Charles Darwin’s 1859 publication, On the Origin of Species, changed the way we look at biology forever. Its central idea, evolution by means of natural selection, explains how all life evolves. No single idea has ever explained so much. It stands apart from most, if not all, scientific discoveries in its outreach and simplicity. As with most great ideas, once grasped, one is inclined to ask: “Why didn’t anyone think of this before?”
Actually, others had similar ideas before Darwin, including fellow naturalist Alfred Russel Wallace. Wallace had figured out that species evolve through natural selection and sent Darwin his version prior to Darwin’s landmark publication. In 1858 they jointly presented their work to the Linnean Society of London. But ultimately, it was Darwin’s detailed explanation in 1859 that history would recognize.
Organisms evolve over time by means of natural selection. Each generation is tested by its environment; the traits that aid an organism to survive and reproduce will tend to be passed on to the next generation. Not necessarily all the time, but often enough or in greater numbers. Traits that are not useful will tend to be discarded when the organism that bears them fails to survive or reproduce.
Through this process survivors are copied with slight random variations, which are then tested many times over. In other words, survivors live longer and usually reproduce more, keeping their survival traits alive in the ensuing generations. Darwin wasn’t the first to suggest that organisms evolve from previous forms, but he provided the mechanism (natural selection).
Darwin delayed the publication of his theory of evolution for about 17 years,
because he feared a public backlash. And he was right in assuming that controversy would follow. His chief concern, I can only speculate, was probably religious. Natural selection can easily be viewed as taking god out of the creation business. If nature is shaping all of life, what is god left to do? Despite some criticism, his book drew worldwide interest. Even today evolution still gets some people upset.
(Darwin’s Tree of Life)
Why is such a profound idea so difficult for some? Let’s look at possible reasons why:
- Religious : Evolution contradicts the bible’s account of creation; however, many people seem to have no problem squaring evolution with the bible. They either don’t really know what the bible says or they don’t take it literally. Whereas literal interpreters of the bible clearly see what evolution means for their faith. For them evolution is akin to a fatal blow.
- Supernatural thinking: If one is inclined to believe that there exists a dimension outside the laws of nature, then anything is possible. Life can then be guided by a supernatural force. If that is the case, evolution is no longer required as an explanation.
- Evolution is confused with natural selection: I suspect that some people think of evolution as simply gradual change over time. In terms of the cause, they can use their imagination. However, the key insight is the means by which change happens. Evolution is the process and natural selection is the mechanism.
- Deep time: There is nothing in everyday experience that can prepare us for the time scales involved in evolution. Simple life emerged on earth (in the ocean to be exact) 3.8 billion years ago. And from there spread to all regions of the planet. That’s 38 million centuries for life to evolve to eventually create you and me. Given enough time, minor variations in each generation can result in changes that may be hard for some to grasp.
- Sometimes the truth hurts: There is no plan in evolution, no final destination that has to be achieved. Furthermore, human beings don’t hold any privileged position in the tree of life. Darwin described life as a family tree, with different species spreading in all directions. Life could no longer be seen as analogues to a ladder, with humans occupying the top rung.
A Scientific Idea
Darwin’s idea was much more than a moment of insight. It was a scientific idea, a theory that he developed based on years of experience as a naturalist. As a young man Darwin sailed across the globe on the HMS Beagle. He accompanied Captain Robert FitzRoy on a 5 year journey, where Darwin collected a multitude of natural specimens and fossils. It is on this voyage, from 1831 to 1836, that Darwin gathered extensive evidence for his theory of evolution.
Darwin collected many fossils; some were from ancient sea creatures, which he found in mountainous regions. This was clear evidence that mountains moved over time—that a high altitude had once been under water. From a geological perspective the earth had changed slowing throughout the ages. This principle of gradual change over time was extended to include life forms. If the earth changed, life could also change.
Influential to forming his ideas, Darwin collected bird specimens (finches) from the Galapagos Islands in South America. He noticed that the shape of the finch’s beaks varied depending on the island they came from. Darwin reasoned that the finches all originated from a common ancestor, and had evolved different beaks. The finches had become isolated on separate islands, thus evolving differently to meet the demands of the local food supply.
These and other similar ideas got the wheels in motion for Darwin, showing him that species were not stable, that they can change dramatically over long periods of time. Some of the fossils he unearthed were from extinct species, distant ancestors that resembled species that were still living. He also examined different mammal skeletons and noticed they were all variations of a similar bone structure. Beyond his own ideas, Darwin corresponded with other naturalist around the world through letters, thus gathering piles of information.
It would eventually culminate in the publication of On the Origin of Species. Darwin surely struggled with the implications of his theory, as it would have been radical in Victorian England. Creationism was the overwhelming belief of the time; however, it became clear to Darwin that organisms where not created in their present form. Darwin must have been apprehensive upon the publication of his book. Nevertheless, he was guided by the overwhelming evidence he observed as a scientist. He had to accept what his scientific mind was telling him, regardless of the belief of the day. Darwin’s Theory of Evolution is a great scientific idea, and that is why it still stands today.
References: The Genius of Charles Darwin, The Science Foundation, https://www.youtube.com/watch?v=ptV9sNezEvk, Published on Jan 12, 2011.