The Outline of Science Part 24

KEANE, A. H., _Man Past and Present_.

KEITH, ARTHUR, _Antiquity of Man_.

LULL, R. S., _Organic Evolution_.

MCCABE, JOSEPH, _Evolution of Civilization_.

MARETT, R. R., _Anthropology_ (Home University Library).

OSBORN, H. F., _Men of the Early Stone Age_.

SOLLAS, W. J., _Ancient Hunters and their Modern Representatives_.

TYLOR, E. B., _Anthropology and Primitive Culture_.

VI

EVOLUTION GOING ON

EVOLUTION GOING ON

Evolution, as we have seen in a previous chapter, is another word for race-history. It means the ceaseless process of Becoming, linking generation to generation of living creatures. The Doctrine of Evolution states the fact that the present is the child of the past and the parent of the future. It comes to this, that the living plants and animals we know are descended from ancestors on the whole simpler, and these from others likewise simpler, and so on, back and back--till we reach the first living creatures, of which, unfortunately, we know nothing.

Evolution is a process of racial change in a definite direction, whereby new forms arise, take root, and flourish, alongside of or in the place of their ancestors, which were in most cases rather simpler in structure and behaviour.

The rock-record, which cannot be wrong, though we may read it wrongly, shows clearly that there was once a time in the history of the Earth when the only backboned animals were Fishes. Ages pa.s.sed, and there evolved Amphibians, with fingers and toes, scrambling on to dry land.

Ages pa.s.sed, and there evolved Reptiles, in bewildering profusion. There were fish-lizards and sea-serpents, terrestrial dragons and flying dragons, a prolific and varied stock. From the terrestrial Dinosaurs it seems that Birds and Mammals arose. In succeeding ages there evolved all the variety of Birds and all the variety of Mammals. Until at last arose the Man. The question is whether similar processes of evolution are still going on.

We are so keenly aware of rapid changes in mankind, though these concern the social heritage much more than the flesh-and-blood natural inheritance, that we find no difficulty in the idea that evolution is going on in mankind. We know the contrast between modern man and primitive man, and we are convinced that in the past, at least, progress has been a reality. That degeneration may set in is an awful possibility--involution rather than evolution--but even if going back became for a time the rule, we cannot give up the hope that the race would recover itself and begin afresh to go forward. For although there have been retrogressions in the history of life, continued through unthinkably long ages, and although great races, the Flying Dragons for instance, have become utterly extinct, leaving no successors whatsoever, we feel sure that there has been on the whole a progress towards n.o.bler, more masterful, more emanc.i.p.ated, more intelligent, and _better_ forms of life--a progress towards what mankind at its best has always regarded as best, i.e. affording most enduring satisfaction. So we think of evolution going on in mankind, evolution chequered by involution, but on the whole _progressive evolution_.

Evolutionary Prospect for Man

It is not likely that man's body will admit of _great_ change, but there is room for some improvement, e.g. in the superfluous length of the food-ca.n.a.l and the overcrowding of the teeth. It is likely, however, that there will be const.i.tutional changes, e.g. of prolonged youthfulness, a higher standard of healthfulness, and a greater resistance to disease. It is justifiable to look forward to great improvements in intelligence and in control. The potentialities of the human brain, as it is, are far from being utilised to the full, and new departures of promise are of continual occurrence. What is of great importance is that the new departures or variations which emerge in fine children should be fostered, not nipped in the bud, by the social environment, education included. The evolutionary prospect for man is promising.

[Ill.u.s.tration: PHOTOGRAPH OF A MEDIAN SECTION THROUGH THE Sh.e.l.l OF THE PEARLY NAUTILUS

It is only the large terminal chamber that is occupied by the animal.]

[Ill.u.s.tration: PHOTOGRAPH OF THE ENTIRE Sh.e.l.l OF THE PEARLY NAUTILUS

The headquarters of the Nautilus are in the Indian and Pacific Oceans.

They sometimes swim at the surface of the sea, but they usually creep slowly about on the floor of comparatively shallow water.]

[Ill.u.s.tration: NAUTILUS

A section through the Pearly Nautilus, _Nautilus pompilius_, common from Malay to Fiji. The sh.e.l.l is often about 9 inches long. The animal lives in the last chamber only, but a tube (S) runs through the empty chambers, perforating the part.i.tions (SE). The bulk of the animal is marked VM; the eye is shown at E; a hood is marked H; round the mouth there are numerous lobes (L) bearing protrusible tentacles, some of which are shown. When the animal is swimming near the surface the tentacles radiate out in all directions, and it has been described as "a sh.e.l.l with something like a cauliflower sticking out of it." The Pearly Nautilus is a good example of a conservative type, for it began in the Tria.s.sic Era. But the family of Nautiloids to which it belongs ill.u.s.trates very vividly what is meant by a dwindling race. The Nautiloids began in the Cambrian, reached their golden age in the Silurian, and began to decline markedly in the Carboniferous. There are 2,500 extinct or fossil species of Nautiloids, and only 4 living to-day.]

[Ill.u.s.tration: _Photo: W. S. Berridge._

s...o...b..LL

A bird of a savage nature, never mixing with other marsh birds.

According to Dr. Chalmers Mitch.e.l.l, it shows affinities to herons, storks, pelicans, and gannets, and is a representative of a type equal to both herons and storks and falling between the two.]

But it is very important to realise that among plant and animals likewise, _Evolution is going on_.

The Fountain of Change: Variability

On an ordinary big clock we do not readily see that even the minute hand is moving, and if the clock struck only once in a hundred years we can conceive of people arguing whether the hands did really move at all. So it often is with the changes that go on from generation to generation in living creatures. The flux is so slow, like the flowing of a glacier, that some people fail to be convinced of its reality. And it must, of course, be admitted that some kinds of living creatures, like the Lamp-sh.e.l.l _Ligula_ or the Pearly Nautilus, hardly change from age to age, whereas others, like some of the birds and b.u.t.terflies, are always giving rise to something new. The Evening Primrose among plants, and the Fruit-fly, Drosophila, among animals, are well-known examples of organisms which are at present in a sporting or mutating mood.

Certain dark varieties of moth, e.g. of the Peppered Moth, are taking the place of the paler type in some parts of England, and the same is true of some dark forms of Sugar-bird in the West Indian islands. Very important is the piece of statistics worked out by Professor R. C.

Punnett, that "if a population contains .001 per cent of a new variety, and if that variety has even a 5 per cent selection advantage over the original form, the latter will almost completely disappear in less than a hundred generations." This sort of thing has been going on all over the world for untold ages, and the face of animate nature has consequently changed.

We are impressed by striking novelties that crop up--a clever dwarf, a musical genius, a calculating boy, a c.o.c.k with a 10 ft. tail, a "wonder-horse" with a mane reaching to the ground, a tailless cat, a white blackbird, a copper beech, a Greater Celandine with much cut up leaves; but this sort of mutation is common, and smaller, less brusque variations are commoner still. _They form the raw materials of possible evolution._ We are actually standing before an apparently inexhaustible fountain of change. This is evolution going on.

The Sporting Jellyfish

It is of interest to consider a common animal like the jellyfish Aurelia. It is admirably suited for a leisurely life in the open sea, where it swims about by contracting its saucer-shaped body, thus driving water out from its concavity. By means of millions of stinging cells on its four frilled lips and on its marginal tentacles it is able to paralyse and la.s.so minute crustaceans and the like, which it then wafts into its mouth. It has a very eventful life-history, for it has in its early youth to pa.s.s through a fixed stage, fastened to rock or seaweed, but it is a successful animal, well suited for its habitat, and practically cosmopolitan in its distribution. It is certainly an old-established creature. Yet it is very variable in colour and in size, and even in internal structure. Very often it is the size of a saucer or a soup-plate, but giants over two feet in diameter are well known. Much more important, however, than variation in colour and size are the inborn changes in structure. Normally a jellyfish has its parts in four or multiples of four. Thus it has four frilled lips, four tufts of digestive filaments in its stomach, and four brightly coloured reproductive organs. It has eight sense-organs round the margin of its disc, eight branched and eight unbranched radial ca.n.a.ls running from the central stomach to a ca.n.a.l round the circ.u.mference. The point of giving these details is just this, that every now and then we find a jellyfish with its parts in sixes, fives, or threes, and with a mult.i.tude of minor idiosyncrasies. _Even in the well-established jellyfish there is a fountain of change._

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Evolution of Plants

It is instructive to look at the various kinds of cabbages, such as cauliflower and Brussels sprouts, kale and curly greens, and remember that they are all scions of the not very promising wild cabbage found on our sh.o.r.es. And are not all the aristocrat apple-trees of our orchards descended from the plebeian crab-apple of the roadside? We know far too little about the precise origin of our cultivated plants, but there is no doubt that after man got a hold of them he took advantage of their variability to establish race after race, say, of rose and chrysanthemum, of potato and cereal. The evolution of cultivated plants is continuing before our eyes, and the creations of Mr. Luther Burbank, such as the stoneless plum and the primus berry, the spineless cactus and the Shasta daisy, are merely striking instances of what is always going on.

There is reason to believe that the domestic dog has risen three times, from three distinct ancestors--a wolf, a jackal, and a coyote. So a multiple pedigree must be allowed for in the case of the dog, and the same is true in regard to some other domesticated animals. But the big fact is the great variety of breeds that man has been able to fix, after he once got started with a domesticated type. There are over 200 well-marked breeds of domestic pigeons, and there is very strong evidence that all are descended from the wild rock-dove, just as the numerous kinds of poultry are descended from the jungle-fowl of some parts of India and the Malay Islands. Even more familiar is the way in which man has, so to speak, unpacked the complex fur of the wild rabbit, and established all the numerous colour-varieties which we see among domestic rabbits. And apart from colour-varieties there are long-haired Angoras and quaint lop-eared forms, and many more besides. All this points to evolution going on.

The Romance of the Wheat

It is well-known that Neolithic man grew wheat, and some authorities have put the date of the first wheat harvest at between fifteen thousand and ten thousand years ago. The ancient civilisations of Babylonia, Egypt, Crete, Greece, and Rome were largely based on wheat, and it is highly probable that the first great wheatfields were in the fertile land between the Tigris and the Euphrates. The oldest Egyptian tombs that contain wheat, which, by the way, never germinates after its millennia of rest, belong to the First Dynasty, and are about six thousand years old. But there must have been a long history of wheat before that.

Now it is a very interesting fact that the almost certain ancestor of the cultivated wheat is at present living on the arid and rocky slopes of Mount Hermon. It is called _Tritic.u.m hermonis_, and it is varying notably to-day, as it did long ago when it gave rise to the emmer, which was cultivated in the Neolithic Age and is the ancestor of all our ordinary wheats. We must think of Neolithic man noticing the big seeds of this Hermon gra.s.s, gathering some of the heads, breaking the brittle spikelet-bearing axis in his fingers, knocking off the rough awns or bruising the spikelets in his hand till the glumes or chaff separated off and could be blown away, chewing a mouthful of the seeds--and resolving to sow and sow again.

That was the beginning of a long story, in the course of which man took advantage of the numerous variations that cropped up in this sporting stock and established one successful race after another on his fields.

Virgil refers in the "Georgics" to the gathering of the largest and fullest ears of wheat in order to get good seed for another sowing, but it was not till the first quarter of the nineteenth century that the great step was taken, by men like Patrick Sheriff of Haddington, of deliberately selecting individual ears of great excellence and segregating their progeny from mingling with mediocre stock. This is the method which has been followed with remarkable success in modern times.

One of the factors that a.s.sisted the Allies in overcoming the food crisis in the darkest period of the war was the virtue of Marquis Wheat, a very prolific, early ripening, hard red spring wheat with excellent milling and baking qualities. It is now the dominant spring wheat in Canada and the United States, and it has enormously increased the real wealth of the world in the last ten years (1921). Now our point is simply that this Marquis Wheat is a fine example of evolution going on.

In 1917 upwards of 250,000,000 bushels of this wheat were raised in North America, and in 1918 upwards of 300,000,000 bushels; yet the whole originated from a single grain planted in an experimental plot at Ottawa by Dr. Charles E. Saunders so recently as the spring of 1903.

[Ill.u.s.tration: THE WALKING-FISH OR MUD-SKIPPER (PERIOPHTHALMUS), COMMON AT THE MOUTHS OF RIVERS IN TROPICAL AFRICA, ASIA, AND NORTH-WEST AUSTRALIA

It skips about by means of its strong pectoral fins on the mud-flats; it jumps from stone to stone hunting small sh.o.r.e-animals; it climbs up the roots of the mangrove-trees. The close-set eyes protrude greatly and are very mobile. The tail seems to help in respiration.]

[Ill.u.s.tration: _Photo: "The Times."_