Buyun Zhao, the Modern Synthesis, 2009 Christ's College, Cambridge.
  7. John Brockman, The Third Culture: Beyond the Scientific Revolution chapter 7, p.133 Simon & Schuster, 1996, ISBN 9780684823447.
  8. Gould, S.J., Is a new and general theory of evolution emerging? Paleobiology 6:119–130 (p.127), 1980, quoted by Batten, Don, Gould Grumbles About Creationist ‘hijacking’, Journal of Creation 16(2):22–24 August 2002.
  9. , Punctuated Equilibrium, Public Broadcasting Service.
  10. Darwin's legacy, Nature Cell Biology 11, 111 (2009) (free registration required to read)
  11. Dawkins, Richard, Richard Dawkins on Charles Darwin, BBC News interview with Owen Bennett Jones, 14 February 2009.
  12. David J. Depew and Bruce H. Weber, The Fate of Darwinism: Evolution After the Modern Synthesis, Biological Theory 6(1):89-102. 8 July 2011.
  13. Eugene V. Koonin, The Origin At 150: Is A New Evolutionary Synthesis In Sight?, 14 October 2009, draft of paper subsequently published in Trends in Genetics 25(11): 473–475, November 2009.
Personal tools
Namespaces

Variants
Actions
visitor navigation
contributor navigation
monitoring
Toolbox