Evening star., 1938-07-21
OF STARS,
MEN AND ATOMS
Notebook of Science PROGRESS
in Field, Laboratory
and Study.
By THOMAS r. HENRY


The human species is subject to
mutation-the sudden appearance OF
characters without any discoverable
hereditary background but which them
selves are inherited by persons de-
scendants.
For the most part, these acquisitions
of the race are bad and lead to dis
ability Of the individual. In natural
societies they probably would bring
about extinction, since their possessors
could not compete efficiently in the
struggle for existence. In human So
ciety they are protected and may estab-
lish family lines.
Two Of these acquisitions are mentioned
in the recent report to the President on
population trends in the United States
by the National Resources Committee.
One is a condition known as crab
claws" the name describing the defect.
Another is the curious defect known as
achondroplasia, the victim of which has
a normal body but very short arms and
legs. Various types Of blindness have
been known to arise in human beings
by mutation.
Mutation in man cannot be neglected
as source Of handicapping characters"
concludes the report.
On the other hand, it can be con-
sidered as evidence that the evolution
of man has not reached stalmate,
that mutations in a beneficial as we'll
as detrimental direction are still pos
sible so long as man is not in perfect
adjustment to his environment, and that
the race of the distant future may be
quite different biological variety than
man of today. The mechanism of
mutation is still only vaguely under
stood. Presumably, such fixed, heredi-
table changes in the human protoplasm
are very rare, but with countless num-
bers of generations the potentialities for
good and bad are almost infinite.
In lower animals. such as fruit flies
and plants, mutations can be induced
experimentally by X-radiation, by ultra
violet light and by various chemicals.
In immense experimental populations
they also occur spontaneously in large
numbers and are mostly deadly in their
effects. The remote chance OF an ultra
violet ray or even a cosmic ray making
a direct hit in a gene, extremely minute
unit Of inheritance, may afford one ex-
planation for these natural changes
and the same might be true for man.
A fruit fly, 1t is estimated, has ap-
proximately 5000 Of these minute
particles as targets. They are split up
into four bundles, or chromosomes. The
number in man cannot even be estl-
mated. He has "a bundles Of them and
perhaps $4,000 to 10000 Of the units
themselves, whose actions and inter-
actions determine so many of his
physical and mental qualities.
The action of the gene can be
changed in various ways. One is per-
haps by direct hit, or injury of some
kind, which changes its chemical make
up Another is the breaking Of a
chromosome The genes in each bundle
are known to interact with each other
and when they are scattered the posi-
bility of this interaction is diminished or
lost New combinations may be formed
which result in new characters Then
there is the newly discovered action OF
the chemical colchichine. obtained from
crocuses, which mysteriously doubles the
number of the chromosomes and has
been made experimentally to produce
beneficial mutations in plants.
Mutations in man doubtless are much
from any statistical survey. One reason
born The mechanics of life are finely
adjusted and not much maladjustment
is needed to stop the wheels altogether.
The chances are highly in favor OF
mutation producing such decided NAL
adjustment that that individual does
not live long enough actually to come
into the world. Still other mutants will
die in early infancy and others will be
hidden away as lifelong invalids in in
stitutions. Only the few whose heredi-
tary peculiarities are not too disabling,
or which may even be beneficial, sur
vive to be counted. Some day science
may be able to produce human muta-
tions. This now appears fantastically
long way off, but probably even more
distant is the day when anybody will
be in a position effectively to direct
ahead the biological course of mankind.
Lamentably little is known about
human heredity, the report of the Ma
tional Resources Committee points out.
It is the factor about which the least
can be done in any effort to control
the future population of the United
States. A very few definite disabilities,
Affecting relatively small numbers, are
known to be transmitted from parents
to children. Concerning some, about
which biologists were almost certain a
few years ago, there now are grave
doubts.
Still, says the report, "the Importance
Of human heredity in producing handi-
Gaping characters is attested by the
fact that more than 120 types of heredi-
tary variations of the eye and its access
sories, most of them pathological, are
listed. There have been reported about
275 apparently hereditary human condi-
tions."
Contrary to popular belief" the re-
port continues, hereditary diseases
may have their onset at any time from
fertilization to senility. Some are con-
genital, developed prior to and recog-
nizable at birth. Some Of these are club
foot, harelip, some types of cataract and
albinism. Others, including other types
OF cataract and muscular atrophy, usu-
ally have their onset during youth. Still
other hereditary disabilities, including
other types of cataract, usually make
their opnooroy,ca ", ,,.iJlln NE