Chapter VII: Part II: Mass Studies in Heredity of Adult Build (2)

Considering next the table of total progeny of the various matings, it appears that the average number of children with recorded build from the recorded matings is variable. In descending order the fecundity of the matings is shown in table 14. This table shows that larger families, on the average, were derived from fleshy parents than from slender parents. Thus the F × F matings yield 2.3 times as many children, on the average, per mating as the S × S matings.

TABLE 14.—_Average number of progeny yielded by each type of mating (based on table 12)._

+-------+---------+-------+---------+
|Mating.| No. of |Mating.| No. of |
| |children.| |children.|
+-------+---------+-------+---------+
|VS × F | 5.00 | S × F | 3.16 |
| F × F | 4.72 | S × VF| 3.09 |
|VF × VF| 4.29 | S × M | 3.03 |
| M × VF| 3.70 | M × F | 2.98 |
| M × M | 3.55 |VS × S | 2.75 |
|VS × M | 3.50 | S × S | 2.04 |
| F × VF| 3.45 | | |
+-------+---------+-------+---------+

REGRESSION OF PROGENY TOWARD MEDIOCRITY.

Galton pointed out, in the case of stature, that, since correlation between parents and progeny is not perfect, the progeny of selected parents will tend to be less extremely selected and hence more nearly mediocre than their parents. It has, indeed, been shown in my studies on stature (1917, p. 341) that the progeny of tall parents do not show this regression to mediocrity as much as the progeny of short parents. This was regarded as evidence that the gametes of tall parents carried fewer recessive allelomorphs than those of short parents; hence were genetically “purer” and comprise more recessive factors. What is the condition in respect to the varying indices of build?

The answer to this question is given in table 15, which in turn is based on table 12. This table shows for each of the 13 matings the average departure of the parents from mediocre build (which for the parents is 34.86) and the corresponding departure of their offspring from mediocre build (which for the progeny is 35.24). In the right-hand column of the table is given the difference between these two departures, which measures the amount of regression toward mediocrity on the part of the progeny. The results of the last column are shown graphically in figure 8.

TABLE 15.—_Average build and regression from parental average of the progeny of the various types of mating. Also matings arranged in order of regression. Sexes combined (based on table 12)._

+-------+--------+--------+--------+-----------+-------+-------+-------+
| | | | | | | Regression.|
| | | | Avg. | | Departure of | |
|Type of| No. of | No. of | build |Avg. build |parents|progeny| |
|mating.|matings.|progeny.| of |of progeny.| from | |
| | | |parents.| | mediocrity. | |
+-------+--------+--------+--------+-----------+-------+-------+-------+
|VS × S | 4 | 11 | 26.13 |28.55 ± .86| -8.73 | -6.69 | +2.04 |
|VS × M | 8 | 28 | 28.38 |32.18 ± .54| -6.48 | -3.06 | +3.42 |
|VS × F | 5 | 25 | 32.00 |35.04 ± .83| -2.86 | -0.20 | +2.66 |
| S × S | 23 | 47 | 29.77 |28.47 ± .24| -5.09 | -6.77 | -1.68 |
| S × M | 101 | 306 | 30.90 |34.01 ± .16| -3.96 | -1.23 | +2.73 |
| S × F | 49 | 155 | 33.85 |34.39 ± .22| -1.01 | -0.85 | +0.16 |
| S × VF| 11 | 34 | 37.91 |35.48 ± .51| +3.05 | +0.24 | +2.81 |
| M × M | 92 | 327 | 33.23 |34.79 ± .15| -1.63 | -0.45 | +1.18 |
| M × F | 114 | 340 | 36.45 |35.41 ± .16| +1.59 | +0.17 | +1.42 |
| M × VF| 30 | 112 | 40.68 |36.53 ± .38| +5.82 | +1.29 | +4.53 |
| F × F | 33 | 156 | 39.21 |37.56 ± .29| +4.35 | +2.32 | +2.03 |
| F × VF| 30 | 100 | 42.97 |38.49 ± .36| +8.11 | +3.25 | +4.86 |
|VF × VF| 7 | 30 | 47.43 |39.20 ± .78| +12.57| +3.96 | +8.61 |
| +--------+--------+--------+-----------+-------+-------+-------+
| Total | 507 | 1671 | 34.86 |35.24 | | | |
+-------+--------+--------+--------+-----------+-------+-------+-------+

Mediocrity for parents, 34.86.
Mediocrity for progeny, 35.24.

MATINGS ARRANGED IN ORDER OF REGRESSION.

+---------+-------+
| S × S | -1.68 |
| S × F | +0.16 |
| M × M | +1.18 |
| M × F | +1.42 |
| F × F | +2.03 |
| VS × S | +2.04 |
| VS × F | +2.66 |
| S × M | +2.73 |
| S × VF | +2.81 |
| VS × M | +3.42 |
| M × VF | +4.53 |
| F × VF | +4.86 |
| VF × VF | +8.61 |
+---------+-------+

Figure 8 shows clearly that, in spite of considerable irregularities, the line of regression descends from the matings of two very fleshy parents at the left, and in general from matings in which the average parental departure from the mean build of parents is positive, to the mating of two slender parents (or, less strikingly the VS × S mating) or in general to the matings in which the average parental departure is extremely negative. This result is most easily explained on the ground that whereas fleshy parents carry all sorts of gametes for build, slender parents carry a preponderance of gametes of their own kind; hence the progeny do not regress so much from the selected parental condition. This suggests that the slender parents are more nearly homozygous than the fleshy parents.

Still another test of the gametic composition of the parents is the variability of their offspring. The facts regarding such variability are given in table 16. From this table it appears that the mating that yields the least variable progeny is that of two slender consorts. The variability in their progeny is measured by 2.41 ± 0.17. The variability of the progeny of the VS × S mating is greater, 4.21 ± 0.61, but on account of the small number of the progeny the probable error is large, and it is possible that this difference in variability between S × S and VS × S progeny is not a significant one. Next to the least variable are the offspring of the M × M mating, 4.06 ± 0.11, and this leads to the conclusion that a large proportion of the M parents are not merely heterozygous, but constitute a “pure race” of medium build. The offspring of the S × F mating have a fairly small variability 4.13 ± 0.16, as befits a first generation (F₁) hybrid. On the other extreme, we have the M × VF mating with a standard deviation of 9.11 ± 0.41. This large standard deviation is due chiefly to the inclusion of one family (Ber-A) which contains 2 progeny of builds 79 and 103, weighing 180 kg. (400 pounds) and 215 kg. (475 pounds) respectively. Otherwise, the variability of this mating is not extreme. It is 5.25 ± 0.24. The next largest variability is from the VF × VF mating, 6.31 ± 0.55, a variability that is due to the absence of any important mode. The progeny of the VS × F mating are highly variable, 6.18 ± 0.59, but this standard deviation has the largest probable error of any except VS × S, so that great stress must not be laid upon its exact position. In general, the progeny of matings with 2 or 1 F or VF parents, belong to the more variable group and those with S (or VS) parents to the less variable group. The meaning of this is clear to the geneticist who has dealt with multiple factors. It indicates that some or all of the factors that make for fleshy build dominate to a greater or less degree over the factors for slenderness. The test of the regression of progeny toward mediocrity and the test of the variability of the progeny of the various matings thus lead to the same result—the factors for fleshiness are imperfectly dominant over those for slenderness, and the latter probably lack some or all of those factors that make for fleshy build.

TABLE 16.—_Progeny of the various types of matings arranged in order of variability or standard deviation (S. D.), together with the probable errors (P. E.) of the means and deviations; also the coefficients of variation (based on table 12)._

+-------+--------+-------------------+------------------+--------------+
|Type of| No. of | Mean build of |Standard deviation|Coefficient of|
|mating.|progeny.|progeny and (P. E.)| and (P. E.) | variability. |
+-------+--------+-------------------+------------------+--------------+
| S × S | 47 | 28.47 ± 0.24 | 2.41 ± 0.17 | 8.97 |
| M × M | 327 | 34.79 ± 0.15 | 4.06 ± 0.11 | 11.67 |
| S × F | 155 | 34.39 ± 0.22 | 4.13 ± 0.16 | 12.01 |
| S × M | 306 | 34.01 ± 0.16 | 4.20 ± 0.11 | 12.35 |
|VS × S | 11 | 28.55 ± 0.86 | 4.21 ± 0.61 | 14.75 |
|VS × M | 28 | 32.18 ± 0.54 | 4.22 ± 0.38 | 13.11 |
| M × F | 340 | 35.41 ± 0.16 | 4.27 ± 0.11 | 12.06 |
| S × VF| 34 | 35.68 ± 0.51 | 4.44 ± 0.36 | 12.44 |
| F × F | 157 | 37.56 ± 0.29 | 5.37 ± 0.20 | 14.30 |
| F × VF| 100 | 38.49 ± 0.36 | 5.38 ± 0.27 | 3.98 |
|VS × F | 25 | 35.04 ± 0.83 | 6.18 ± 0.59 | 17.64 |
|VF × VF| 30 | 39.20 ± 0.78 | 6.31 ± 0.55 | 16.10 |
| M × VF| 112 | 37.64 ± 0.58 | 9.11 ± 0.41 | 24.17 |
+-------+--------+-------------------+------------------+--------------+

HYPOTHESIS.

The foregoing brief studies of the progeny of classes of matings suggest the following hypothesis:

Fleshy build results from the action of several positive (dominant) factors that make for stoutness, while slenderness results from the absence of one or more of such factors, or is due to recessive factors. Fleshy parents may, and frequently do, carry gametes which lack the “fleshy” or carry the “slender” factor, while in slender parents for the most part the gametes carry only the slender factor, hence the gametes of slender parents are more nearly homogeneous. This hypothesis may be further developed as follows:

Assuming that there are two independent factors A and B for build, then these may be found in different zygotes in the following combinations:

AABB AaBB aABB aaBB
AABb AaBb aABb aaBb
AAbB AabB aAbB aabB
AAbb Aabb aAbb aabb

Or, disregarding order of the letters, and considering only the number and kind of genes in each kind of zygote, we have:

AABB 2AaBB aaBB
2AABb 4AaBb 2aaBb
AAbb 2Aabb aabb

in which the coefficients indicate the relative frequency of the different combinations.

We may assume that:

4 positive factors in a zygote correspond to a very fleshy person.
3 factors correspond to a fleshy person.
2 factors correspond to a person of medium build.
1 factor corresponds to a slender person.
0 factor corresponds to a very slender person.

Table 17 indicates the possible matings and their progeny.

TABLE 17.—_Percentage distribution of the progeny of the various matings, on the assumption that extreme fleshy build is dependent upon 4 zygotic factors in the parents._

+-----+-----+-------------+-----------+-------------------------------+
| | | | | Percentage of each number of |
|One |Other| Zygotic | Gametic | zygotes in progeny. |
| parent. | formulæ. | formulæ. +------+-----+-----+-----+------+
| | | | |0 (VS)|1 (S)|2 (M)|3 (F)|4 (VF)|
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| 4 | 4 | AABB × AABB | AB × AB | | | | | 100 |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| 4 | 3 | AABB × AABb |{ AB × AB }| | | | 50 | 50 |
| | | |{ AB × Ab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| | | AABB × AAbb | AB × Ab | | | | 100 | |
| | | | | | | | | |
| 4 | 2 | |{ AB × AB }| | | | | |
| | | AABB × AaBb |{ AB × Ab }| | | 25 | 50 | 25 |
| | | |{ AB × aB }| | | | | |
| | | |{ AB × ab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| 4 | 1 | AABB × Aabb |{ AB × Ab }| | | 50 | 50 | |
| | | |{ AB × ab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| 4 | 0 | AABB × aabb | AB × ab | | | 100 | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| | | |{ AB × AB }| | | | | |
| 3 | 3 | AABb × AABb |{ AB × Ab }| | | 25 | 50 | 25 |
| | | |{ Ab × AB }| | | | | |
| | | |{ Ab × Ab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| 3 | 2 | AABb × AAbb |{ AB × Ab }| | | 50 | 50 | |
| | | |{ Ab × Ab }| | | | | |
| | | | | | | | | |
| | | |{ AB × AB }| | | | | |
| | | |{ AB × Ab }| | | | | |
| | | |{ AB × aB }| | | | | |
| | | |{ AB × ab }| | | | | |
| | | AABb × AaBb |{ Ab × AB }| | 12.5| 37.5| 37.5| 12.5|
| | | |{ Ab × Ab }| | | | | |
| | | |{ Ab × aB }| | | | | |
| | | |{ Ab × ab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| | | |{ AB × Ab }| | | | | |
| 3 | 1 | AABb × Aabb |{ AB × ab }| | 25 | 50 | 25 | |
| | | |{ Ab × Ab }| | | | | |
| | | |{ Ab × ab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| | | |{ AB × ab }| | | | | |
| 3 | 0 | AABb × aabb |{ Ab × ab }| | 50 | 50 | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| | | AAbb × AAbb | Ab × Ab | | |100 | | |
| | | | | | | | | |
| | | |{ Ab × AB }| | | | | |
| | | AAbb × AaBb |{ Ab × Ab }| | 25 | 50 | 25 | |
| | | |{ Ab × aB }| | | | | |
| | | |{ Ab × ab }| | | | | |
| | | | | | | | | |
| | | |{ AB × Ab }| | | | | |
| | | AaBb × AAbb |{ Ab × Ab }| | 25 | 50 | 25 | |
| | | |{ aB × Ab }| | | | | |
| | | |{ ab × Ab }| | | | | |
| 2 | 2 | | | | | | | |
| | | |{ AB × AB }| | | | | |
| | | |{ AB × Ab }| | | | | |
| | | |{ AB × aB }| | | | | |
| | | |{ AB × ab }| | | | | |
| | | |{2Ab × AB }| | | | | |
| | | AaBb × AaBb |{2Ab × Ab }| 6.25| 25 | 37.5| 25 | 6.25|
| | | |{2Ab × aB }| | | | | |
| | | |{2Ab × ab }| | | | | |
| | | |{ ab × AB }| | | | | |
| | | |{ ab × Ab }| | | | | |
| | | |{ ab × aB }| | | | | |
| | | |{ ab × ab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| | | |{ Ab × Ab }| | | | | |
| | | AAbb × Aabb |{ Ab × ab }| | 50 | 50 | | |
| | | | | | | | | |
| | | |{ AB × Ab }| | | | | |
| | | |{ Ab × Ab }| | | | | |
| 2 | 1 | |{ AB × ab }| | | | | |
| | | AABb × Aabb |{ Ab × ab }| 12.5| 37.5| 37.5| 12.5| |
| | | |{ aB × Ab }| | | | | |
| | | |{ aB × aB }| | | | | |
| | | |{ ab × Ab }| | | | | |
| | | |{ ab × ab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| | | AAbb × aabb | Ab × ab | |100 | | | |
| | | | | | | | | |
| | | |{ AB × ab }| | | | | |
| 2 | 0 | AaBb × aabb |{ Ab × ab }| 25 | 50 | 25 | | |
| | | |{ aB × ab }| | | | | |
| | | |{ ab × ab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| | | |{ Ab × Ab }| | | | | |
| 1 | 1 | Aabb × Aabb |{ AB × ab }| | 50 | 50 | | |
| | | |{ ab × Ab }| | | | | |
| | | |{ ab × ab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| 1 | 0 | Aabb × aabb |{ Abab }| 50 | 50 | | | |
| | | |{ abab }| | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+
| 0 | 0 | aabb × aabb | | 100 | | | | |
+-----+-----+-------------+-----------+------+-----+-----+-----+------+

On the hypothesis of 6 zygotic factors for build, the possible combinations in the progeny are much more numerous. Seven classes of zygotic combinations are possible. We recognize in our work only 5 classes of build. Accordingly, it would be necessary to redistribute our classes of build into 7 or else assume that the two lowest classes are both comprised in “very slender” and the two highest in “very fleshy.” The former operation would require an amount of work hardly justified by the possible advantage; so the latter procedure was adopted as perhaps a sufficiently close approximation. The distributions are given in table 18 which is given in detail only in part.

TABLE 18.—_Percentage distribution of the progeny of the various matings on the assumption that extreme fleshy build is dependent on 6 zygotic factors in the parents._

+----------+-----------------------------------------------------------+
| No. of | |
|factors in| Percentage of each class of zygotic factors. |
+----+-----+---------+-------+--------+------+--------+-------+--------+
|One |Other| 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| parent. | | | | | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 6 | 6 | 100 | | | | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 6 | 5 | 50 | 50 | | | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 6 | 4 |{ |100 | | | | | |
| | |{ 25 | 50 | 25 | | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 6 | 3 |{ | 50 | 50 | | | | |
| | |{ 12.5 | 37.5 | 37.5 | 12.5 | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 6 | 2 |{ | |100 | | | | |
| | |{ | 25 | 50 | 25 | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 6 | 1 | | | 50 | 50 | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 6 | 0 | | | |100 | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 5 | 5 | 25 | 50 | 25 | | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 5 | 4 |{ | 50 | 50 | | | | |
| | |{ 12.5 | 37.5 | 37.5 | 12.5 | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 5 | 3 |{ 6.25 | 25 | 37.5 | 25 | 6.25 | | |
| | |{ | 25 | 50 | 25 | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 5 | 2 |{ | 12.5 | 37.5 | 37.5 | 12.5 | | |
| | |{ | | 50 | 50 | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 5 | 1 | | | 25 | 50 | 25 | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 5 | 0 | | | | 50 | 50 | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| | |{ 6.25 | 25 | 37.5 | 25 | 6.25 | | |
| 4 | 4 |{ | 25 | 50 | 25 | | | |
| | |{ | 25 | 50 | 25 | | | |
| | |{ | |100 | | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| | |{ 3.125 | 15.625| 31.25 | 31.25| 15.625 | 3.125| |
| 4 | 3 |{ | 12.5 | 37.5 | 37.5 | 12.5 | | |
| | |{ | 12.5 | 37.5 | 37.5 | 12.5 | | |
| | |{ | | 50 | 50 | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| | |{ | 6.25 | 25 | 37.5 | 25 | 6.25 | |
| 4 | 2 |{ | | 25 | 50 | 25 | | |
| | |{ | | 25 | 50 | 25 | | |
| | |{ | | |100 | | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 4 | 1 |{ | | | 50 | 50 | | |
| | |{ | | 12.5 | 37.5 | 37.5 | 12.5 | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 4 | 0 | | | | 25 | 50 | 25 | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| | |{ 1.5625| 9.375| 23.4375| 31.25| 23.4375| 9.375| 1.5625|
| 3 | 3 |{ | 6.25 | 25 | 37.5 | 25 | 6.25 | |
| | |{ | 6.25 | 25 | 37.5 | 25 | 6.25 | |
| | |{ | | 25 | 50 | 25 | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| | |{ | 3.125| 16.625 | 31.25| 31.25 | 16.625| 3.125 |
| 3 | 2 |{ | | 12.5 | 37.5 | 37.5 | 12.5 | |
| | |{ | | 12.5 | 37.5 | 37.5 | 12.5 | |
| | |{ | | | 50 | 50 | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 3 | 1 |{ | | 6.25 | 25 | 37.5 | 25 | 6.5 |
| | |{ | | | 25 | 50 | 25 | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 3 | 0 |{ | | | 12.5 | 37.5 | 37.5 | 12.5 |
| | |{ | | | | 50 | 50 | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| | |{ | | 6.25 | 25 | 37.5 | 25 | 6.25 |
| 2 | 2 |{ | | | | 50 | 50 | |
| | |{ | | | |100 | | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 2 | 1 |{ | | | 12.5 | 37.5 | 37.5 | 12.5 |
| | |{ | | | | 50 | 50 | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 2 | 0 |{ | | | | 25 | 50 | 25 |
| | |{ | | | | |100 | |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 1 | 1 | | | | | 25 | 50 | 25 |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 1 | 0 | | | | | | 50 | 50 |
+----+-----+---------+-------+--------+------+--------+-------+--------+
| 0 | 0 | | | | | | |100 |
+----+-----+---------+-------+--------+------+--------+-------+--------+

MATE SELECTION IN BUILD.

Statistics on temperament and stature of consorts (Davenport, 1915, p. 106; 1917, p. 329) seem clearly to show that there is an assortative mating in respect to these traits. The question arises: Is there assortative mating in respect to build? The inquiry is rendered the more difficult, inasmuch as build changes to such an extent with age. Nevertheless, as there appears to be a considerable correlation (though not yet calculated) between build at 25 and at 50 years, it is fair to assume that some degree of the mature build is already indicated at the period just before marriage.

If, now, there is no assortative mating in respect to build, we should find that persons of any given build, say slender, would have very slender, slender, medium, fleshy, and very fleshy consorts in the respective proportions in which such classes of build occur in the whole population of parents. A marked deviation from this expectation would indicate the falseness of this hypothesis and that there is an assortative mating in respect to build.

To test the hypothesis we can make use of 531 matings, including those which are employed in the main tables. We find the male and the female consorts in these matings to occur in the different classes in the numbers and proportions shown in table 19.

TABLE 19.—_Percentage distribution of parents of each sex among the various classes of build as found in 531 selected matings. Based on Appendix tables._

+----------+----------------------+----------------------+
| | Males. | Females. |
| +----------+-----------+----------+-----------+
| Classes. | | | | |
| |Frequency.| Per cent. |Frequency.| Per cent. |
+----------+----------+-----------+----------+-----------+
| VS | 22 | .38 | 18 | 3.39 |
| S | 97 | 18.27 | 127 | 23.92 |
| M | 230 | 43.31 | 210 | 39.55 |
| F | 158 | 29.75 | 120 | 22.59 |
| VF | 44 | 8.29 | 56 | 10.55 |
| +----------+-----------+----------+-----------+
| Total | 531 | 100 | 531 | 100 |
+----------+----------+-----------+----------+-----------+

In applying the test to the hypothesis we may assume in turn that the groom has done the selecting and that the bride has done the selecting. We then compare, in the selections made by the grooms, the expected proportion of the classes of build on the assumption of no assortative mating, with the proportions actually found in the brides. Similarly, with suitable changes for the selections made by the brides. The results are given in table 20.

TABLE 20.—_Percentage distribution of build of consorts selected by grooms and by brides belonging to each of the classes of build, and comparison with the standards of table 19._

P, percentages found or expected. E, percentage excess of found over expected.

+----------+-----------+----------+----------+----------+----------+---+
| | | | | | | T |
| | VS | S | M | F | VF | o |
| | | | | | | t |
| +----+------+----+-----+----+-----+----+-----+----+-----+ a |
| | P | E | P | E | P | E | P | E | P | E | l |
+----------+----+------+----+-----+----+-----+----+-----+----+-----+---+
| SELECTIONS MADE BY GROOMS. |
+----------+----+------+----+-----+----+-----+----+-----+----+-----+---+
|Expected | | | | | | | | | | | |
| build | | | | | | | | | | | |
| of | | | | | | | | | | | |
| brides, | | | | | | | | | | | |
| random | | | | | | | | | | | |
| selection|3.4 | |23.9| |39.6| |22.6| |10.6| |100|
| | | | | | | | | | | | |
|Selections| | | | | | | | | | | |
| by | | | | | | | | | | | |
| _slender_| | | | | | | | | | | |
| grooms |5.2 | +52.9|24.7| +3.3|37.1| +6.3|23.7| +4.9| 9.3|-12.3| |
| | | | | | | | | | | | |
|Selections| | | | | | | | | | | |
| by | | | | | | | | | | | |
| _medium_ | | | | | | | | | | | |
| grooms |3.5 | +2.9 |28.3|+18.4|40.4| +2.0|22.3| -1.3| 5.6|-47.2| |
| | | | | | | | | | | | |
|Selections| | | | | | | | | | | |
| by | | | | | | | | | | | |
| _fleshy_ | | | | | | | | | | | |
| grooms |3.2 | -5.9 |18.3|-23.4|40.5| +2.3|21.5| -4.9|16.5|+55.7| |
| | | | | | | | | | | | |
|Selections| | | | | | | | | | | |
| by _very | | | | | | | | | | | |
| fleshy_ | | | | | | | | | | | |
| grooms |0.0 | -100 |15.9|-33.5|38.6| -2.5|27.3|+20.8|18.2|+71.7| |
| | | | | | | | | | | | |
+----------+----+------+----+-----+----+-----+----+-----+----+-----+---+
| SELECTIONS MADE BY BRIDES. |
+----------+----+------+----+-----+----+-----+----+-----+----+-----+---+
| | | | | | | | | | | | |
|Expected | | | | | | | | | | | |
| build | | | | | | | | | | | |
| of | | | | | | | | | | | |
| grooms, | | | | | | | | | | | |
| random | | | | | | | | | | | |
| selection|0.4 | |18.3| |43.3| |29.8| | 8.3| |100|
| | | | | | | | | | | | |
|Selections| | | | | | | | | | | |
| by | | | | | | | | | | | |
| _slender_| | | | | | | | | | | |
| brides |1.59|+297.5|18.9| +3.3|51.2|+18.2|22.8|-23.5| 5.5|-33.7| |
| | | | | | | | | | | | |
|Selections| | | | | | | | | | | |
| by | | | | | | | | | | | |
| _medium_ | | | | | | | | | | | |
| brides |0.0 | -100 |17.1| -6.6|44.3| +2.3|30.5| +2.3| 8.1| -2.4| |
| | | | | | | | | | | | |
|Selections| | | | | | | | | | | |
| by | | | | | | | | | | | |
| _fleshy_ | | | | | | | | | | | |
| brides |0.0 | -100 |19.2| +4.9|42.5| -1.8|28.3| -5.0|10.0|+20.5| |
| | | | | | | | | | | | |
|Selections| | | | | | | | | | | |
| by _very | | | | | | | | | | | |
| fleshy_ | | | | | | | | | | | |
| brides |0.0 | -100 |16.1|-12.0|23.2|-46.4|46.4|+55.7|14.3|+72.3| |
| | | | | | | | | | | | |
+----------+----+------+----+-----+----+-----+----+-----+----+-----+---+

An inspection of tables 19 and 20 shows that the hypothesis that wives and husbands of men of each different class of build are merely random samples of the whole population of parents is not supported by the facts. Thus on the part of both very fleshy grooms and brides over 70 per cent more consorts, who will ultimately be very fleshy are selected than are expected on the hypothesis of random sampling. Also, among fleshy fathers there is a marked excess of very fleshy wives. Slender parents have an excess of similar consorts. Medium parents have selected consorts nearly at random so far as regards build. Slender parents have selected a smaller proportion of very fleshy consorts than expectation on random choice, and very fleshy parents have selected less than the average of very slender and slender consorts. In a word, there is some degree of assortative mating and, indeed, a mating of similars. This result agrees with the findings in respect to stature; similars tend to mate; while in the case of temperament, dissimilars tend to marry each other.

THE BASAL TABLES.

In the Appendix are given in tabular form details concerning the different types of matings, with some information concerning the grandparents, the sibs of parents, and the children. These are the tables that have been used for the mass study and from which table 11 was drawn up.[2] They will afford much of our data for the detailed Mendelian studies, and will be briefly considered in this section.

[2] The families in the tables of the Appendix which are marked by an asterisk (*) are not included in table 11. The reason is that they were selected families, usually because containing very fleshy persons. It was deemed undesirable to combine these selected families with the unselected families that make up most of table 11; a table which forms the basis for figure 7. To have included them would have distorted the form of that figure.

These tables are derived chiefly from the Records of Family Traits; some from special schedules and, in a few cases, from the A file of the Eugenics Record Office.

_Table I._—Mating of very slender, 1.50 to 1.75 metric (21 to 25
English) × very slender. This combination does not occur in our
506 standard matings.

_Table II._—Matings of very slender × slender, 1.80 to 2.10 (26
to 30). There are seven matings altogether. They yielded 20
progeny: 4 VS, 12 S, 2 M, and 2 F. Four-fifths of the progeny
thus fall in the parental groups; the distribution shows little
variability (fig. 9).

_Table III._—Matings of very slender × medium, 2.2 to 2.6 (31 to
36). 28 children derived from 8 matings have indices of build
as follows: 1 VS, 7 S, 17 M, 3 F. The mode of the progeny, as
compared with table 2, has shifted to the medium grade (fig. 10).

_Table IV._—Matings of very slender × fleshy, 2.6 to 3.0 (37 to
43). There are 5 matings. These yielded 25 progeny: 1 VS, 5 S,
10 M, 7 F, and 2 VF. The mode is at medium grade, but the whole
distribution is much more variable than in tables 2 and 3 (fig.
11).

_Table V._—Matings of very slender × very fleshy, 3.1 to 4.5 (44
to 64). There is only 1 mating in this class, so that no table
is formed. It is described in full on page 97. It produced 7
children: 3 S, 3 M, and 1 VF.

_Table VI._—Matings of slender × slender. There are 24 matings of
this type. They yielded 51 progeny: 5 VS, 35 S, 11 M. The mode
is strongly in the S grade; the progeny show relatively little
variability (fig. 12).

_Table VII._—Matings of slender × medium parents. There are 101
matings of this type. They yielded 313 progeny: 49 S, 200 M, 53
F, 11 VF. The mode is at medium; the progeny show rather low
variability (fig. 13).

_Table VIII._—Matings of slender × fleshy parents. There are 52
matings of this type. They yielded 179 progeny: 5 VS, 25 S, 85 M,
57 F, 7 VF. The mode is at medium: the progeny show rather low
variability (fig. 14).

_Table IX._—Matings of slender × very fleshy parents. There are
16 matings of this type. They yielded 50 progeny: 7 S, 18 M, 17
F, 8 VF. The progeny are very variable (fig. 15).

_Table X._—Matings of medium × medium parents. There are 93
matings of this type. They yielded 332 offspring: 2 VS, 40 S,
201 M, 82 F, 7 VF. The progeny are not very variable (fig.
16), indicating that all individuals of medium build are not
“heterozygotes”; but that there is also a “medium” race.

_Table XI._—Matings of medium × fleshy parents. There are 115
matings of this type. They yielded 346 offspring: 31 S, 210 M, 88
F, 17 VF. The progeny show an intermediate degree of variability
(fig. 17).

_Table XII._—Matings of medium × very fleshy parents. There are
30 matings of this type. They yielded 112 offspring: 2 VS, 7 S,
50 M, 36 F, 17 VF. The progeny show considerable variability
(fig. 18).

_Table XIII._—Matings of fleshy × fleshy parents. There are 33
matings of this type. They yielded 159 offspring: 15 S, 62 M, 61
F, 21 VF. The progeny show a rather high variability (fig. 19).

_Table XIV._—Matings of fleshy × very fleshy parents. There are
30 matings of this type. They yielded 146 offspring: 1 VS, 7 S,
52 M, 51 F, 35 VF. The progeny are very variable (fig. 20).

_Table XV._—Matings of very fleshy × very fleshy parents. There
are 7 matings of this type. They yielded 37 offspring: 1 S, 12 M,
11 F, 13 VF. The progeny are exceedingly variable (fig. 21).

The diversity of the distributions of the progeny of the various matings and the great difference in their variabilities indicates that there is not only an inheritance of tendencies to particular types of build, but also that there is a strong evidence of some sort of Mendelian inheritance.