Evening Star Newspaper, October 18, 1931, Page 95

_— — THE SUNDAY STAR, WASHINGTON, D. C, OCTOBER 18, 1931 This is what the landscape of Nebraska looked like 20,000,000 years age. as restored in a painting by Charles R. Knight, presented to the Field Musecum by Ernest R. Gra- ham. At the left are prehistoric camels, with small rhinoceFoses and dwarf horses in the left foreground. In front are gizantic prehistoric pigs, and at the right is a creas ture that was a sort of a cross between rhinoceros and horse. Interesting Nezw Theory of the Whys and the Wherefores of Animal Evolution, and How the Animals Spread Over the Earth to Find Their Present Habitats. BY DR. FRANK THONE. NE of the last writings by the late Prof. W. D. Matthew of the Uni- versity of California was an in- quiry into the causes of animal migrations and evolutions during the last hundred million years or so. He found, as the result of his years of study of animal evolution as discloscq by the fossil record, that there has been a sort of long rhythm in the development of life. There have been long, peaceful periods of uniform, mod- erate climate all over the earth, when animals have been pretty well satisfied with things as they found them and have not bothered to change much. Then there have come other periods of tur- moil and change—heaving up of mountains and plateaus, gathering snows on their tops turning into vast glaciers, climates no longer uniform but sliced up into zones; life no longer easy and comfortable, but full of change and un- certainty, so that a species must meet outer change with inner change or die. Three times at least, as Prof. Matthew read the record, have such major revolutions upset the earth, prodding the plodding steps of evo- lution into a jazzier tempo. Three such major revolutions, with other lesser revolutions in be- tween, some of them possibly more or less local in their effects. The first of these revolutions came a most unimaginably long time ago, long before the Age of Coal, long before the Age of Fishers that preceded it. What that revolution ended is unknown. What it started was a livelier de- velopment of the lower orders of life, and either the beginning or-—more likely—the energetic unfolding of the vertebrate family tree. Expressed at first only as fishes, this evolu- tion of the backboned animals got as far as the beginnings of the lowest land-dwelling, air- breathing animals, relatives of toads and sala- manders, before the second great revolution ended the epoch and initiated a new age. HE aristocracy of this second dispensation were the famcus dinosaurs. But while these ponderous gentry were ruling the earth and caring no whit about changes to come, meek little primitive mammals, weak of body but beginning to be nimble of wit, kept out of their way as well as possible and prepared to -inherit the earth. The dinosaurs had their day. but in the end they ceased to be. They ceased to be, perhaps, because the earth was coming to a long period of change, of mountain upheavals and plateau liftings, of “beginnings of zonation in climate that cul- minated in the most recent and perhaps the most severe of all the ice ages the earth has knewn. The world is still but half emerged from this ice age, for Greenland and Antarc- tica are still buried under permanent ice, and every Winter 2 wide snow cape spreads itself” over most of the temperate zones. The ages that stretched themselves between the end of the dinosaurs’ dominance and the melting away of the glaciers that covered most of Europe and more than half of North Amer- ica were times of the most rapid animal evolu- tion that the world has ever seen. Together they are lumped by geologists as “Tertiary” time. It is an old-fashioned name, and does not mean today what it did when first applied, but it is a convenient classification. But better than “Tertiary” is the name Age of Mammals. For it was during this time that the warm-blooded, milk-giving creatures, to which man himself as a physical being is re- lated, went through the series of changes that brought them to their present state. More swiftly than any other great class of animals ever evolved, the mammals deployed them- selves, tried out and discarded experimental models by the dozen and hundred, and at the end got down to something like 1931 designs. This speed in evolutionary change was due to a restlessness in the earth itself, Dr. Matthew believed. There was mountain building at in- tervals all during Tertiary time. Some of the greatest ranges, such as the Rockies, the Sierras and the Himalayas, were either lifted up entire- ly or received notable additions during that epoch. ATURALLY, with so much disturbance go- ing on, there must have been grave up- gets in the woodland and pasture economies of the animal world. Even though the changes Man also was driven south by the great ice age, and his ranks were probably filled with creatures who looked much like this restoration of Neanderthal Man. may have taken many thousands of :‘ears. they brought about new climates, and new climates produced droughts or excessive rains, over-long Winters or too hot Summers. Confronted with increasing rigors, the aui- mals in such regions had but three choices: Adapt themselves, move out in seash of & new home like the old one before the change, or— die. But to adapt means to evolve on the spot; to move means to face the competition of new neighbors, forcing adaptation again. Even to die worked as a cause of adaptation, for if you didn't change, the neighbor who moved into the place you vacated probably did. Thus did na- ture force many alterations. But not only did the uneasy earth thus com- pel its animal tenants to change with its own changes; it guided the migrations t’.at its new climates brcught about. Through the shape of the lands, the trend of its mountain ranges, the distribution of its deserts and inland seas, it made highways in certain directions and placed barriers across roads in others. It pushed warmth-loving animals southward with lengthening Winters and at last with mile- thick ice in permanent glacial caps; and as they moved in search of more Summer and less Winter, it either encouraged them with a Mis- sissippi Valley or halted them with Himalayas and Carcasus and Alps. HE disposal of the continents, Prof. Mat- thew pointed out, has a strong bearing on the history of animal migrations. If you will examine a globe,, ycu will see that most of the land area of the world lies in a huge circle around the Atlantic Ocean. What lies below the Equator can be counted as mere peninsulas; the pointed ends of Africa and South America, and the island continent of Australia, connected to the mainland through a chain of smaller islands. There are two gaps breaking this land ring at present, a narrow one at Bering Strait and a wider one across the North Atlantic. Bering Strait has unquestionably been closed by a land bridge, not once, but many times. And land bridges by way of °nland and Iceland to Europe may have e also: the ocean is comparatively shallow at that end, most of the way. What these Northern lands may have been like, in days when there was no permanent ice, can be left to the romantic imagination. Fos< sil leaves of trees like those now found in Calie fornia and the Gulf States, as well as those of the cooler, but still rich lands of Michigan and New York, have been found in Greenland. AST stretches of Northern Siberia and Can- ada, now dreary tundra and swamp and muskeg, or at best dense spruce growth, were once covered with game-filled hardwood timber like the virgin forests of the Ohio and Missise sippi Valleys. Only thev had stranger beu_tl' in them—rhinoceros and elephant and giant bison, as well as the more familiar deer and wild pig. E Then the uneasiness of slow upheaval, the increasing chill, the shortening Summer and the diminishing of the familiar food supplies. Some beasts perish, some change their habits to meet the new conditions: perhaps, most of them wander restlessly southward, edging year by year a little more toward the lands of the sun. ; Perhaps, some of the migrants might try oc- casionally to go back to the old home. but they would always run into forests where they eould not find the right kind of food. or cold nights that made them glad to resume their southward trek, or quaking bogs that would swallow them, meat and bones, if they persisted in attempting to cross. If any of them had been able to push on northward, after a suitable lapse of centuries, they would have come at last to a barrier that nothing without wings could cross; mountainous ice, stretching endlessly back toward the North, This ice was more than a blockade to northe ward travel on either continent; it was a closed door. The ring of land around the Pole was broken; East was East and West was Wesi, and the anilmals of America, cut off from those of the Old World, could no longer intermigrate and interbreed. Hence the development of separate species below the barrier. Strangely encugh, although ice covered Amer= ica about as far South as the Ohio River, and Europe from the Arctic Ocean to the Alps, there was no glaciation in Asia. All of Mane churia, Mongolia, Eastern Siberia, were icee free. HAT does not mean that they were not coldy They probably had very severe Winters, but in Summer the ground thawed out and raised its usua! crop of plants, and herds of animals grazed and browsed and wandered where they would. Interior Alaska was also unglaciated, and probably there was a land bridge to Asia, so that during that time there was free migration of such creatures as the great hairy mammoth and the musk-ox between the two continents, Only they could not get southward, for ade vance along the West coast of North America was blocked by the Cordilleran glacier front coming down to the sea. The southward migration of the animals did not take place as a single, gradual, co-ordinated movement, in Prof. Matthew’s opinion. Ine stead there were a number of separate dispers< als, or waves of migration; perhaps, one to each slow convulsion of the earth. The most advanced of animals, Prof. Mat- thew pointed cut, came down out of the cold lands latest and are still found predominantly in north temperate and subtropical regions; dogs and wolves, bears and raccoons, weasels and otters, deer and horses, and cats of all degrees. Man himself is no exception. Australia, which gives asylum to the largest remnant of the primitive first dispersal wave of animals, also has the most primitive of living human races. Other dark races, less primitive, bufi still unadvanced, occupy the forest lands of the Southern continental projections—sharing them, by the way, with man’s lesser cousins, the apes and monkeys. In the North, nearest the roots of the ol glaciers, the most intelligent and pr y races have built their civilizations in Europe and Asia, and have transplanted their culture to that other glacier-seoured continent; Neorth:: ' America. X