Neo-Darwinism
Encyclopedia
Neo-Darwinism is the 'modern synthesis
' of Darwinian
evolution through natural selection
with Mendelian genetics, the latter being a set of primary tenets specifying that evolution involves the transmission of characteristics from parent to child through the mechanism of genetic
transfer, rather than the 'blending process' of pre-Mendelian evolutionary science. Neo-Darwinism also separates Darwin's ideas of natural selection from his hypothesis of Pangenesis
as a Lamarckian
source of variation involving blending inheritance.
As part of the disagreement about whether natural selection alone was sufficient to explain speciation
, George Romanes
coined the term neo-Darwinism to refer to the version of evolution advocated by Alfred Russel Wallace
and August Weismann
with its heavy dependence on natural selection. Weismann and Wallace rejected the Lamarckian idea of inheritance of acquired characteristics, something that Darwin had not ruled out. The term was first used in 1895 to explain that evolution occurs solely through natural selection
, in other words, without any mechanism involving the inheritance of acquired characteristics resulting from use or disuse. These two scientists' complete rejection of Lamarckism
came from Weismann's germ plasm
theory. Weismann realised that the cells that produce the germ plasm, or gametes (such as sperm and egg in animals), separate from the somatic
cells that go on to make other body tissues at an early stage in development. Since he could see no obvious means of communication between the two he asserted that the inheritance of acquired characteristics was therefore impossible; a conclusion now known as Weismann's barrier.
From the 1880s to the 1930s the term continued to be applied to the panselectionist school of thought, which argued that natural selection was the main and perhaps sole cause of all evolution. From then until around 1947 the term was used for the panselectionist followers of R. A. Fisher.
, now generally referred to as the synthetic view of evolution or the modern synthesis, the term neo-Darwinian is often used to refer to contemporary evolutionary theory. However, such usage has been described by some as incorrect; with Ernst Mayr
writing in 1984:
Despite this, publications such as the Encyclopaedia Britannica, use this term to refer to current evolutionary theory. This term is also used in the scientific literature, with the academic publishers Blackwell Publishing referring to "neo-Darwinism as practised today", and some figures in the study of evolution like Richard Dawkins
and Stephen Jay Gould
, using the term in their writings and lectures.
Modern evolutionary synthesis
The modern evolutionary synthesis is a union of ideas from several biological specialties which provides a widely accepted account of evolution...
' of Darwinian
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
evolution through natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
with Mendelian genetics, the latter being a set of primary tenets specifying that evolution involves the transmission of characteristics from parent to child through the mechanism of genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
transfer, rather than the 'blending process' of pre-Mendelian evolutionary science. Neo-Darwinism also separates Darwin's ideas of natural selection from his hypothesis of Pangenesis
Pangenesis
Pangenesis was Charles Darwin's hypothetical mechanism for heredity. He presented this 'provisional hypothesis' in his 1868 work The Variation of Animals and Plants under Domestication and felt that it brought 'together a multitude of facts which are at present left disconnected by any efficient...
as a Lamarckian
Lamarckism
Lamarckism is the idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring . It is named after the French biologist Jean-Baptiste Lamarck , who incorporated the action of soft inheritance into his evolutionary theories...
source of variation involving blending inheritance.
As part of the disagreement about whether natural selection alone was sufficient to explain 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...
, George Romanes
George Romanes
George John Romanes FRS was a Canadian-born English evolutionary biologist and physiologist who laid the foundation of what he called comparative psychology, postulating a similarity of cognitive processes and mechanisms between humans and other animals.He was the youngest of Charles Darwin's...
coined the term neo-Darwinism to refer to the version of evolution advocated by Alfred Russel Wallace
Alfred Russel Wallace
Alfred Russel Wallace, OM, FRS was a British naturalist, explorer, geographer, anthropologist and biologist...
and August Weismann
August Weismann
Friedrich Leopold August Weismann was a German evolutionary biologist. Ernst Mayr ranked him the second most notable evolutionary theorist of the 19th century, after Charles Darwin...
with its heavy dependence on natural selection. Weismann and Wallace rejected the Lamarckian idea of inheritance of acquired characteristics, something that Darwin had not ruled out. The term was first used in 1895 to explain that evolution occurs solely through natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
, in other words, without any mechanism involving the inheritance of acquired characteristics resulting from use or disuse. These two scientists' complete rejection of Lamarckism
Lamarckism
Lamarckism is the idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring . It is named after the French biologist Jean-Baptiste Lamarck , who incorporated the action of soft inheritance into his evolutionary theories...
came from Weismann's germ plasm
Germ plasm
Germ plasm or polar plasm is a zone found in the cytoplasm of the egg cells of some model organisms , which contains determinants that will give rise to the germ cell lineage. As the zygote undergoes mitotic divisions the germ plasm is ultimately restricted to a few cells of the embryo...
theory. Weismann realised that the cells that produce the germ plasm, or gametes (such as sperm and egg in animals), separate from the somatic
Somatic
The term somatic means 'of the body',, relating to the body. In medicine, somatic illness is bodily, not mental, illness. The term is often used in biology to refer to the cells of the body in contrast to the germ line cells which usually give rise to the gametes...
cells that go on to make other body tissues at an early stage in development. Since he could see no obvious means of communication between the two he asserted that the inheritance of acquired characteristics was therefore impossible; a conclusion now known as Weismann's barrier.
From the 1880s to the 1930s the term continued to be applied to the panselectionist school of thought, which argued that natural selection was the main and perhaps sole cause of all evolution. From then until around 1947 the term was used for the panselectionist followers of R. A. Fisher.
Modern evolutionary synthesis
Following the development, from about 1937 to 1950, of the modern evolutionary synthesisModern evolutionary synthesis
The modern evolutionary synthesis is a union of ideas from several biological specialties which provides a widely accepted account of evolution...
, now generally referred to as the synthetic view of evolution or the modern synthesis, the term neo-Darwinian is often used to refer to contemporary evolutionary theory. However, such usage has been described by some as incorrect; with 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...
writing in 1984:
Despite this, publications such as the Encyclopaedia Britannica, use this term to refer to current evolutionary theory. This term is also used in the scientific literature, with the academic publishers Blackwell Publishing referring to "neo-Darwinism as practised today", and some figures in the study of evolution like Richard Dawkins
Richard Dawkins
Clinton Richard Dawkins, FRS, FRSL , known as Richard Dawkins, is a British ethologist, evolutionary biologist and author...
and Stephen Jay Gould
Stephen Jay Gould
Stephen Jay Gould was an American paleontologist, evolutionary biologist, and historian of science. He was also one of the most influential and widely read writers of popular science of his generation....
, using the term in their writings and lectures.
See also
- Developmental systems theoryDevelopmental systems theoryIn developmental psychology, developmental systems theory is an overarching theoretical perspective on biological development, heredity, and evolution . It emphasizes the equal contributions of genes, environment, and epigenetic factors on developmental processes...
- Evolutionary developmental biologyEvolutionary developmental biologyEvolutionary 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...
- Neo-Lamarckism
- SymbiogenesisSymbiogenesisSymbiogenesis is the merging of two separate organisms to form a single new organism. The idea originated with Konstantin Mereschkowsky in his 1926 book Symbiogenesis and the Origin of Species, which proposed that chloroplasts originate from cyanobacteria captured by a protozoan...