Galton's Laws of Heredity

GALTON'S LAWS of heredity (Galton) were established by him on the basis of statistical research. There are two of them: the first, so-called "law of regression" (1889), and the second-"law of inheritance from ancestors" (1897). The law of regression (law of filial regression) states that if parents deviate from the average value of a trait for a given population, their children will deviate from the average in the same direction but to a lesser extent. Therefore, outstanding parents cannot expect to have children who are equally outstanding, while parents of little value (in terms of giftedness) avoid the danger of having children who are equally of little value. This law was derived by Galton from the study of the height of 205 pairs of parents and 930 of their adult children. The result of this research is as follows (in English inches): Average height of parents 64.5, 65.5, 66.5, 67.5, 68.5, 69.5, 70.5, 71.5, 72.5 Average height of children 65.8, 66.7, 67.2, 67.7, 68.3, 68.9, 69.5, 69.9, 72.2 In each group of parents with height below average (68.5), children turn out to be taller than their parents, while in each group of tall parents, children are shorter than them. On average, children inherited from their parents only ²/3 of the amount by which parents deviated from the average height of the entire population, while one third was regression, as if a return to the average height. This law was also verified by Galton on sweet peas-the weight of seeds was studied, showing regression in ²/₃. The law of inheritance from (more distant) ancestors (law of ancestral inheritance), theoretically developing the first, explains regression by the fact that the characteristics of children are determined not only by parents but also by more distant ancestors. Each of us has 2 parents, 4 grandparents, 8 great-grandparents, etc. The average height of this multitude of ancestors is equal to the average height of the entire population, which forces children to regress to the average height. Galton assumed that in the formation of the hereditary mass, both parents contribute ¹/₂, four grandparents-¹/₄, and so on, i.e., a series is obtained, the sum of which in the limit equals 1. This law was confirmed by G. through the study of inheritance of "piebald coloring" in the tricolor breed of piebald dachshunds. Theoretical calculations coincided with the observed facts. At present, the phenomena that served Galton to establish his laws stand before us in a completely different form. If it is true that tall people have shorter children, while short people have taller children than their parents, this may depend on two reasons. Firstly, because the category of "tall" parents includes those who are tall for genotypic reasons, and those who are tall only phenotypically. Since phenotypic traits, according to the teaching of most modern geneticists, are not inherited, it should be assumed that children of phenotypically tall parents will return to the height that corresponds to their genotype. The more homogeneous the genotype of the people being compared, the stronger the regression will be, and in pure lines it will reach 100%, and the offspring of the tallest and the offspring of the shortest will be the same. In the presence of long-term modifications, this return may be delayed for 1-2 generations, but it will still occur. On the other hand, if parents are genotypically tall, they will give children based on Mendelian laws. Davenport showed that in humans, height depends on several genes, but that tall height is largely recessive, while short height is dominant. Therefore, in short people, some children will be short, and some (extracted recessives) will be tall or of average height, while tall parents will not have children of short height. In other words, the degree of regression on the basis of splitting will be different from the side of short groups and from the side of tall groups, and any attempt to give a general formula for this regression (e.g., inherited ²/3, regression ¹/3) is doomed to failure. Even less compatible with modern genetics is the second law. The "hereditary mass" in the form of chromosomes reaches a person equally through the egg and through the sperm. The chromosomes that came from parents were also in grandparents and great-grandparents; therefore, it is impossible to say that among the chromosomes of a given person, some are paternal, some are grandpaternal, some are great-grandpaternal, etc. And if in offspring appear traits that were not in parents but were in grandparents and great-grandparents, then any general formulation of this phenomenon can be given only for some ideal example.