JAMA Revisited March 5, 1898
Quantitative Heredity The usual views of hereditary transmission of qualities from parent to child have been contentedly vague as to the exact amount derived from either parent or grandparent or more remote ancestor. It has been probably assumed by most of those who have given any thought to the subject that such calculations were impossible or that at least that the laws governing such transmission depended upon so many and so different conditions as yet, and probably long to be, unknown to us, that it was useless to try to seek them out. We know as physicians that certain pathologic heredities are more or less special to one or the other sex, that in some prominent instances a feature or cast of countenance, mental or moral trait seem to be a family characteristic, while in others there is apparently nothing to indicate descent in the way of family traits or features. Once in a while a known ancestral character makes its appearance, having skipped one or more generations, and to this we give the name of atavism and leave further explanation as useless or impracticable. The hitherto recognized laws of heredity are few and hardly touch the question on its quantitative side; the distribution of ancestral traits has been considered to be too capricious as a rule to afford the data for generalizations in this particular direction, at least in the human species, where all matters involving faculty or capacity are so much more complex than in the lower animals. Several years ago Mr. Francis Galton, one of the most active investigators of this subject, published a theory of heredity that takes account especially of the respective portion due to each parent and ancestor. Counting the total of the organism as 100, he held that one-half, or 50 per cent., is derived from the progenitors, one-half of this from each parent. They in turn derive half their traits and features from their respective parents, and so on to the most distant ancestral relative. Any individual may therefore be reckoned as owing one-quarter of his peculiarities to each of his parents, and through them one-sixteenth to each of his four grandparents, one-sixty-fourth to each of his eight great-
Editor’s Note: JAMA Revisited is transcribed verbatim from articles published previously, unless otherwise noted. 866
grandparents, and so on in a continually decreasing ratio to his remotest forefathers. In a more recent publication Galton has given facts confirming this theory which were derived from a study of a well-known breed of dogs showing certain markings and peculiarities that facilitated this particular line of inquiry, and it may perhaps be accepted as a fairly probable working hypothesis. What is true of the lower animals is also within certain limits applicable to the higher ones and from this point of view Galton's theory is of interest to us as physicians. It will help us to a provisional estimate at least of the possibilities and dangers of intermarriage, of the risks of inherited disease, etc. One consideration, however, must not be overlooked; it must not be assumed, to use a somewhat vulgar comparison, that the cards are thoroughly shuffled at each re-deal, that the transmission of qualities is general rather than special in every individual case. The inheritance transmitted from parent to child may be in large part that which the former received from his ancestor; this is the basal fact of evolution and of the perpetuation of species as well. We see it in the family features transmitted through many generations, of which the Hapsburg lip and the Bourbon nose are historic examples. This fact, however, is perfectly compatible with Galton's theory of heredity, though it would probably so complicate the observations that it might sometimes make it the more difficult of confirmation in carrying out the investigation in the higher animals and especially in applying the theory to the heredity of human faculties and traits. It would be of especial interest could we also find some law that governs the apparently so capricious selection of qualities in inheritance, irrespective of the amount derived from either parent, but that is a problem for the future. Galton's theory, if it is capable of being sufficiently demonstrated as a fact, is certainly a valuable addition to our resources for the study of heredity, not only in a general scientific point of view, but also in all appearance and probability in its special application to the facts of hereditary disease. JAMA. 1898;30(10):559-560.
Section Editor: Jennifer Reiling, Assistant Editor.
JAMA February 26, 2014 Volume 311, Number 8
Copyright 2014 American Medical Association. All rights reserved.
Downloaded From: http://jama.jamanetwork.com/ by a Ndsu Library Periodicals User on 05/17/2015
jama.com
Quantitative Heredity The usual views of hereditary transmission of qualities from parent to child have been contentedly vague as to the exact amount derived from either parent or grandparent or more remote ancestor. It has been probably assumed by most of those who have given any thought to the subject that such calculations were impossible or that at least that the laws governing such transmission depended upon so many and so different conditions as yet, and probably long to be, unknown to us, that it was useless to try to seek them out. We know as physicians that certain pathologic heredities are more or less special to one or the other sex, that in some prominent instances a feature or cast of countenance, mental or moral trait seem to be a family characteristic, while in others there is apparently nothing to indicate descent in the way of family traits or features. Once in a while a known ancestral character makes its appearance, having skipped one or more generations, and to this we give the name of atavism and leave further explanation as useless or impracticable. The hitherto recognized laws of heredity are few and hardly touch the question on its quantitative side; the distribution of ancestral traits has been considered to be too capricious as a rule to afford the data for generalizations in this particular direction, at least in the human species, where all matters involving faculty or capacity are so much more complex than in the lower animals. Several years ago Mr. Francis Galton, one of the most active investigators of this subject, published a theory of heredity that takes account especially of the respective portion due to each parent and ancestor. Counting the total of the organism as 100, he held that one-half, or 50 per cent., is derived from the progenitors, one-half of this from each parent. They in turn derive half their traits and features from their respective parents, and so on to the most distant ancestral relative. Any individual may therefore be reckoned as owing one-quarter of his peculiarities to each of his parents, and through them one-sixteenth to each of his four grandparents, one-sixty-fourth to each of his eight great-
Editor’s Note: JAMA Revisited is transcribed verbatim from articles published previously, unless otherwise noted. 866
grandparents, and so on in a continually decreasing ratio to his remotest forefathers. In a more recent publication Galton has given facts confirming this theory which were derived from a study of a well-known breed of dogs showing certain markings and peculiarities that facilitated this particular line of inquiry, and it may perhaps be accepted as a fairly probable working hypothesis. What is true of the lower animals is also within certain limits applicable to the higher ones and from this point of view Galton's theory is of interest to us as physicians. It will help us to a provisional estimate at least of the possibilities and dangers of intermarriage, of the risks of inherited disease, etc. One consideration, however, must not be overlooked; it must not be assumed, to use a somewhat vulgar comparison, that the cards are thoroughly shuffled at each re-deal, that the transmission of qualities is general rather than special in every individual case. The inheritance transmitted from parent to child may be in large part that which the former received from his ancestor; this is the basal fact of evolution and of the perpetuation of species as well. We see it in the family features transmitted through many generations, of which the Hapsburg lip and the Bourbon nose are historic examples. This fact, however, is perfectly compatible with Galton's theory of heredity, though it would probably so complicate the observations that it might sometimes make it the more difficult of confirmation in carrying out the investigation in the higher animals and especially in applying the theory to the heredity of human faculties and traits. It would be of especial interest could we also find some law that governs the apparently so capricious selection of qualities in inheritance, irrespective of the amount derived from either parent, but that is a problem for the future. Galton's theory, if it is capable of being sufficiently demonstrated as a fact, is certainly a valuable addition to our resources for the study of heredity, not only in a general scientific point of view, but also in all appearance and probability in its special application to the facts of hereditary disease. JAMA. 1898;30(10):559-560.
Section Editor: Jennifer Reiling, Assistant Editor.
JAMA February 26, 2014 Volume 311, Number 8
Copyright 2014 American Medical Association. All rights reserved.
Downloaded From: http://jama.jamanetwork.com/ by a Ndsu Library Periodicals User on 05/17/2015
jama.com
