What is Darwins Theory of Evolution? Despite advances that have allowed humans to profoundly alter our environment, natural selection continues to work on our species. Pin It Despite advances that have allowed humans to profoundly alter our environment, natural selection continues to work on our species. Credit: imageZebra | Shutterstock View full size image More than 150 years after Charles Darwin published his theory, evolution remains controversial. Some politicians and religious leaders denounce it and would invoke a higher being as a designer to explain the complex world of living things, especially such specimens as humans. School boards debate whether the theory of evolution should be taught alongside other ideas, such as intelligent design or creationism. Mainstream scientists see no controversy. Evolution is well supported by many examples of changes in various species leading to the diversity of life seen today. So just what is evolution, and how does it work? In the first edition of The Origin of Species in 1859, Charles Darwin speculated about how natural selection could cause a land mammal to turn into a whale. As a hypothetical example, Darwin used North American black bears, which were known to catch insects by swimming in the water with their mouths open: I can see no difficulty in a race of bears being rendered, by natural selection, more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale, he speculated. The idea didnt go over very well with the public. Darwin was so embarrassed by the ridicule he received that the swimming-bear passage was removed from later editions of the book. Scientists now know that Darwin had the right idea but the wrong animal: instead of looking at bears, he should have instead been looking at cows and hippopotamuses. The story of the origin of whales is one of evolutions most fascinating tales and one of the best examples scientists have of natural selection. Natural selection Darwins theory of evolution by natural selection is one of the best substantiated theories in the history of science, supported by evidence from a wide variety of scientific disciplines, including paleontology, geology, genetics and developmental biology. To understand the origin of whales, its necessary to have a basic understanding of how natural selection works: It is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits. Changes that allow an organism to better adapt to its environment will help it survive and have more offspring. Natural selection can change a species in small ways, causing a population to change color or size over the course of several generations. This is called microevolution. But natural selection is also capable of much more. Given enough time and enough accumulated changes, natural selection can create entirely new species. It can turn dinosaurs into birds, apes into humans and amphibious mammals into whales. Mutations The physical and behavioral changes that make natural selection possible happen at the level of DNA and genes. Such changes are called mutations. Mutations can be caused by chemical or radiation damage or errors in DNA replication. Mutations can even be deliberately induced in order to adapt to a rapidly changing environment. Most times, mutations are either harmful or neutral but in rare instances, a mutation might prove beneficial to the organism. If so, it will become more prevalent in the next generation and spread throughout the population. In this way, natural selection guides the evolutionary process, preserving and adding up the beneficial mutations and rejecting the bad ones.
Posted on: Mon, 19 Jan 2015 09:38:41 +0000
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