Genetic determinism
Encyclopedia
Genetic determinism is the belief that gene
s determine morphological
and behavioral traits and do so with little or no influence from environmental factors.
This perspective has been largely abandoned by modern science in factor of nature-nurture interactionism. CH Waddington
wrote in 1957, "It is of course a truism which has long been recognised that the development of any individual is affected both by the hereditary determinants which come into the fertilised egg from the two parents and also by the nature of the environment in which the development takes place." Geneticists
and molecular biologists
now believe that the environment is essential in the development
of the organism
from egg to adult. In fact theorists and researchers long ago understood that genetic effects cannot be studied in isolation of the environment and that all measurements of such effects are only relative to stable external conditions. Also known since at least the 1950s is the means by which the environment influences embryonic and juvenile development, namely the epigenetic
control of gene activation and deactivation.
, who proposed in the 1890s that the key actors in the struggle for survival are not organisms but their genes, which he called determinants. While Darwin’s
concept of natural selection was intended to apply to whole organisms, Weismann modified Darwin's idea according to a process he called "germinal selection." Since the fittest determinants would be whichever ones correlate to the most useful phenotypic traits, germinal selection would result in the fittest organisms surviving and reproducing. Weismann referred to the chemical carrier of these determinants as the germ plasm, now known to be DNA
.
Weismann’s view was founded on the belief that biological inheritance is inconceivable except by way of germ plasm from parents to offspring. As Stephen Jay Gould
pointed out, this belief was not based on empirical observation. "We accept it," wrote Weismann, "not because we are able to demonstrate the process in detail... but simply because we must, because it is the only possible explanation that we can conceive." On the assumption that behavior cannot affect genes, Weismann argued that only genetic mutation, not adaptations on the part of a struggling organism, could significantly alter the developmental patterns inherited by progeny. Though contrary to Darwin's view, Weismann's belief that determinants shape the body, and never vice versa, has long been known as the central dogma of modern biology.
Weismann’s developmental concept was based on a mistaken interpretation of an 1882 experiment carried about by Wilhelm Roux
, in which Roux killed one of the cells of a frog embryo at the two-cell stage. The remaining cell then led to half an embryo, leading Weismann to believe that the determinants for the embryo were divided along with each cell division. As Hans Driesch and other researchers discovered, when the dead cell is removed, the other cell produces a whole organism, not half. It's now well known that all the cells in a given organism contain the same set of genes.
genes, hardly vary at all across vast portions of the phylogenetic tree. Everything from flies to humans share roughly the same set of developmental genes. What differs between the species is not the genes themselves but the way they are expressed.
, JBS Haldane, Sewall Wright
, Ernst Mayr
and Theodosius Dobzhansky
contributed to the synthesis of Mendel and Darwin's concept of natural selection. In contrast to Weismann, the modern synthesis rejected the notion that the organism is ultimately reducible to physical principles. According to Mayr, the organism responds to a dual causation, one based on laws of physics, the other based on a genetic program. Thus the organism reflects not just the mechanics of its constituent parts but the phylogenetic history encoded in its genes. Genetic information both reflects a species' descent and directs an organism’s development. The key to genes is not their chemical makeup but the information they carry. According to esteemed researcher Christiane Nusslein-Volhard
, what distinguishes genes from proteins is that genes are chemically identical and differ only in terms of their sequence of nucleic acids and the information encoded in that sequence.
and James Watson
explained the structure of DNA. This event was heralded as the discovery of the book of life, a view still prevalent in the popular press and among many scientists. However, nearly 50 years later, when a “first draft” of the human genome became available, the book of life turned out to be considerably less extensive than had been anticipated. Instead of the expected 100,000 characters, the genome contains less than 30,000. As Nusslein-Volhard points out, morphological complexity does not correlate with size of genome.
A given organic form is thought to emerge at a particular place in the embryo on the basis of its distance from an "organizer," a set of cells that influence how other cells develop. By generating a chemical gradient that permeates the embryo, the organizer establishes zones of development. Depending on which zone a cell is located in, some of its genes are expressed while others are repressed. “Through an interplay of mutual activation and repression, more and more complex molecular patterns emerge.”
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s determine morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
and behavioral traits and do so with little or no influence from environmental factors.
This perspective has been largely abandoned by modern science in factor of nature-nurture interactionism. CH Waddington
Conrad Hal Waddington
Conrad Hal Waddington CBE FRS FRSE was a developmental biologist, paleontologist, geneticist, embryologist and philosopher who laid the foundations for systems biology...
wrote in 1957, "It is of course a truism which has long been recognised that the development of any individual is affected both by the hereditary determinants which come into the fertilised egg from the two parents and also by the nature of the environment in which the development takes place." Geneticists
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
and molecular biologists
Molecular biology
Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...
now believe that the environment is essential in the development
Developmental biology
Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis", which is the process that gives rise to tissues, organs and anatomy.- Related fields of study...
of the organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
from egg to adult. In fact theorists and researchers long ago understood that genetic effects cannot be studied in isolation of the environment and that all measurements of such effects are only relative to stable external conditions. Also known since at least the 1950s is the means by which the environment influences embryonic and juvenile development, namely the epigenetic
Epigenetics
In biology, and specifically genetics, epigenetics is the study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence – hence the name epi- -genetics...
control of gene activation and deactivation.
Origins
Genetic determinism, which identifies the gene as the biological source of morphology and instinct, can be traced back to Austrian theorist August WeismannAugust 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...
, who proposed in the 1890s that the key actors in the struggle for survival are not organisms but their genes, which he called determinants. While Darwin’s
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...
concept of natural selection was intended to apply to whole organisms, Weismann modified Darwin's idea according to a process he called "germinal selection." Since the fittest determinants would be whichever ones correlate to the most useful phenotypic traits, germinal selection would result in the fittest organisms surviving and reproducing. Weismann referred to the chemical carrier of these determinants as the germ plasm, now known to be DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
.
Weismann’s view was founded on the belief that biological inheritance is inconceivable except by way of germ plasm from parents to offspring. As 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....
pointed out, this belief was not based on empirical observation. "We accept it," wrote Weismann, "not because we are able to demonstrate the process in detail... but simply because we must, because it is the only possible explanation that we can conceive." On the assumption that behavior cannot affect genes, Weismann argued that only genetic mutation, not adaptations on the part of a struggling organism, could significantly alter the developmental patterns inherited by progeny. Though contrary to Darwin's view, Weismann's belief that determinants shape the body, and never vice versa, has long been known as the central dogma of modern biology.
The machine theory
Weismann believed that the initial division of the egg into two cells causes determinates to be divided into two groups, such that one cell will develop, say, the left half of the embryo, while the other cell will generate the right half. With each subsequent division, determinants continue to be meted out differently to different cells until the stage is reached where each cell type is in place. At this point the distinct set of determinants in each cell type produce the developmental machinery that will generate the tissue, organ or system associated with that type of cell.Weismann’s developmental concept was based on a mistaken interpretation of an 1882 experiment carried about by Wilhelm Roux
Wilhelm Roux
Wilhelm Roux was a German zoologist and pioneer of experimental embryology.Roux was born and educated in Jena, Germany where he attended university and studied under Ernst Haeckel. He also attended university in Berlin and Strasbourg and studied under Gustav Schwalbe, Friedrich Daniel von...
, in which Roux killed one of the cells of a frog embryo at the two-cell stage. The remaining cell then led to half an embryo, leading Weismann to believe that the determinants for the embryo were divided along with each cell division. As Hans Driesch and other researchers discovered, when the dead cell is removed, the other cell produces a whole organism, not half. It's now well known that all the cells in a given organism contain the same set of genes.
Developmental genes
Weismann also assumed that different species contain different developmental determinants. The lizard's germ plasm naturally contains different developmental instructions than the cow's germ plasm. Only in the late 20th century did scientists learn that developmental genes, now known as homeoboxHomeobox
A homeobox is a DNA sequence found within genes that are involved in the regulation of patterns of anatomical development in animals, fungi and plants.- Discovery :...
genes, hardly vary at all across vast portions of the phylogenetic tree. Everything from flies to humans share roughly the same set of developmental genes. What differs between the species is not the genes themselves but the way they are expressed.
The modern synthesis
Following the rediscovery of Mendel's principles of genetics, several theorists such as RA FisherRonald Fisher
Sir Ronald Aylmer Fisher FRS was an English statistician, evolutionary biologist, eugenicist and geneticist. Among other things, Fisher is well known for his contributions to statistics by creating Fisher's exact test and Fisher's equation...
, JBS Haldane, Sewall Wright
Sewall Wright
Sewall Green Wright was an American geneticist known for his influential work on evolutionary theory and also for his work on path analysis. With R. A. Fisher and J.B.S. Haldane, he was a founder of theoretical population genetics. He is the discoverer of the inbreeding coefficient and of...
, 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...
and Theodosius Dobzhansky
Theodosius Dobzhansky
Theodosius Grygorovych Dobzhansky ForMemRS was a prominent geneticist and evolutionary biologist, and a central figure in the field of evolutionary biology for his work in shaping the unifying modern evolutionary synthesis...
contributed to the synthesis of Mendel and Darwin's concept of natural selection. In contrast to Weismann, the modern synthesis rejected the notion that the organism is ultimately reducible to physical principles. According to Mayr, the organism responds to a dual causation, one based on laws of physics, the other based on a genetic program. Thus the organism reflects not just the mechanics of its constituent parts but the phylogenetic history encoded in its genes. Genetic information both reflects a species' descent and directs an organism’s development. The key to genes is not their chemical makeup but the information they carry. According to esteemed researcher Christiane Nusslein-Volhard
Christiane Nüsslein-Volhard
Christiane Nüsslein-Volhard is a German biologist who won the Albert Lasker Award for Basic Medical Research in 1991 and the Nobel Prize in Physiology or Medicine in 1995, together with Eric Wieschaus and Edward B...
, what distinguishes genes from proteins is that genes are chemically identical and differ only in terms of their sequence of nucleic acids and the information encoded in that sequence.
Crick and Watson
The chemical nature of the germ plasm was discovered in 1953, when Francis CrickFrancis Crick
Francis Harry Compton Crick OM FRS was an English molecular biologist, biophysicist, and neuroscientist, and most noted for being one of two co-discoverers of the structure of the DNA molecule in 1953, together with James D. Watson...
and James Watson
James D. Watson
James Dewey Watson is an American molecular biologist, geneticist, and zoologist, best known as one of the co-discoverers of the structure of DNA in 1953 with Francis Crick...
explained the structure of DNA. This event was heralded as the discovery of the book of life, a view still prevalent in the popular press and among many scientists. However, nearly 50 years later, when a “first draft” of the human genome became available, the book of life turned out to be considerably less extensive than had been anticipated. Instead of the expected 100,000 characters, the genome contains less than 30,000. As Nusslein-Volhard points out, morphological complexity does not correlate with size of genome.
The contemporary view
According to Nusslein-Volhard, who won a Nobel for her research into molecular mechanisms of development, the genome is a "building plan," DNA a "language of four letters that can be read faultlessly... In the fertilized egg, the genetic program is complete." She reiterates the reductionist approach even as she fleshes out a model of development based not on genetic information but the way genes are “expressed.” She notes that it's rare that one gene determines a specific structure in a specific position. Rather than provide anything like a blueprint for the finished organism, homeobox genes guide development by regulating other genes.A given organic form is thought to emerge at a particular place in the embryo on the basis of its distance from an "organizer," a set of cells that influence how other cells develop. By generating a chemical gradient that permeates the embryo, the organizer establishes zones of development. Depending on which zone a cell is located in, some of its genes are expressed while others are repressed. “Through an interplay of mutual activation and repression, more and more complex molecular patterns emerge.”
In fiction
- Children of the revolution, a comedy about Stalin's son's inescapable path into rebellion and eventually a revolution of any sort
- AndromedaAndromeda (TV series)Andromeda is a Canadian-American science fiction television series, based on unused material by the late Star Trek creator Gene Roddenberry, developed by Robert Hewitt Wolfe, and produced by Roddenberry's widow, Majel Barrett Roddenberry. It starred Kevin Sorbo as High Guard Captain Dylan Hunt...
, a television series in which the nietzschean species was genetically programmed to be ambitious, treacherous, and brutal - GattacaGattacaGattaca is a 1997 science fiction film written and directed by Andrew Niccol. It stars Ethan Hawke, Uma Thurman and Jude Law with supporting roles played by Loren Dean, Ernest Borgnine, Gore Vidal and Alan Arkin....
, a 1997 film starring Ethan Hawke, Uma Thurman and Jude Law
See also
- Biological determinismBiological determinismBiological determination is the interpretation of humans and human life from a strictly biological point of view, and it is closely related to genetic determinism...
- Council for Responsible GeneticsCouncil for Responsible GeneticsThe Council for Responsible Genetics is a non-profit NGO with a focus on biotechnology.- History :The Council for Responsible Genetics was founded in 1983 in Cambridge, Massachusetts....
- Nature versus nurtureNature versus nurtureThe nature versus nurture debate concerns the relative importance of an individual's innate qualities versus personal experiences The nature versus nurture debate concerns the relative importance of an individual's innate qualities ("nature," i.e. nativism, or innatism) versus personal experiences...
- Tabula rasaTabula rasaTabula rasa is the epistemological theory that individuals are born without built-in mental content and that their knowledge comes from experience and perception. Generally proponents of the tabula rasa thesis favour the "nurture" side of the nature versus nurture debate, when it comes to aspects...
- Conscious RobotsConscious RobotsConscious Robots is a book exploring hard determinism written by Paul Kwatz and published in 2005. Kwatz argues that the illusion of free will can be dispelled by considering our personal experience and scientific knowledge....