Relation of Production of Young to Danger of Extinction

There is evidence that, among oviparousa animals, the number of eggs produced by an individual parent depends on the dangers to which the eggs or the newborn offspring are exposed. For example, the common oyster produces about 50 million eggs at one time. To practically all sea animals these eggs are a tasty dish. And they get opportunity to eat millions of them, for the eggs float for several days before attaching permanently to a site, where they develop to maturity. Though millions of eggs are eaten, enough survive so that the oyster population is maintained. Yet the oyster obviously has no ability to know what happens to the eggs. Similarly, though not as prolific as the oyster, many other sea animals that do not have other means of protecting their eggs lay a prodigious number of them.

On the other hand, the golden eagle lays one to four eggs at a time, and the bald eagle one to three eggs. These birds build nests that are very high and difficult of access, and with their flying ability and their strong talons they can protect their nests. Therefore a great number of eggs would be superfluous.

With regard to the overall effect of such varied production on the part of different species of animals, the Encyclopædia Britannicab states:

“Most animal populations are not, on the average, either increasing or decreasing markedly, and in such populations . . . the natality or reproductive rate equals the total mortality of eggs, young, and adults.”

Some believers in evolution hold that the equality or balance between natality and mortality is an evolutionary mechanism to prevent overpopulation. Others argue from the viewpoint of natural selection. But when a person thinks of all the factors involved​—climate, procreation, food supply, and others—​can he really believe, on any logical basis, that nonintelligent forces assessed and directed this extremely complex situation with such eminent success?

An example of the intricacy in keeping a balance in the ecology is the turtle, which lays 100 or so eggs a year. The female comes ashore in the dark and digs holes in the sand, where she deposits her eggs and covers them. She then leaves them on their own. When hatching time arrives, the young turtle feels the urge to break out of his shell. For this escape he has a special hard point on his head by which he pierces the shell. Then he digs out of the sand and, without hesitation, flaps hurriedly toward the sea. On the way he is in great danger of being caught by predators, especially birds. Though he does not know this, he, nevertheless, urgently moves over all obstacles, and, if picked up and turned around, immediately turns back to get to the protection of his natural element, the sea. Even there he is in danger, and many baby turtles are eaten by fish. Birds and fish therefore are furnished a share of their food by the turtles, but a sufficient number survive to ensure the continuation of the turtle population.

Could blind chance direct every turtle so unerringly and determinedly toward the sea? How does he know that he must break out of his shell and his sandy incubation place? Did it just happen that he has been provided with special equipment to break his shell? Every one of the devices, from his mother’s coming ashore in the dark and burying the eggs so that they are safe from most predators, until the turtle reaches the sea, is essential. If one link in the chain were to fail, the turtle species would be extinct within a very short time.

Hunting Equipment

A small Caribbean fish named Anableps dowei likes to feed on tidbits floating on the water’s surface. He must be able to watch both above the surface for food and below the surface for enemies. This would be impossible for eyes with a single focus. But Anableps has “bifocals.” By means of two pupils, he can see above water through the short dimension of the lens and under water through the long dimension of the lens. By this means he takes care of the fact that light travels at different speeds through air and water. To keep the upper pupils moist, he ducks his head under water every few minutes.

Another fish that is equipped marvelously for overcoming the light refraction property of water is the archer fish. Almost everyone has noticed that an object under water appears to be closer to the viewer from above the water, or that a pole stuck into the water at an angle looks bent. If one should aim an arrow or a gun at a small object in the water one would need to make quite a complex calculation to hit the object. The archer fish has this problem in reverse. He sees an insect on a hanging branch. He quickly projects his head, or just his mouth, out of the water and shoots down the insect as by “antiaircraft” with a stream of water. In order to do this, he must take aim as he is coming to the surface of the water, compensating for the water’s refraction as he does so. Is this ability for instant mathematical computation built into the archer fish by design, or did a complex pattern of many factors just happen to imprint itself in some early archer fish’s bodily mechanism and thereafter stay with all his descendants?