What a life

To write about the infinite variety of our planet is a masterly act and I think no one has far excelled Sir David Attenborough in it. He has produced numerous televised documentaries for BBC on plant and animal life - working toward the conservation of natural history. In fact, as he begins his journey on one of his documentaries Our Living Planet he believes that there is as much undiscovered life on earth as there are unfulfilled potentials in us.

Recently, there has been great fanfare for the good old man of biology, Charles Darwin. His theory of evolution has transfixed so many disciplines from zoology to psychology. And as the great evolutionary biologist Theodosius Dobzhansky has said noting in biology makes sense except in the light of evolution. Attenborough succinctly explains why evolution has such special importance to us.

(Most sentences are verbatim reproduction of stuff in the book Our Living Planet as Attenborough has expressed in such arresting style that I feel that there is little need for me to scurry through my limited vocabulary to re-present the content)

Till 1832, the conventional view was that all species were immutable and each one of them was individually and separately created by God. But, Charles Darwin who set sail on HMS Beagle for a zoological expedition was to be taken by surprise at the immense variety of species. When he reached Rio de Janeiro, he was astonished to find 68 different varieties of species of small beetle. During the next 3 years, the Beagle sailed down the east coast of South America, rounded Cape Horn and came north again up the coast of Chile.

The expedition then sailed out into the Pacific until, 600 miles away from the mainland, they came to the lonely islands of Galapagos. It is a collection of islands owned by Ecuador and with its unusual animal life, it fortunately allured the young Darwin. On these islands, Darwin found fresh variety and fascination for the Galapagos animals which had a general resemblance to those on the mainland but they differed from them in detail.

There were cormorants, black, long neck diving birds like those that fly low along Brazilian rivers, but in the Galapagos, their wings were so small with stunted feathers that they had lost their power of flight.

There were iguanas, large lizards with a crest of scales along their backs. Those on the continent climbed trees and ate leaves. Here on the Galapagos, with less vegetation, one species fed on seaweed and clung to rocks among the surging waves with unusually long and powerful claws.

Giant tortoises so huge that humans can rid on them were everywhere. Those that lived on relatively well-watered islands where there was ground vegetation to be cropped, had a gently curving front edge to their shells just above their neck. Those that came from arid islands and had to crane their necks in order to reach cactus branches or tree leaves, had much longer neck and a high peak in front of their necks to enable them to stretch their necks almost vertically upwards. There were finches whose beaks varied greatly, and numerous other animals that astounded Darwin with their mishmash of multiplicity.

Darwin’s mind was suspecting that species were not fixed for ever. Perhaps, one could change into another. May be, thousands of years ago, birds and reptiles from continental South America had reached the Galapagos, ferried on rafts of vegetation that float down the rivers ad out to sea. Once there, they had changed, as generation succeeded after generation, to suite their new homes until they become their present species. The differences between them and their mainland cousins were only small, but if such changes had taken place, was it not possible that over millions of years, the cumulative effects on dynasty of animals was so great that they could bring about major transformations?

Just read this crisp climax of the above observations of Darwin written in sparse prose…

May be fish had developed muscular fins and crawled onto land to become amphibians; may be amphibians in their turn had developed their water-tight skins and become reptiles; may be, even some apelike creatures stood upright and became human ancestors.

Though many others before Darwin had suggested the interrelation among life on earth, Darwin’s revolutionary insight was to perceive the mechanism that brought about these changes. By doing so, Darwin had replaced philosophical speculation with detailed description of a process, supported by an abundance of evidence that could be tested and verified; ultimately, the reality of theory of evolution cannot be denied.

Put briefly, Darwin’s argument is this. All individuals of the same species are not identical. In one clutch of eggs of, for example, a giant tortoise, there will be hatchlings which because of their genetic constitution will develop longer necks than others. Their brothers and sisters with shorter necks will starve and die. So, those best fitted to their surroundings will be selected and will be able to transmit their characteristics to their offspring. After a great many number of generations, tortoise on the arid islands will have longer necks than those on the watered islands.

I’ve never read a 90-word summary of Darwin’s evolutionary theory as is summarized in the above paragraph.