Megaevolution

Last updated

Megaevolution describes the most dramatic events in evolution. It is no longer suggested that the evolutionary processes involved are necessarily special, although in some cases they might be. Whereas macroevolution can apply to relatively modest changes that produced diversification of species and genera and are readily compared to microevolution, "megaevolution" is used for great changes. Megaevolution has been extensively debated because it has been seen as a possible objection to Charles Darwin's theory of gradual evolution by natural selection. [1]

Contents

A list was prepared by John Maynard Smith and Eörs Szathmáry which they called The Major Transitions in Evolution . [2] [3] On the 1999 edition of the list they included:

  1. Replicating molecules: change to populations of molecules in protocells
  2. Independent replicators leading to chromosomes
  3. RNA as gene and enzyme change to DNA genes and protein enzymes
  4. Bacterial cells (prokaryotes) leading to cells (eukaryotes) with nuclei and organelles
  5. Asexual clones leading to sexual populations
  6. Single-celled organisms leading to fungi, plants and animals
  7. Solitary individuals leading to colonies with non-reproducing castes (termites, ants & bees)
  8. Primate societies leading to human societies with language

Some of these topics had been discussed before. [4] [5] [6] [7] [8] [9] [10] [11]

Numbers one to six on the list are events which are of huge importance, but about which we know relatively little. All occurred before (and mostly very much before) the fossil record started, or at least before the Phanerozoic eon.

Numbers seven and eight on the list are of a different kind from the first six, and have generally not been considered by the other authors. Number four is of a type which is not covered by traditional evolutionary theory, The origin of eukaryotic cells is probably due to symbiosis between prokaryotes. This is a kind of evolution which must be a rare event. [12] [13] [14]

The Cambrian radiation example

When it was first described, the Cambrian fossil Opabinia was thought to be unrelated to any known phylum. Later discoveries have shown it to be closely related to the ancestors of arthropods. Opabinia BW2.jpg
When it was first described, the Cambrian fossil Opabinia was thought to be unrelated to any known phylum. Later discoveries have shown it to be closely related to the ancestors of arthropods.
The Cambrian organism Marrella, was clearly an arthropod, but with features not seen in modern organisms. Marrella (fossil).png
The Cambrian organism Marrella , was clearly an arthropod, but with features not seen in modern organisms.
Dickinsonia, an organism of the Ediacaran Period that precedes the Cambrian, whose affinity is still unknown. DickinsoniaCostata.jpg
Dickinsonia , an organism of the Ediacaran Period that precedes the Cambrian, whose affinity is still unknown.

The Cambrian explosion or Cambrian radiation was the relatively rapid appearance of most major animal phyla around 530 million years ago (mya) in the fossil record, some of which are now extinct. [15] [16] [17] It is the classic example of megaevolution. "The fossil record documents two mutually exclusive macroevolutionary modes separated by the transitional Ediacaran period". [18]

Before about 580 mya it seems that most organisms were simple. They were made of individual cells occasionally organized into colonies. Over the following 70 or 80 million years the rate of evolution accelerated by an order of magnitude. [18] Normally rates of evolution are measured by the extinction and origination rate of species, but here we can say that by the end of the Cambrian every phylum, or almost every phylum, existed.

The diversity of life began to resemble that of today. [19]

The Cambrian explosion has caused much scientific debate. The seemingly rapid appearance of fossils in the 'primordial strata' was noted as early as the mid 19th century, [20] and Charles Darwin saw it as one of the main objections that could be made against his theory of evolution by natural selection. [1]

See also

Related Research Articles

Evolution Change in the heritable characteristics of biological populations over successive generations

Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation. Evolution occurs when evolutionary processes such as natural selection and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population. The evolutionary pressures that determine whether a characteristic should be common or rare within a population constantly change, resulting in the change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms and molecules.

John Maynard Smith English biologist and geneticist (1920–2004)

John Maynard Smith was a British theoretical and mathematical evolutionary biologist and geneticist. Originally an aeronautical engineer during the Second World War, he took a second degree in genetics under the well-known biologist J. B. S. Haldane. Maynard Smith was instrumental in the application of game theory to evolution with George R. Price, and theorised on other problems such as the evolution of sex and signalling theory.

Macroevolution Evolution on a scale at or above the level of species

Macroevolution in the modern sense is evolution that is guided by selection among interspecific variation, as opposed to selection among intraspecific variation in microevolution. This modern definition differs from the original concept, which referred macroevolution to the evolution of taxa above the species level.

Paleontology Study of life before 11,700 years ago

Paleontology, also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch. It includes the study of fossils to classify organisms and study their interactions with each other and their environments. Paleontological observations have been documented as far back as the 5th century BCE. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy, and developed rapidly in the 19th century. The term itself originates from Greek παλαιός, ὄν, and λόγος.

Maotianshan Shales Series of Early Cambrian deposits in the Chiungchussu Formation

The Maotianshan Shales are a series of Early Cambrian deposits in the Chiungchussu Formation, famous for their Konservat Lagerstätten, deposits known for the exceptional preservation of fossilized organisms or traces. The Maotianshan Shales form one of some forty Cambrian fossil locations worldwide exhibiting exquisite preservation of rarely preserved, non-mineralized soft tissue, comparable to the fossils of the Burgess Shale. They take their name from Maotianshan Hill in Chengjiang County, Yunnan Province, China.

Eörs Szathmáry is a Hungarian theoretical evolutionary biologist at the now-defunct Collegium Budapest Institute for Advanced Study and at the Department of Plant Taxonomy and Ecology of Eötvös Loránd University, Budapest. He is the co-author with John Maynard Smith of The Major Transitions in Evolution, a seminal work which continues to contribute to ongoing issues in evolutionary biology. He is a member of the Batthyány Society of Professors.

Index of evolutionary biology articles

This is a list of topics in evolutionary biology.

The Major Transitions in Evolution is a book written by John Maynard Smith and Eörs Szathmáry. At the time of its publication, Egbert Giles Leigh, Jr reviewing for Evolution commented that it "may be the most important book on evolution since R.A. Fisher's (1930) The Genetical Theory of Natural Selection".

<i>Wonderful Life</i> (book) 1989 book by Stephen Jay Gould

Wonderful Life: The Burgess Shale and the Nature of History is a 1989 book on the evolution of Cambrian fauna by Harvard paleontologist Stephen Jay Gould. The volume made The New York Times Best Seller list, was the 1991 winner of the Royal Society's Rhone-Poulenc Prize, the American Historical Association's Forkosch Award, and was a 1991 finalist for the Pulitzer Prize. Gould described his later book Full House (1996) as a companion volume to Wonderful Life.

Unit of selection

A unit of selection is a biological entity within the hierarchy of biological organization that is subject to natural selection. There is debate among evolutionary biologists about the extent to which evolution has been shaped by selective pressures acting at these different levels.

History of Earth Development of planet Earth from its formation to the present day

The history of Earth concerns the development of planet Earth from its formation to the present day. Nearly all branches of natural science have contributed to understanding of the main events of Earth's past, characterized by constant geological change and biological evolution.

A metasystem transition is the emergence, through evolution, of a higher level of organization or control.

Body plan Set of morphological features common to members of a phylum of animals

A body plan, Bauplan, or ground plan is a set of morphological features common to many members of a phylum of animals. The vertebrates share one body plan, while invertebrates have many.

Mosaic evolution Evolution of characters at various rates both within and between species

Mosaic evolution is the concept, mainly from palaeontology, that evolutionary change takes place in some body parts or systems without simultaneous changes in other parts. Another definition is the "evolution of characters at various rates both within and between species".408 Its place in evolutionary theory comes under long-term trends or macroevolution.

Objections to evolution Arguments that have been made against evolution

Objections to evolution have been raised since evolutionary ideas came to prominence in the 19th century. When Charles Darwin published his 1859 book On the Origin of Species, his theory of evolution initially met opposition from scientists with different theories, but eventually came to receive overwhelming acceptance in the scientific community. The observation of evolutionary processes occurring has been uncontroversial among mainstream biologists since the 1940s.

History of life Processes by which organisms evolved on Earth

The history of life on Earth traces the processes by which living and fossil organisms evolved, from the earliest emergence of life to present day. Earth formed about 4.5 billion years ago and evidence suggests that life emerged prior to 3.7 Ga. Although there is some evidence of life as early as 4.1 to 4.28 Ga, it remains controversial due to the possible non-biological formation of the purported fossils.

<i>Dawkins vs. Gould</i> Book by Kim Sterelny

Dawkins vs. Gould: Survival of the Fittest is a book about the differing views of biologists Richard Dawkins and Stephen Jay Gould by philosopher of biology Kim Sterelny. When first published in 2001 it became an international best-seller. A new edition was published in 2007 to include Gould's The Structure of Evolutionary Theory finished shortly before his death in 2002, and more recent works by Dawkins. The synopsis below is from the 2007 publication.

The Cambrian explosion, Cambrian radiation,Cambrian diversification, or the Biological Big Bang refers to an interval of time approximately 538.8 million years ago in the Cambrian Period when practically all major animal phyla started appearing in the fossil record. It lasted for about 13 – 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well.

Martin David Brasier FGS, FLS was an English palaeobiologist and astrobiologist known for his conceptual analysis of microfossils and evolution in the Precambrian and Cambrian.

References

  1. 1 2 Darwin, Charles (2007). On the origin of species by means of natural selection. Cosimo Classics. pp. 315–31. ISBN   9781602061453. OCLC   176630493.
  2. ↑ Maynard Smith J. & Szathmáry E. 1995. The major transitions in evolution. Oxford University Press, p6. ISBN   0-19-850294-X
  3. ↑ Maynard Smith J. & Szathmáry E. 1995. 1999. The origins of life: from the birth of life to the origins of language. Oxford University Press, p6. ISBN   0-19-286209-X
  4. ↑ Oparin A.I. 1952. The origin of life. New York: Dover.
  5. ↑ Penrose L.S. 1962. On living matter and self-replication. In J.B. Good (ed) The scientist speculates: an anthology of partly-baked ideas.
  6. ↑ Calvin, Melvin. 1969. Chemical evolution: molecular evolution towards the origin of living systems on the earth and elsewhere. Oxford University Press. ISBN   0198553420
  7. ↑ Cairns-Smith A.G. 1982. Genetic takeover and the mineral origins of life. Cambridge University Press. ISBN   0-521-23312-7
  8. ↑ Martin, William & Russel, Michael J. 2003. (2003). "On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleated cells". Phil. Trans. R. Soc. B. 358 (1429): 59–85. doi:10.1098/rstb.2002.1183. PMC   1693102 . PMID   12594918.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. ↑ Hazen, Robert M. (2005). Genesis : the scientific quest for life's origins . Washington, DC: Henry Press. ISBN   978-0-309-09432-0.
  10. ↑ Cavalier-Smith, Thomas; Brasier, Martin; Embley, T. Martin (2006). "Introduction: how and when did microbes change the world?". Philosophical Transactions of the Royal Society B: Biological Sciences. 361 (1470): 845–850. doi:10.1098/rstb.2006.1847. ISSN   0962-8436. PMC   1626534 . PMID   16754602.
  11. ↑ Leach, Sydney; Smith I.W.M. and Cockell, Charles S (eds) 2006. Introduction: conditions for the emergence of life on the early Earth. Phil. Trans. R. Soc. B361 1675-1679.
  12. ↑ Sapp J. 1994. Evolution by association: a history of symbiosis. Oxford University Press.
  13. ↑ Margulis, Lynn 1998. The symbiotic planet: a new look at evolution. Weidenfeld & Nicolson, London.
  14. ↑ Lake, James A. Evidence for an early prokaryote symbiogenesis. Nature460 967–971.
  15. ↑ "The Cambrian Period". University of California Museum of Paleontology. Retrieved 12 September 2017.
  16. ↑ Lane, Abby (20 January 1999). "The Cambrian explosion - timing". Earth Sciences. University of Bristol. Archived from the original on 7 March 2018. Retrieved 12 September 2017.
  17. ↑ Butterfield N.J. (2001). "Ecology and evolution of Cambrian plankton" (PDF). The ecology of the Cambrian radiation. Columbia University Press, New York. pp. 200–216. ISBN   9780231106139 . Retrieved 2007-08-19.
  18. 1 2 Butterfield, N.J. (2007). "Macroevolution and macroecology through deep time". Palaeontology. 50 (1): 41–55. doi: 10.1111/j.1475-4983.2006.00613.x .
  19. ↑ Bambach R.K.; Bush A.M.; Erwin D.H. (2007). "Autecology and the filling of ecospace: key metazoan radiations". Palæontology. 50 (1): 1–22. doi: 10.1111/j.1475-4983.2006.00611.x .
  20. ↑ Buckland, W. (1841). Geology and mineralogy considered with reference to natural theology. Lea & Blanchard. ISBN   978-1147868944.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.