Body-Build and Its Inheritance

Part I. Build, Its Definition and Its Ontogeny 3

A. General considerations 3

Types of variation in build 4

The measurement of build 4

Ontogenetic 4

Adult 5

Sexual differences in build 5

Racial differences in build 7

Geographical differences in build 7

B. The ontogeny of build 8

Materials and methods 8

The ontogenetic curve of build 11

Later ontogenetic changes in individual build 16

Relation of juvenile to adult build 19

Part Ii. Mass Studies in Heredity of Adult Build 22

Methods and materials 23

The adult index of build 24

Classification of build 26

Significance of variations in build 28

Diseases in relation to build 29

Mass study of variation and heredity in build 36

Regression of progeny toward mediocrity 37

Hypothesis 40

Mate selection in build 44

The basal tables 46

Part Iii. Family Studies in Heredity of Build 51

A. Statement of problem 51

B. Discussion of special matings 51

CLASS I. Both parents slender 51

Mating 1. One parent is very slender of slender stock; the other slender 51

Mating 2. Both parents are slender, of slender stock 53

Mating 3. Other slender × very slender matings 54

Mating 4. Other slender × slender matings 56

Summary of slender × slender matings 68

CLASS II. Both parents fleshy 69

Mating 1. One parent is very fleshy, the other fleshy of fleshy stock 69

Mating 2. Both parents fleshy of fleshy stock 77

Mating 3. Other very fleshy × very fleshy matings 80

Summary 85

CLASS III. Mating of slender with fleshy stock. The F₁ generation 86

Mating 1. One parent slender, of slender stock, the other fleshy of fleshy stock 86

Mating 2. Other slender × fleshy matings 93

Mating 3. Very slender × very fleshy 97

Mating 4. Slender × very fleshy matings 98

Summary 105

CLASS IV. Matings of probably heterozygous parents. The F₂ generation 107

Mating 1. Both parents either medium or fleshy, and probably carrying gametes for slenderness as well as fleshiness 107

Mating 2. Other medium × medium matings 118

Summary and discussion 119

CLASS V. The back cross 119

Mating 1. Heterozygous medium or fleshy × slender 119

Mating 2. Fleshy × heterozygous fleshy parents 132

Summary and discussion 140

C. General discussion 141

Heredity and environment in build 141

Endocrine glands as links between chromosomes and somatic qualities 145

Evidence of segregation in the heredity of build 146

On the number of factors involved in fleshy build 149

D. Summary of conclusions 152

Appendix 155

Literature cited 175

Plates 177

BODY-BUILD AND ITS INHERITANCE

BY CHARLES BENEDICT DAVENPORT Director of Department of Genetics, Carnegie Institution of Washington

PART I.. Build, Its Definition and Its Ontogeny.

BUILD, ITS DEFINITION AND ITS ONTOGENY.

A. GENERAL CONSIDERATIONS.

If a hundred men of about the same stature be compared, it is seen that they vary greatly in weight. At the same time they vary in form, and especially in bulk. This variation is popularly recognized by the variety of terms applied to build. It may be of interest to pause a moment to consider popular terminology relating to build. We have, first, terms expressing a marked deviation below the normal build. We speak of persons as “slender,” “thin,” “gaunt,” “slim,” “slight,” “spare,” “lank,” and “spindling.” These terms are not exactly synonyms. “Lank” implies angularity; “gaunt” connotes the ravage of disease; “thin” connotes a loss of weight; “slight” connotes lightness and smallness of bone; “spindling” is used especially of youth in the period of rapid growth preceding adolescence; “slim” has a faint connotation of insufficiency; “slender” best expresses the idea which we shall want to use in this work where we have a relatively small interest in stature and where we wish to avoid connotation of disease, developmental changes, etc. In other languages there exists a series of terms which similarly differ slightly in connotation. Thus, in French, there is “maigre,” in German “mager,” which often connote a loss of weight through disease, “dünn,” which connotes loss of a former more nearly average weight, and “schlank,” which is close to the English “slender.” On the other hand, the English language contains a variety of terms applicable to deviation in build above the average. Thus we have the words “stout,” “portly,” “fleshy,” “corpulent,” “thick-set,” “obese,” “chubby,” and “fat.” The word “stout” usually carries a connotation of vigor. The term “portly” connotes large size with a tendency to excessively great circumference. “Fleshy” is nearly synonymous with “portly” but has less connotation of majesty of size. “Corpulent” usually carries a connotation of abdominal enlargement. “Thick-set” implies a large bony frame. “Obese” frequently connotes excessive, strictly pathological, increase of build. “Chubby” is applied especially to infants. “Fat” connotes excessive production of fat in the body, as opposed to an unusually large muscular development. Perhaps of all of these terms “fleshy” is as satisfactory as any as an expression for build without connotation in respect to degree or source of great weight, whether due to fat, muscle, or bone. In the German language there are the terms, “plump,” and “schwerfällig,” which serve to express large build. In the French language there are the terms, “gros,” “obese,” and “embonpoint,” which is near to the English equivalent “stout” or “fleshy.” In the present work the term “fleshy” is used, despite its slight suggestion of muscular development merely, largely because it begins with a different letter from slender. The word “slender” will be used for the other extreme of build. It has been found convenient to indicate those terms by their initial letters “S” and “F” respectively.

Our main problem is, in how far does this difference in build between slender and fleshy persons depend on constitutional factors?

TYPES OF VARIATION IN BUILD.

Two types of variation in build have to be distinguished: (a) the ontogenetic change in normal build during development with increasing stature, and (b) the change in weight in adults of relatively invariable stature. In type a, stature and other proportions are rapidly changing, but in type b, stature remains constant, and, throughout the race, stature does not differ as much in mature persons as it does from birth to maturity. These two types follow different laws and must be studied by different methods. Consequently they are considered in distinct parts of the present paper.

THE MEASUREMENT OF BUILD.

It is now necessary to consider how build may best be expressed quantitatively. The subject of the best index of build has been much discussed, but without sufficiently differentiating between the two types of variation in build, the ontogenetic and the adult. One of the latest authors to consider the matter is Bardeen (1920, p. 486), who mentions the desirability of recording the volume of the body as a whole, notes its impracticability, and concludes that we may estimate volume from weight. It may, however, be doubted if volume is really involved in the popular notion of build. At least, it is equally probable that the idea of build, as popularly conceived, is a relation of transverse to vertical diameters. When I look at a man, or a photograph of one as in plate 1, and think, “he is slender,” it is because I make a mental comparison of his breadth (of shoulders or chest) with his height and find that his breadth in comparison with that of most men I know of that height is small; or if he is stout the diameter of the chest is large in relation to stature (plate 2). It seems probable that breadth in relation to height gives the best expression of the popular idea of build. By the use of this relation, build can be easily expressed for any age, since chest circumference (which bears a nearly constant relation to chest diameter) has been recorded for many persons of all ages.

Ontogenetic.—Since in so many children and young people the stature and chest circumference have been measured, it is possible to use these data in finding the law of normal ontogenetic changes in build from birth to maturity. This ratio, chest-girth ÷ stature, has thus been used in discussing this law, as more fully described in section B. This relation can be used for tracing the change in build of the same developing child or for tracing the average change of build.

Adult.—In the study of adult changes of build we start with the condition that in the individual the stature is fixed. Consequently, in an individual whose weight is changing, the relation of the build at a years is to that at another period n years later as chest-girth at a years : chest-girth at a + n years. Thus, in the adult period, changes of build are proportional to chest-girth. In different persons, of differing stature, the stature has to be taken into account, and the differences in build are measured by the relation of relative chest-girth as in children. Unfortunately, in our study of heredity in adult build, we usually do not know the chest-girth of the different members of the family, but only their stature and weight. Our problem is, then, to find a relation between chest-girth and weight that will enable us to infer the one from the other. This problem will be further considered in a later section (p. 24).

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