Extraterrestrial Civilizations - Isaac Asimov [87]
Viewed from this angle, the sea is ideal as an incubator of life, but is very poor as an incubator of intelligence. The most valuable and information-rich sense that we can imagine life possessing (without veering into fantasy) is that of vision. Under water, vision is limited, for water absorbs light to a far greater extent than air does. In air, vision is a long-distance sense; in water, only a short-distance sense. (To be sure, hearing is even more efficient in water than in air and can perform wonders, but the smallest sound waves used by life forms are still far longer than the tiny light waves, and therefore incapable of transmitting as much information.)
When it comes to manipulative organs, as I mentioned earlier in the book, the necessity for streamlining to allow rapid travel through the viscous medium of water eliminates almost any chance for developing a manipulative organ. What manipulation a sea organism can perform usually involves the mouth, the tail, or the full weight of the body, and it is rarely delicate in its nature.
One exception to this is the octopus and its relatives. The octopus has developed a set of sensitive and limber tentacles with which there can be fine manipulation of the environment, yet when it wishes to travel quickly it can trail them behind and be streamlined. Then, too, the octopus has an excellent eye, the closest approach to the vertebrate eye in any nonvertebrate creature.
But though we may admire the intelligence of the octopus, it is certainly far from intelligent enough to build what we would consider to be a civilization.
There are, of course, sea animals far more intelligent than the octopus, but these—sea otters, seals, penguins—are all land creatures who had secondarily adapted to the water again. Even the whales and dolphins have land animals among their ancestry, and it is undoubtedly in the course of the period during which their ancestors inhabited the land that the cetacean brain developed.
For real intelligence of the level in which this book is interested, then, we must consider land organisms—land organisms who can make use of sight as a long-distance sense of incredible detail and richness; who can develop manipulative organs; and who live surrounded by free oxygen so that they can tame fire and develop a technology.
And yet when all life existed in the sea only, the land was an environment extremely hostile to life; as hostile as space is to us. We, at least, in conquering space can make use of our technology and devise artificial protective devices. Sea life, hundred of millions of years ago, had to develop protection as part of their bodies through the slow course of evolution.
Consider the difficulties they had to overcome:
In the sea, organisms need not fear thirst and drought; they are always surrounded by water, the essential chemical background to life. On the land, on the other hand, life is a continual battle to avoid water loss; water must either be conserved, or it must be replaced by drinking.
In the sea, oxygen is easily absorbed from the water in which it is dissolved. On the land, oxygen must first be dissolved in the fluid lining the lungs and then absorbed, and the lungs must not be allowed to dry out in the process.
In the sea, eggs can be laid in the water and allowed to develop and hatch without care (or with minimal care) in a congenial environment. On the land, eggs must be developed that have a shell that will prevent water loss while allowing gases to pass through freely so that oxygen can reach the developing embryo.
In the sea, temperature scarcely varies. On the land, there are extremes of hot and cold.
In the sea, gravity is almost nil. On the land, it is a powerful force, and organisms must develop sturdy legs that can lift them free of the land, or else they are condemned to crawl.