Soft inheritance
Encyclopedia
Soft inheritance is the term coined by Ernst Mayr
to include such ideas as Lamarckism
, that an organism can pass on characteristics that it acquired during its lifetime to its offspring. It contrasts with modern ideas of inheritance, which Mayr called hard inheritance
. Since Mendel
, modern genetics has held that the hereditary material is impervious to environmental influences (except, of course, mutagenic effects). In soft inheritance "the genetic basis of characters could be modified either by direct induction by the environment, or by use and disuse, or by an intrinsic failure of constancy, and that this modified genotype was then transmitted to the next generation." Concepts of soft inheritance are usually associated with the ideas of Lamarck and Geoffroy
. The concept of hard inheritance
holds sway today.
One of the first statements in favour of hard inheritance was made by the English surgeon William Lawrence in 1819. His ideas on heredity were many years ahead of their time, as this extract shows: "The offspring inherit only [their parents'] connate peculiarities and not any of the acquired qualities". This is as clear a rejection of soft inheritance as one can find. However, Lawrence qualified it by including the origin of birth defects owing to influences on the mother (an old folk superstition). So Mayr
places Wilhelm His, Sr.
in 1874 as the first unqualified rejection of soft inheritance. August Weismann
, in 1883, gave a comprehensive denial of Lamarckism
(soft inheritance) and with his distinction between germ and soma provided a general ideology of hard inheritance which survives to the present day.
Recent work in plants and mammals on the role of the environment on epigenetic modifications of DNA
have led to the argument that inherited epigenetic variation
is a kind of soft inheritance.
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...
to include such ideas as 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...
, that an organism can pass on characteristics that it acquired during its lifetime to its offspring. It contrasts with modern ideas of inheritance, which Mayr called hard inheritance
Hard inheritance
Hard inheritance is the exact opposite of the term soft inheritance, coined by Ernst Mayr to contrast ideas about inheritance. Hard inheritance states that characteristics of an organism's offspring will not be affected by the actions that the parental organism performs during its lifetime...
. Since Mendel
Gregor Mendel
Gregor Johann Mendel was an Austrian scientist and Augustinian friar who gained posthumous fame as the founder of the new science of genetics. Mendel demonstrated that the inheritance of certain traits in pea plants follows particular patterns, now referred to as the laws of Mendelian inheritance...
, modern genetics has held that the hereditary material is impervious to environmental influences (except, of course, mutagenic effects). In soft inheritance "the genetic basis of characters could be modified either by direct induction by the environment, or by use and disuse, or by an intrinsic failure of constancy, and that this modified genotype was then transmitted to the next generation." Concepts of soft inheritance are usually associated with the ideas of Lamarck and Geoffroy
Étienne Geoffroy Saint-Hilaire
Étienne Geoffroy Saint-Hilaire was a French naturalist who established the principle of "unity of composition". He was a colleague of Jean-Baptiste Lamarck and expanded and defended Lamarck's evolutionary theories...
. The concept of hard inheritance
Hard inheritance
Hard inheritance is the exact opposite of the term soft inheritance, coined by Ernst Mayr to contrast ideas about inheritance. Hard inheritance states that characteristics of an organism's offspring will not be affected by the actions that the parental organism performs during its lifetime...
holds sway today.
One of the first statements in favour of hard inheritance was made by the English surgeon William Lawrence in 1819. His ideas on heredity were many years ahead of their time, as this extract shows: "The offspring inherit only [their parents'] connate peculiarities and not any of the acquired qualities". This is as clear a rejection of soft inheritance as one can find. However, Lawrence qualified it by including the origin of birth defects owing to influences on the mother (an old folk superstition). So 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...
places Wilhelm His, Sr.
Wilhelm His, Sr.
Wilhelm His, Sr. was a Swiss anatomist and professor who invented the microtome...
in 1874 as the first unqualified rejection of soft inheritance. 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...
, in 1883, gave a comprehensive denial 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...
(soft inheritance) and with his distinction between germ and soma provided a general ideology of hard inheritance which survives to the present day.
Recent work in plants and mammals on the role of the environment on epigenetic modifications of 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...
have led to the argument that inherited epigenetic variation
Transgenerational epigenetics
Epigenetic inheritance is the transmittance of information from one generation to the next that affects the traits of offspring without alteration of the primary structure of DNA or from environmental cues...
is a kind of soft inheritance.
Further reading
- Burkeman, Oliver. Why everything you've been told about evolution is wrong, The Guardian, March 19, 2010.