The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1908-07-25
HEREDITY SHOWN IN HAIR.
Why Some Have Straight and Others
Curly Locks.
Literary Digest.)

Literary Digest)
Data that appear to make il possible
to predict from the hair of parents the
form of hair of the children-that is.
whether it will be straight, wavy. curly
or 'kinky"-have been gathered by
Gertrude and Charles Davenport of the
Carnegie institutions station of ex-
perimental evolution at Cold Spring
Harbor. N. Y The collection of these
data and the writer's inference from
them are described in an article entitled
Heredity of Hair-form in Man in the
American Naturalist. The writer's de-
scribe at the outset the various NOR
biological types shown by human hair
They say:
Between straight hair. on the one
hand, and woody hair on the other
there are all degrees of closeness of
spiral For convenience three interme-
dlate grades may be recognized; wavy,
having very slight or open spiral in
yoiving the entire hair from root to
TIP; curly, having a closer spiral in
volving the distal half of the hair: and
friZZy or kinky, a close, tight spiral of
small diameter. Now, although the
conditions thus named are not discon-
tinuous, they stand for types that are
fairly well appreciated and distin-
guished popularity, so that in a ran
dom lot of people practically all would
place a given sort of hair in the same
category.
Types of Hair-Form.
These different types of hair-form
are associated with certain differences
of the hair on crOss-SectiOn as well as
in its method of growth Thus straight
hair is nearly circular on cross-section
while in woolly hair the cross-section
| is elliptical and the long axis is to the
short as 100.40 or 100.50 In wavy hair
the proportions are as 10000 or 30. The
straight hair of the japanese has the
proportion of 100.S5.
Since the hair of most mammals is
straight and nearly circular on cross
section, we may regard this as the
basal condition and the fiattened hair
as specialized form marking an ad-
vance in the differentiation of axes. In
addition to this difference in cross-sec-
| ton hairs differ in the form of the hair
follicle, which is in woOlly hair not
| only fiattened, but curved in an arc
| through quarter of "a circle. Emerg-
| ing from an incurvated mold. il can
| only continue to roll up outside, given
especially its fiattened shape; il rolls
up into a spiral the plane of which, at
| the beginning. is perpendicular to the
surface of the skin. AS all gr2dations
exist between straight hair and wool
| in other characters, so probably in the
| initial curvature. The intermediate ma
ture of waviness is probably due to an
| intermediate degree of curvature be-
| intermediate degree of curvature be-
| follicle, again, is a departure from the
| usual mammalian condition and is in
| the line of differentiation or advance.
Data Collected.
we are now in a nOsitjon tn forum
late our problem. How do the more
] specialized types of hair-form-much
| fattened and much curved woolly hair
and slightly f1attened slightly curved
wavy hair-behave in heredity toward
each other and toward the nearly cylin-
drical straight hair?
| THE data for this study include the
ancestral characteristics of about SOC
children for two ascending generations
About 230 families are involved"
The data collected by the Davenports
indicate strongly that, as between
straight and spiral hair. the latter is
the dominant form. Regarding wavy
| hair. they conclude that ii carries bo.h
straight and curly germ cells. The re-
| suits of their study they formulate as
follows combining them in part with
those obtained for eye color by the
same methods:
Two blue-eyed STRAIGHTFORWARD par
ents will have only blue-eyed. straight
| haired children. Two wavy-haireC
parents may have straight, wavy oil
curly-haired children. but the chances
for curly hair are slight. Two curly
haired parents may have children with
either straight. wavy or curly hair. and
the proportion of curly-haired offspring
will probably be large"