Evening star., 1935-10-19

An Eden of time was the dawn age
of the biologists, 100000 years ago.
Then appeared almost contempora-
neouSly the mammals, the birds, most of
the insects and the Towering plants.
Practically all the orders known today
emerged at that time and. with the sin
gle exception of man. no significant new
type has been developed since. Also
still with the possible exception of man
there is very little possibility that any
of the existing orders of life will give
rise to anything new. Everything is too
specialized.
Such are the conclusions of Dr. Robert
Broom, presented recently before the
South African Academy of Sciences,
based larged on his studies of the large
variety of fossil reptiles contained in the
so-called Karoo shales. Here are to be
found the bones of some of the crea-
lures who became the ancestors of the
warm-blooded animals.
ut almost looks" he says. "as if the
world in eocene times came under q
new management. The percentage of
carbonic acid gas in the atmosphere may
nave become appreciably reduced when
the land became covered with grass.
llC pCSdli W ChOA'C ouA "a 40
ingly in many directions. and by the
middle of the eocene all the known or
derS were established"
The progress of organic evolution from
the beginning, Dr. Broom holds, has
been by mighty jumps instead of by i'm
perceptible changes. There have been
periods of intense activity, probably in
duced by meteorological changes, fol-
L., 81 ., 1;aI,
nothing has happened. Somewhere
toward the end of the carboniferous
period. approximately 250000,000 years
ago, the reptiles made their appearance.
They continued the dominant creatures
on earth for almost 160,000,000 years.
There was considerable specialization
and adaptation to the various habitatS
the world afforded, but there were no
new orders. The dinosaurs. the ichthyo-
saurs, the pleSioSaurS and the flying
pterodactyls could not give rise to any
thing new. Sometime in the upper
triassic, about 10000, 900 years ago, the
first mammals made their appearance,
developing from the least specialized
order of the reigning reptiles. But for
more than 100000 years they were
barely able to exist in competition with
the cold-blooded, Scaly monsters.
Then, at the very beginning of the
eocene, or possibly little before. the
great reptiles disappeared and the man.
mails underwent, probably in a compar-
atively few generations, their major de-
velopment and diversification. All the
orders known today appeared - the
pouchee marsupials, the hoofed animals,
the carnivores, the insectivores from
which man is supposed eventually to
have arisen, the bats, the primates, the
whales, the seals and the edentates.
The great diversification stopped almost
as abruptly as it started.
The story of the birds Is very similar.
The first birdlike creature, the archae-
opteryx, lived at about the middle Of
the jarrasic geological period-about
$50, ,0O00 900 years ago. For the next
100000 years there was practically no
change, until the great squirt came at
the start of the eocene. Every known
order of birds evolved at that time, ex-
cept, possibly, the parrots and the pig
cons. For 100000 years there has
been no notable evolution of birds
only increasing specialization.
The great diversification and spread
Of Towering plants came only few mil
lion years before the critical period in
the history of the birds and mammals.
Dr.. Broom thinks they may have been