Introduction to Evolution
Where do we came from? Who we are ? Where we are going?
These questions arise time to time before, and answer to these questions we always in search of, but when science and particularly Charles Darwin’s term “Evolution” came in to picture the religious belief questioned. From there finding answer to these questions is become a curiosity. So we are trying to understand what is evolution?
Evolution is one of the most important concepts in the Biology. In fact Biology simply does not make sense without Evolution. Evolution is the idea that all living things arose from a common ancestor in the past and that life continues to diversify today as new species. Evolution explains why we can classify organisms into different groups. Evolution explains why the cells of all organisms use the same kind of biochemical machinery.
All living things share a common ancestor in the distant past and all living things are related to one another. In much the same way that we might draw a family tree of our own ancestors, we know ‘Tree of Life’ which show how all living things are related. Evolution is the process by which one species gives rise to another and the Tree of Life grows. There is often considerable confusion as to whether the concept of evolution is a theory or a fact. Actually it is both! Evolutionary theory deals with how evolution happens. This is an area of active research and new insights are constantly emerging to explain how one species gives rise to another. However, Evolution is also a fact because there is a great deal of indisputable evidence, as we will see in this talk, in support of its occurrence. What is uncertain is exactly HOW it happened? , and whether it has happened at all?
So let’s start by thinking about the discovery of Evolution. Beginning in Classical times and persisting until long after the Renaissance, scientists thought species were fixed and immutable. Their reasoning was like if God’s creation was perfect from the start, why would he bother to tinker with it at a later date? However, around 1800, some scientists began think if species transmute and one of them was French scientist, Jean Baptiste de Lamarck (1744-1829). Lamarck thought that if an animal acquired a characteristic during its lifetime, it could pass it onto its offspring. One of his favourite examples was the giraffe. In his view, the giraffe got its long neck through straining to reach the leaves on high branches, and this characteristic got passed down the generations. Most scientists of his day thought that Lamarck was wrong. At that time, only a few radical thinkers like Charles Darwin’s grandfather, Erasmus, agreed that species could change over time.
So let’s start by thinking about the discovery of Evolution. Beginning in Classical times and persisting until long after the Renaissance, scientists thought species were fixed and immutable. Their reasoning was like if God’s creation was perfect from the start, why would he bother to tinker with it at a later date? However, around 1800, some scientists began think if species transmute and one of them was French scientist, Jean Baptiste de Lamarck (1744-1829). Lamarck thought that if an animal acquired a characteristic during its lifetime, it could pass it onto its offspring. One of his favourite examples was the giraffe. In his view, the giraffe got its long neck through straining to reach the leaves on high branches, and this characteristic got passed down the generations. Most scientists of his day thought that Lamarck was wrong. At that time, only a few radical thinkers like Charles Darwin’s grandfather, Erasmus, agreed that species could change over time.
About the same time that these radical thinkers were discussing the transmutation (or evolution) of species, geologists like William Smith were beginning to map the rocks and fossils of Britain. Smith and others were able to show that rocks were laid down in a certain order and that the different fossils in different layers lived at different intervals of geological time. Here was clear evidence that different species had existed in the past compared with today. However, Smith did not go on to ask the question, ‘Why?’ or to consider that this might be evidence for evolution.In the early nineteenth century, Charles Darwin (1809-1882) rekindled ideas about evolution. In a sense, Evolution was in Darwin’s blood because, as we’ve already noted, his grandfather was an early supporter of the concept. From 1831-1836, Darwin toured the world on HMS Beagle as a young naturalist. He was dazzled by the amazing diversity of life, including some amazing fossils such as rodents the size of hippopotamuses and started to wonder how it might have originated.On his return from the Beagle the jigsaw pieces started to fit together in his mind. Around 1842 Darwin read an essay about human population growth by Malthus. Malthus had argued that human population would grow more quickly than food supply.
Consequently competition for food would become intense and only the fittest and most able would survive. Darwin applied these ideas to all of life and came up with his now famous concept of Natural Selection. Darwin reasoned that if an organism possessed a character that improved its chances of survival, then it would be more likely to pass on that character to the next generation. Therefore organisms would become progressively adapted to their environment, leading to the evolution of new species. Darwin published this idea in his “Origin of Species by means of Natural Selection” in 1859.However, Darwin’s concept of Evolution by Natural Selection was met with considerable controversy and debate. Although some religious fundamentalist were willing to accept Evolution, if God was allowed to guide the process, most were opposed to the idea of Evolution being driven by random competition and natural laws. However, some leading scientists did embrace Evolution. One of these was Thomas Henry Huxley (1825-1895), who became known as “Darwin’s bulldog” for his ferocious support of Darwin. On 30 June 1860, Huxley debated Evolution with Bishop Wilberforce at a British Association meeting in Oxford. In the debate, Wilberforce infamously inquired of Huxley whether it was through his grandfather or grandmother that he claimed descent from a monkey! Huxley then rose to the defence of Evolution, finishing his speech with the now legendary ‘put-down’ that he was not ashamed to have a monkey for his ancestor, but he would be ashamed to be connected with a man who used great gifts to obscure the truth! This debate saw many people come to accept Evolution. However, there was little support or enthusiasm for Darwin’s mechanism of Natural Selection.
While all this was going on, an Austrian monk called Gregor Mendel (1822-1884) was carrying out important experiments that would eventually prove that Darwin’s Natural Selection was in fact correct. For seven years, Mendel cross-bred different strains of pea plants to investigate how characteristics like the colour of the flowers got passed down the generations. In a quite amazing feat, he cultivated almost thirty thousand pea plants and in doing so figured out the basic principles of, what would later become known as, Genetics. He showed that offspring received characteristics from both parents, but only the dominant characteristic was expressed. This was contrary to the prevailing view at the time that the characteristics of both parents were somehow “blended” together. Unfortunately, Mendel’s work was overlooked by scientists in the West, only coming to light long after his death.When Mendel’s work on Genetics was finally “re-discovered” in 1900, it started to make sense of evolution in a new way and stimulated renewed interest in Darwin’s work of fifty years earlier. Building on Mendel’s work, studies showed how genetic traits in a population of animals or plants could be selected by environmental pressures and how a population could become progressively adapted to its environment. However, despite becoming universally accepted by the scientific community in the early 20th century, Evolution by Natural Selection continued to meet strong opposition by certain religious groups. In 1925, the State of Tennessee, USA outlawed the teaching of Evolution completely. When one teacher, John Scopes, continued to teach evolution he was tried and found guilty in what is now infamously known as the “Scopes Monkey Trial”! This religious opposition to Evolution has continued to the present day. However, today opposition to Evolution is often more subtle. This fact is supported by an article published in latest issue of science entitled “Why many U.S. biology teachers are ‘wishy-washy’.
Article by : Shaktiprasad Ingale