Heterosis
From Freepedia
- Heterotic string theory is a field of physics.
Heterosis is increased strength of different characteristics in hybrids; the possibility to obtain a "better" individual by combining the virtues of its parents.
This is commonly known as hybrid vigor. It is an observable phenomenon in which a hybrid plant or animal may exhibit greater strength, health or faster rate of growth than its parents. The term often causes controversy, particularly in terms of domestic animals, because it is sometimes believed that all crossbred plants or animals are better than their parents; this is untrue. Rather, when a hybrid is seen to be superior to its parents, this is known as hybrid vigor. Heterosis is an example of heterozygous advantage.
It may also happen that a hybrid inherits and exhibits the worst qualities of each of its parents, or is inferior to each.
One study suggests that hybrid vigor may be associated with increased intelligence in humans. Nagoshi and Johnson (1986) found that children of Japanese-Caucasian cross-ethnic matings scored .26 SD higher on several cognitive tests than those from within-ethnic matings, despite having virtually identical parental educational and occupational backgrounds (p. 204). The increase in scores tended to be higher on cognitive tests that were more g-loaded, suggesting that hybrid vigor improves g. To become more reliable, the study would have to match the intelligence averages of the parents as well as compute the intelligence scores of their children. Mingroni (2004) has argued that heterosis may be partially responsible for the Flynn effect.
The Minnesota Transracial Adoption Study shows children of Negroid-Caucasian cross-ethnic mating score .47 SD lower on cognitive tests taken at age 17 than adopted children of Caucasian heritage, and .67 SD higher than adopted children of Negroid heritage. The average IQ of the adopting parents was more than 1 standard deviation above the population mean of 100. The exact interpretation of this study is disputed.
Heterosis in Fiction
The idea of hybrid vigor has taken hold in the popular consciousness in various ways. One example is the fictional character Spock, a half-human, half-Vulcan scientist from the television series Star Trek. While Spock is literally the offspring of a human and an extra-terrestrial, metaphorically his character was intended to represent inter-racial friendship and inter-marriage. Rather than portraying the tragic mulatto of 19th century American fiction, he is the vigorous hybrid of the scientific age. He is an extraordinary individual with great physical endurance and intellectual accomplishment. He refers to himself as a "hybrid" and asserts his superiority to pure-bred humans.
The short story "Tonio Kröger" by Thomas Mann describes the fate of man whose mother was Italian in a close-minded North German town. Tonio Kröger is described as having superior characteristics because of the fusion of physical attributes and cultures, as well as superior intelligence. Ultimately, he is forced to leave his hometown (echoes of the tragic mulatto) due to the intolerance of his neighbors.
William Faulkner's Light in August character Joe Christmas can also be seen as a comment on hybrid vigor.
See also
References
- HYBRID VIGOR IN PLANTS AND ITS RELATIONSHIP TO INSECT POLLINATION - a section from Insect Pollination Of Cultivated Crop Plants by S.E. McGregor, USDA
- F1 Hybrids General Discussion - professor's notes from a Oregon State University course
- Hybrids & Heirlooms - an article from University of Illinois Extension
- Mingroni, M.A. (2004). The secular rise in IQ: Giving heterosis a closer look. Intelligence 32: 65–83.
- Nagoshi, C. T. & Johnson, R. C. (1986). The ubiquity of g. Personality and Individual Differences 7: 201–207.
