Macroevolution
Encyclopedia
Macroevolution is evolution
on a scale of separated gene pool
s. Macroevolutionary studies focus on change that occurs at or above the level of species
, in contrast with microevolution
, which refers to smaller evolutionary changes (typically described as changes in allele frequencies) within a species or population.
The process of speciation
may fall within the purview of either, depending on the forces thought to drive it. Paleontology
, evolutionary developmental biology
, comparative genomics
and genomic phylostratigraphy
contribute most of the evidence for the patterns and processes that can be classified as macroevolution. An example of macroevolution is the appearance of feathers during the evolution of birds from theropod dinosaurs.
Abrupt transformations from one biologic system to another, for example the passing of life from water into land or the transition from invertebrates to vertebrates, are rare. Few major biological types have emerged during the evolutionary history of life
and most of them survive till today. When lifeforms take such giant leaps, they meet little to no competition and are able to exploit a plethora of available niche
s, following a pattern of adaptive radiation
. This can lead to convergent evolution
, where unrelated populations display similar adaptations.
The evolutionary course of Equidae
(wide family including all horses and related animals) is often viewed as a typical example of macroevolution. The earliest known genus, Hyracotherium
(now reclassified as a palaeothere), was a herbivore animal resembling a dog that lived in the early Cenozoic
. As its habitat transformed into an open arid grassland, selective pressure required that the animal become a fast grazer. Thus elongation of legs and head as well as reduction of toes gradually occurred, producing the only extant genus of Equidae, Equus
.
Yuri Filipchenko
first coined the terms "macroevolution" and "microevolution" in 1927 in his German language work, "Variabilität und Variation". Since the inception of the two terms, their meanings have been revised several times and the term macroevolution fell into limited disfavour when it was taken over by such writers as the geneticist Richard Goldschmidt
(1940) and the paleontologist Otto Schindewolf
to describe their orthogenetic theories.
A more practical definition of the term describes it as changes occurring on geological time scales, in contrast to microevolution, which occurs on the timescale of human lifetimes. This definition reflects the spectrum between micro- and macro-evolution, whilst leaving a clear difference between the terms: because the geological record rarely has a resolution better than 10,000 years, and humans rarely live longer than 100 years, "meso-evolution" is never observed.
As a result, apart from Dobzhansky, Bernhard Rensch
and Ernst Mayr
, very few neo-Darwinian writers used the term, preferring instead to talk of evolution as changes in allele frequencies without mention of the level of the changes (above species level or below). Those who did were generally working within the continental European traditions (as Dobzhansky, Ernst Mayr
, Bernhard Rensch
, Richard Goldschmidt
, and Otto Schindewolf
were) and those who didn't were generally working within the Anglo-American tradition (such as John Maynard Smith
and Richard Dawkins
). Hence, use of the term "macroevolution" is sometimes wrongly used as a litmus test of whether the writer is "properly" neo-Darwinian or not.
school of thought, macroevolution is thought of as the compounded effects of microevolution. Thus, the distinction between micro- and macroevolution is not a fundamental one the only difference between them is of time and scale. As Ernst W. Mayr observes, "transspecific evolution is nothing but an extrapolation and magnification of the events that take place within populations and species...it is misleading to make a distinction between the causes of micro- and macroevolution”. However, time is not a necessary distinguishing factor macroevolution can happen without gradual compounding of small changes; whole-genome duplication
can result in speciation occurring over a single generation - this is especially common in plants.
Changes in the genes regulating development have also been proposed as being important in producing speciation through large and relatively sudden changes in animals' morphology.
, usually used by creationists alleging a significant difference between the evolutionary changes observed in field and laboratory studies and the larger scale macroevolutionary changes that scientists believe to have taken thousands or millions of years to occur. They may accept that evolutionary change is possible within species ("microevolution"), but deny that one species can evolve into another ("macroevolution"). Contrary to this belief among the anti-evolution movement proponents, evolution of life forms beyond the species level ("macroevolution", i.e. speciation
in a specific case) has indeed been observed multiple times under both controlled laboratory conditions and in nature. The claim that macroevolution does not occur, or is impossible, is thus demonstrably false and without support in the scientific community
.
Such claims are rejected by the scientific community on the basis of ample evidence that macroevolution is an active process both presently and in the past. The terms macroevolution and microevolution relate to the same processes operating at different scales, but creationist claims misuse the terms in a vaguely defined way which does not accurately reflect scientific usage, acknowledging well observed evolution as "microevolution" and denying that "macroevolution" takes place. Evolutionary theory (including macroevolutionary change) remains the dominant scientific paradigm for explaining the origins of Earth
's biodiversity. Its occurrence is not disputed within the scientific community.
While details of macroevolution are continuously studied by the scientific community
, the overall theory behind macroevolution (i.e. common descent
) has been overwhelmingly consistent with empirical data. Predictions of empirical data from the theory of common descent have been so consistent that biologists often refer to it as the "fact of evolution
".
Nicholas Matzke and Paul R. Gross
have accused creationists
of using "strategically elastic" definitions of micro- and macroevolution when discussing the topic. The actual definition of macroevolution accepted by scientists is "any change at the species level or above" (phyla, group, etc.) and microevolution is "any change below the level of species." Matzke and Gross state that many creationist critics define macroevolution as something that cannot be attained, as these critics describe any observed evolutionary change as "just microevolution".
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
on a scale of separated gene pool
Gene pool
In population genetics, a gene pool is the complete set of unique alleles in a species or population.- Description :A large gene pool indicates extensive genetic diversity, which is associated with robust populations that can survive bouts of intense selection...
s. Macroevolutionary studies focus on change that occurs at or above the level of species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, in contrast with microevolution
Microevolution
Microevolution is the changes in allele frequencies that occur over time within a population. This change is due to four different processes: mutation, selection , gene flow, and genetic drift....
, which refers to smaller evolutionary changes (typically described as changes in allele frequencies) within a species or population.
The process of speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
may fall within the purview of either, depending on the forces thought to drive it. Paleontology
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
, evolutionary developmental biology
Evolutionary developmental biology
Evolutionary developmental biology is a field of biology that compares the developmental processes of different organisms to determine the ancestral relationship between them, and to discover how developmental processes evolved...
, comparative genomics
Comparative genomics
Comparative genomics is the study of the relationship of genome structure and function across different biological species or strains. Comparative genomics is an attempt to take advantage of the information provided by the signatures of selection to understand the function and evolutionary...
and genomic phylostratigraphy
Genomic phylostratigraphy
Genomic phylostratigraphy is a statistical approach for reconstruction of macroevolutionary trends based on the principle of founder gene formation and punctuated emergence of protein families. Phylostratigraphy, a novel statistical method, was developed by Tomislav Domazet-Lošo at the Ruđer...
contribute most of the evidence for the patterns and processes that can be classified as macroevolution. An example of macroevolution is the appearance of feathers during the evolution of birds from theropod dinosaurs.
Abrupt transformations from one biologic system to another, for example the passing of life from water into land or the transition from invertebrates to vertebrates, are rare. Few major biological types have emerged during the evolutionary history of life
Evolutionary history of life
The evolutionary history of life on Earth traces the processes by which living and fossil organisms have evolved since life on Earth first originated until the present day. Earth formed about 4.5 Ga and life appeared on its surface within one billion years...
and most of them survive till today. When lifeforms take such giant leaps, they meet little to no competition and are able to exploit a plethora of available niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
s, following a pattern of adaptive radiation
Adaptive radiation
In evolutionary biology, adaptive radiation is the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. Starting with a recent single ancestor, this process results in the speciation and phenotypic adaptation of an array of species exhibiting different...
. This can lead to convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
, where unrelated populations display similar adaptations.
The evolutionary course of Equidae
Equidae
Equidae is the taxonomic family of horses and related animals, including the extant horses, donkeys, and zebras, and many other species known only from fossils. All extant species are in the genus Equus...
(wide family including all horses and related animals) is often viewed as a typical example of macroevolution. The earliest known genus, Hyracotherium
Hyracotherium
Hyracotherium , also known as Eohippus or the dawn horse, is an extinct genus of very small perissodactyl ungulates that lived in the woodlands of the northern hemisphere, with species ranging throughout Asia, Europe, and North America during the early Tertiary Period and the early to mid Eocene...
(now reclassified as a palaeothere), was a herbivore animal resembling a dog that lived in the early Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
. As its habitat transformed into an open arid grassland, selective pressure required that the animal become a fast grazer. Thus elongation of legs and head as well as reduction of toes gradually occurred, producing the only extant genus of Equidae, Equus
Equus (genus)
Equus is a genus of animals in the family Equidae that includes horses, donkeys, and zebras. Within Equidae, Equus is the only extant genus. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. This article deals primarily with the extant species.The term equine...
.
Origin of the term
Russian entomologistEntomology
Entomology is the scientific study of insects, a branch of arthropodology...
Yuri Filipchenko
Yuri Filipchenko
thumb|Yuri FilipchenkoYuri Filipchenko was a Russian entomologist and coiner of the terms microevolution and macroevolution. Mentor of Theodosius Dobzhansky...
first coined the terms "macroevolution" and "microevolution" in 1927 in his German language work, "Variabilität und Variation". Since the inception of the two terms, their meanings have been revised several times and the term macroevolution fell into limited disfavour when it was taken over by such writers as the geneticist Richard Goldschmidt
Richard Goldschmidt
Richard Benedict Goldschmidt was a German-born American geneticist. He is considered the first to integrate genetics, development, and evolution. He pioneered understanding of reaction norms, genetic assimilation, dynamical genetics, sex determination, and heterochrony...
(1940) and the paleontologist Otto Schindewolf
Otto Schindewolf
Otto Heinrich Schindewolf was a German paleontologist who studied the evolution of corals and cephalopods....
to describe their orthogenetic theories.
A more practical definition of the term describes it as changes occurring on geological time scales, in contrast to microevolution, which occurs on the timescale of human lifetimes. This definition reflects the spectrum between micro- and macro-evolution, whilst leaving a clear difference between the terms: because the geological record rarely has a resolution better than 10,000 years, and humans rarely live longer than 100 years, "meso-evolution" is never observed.
As a result, apart from Dobzhansky, Bernhard Rensch
Bernhard Rensch
Bernhard Rensch was a German evolutionary biologist, and ornithologist who did field work in Indonesia and India. He is probably best known as one of the architects of the modern evolutionary synthesis, which he popularised in Germany...
and Ernst Mayr
Ernst Mayr
Ernst Walter Mayr was one of the 20th century's leading evolutionary biologists. He was also a renowned taxonomist, tropical explorer, ornithologist, historian of science, and naturalist...
, very few neo-Darwinian writers used the term, preferring instead to talk of evolution as changes in allele frequencies without mention of the level of the changes (above species level or below). Those who did were generally working within the continental European traditions (as Dobzhansky, Ernst Mayr
Ernst Mayr
Ernst Walter Mayr was one of the 20th century's leading evolutionary biologists. He was also a renowned taxonomist, tropical explorer, ornithologist, historian of science, and naturalist...
, Bernhard Rensch
Bernhard Rensch
Bernhard Rensch was a German evolutionary biologist, and ornithologist who did field work in Indonesia and India. He is probably best known as one of the architects of the modern evolutionary synthesis, which he popularised in Germany...
, Richard Goldschmidt
Richard Goldschmidt
Richard Benedict Goldschmidt was a German-born American geneticist. He is considered the first to integrate genetics, development, and evolution. He pioneered understanding of reaction norms, genetic assimilation, dynamical genetics, sex determination, and heterochrony...
, and Otto Schindewolf
Otto Schindewolf
Otto Heinrich Schindewolf was a German paleontologist who studied the evolution of corals and cephalopods....
were) and those who didn't were generally working within the Anglo-American tradition (such as John Maynard Smith
John Maynard Smith
John Maynard Smith,His surname was Maynard Smith, not Smith, nor was it hyphenated. F.R.S. was a British theoretical 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....
and Richard Dawkins
Richard Dawkins
Clinton Richard Dawkins, FRS, FRSL , known as Richard Dawkins, is a British ethologist, evolutionary biologist and author...
). Hence, use of the term "macroevolution" is sometimes wrongly used as a litmus test of whether the writer is "properly" neo-Darwinian or not.
Macroevolution and the modern evolutionary synthesis
Within the Modern SynthesisModern evolutionary synthesis
The modern evolutionary synthesis is a union of ideas from several biological specialties which provides a widely accepted account of evolution...
school of thought, macroevolution is thought of as the compounded effects of microevolution. Thus, the distinction between micro- and macroevolution is not a fundamental one the only difference between them is of time and scale. As Ernst W. Mayr observes, "transspecific evolution is nothing but an extrapolation and magnification of the events that take place within populations and species...it is misleading to make a distinction between the causes of micro- and macroevolution”. However, time is not a necessary distinguishing factor macroevolution can happen without gradual compounding of small changes; whole-genome duplication
Polyploidy
Polyploid is a term used to describe cells and organisms containing more than two paired sets of chromosomes. Most eukaryotic species are diploid, meaning they have two sets of chromosomes — one set inherited from each parent. However polyploidy is found in some organisms and is especially common...
can result in speciation occurring over a single generation - this is especially common in plants.
Changes in the genes regulating development have also been proposed as being important in producing speciation through large and relatively sudden changes in animals' morphology.
Research topics
Some examples of subjects whose study falls within the realm of macroevolution:- Adaptive radiationAdaptive radiationIn evolutionary biology, adaptive radiation is the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. Starting with a recent single ancestor, this process results in the speciation and phenotypic adaptation of an array of species exhibiting different...
s such as The Cambrian ExplosionCambrian explosionThe Cambrian explosion or Cambrian radiation was the relatively rapid appearance, around , of most major phyla, as demonstrated in the fossil record, accompanied by major diversification of other organisms, including animals, phytoplankton, and calcimicrobes...
. - Changes in biodiversity through time.
- Genomic evolutionThe Evolution of the GenomeThe Evolution of the Genome is a book edited by Dr. T. Ryan Gregory of the University of Guelph, in Guelph, Ontario, Canada, covering a wide range of topics in the study of genome evolution...
, like horizontal gene transferHorizontal gene transferHorizontal gene transfer , also lateral gene transfer , is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism...
, genome fusions in endosymbioses, and adaptive changes in genome size. - Mass extinctionsExtinction eventAn extinction event is a sharp decrease in the diversity and abundance of macroscopic life. They occur when the rate of extinction increases with respect to the rate of speciation...
. - SpeciationSpeciationSpeciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
and extinctionExtinctionIn biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
rates. - The debate between punctuated equilibriumPunctuated equilibriumPunctuated equilibrium is a theory in evolutionary biology which proposes that most species will exhibit little net evolutionary change for most of their geological history, remaining in an extended state called stasis...
and gradualismGradualismGradualism is the belief in or the policy of advancing toward a goal by gradual, often slow stages.-Politics and society:In politics, the concept of gradualism is used to describe the belief that change ought to be brought about in small, discrete increments rather than in abrupt strokes such as...
. - The role of development in shaping evolution, particularly such topics as heterochronyHeterochronyIn biology, heterochrony is defined as a developmental change in the timing of events, leading to changes in size and shape. There are two main components, namely the onset and offset of a particular process, and the rate at which the process operates...
and phenotypic plasticityPhenotypic plasticityPhenotypic plasticity is the ability of an organism to change its phenotype in response to changes in the environment. Such plasticity in some cases expresses as several highly morphologically distinct results; in other cases, a continuous norm of reaction describes the functional interrelationship...
. - At present-day there is developping an interdisciplinary approach which aims at considering macroevolution at a transdisciplinary scale, and concentrates on the comparison between biological and social macroevolution as this gives new significant possibilities to understand peculiarities of each of the two types of macroevolution.
Misuse
The term "macroevolution" frequently arises within the context of the evolution/creation debateCreation-evolution controversy
The creation–evolution controversy is a recurring cultural, political, and theological dispute about the origins of the Earth, humanity, life, and the universe....
, usually used by creationists alleging a significant difference between the evolutionary changes observed in field and laboratory studies and the larger scale macroevolutionary changes that scientists believe to have taken thousands or millions of years to occur. They may accept that evolutionary change is possible within species ("microevolution"), but deny that one species can evolve into another ("macroevolution"). Contrary to this belief among the anti-evolution movement proponents, evolution of life forms beyond the species level ("macroevolution", i.e. speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
in a specific case) has indeed been observed multiple times under both controlled laboratory conditions and in nature. The claim that macroevolution does not occur, or is impossible, is thus demonstrably false and without support in the scientific community
Scientific community
The scientific community consists of the total body of scientists, its relationships and interactions. It is normally divided into "sub-communities" each working on a particular field within science. Objectivity is expected to be achieved by the scientific method...
.
Such claims are rejected by the scientific community on the basis of ample evidence that macroevolution is an active process both presently and in the past. The terms macroevolution and microevolution relate to the same processes operating at different scales, but creationist claims misuse the terms in a vaguely defined way which does not accurately reflect scientific usage, acknowledging well observed evolution as "microevolution" and denying that "macroevolution" takes place. Evolutionary theory (including macroevolutionary change) remains the dominant scientific paradigm for explaining the origins of Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's biodiversity. Its occurrence is not disputed within the scientific community.
While details of macroevolution are continuously studied by the scientific community
Scientific community
The scientific community consists of the total body of scientists, its relationships and interactions. It is normally divided into "sub-communities" each working on a particular field within science. Objectivity is expected to be achieved by the scientific method...
, the overall theory behind macroevolution (i.e. common descent
Common descent
In evolutionary biology, a group of organisms share common descent if they have a common ancestor. There is strong quantitative support for the theory that all living organisms on Earth are descended from a common ancestor....
) has been overwhelmingly consistent with empirical data. Predictions of empirical data from the theory of common descent have been so consistent that biologists often refer to it as the "fact of evolution
Evolution as theory and fact
"Evolution is both fact and theory" is a statement that appears in numerous publications on biological evolution. The statement is framed to clarify misconceptions about the philosophy of evolution primarily in response to creationist statements that "evolution is only a theory"...
".
Nicholas Matzke and Paul R. Gross
Paul R. Gross
Paul R. Gross is a biologist and author, perhaps best known to the general public for Higher Superstition , written with Norman Levitt. Gross is the University Professor of Life Sciences at the University of Virginia; he previously served the university as Provost and Vice-President...
have accused creationists
Creationism
Creationism is the religious beliefthat humanity, life, the Earth, and the universe are the creation of a supernatural being, most often referring to the Abrahamic god. As science developed from the 18th century onwards, various views developed which aimed to reconcile science with the Genesis...
of using "strategically elastic" definitions of micro- and macroevolution when discussing the topic. The actual definition of macroevolution accepted by scientists is "any change at the species level or above" (phyla, group, etc.) and microevolution is "any change below the level of species." Matzke and Gross state that many creationist critics define macroevolution as something that cannot be attained, as these critics describe any observed evolutionary change as "just microevolution".
See also
- List of transitional fossils
- Transitional fossilTransitional fossilA transitional fossil is any fossilized remains of a lifeform that exhibits characteristics of two distinct taxonomic groups. A transitional fossil is the fossil of an organism near the branching point where major individual lineages diverge...
- MicroevolutionMicroevolutionMicroevolution is the changes in allele frequencies that occur over time within a population. This change is due to four different processes: mutation, selection , gene flow, and genetic drift....
- SpeciationSpeciationSpeciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
External links
- Introduction to macroevolution
- Macroevolution as the common descent of all life
- Macroevolution in the 21st Century Macroevolution as an independent discipline.
- Macroevolution FAQ