One hundred and fifty year anniversary of 
The Theory of Natural Selection

Charles Darwin remains one of the best known scientists of the world, although not many people understand his theory of evolution. This is somewhat similar to Einstein and E = mc2, which everyone knows and hardly anyone understands!
However that may be, it is clear that one of the most profound ideas was made known to mankind, almost exactly one hundred and fifty years ago. Here is the story.
Charles Robert Darwin was born on 12 February, 1809, in England. He was actually a collector and a geologist. His journeys around the world led to his collecting scientific evidence which led to his theory of natural selection.
His theory was that all species of life have evolved over time from common ancestors. He called the process by which this evolution took place as natural selection. Although it was a revolutionary idea, it became accepted by both the scientific community and the general public in his own lifetime. In fact his theory of natural selection came to be widely seen as the primary explanation of the process of evolution in the 1930s. It now forms the basis of modern evolutionary theory but in modified form.
There are so many different kinds of living things: animals birds insects. Within each type, there is a large variety, and within this variety there are individual variations. This is called the diversity of life. Darwin's scientific discovery in fact remains the foundation of biology as it provides a unifying logical explanation for this diversity of life.
Darwin started out his explorations as an unpaid gentleman's companion to Robert FitzRoy, the captain of the ship HMS Beagle. The plan was a two-year expedition to chart the coastline of South America. This was to be its second voyage.
The Beagle survey took five years, two-thirds of which Darwin spent on land. He carefully noted a rich variety of geological features, fossils and living organisms, and methodically collected an enormous number of specimens, many of them new to science. At intervals during the voyage he sent specimens to Cambridge together with letters about his findings, and these established his reputation as a naturalist. His extensive detailed notes showed his gift for theorising and formed the basis for his later work. The journal he originally wrote for his family was published as The Voyage of the Beagle. He wrote not only of the geology he saw and specimens he had collected but also of the people he met.
During the journey he made numerous geological discoveries. That is, discoveries about land formation, rock type, etc. He followed the book on geology by the well-known scientist Charles Lyell. He used his observations to prove (and disprove!) a lot of theories in geology.
As HMS Beagle surveyed the coasts of South America, Darwin began to theorise about the wonders of nature around him. Lyell's second book talked about species being distributed around centres of creation. It was essentially an argument against evolution.
But on the Galapagos Islands he collected birds, and noted that mockingbirds differed depending on which island they came from. He also heard that local Spaniards could tell from their appearance on which island tortoises originated. Thus he noticed that animals showed variations because of the place that they had adapted to live in. Thus began his ideas on transmutation of species.
When organising his notes on the return journey, Darwin wrote that if his growing suspicions about the mockingbirds and the tortoises were correct, such facts decrease the stability of Species. He later wrote that such facts seemed to throw some light on the origin of species.
He also noticed that different humans were treated differently. He hated the slavery he saw elsewhere in South America, and was saddened by the effects of European settlement on Aborigines (original or indigenous australians) in Australia and Maori in New Zealand.
When Captain FitzRoy realised how detailed his observations were, he asked him to provide the natural history report on the Beagle voyages. By the time the Beagle returned on 2 October, 1836, Darwin was a celebrity in scientific circles and was presenting papers both in geology and biology. Secretly he was studying his records and making his first sketch of an evolutionary tree.
Darwin soon had the framework of his theory of natural selection. His research subsequently included animal husbandry and extensive experiments with plants. For more than a decade this work went hand in hand with the publication of the results of the Beagle voyage. However he did not publish any of the work since Lyell and other influential scientists still did not believe in such a theory.
In eight years of work on barnacles, Darwin found evidence that supported his theory by showing that slightly changed body parts could serve different functions to meet new conditions. He resumed work on his theory of species in 1854, and in November realised that differences in creatures descended from the same parents could be explained by adaptation: the descendents or children had grown up in different places and had adjusted to these differences.
His friend Hooker increasingly doubted the traditional view that species were fixed and unchanging, but another friend Thomas Huxley was firmly against evolution. Lyell was puzzled and excited by Darwin's theory but he did not realise their full implication.
In 1856 Lyell read a paper by Alfred Russel Wallace on the Introduction of species. He saw similarities with Darwin's thoughts and ideas. So he asked Darwin to publish his work immediately. Since Darwin was still working on his theory secretly, he was afraid that Wallace would get all the credit after so many years of hard work by Darwin.
Darwin was not very concerned since he believed that no-one else had such detailed evidence about the theory of natural selection. However he did not want to present the theory until he had answers to all the questions. So he decided to continue to do more research.
In December 1857, Darwin received a letter from Wallace (who was in Borneo and had been sending specimens to Darwin) asking if Darwin's book would examine the origin of human beings. Darwin said that he would avoid that subject, since it would upset many people. But he wrote encouraging Wallace to continue with his work.
Darwin's book was half way when, on 18 June, 1858, he received a paper from Wallace describing natural selection. This time he was shocked since he did not believe that anyone else would discover this theory. Still, Darwin sent the paper on to Lyell, and also offered to send it to any journal that Wallace chose.
Home matters began to trouble Darwin with his family falling sick of scarlet fever. He decided to leave all matters in the hands of Lyell and Hooker who proposed a double announcement, so that Darwin and Wallace's work would be presented jointly and so that both of them would get the credit.
Darwin agreed and sent them selections from his writings that explained his views. Lyell and Hooker presented these and Wallace's essay at an extra meeting of the Linnean Society. Often described as a joint paper, it was rather two independent statements of the same idea. One hundred and fifty years ago, at a meeting on 1 July 1858, Lyell and Hooker communicated the paper titled "On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection" to the Linnean Society.
Actually neither author was present: Darwin was mourning the death of his young child and Wallace was seriously ill.
His book was finally ready and published in 1859. Called On the Origin of Species, it established that evolution by common descent was the dominant scientific explanation of diversification in nature. At the end of the book he concluded that; 
    There is grandeur in this view of life, with its several powers,
    having been originally breathed into a few forms or into one;
    and that, whilst this planet has gone cycling on according to the
    fixed law of gravity, from so simple a beginning endless forms most
    beautiful and most wonderful have been, and are being, evolved.

"Darwinism" became widely accepted by the 1870s and today is the accepted theory of the origin of species.

Adapted from Wikipedia, the on-line Encyclopedia