FROM THE TELEGRAPH OF 3 AUGUST 2006
On our descent
from monkeys
Charles Darwin is perhaps the world’s
best known scientist. Every schoolboy knows him as the originator of the theory
of evolution. But today, the idea that various species evolved out of natural
selection – that is, out of mutual competition and adaptation to the
environment – looks obvious. Why did it need to be propagated??
As soon as the
first human – or dinosaur as the case may be – learnt to think, he ran into
certain elementary questions. Where was I before I was born? Where did my
father go when he ceased to breathe? The questions in themselves imply the
existence of other worlds which we can know nothing about. Many models of such
worlds can be imagined. None of them is testable, and all of them are speculative.
Elaborate stories can be told, retold and passed on to posterity.
The story in the tribe in which Darwin
was born was that there was one God, and that he constructed the world in six
days and rested on the seventh. The world included all living beings. Thus from
the day the world was finished some 6000 years ago, every species from
jellyfish to anteater had existed unmodified. The Bible begins with this story,
and its repudiation entailed the dismantling of an element of the Christian
faith – the creationist element. Darwin propagated what was then considered
blasphemy.
But he was no
Galileo. He was the son of a doctor who sent him to Christ’s College,
Cambridge, in the hope that he would become a clergyman or classicist. Charles
showed aptitude for neither. But he used to go for walks in the countryside
with J S Henslow, the Professor of Botany. When the Admiralty decided to send a
ship to survey the southern hemisphere, Henslow recommended Charles, who was
taken on it as naturalist. HMS Beagle, a ten-gun brig, left
Davenport on 27 December 1831 after being beaten back twice by unfavourable
winds. It sailed to Cape Verde Islands, and then down the east coast of South
America. It sailed across the Magellan Strait and up the coast of Chile and
Peru, and stopped in the Galapagos. Then it sailed across the Pacific to New
Zealand and Australia, and on to Mauritius.
In Port Louis,
he saw his first Indians. “Convicts from India are banished here for life; at
present there are about 800, and they are employed in various public works.
Before seeing these people, I had no idea that the inhabitants of India were
such noble-looking figures. Their skin is extremely dark, and many of the older
men had large mustaches and beards of a snow-white colour; this, together with
the fire of their expression, gave them quite an imposing aspect. The greater
number had been banished for murder and the worst crimes; others for causes
which can scarcely be considered as moral faults, such as for not obeying, from
superstitious motives, the English laws. These men are generally quiet and
well-conducted; from their outward conduct, their cleanliness, and faithful
observance of their strange religious rites, it was impossible to look at them
with the same eyes as on our wretched convicts in New South Wales.” Then The
Beagle rounded the Cape of Good Hope, and finally reached Falmouth on 2
October 1836.
On that voyage, he
encountered animals and birds of South America and Australasia. So he started
thinking about the variety of living beings and how it came about. He planned a
detailed treatise, and would have spent a lifetime writing it. But in 1858 – 22
years after the Beagle returned – Alfred Wallace, a self-made
naturalist, sent Darwin a paper which applied Malthus’s idea of survival of the
fittest to all life and thus anticipated the theory of natural selection. In a
quandary, Darwin consulted Charles Lyell (Professor of geology in King’s
College, London) and Joseph Hooker (leading naturalist of the mid-nineteenth
century). They placed Wallace’s paper before the Linnaean Society, together
with scattered writings of Darwin that established his priority. After that,
Darwin was compelled to put down his ideas on paper. The Origin of Species
was first published in 1858. Although close to 200,000 words, it was supposed
to be a summary of his views; he never managed to write the extended version.
Although the
book is an attack on received theory, Darwin does not criticize any of its
proponents by name; instead, he draws support from as many of his predecessors
as possible. Instead of claiming priority or novelty for his own views, he
makes it out as if wiser men had thought them first. Darwin takes one contrary
argument after another, and sets out to controvert it as gently as possible. He
marshals masses of evidence, but concedes its weaknesses.
Thus,
creationists used to cite the sterility of cross-breeds, such as mules, as
evidence that God had a monopoly of creation of species. Darwin says that
sterility resulted when crossing disturbed reproductive systems, and was by no
means universal; in many cases of controlled cross-breeding, fertility actually
increased.
If all species
evolved by gradual modification in response to the environment, the world
should display all the minor intermediate variations. For instance, world’s
cattle should not be divided into a few breeds, but must include many minute
variations. The reason they do not, according to Darwin, lies in competition.
Successful varieties multiply faster; their competition leads less successful
variations to become extinct. Thus natural selection leads to a small number of
numerous varieties.
If intermediate
varieties died out, they should be found amongst fossils, the entire range,
extinct and surviving, should have been preserved in rocks. But actually,
fossils belong to a much smaller number of strongly varying species than do
live animals. This, according to Darwin, is because geological evidence is
extremely incomplete. Fossils are found in sedimentary rocks. In other words,
animals were fossilized when land was sinking, and skeletons were submerged in
water and buried in sand. Except in periods and regions where this happened,
the record of skeletons would be wiped out. So the wide differences amongst
fossilized species only reflect the rarity of fossilization.
Many animals,
birds and plants are found on islands and in areas between which there is no
land connection; that could be evidence that God had created them separately in
situ. Darwin rejects the idea that the common species must have been separated
when continents drifted apart and islands were created. Birds, according to
him, fly enormous distances. Animals and insects are often carried long
distances on driftwood. But most of the separation of common species must have
occurred when the last ice age ended and ice bridges across seas melted. He
shows that species, such as bats, which can fly long distances, are more widely
diffused across the world than those that cannot; and that the further away an
island is from the nearest continent, the fewer varieties it has.
Despite his
detailed argument and conciliatory approach, Darwin’s theory won ground only
slowly; there are Americans even now who believe that God created all beings at
the same time. The Origin of Species is still worth reading for its
courtly language, and as an exercise in persuasion.
