3 July 2010

The Aquatic Ape?

Even here, lying on a towel in the sunshine by the swimming pool, there is plenty to occupy the student of natural history. For the final focus of the naturalist must be his own species, Homo sapiens, the animal that has inherited the Earth.

The planet has been waiting for this creature for over 4500 million years. There was a false start: the age of dinosaurs would probably, in time, have produced a two-legged lizard with the power to classify and manipulate its environment. But the age of dinosaurs was cut short, perhaps by the crash of a gigantic meteorite causing a centuries-long chill which the reptiles could not endure. The cold would favour one of evolution’s newer experiments, the warm-blooded mammals.

At that time the mammals were primitive, nondescript, tiny animals, unlikely forerunners of the final inheritor of the kingdom.

Even during the next tens of millions of years no real candidate seemed to be emerging. The most advanced of the ancestral apes so far discovered was a primate called Ramapithecus. The next most advanced primate we know of is Australopithecus, a man-like ape which is believed to be a forerunner of the genus Homo, which of course includes modern man.

Between Ramapithecus and Australopithecus there is a quantum leap in potential. We owe our position in the scheme of things to a number of factors, two of which are of supreme importance. The first is the ability to walk on two legs rather than four, freeing our forelimbs for manipulation of tools. The second, eclipsing all else, is the power of speech.

Speech requires language, which is the ability to classify. This ability gives rise to abstract thought, logic, foresight, and the handing on of knowledge to succeeding generations. With the invention of writing, speech can be preserved indefinitely. Writing gives rise to science, to mastery of the environment.

So how and where did this quantum leap take place? No one yet knows for sure, but clues might be here today, at the swimming pool.

Why is it that human beings are drawn so much to water? Other modern primates – the chimpanzee or gorilla, say – are generally afraid of water and will do anything to avoid swimming. Yet, at every available opportunity, it seems that Homo sapiens takes his family off to the beach. If he cannot get to a beach he will go to a specially constructed waterhole instead, like this one.

Observe if you will the infants in the shallow end. There is a baby with its mother, too tiny even to sit up on its own. gurgling and splashing as if water were its natural habitat. Observe also the other adult humans who, like yourself, are sunbathing between swims.

They are without fur; they have (some more than others) a layer of fat under the skin; and if you look closely, you will see that they have the vestiges of webbing between their fingers and toes. All of these are uniquely the characteristics associated with aquatic mammals such as the whale or dolphin. None of them is to be found in any other living primate.

Several of the sunbathers are overheating and beginning to sweat. The possession of abundant sweat-glands has been described by one professor of dermatology as a “major biological blunder”, costing the human animal vast amounts of precious water and depleting the system of essential salts. Strange that in a creature so perfectly fashioned there should be such an evolutionary mistake – assuming, of course, that Man evolved entirely on dry land.

Notice again the mother and baby in the shallow end. The mother is walking about on the bottom, holding her baby on the surface. The same technique of wading is used by primitive fishermen, enabling them to exploit food supplies denied to land-bound animals.

As yet there has been no fossil evidence to support it, but some zoologists have put forward the idea that the seeds of the genus Homo were sown some time between 9 and 3.7 million years ago. when a huge area of East Africa became flooded. Populations of forest apes were marooned and had to adapt or die out.

Man’s pelvis, unlike that of other modern primates, is angled so that, when stretched out in the water, he is able to swim “in line”, exactly like a penguin or dolphin.

Another feature which man shares with aquatic animals is the “diving reflex”, in which the heart rate slows down during diving, reducing oxygen consumption. Expert pearl divers can remain submerged for up to 3 minutes and reach a depth of 262 feet, during which their heart rate falls by about 50%. The diving reflex is usually found together with a marked improvement in breath control – and breath control is one of the essentials of speech.

The colonization of a new medium, water, requires the acquisition of a whole new set of locomotor skills: swimming, diving, an acute sense of balance and direction. An increased locomotor repertoire, as it is called, leads to an increased brain capacity, a phenomenon which is plainly to be seen among the highly intelligent whales and dolphins. These animals, incidentally, also have superb breath control and a complex system of calls which might, if we could only understand it, turn out to be a language of abstract as well as concrete ideas.

When the floods receded, the mooted semi-aquatic ape then had to adapt all over again, enlarging its locomotor repertoire still more. Already adapted to going on two legs, the advantages of this method of walking encouraged evolution to refine and perfect the systems that make it possible. From the region of the flood the apes gradually migrated, spreading out along the Rift Valley, which is where the remains of Australopithecus were found.

From Australopithecus to Homo sapiens is quite a jump: from the Tiger Moth to the Space Shuttle. But that is nothing like the earlier jump that had to be made to give man his unique set of advantages. It is a fascinating subject to speculate on; and fascinating to wonder whether echoes of the aquatic lifestyle of our remote ancestors live on today, here in the blue waters of Bushey baths.

But that’s quite enough theory for now. I think I’m going in for another dip. Coming?

(Introduction to these pieces; see all)

No comments: