(My latest book God vs. Darwin: The War Between Evolution and Creationism in the Classroom has just been released and is now available through the usual outlets. You can order it from Amazon, Barnes and Noble, the publishers Rowman & Littlefield, and also through your local bookstores. For more on the book, see here. You can also listen to the podcast of the interview on WCPN 90.3 about the book.)
Making a Gestalt-type switch is often aided by nudges from outside sources, and in the case of evolution, two such factors came into play: the age of the Earth and concerns about the effects of human population growth.
Darwin was fortunate that he lived in a time when advances in knowledge in other areas, such as the idea of uniformitarianism in geology, were coming along at the same time that he was pondering all the things he was observing on his voyage on the Beagle. The first edition of the first volume of Charles Lyell’s highly influential book The Principles of Geology was published in 1830 and was given to Darwin to read on his voyage on the Beagle that began in 1831. Its argument that small changes (such as erosion) can accumulate over long periods of time to produce major geological features such as mountains and gorges had an impact on him.
By measuring the rates of erosion and sedimentation that were occurring in his own time and calculating how long it would take at that rate to produce the existing rivers and canyons, Lyell concluded that the Earth must be hundreds of millions of years old. Furthermore, Lyell’s books discussed some of the fossil evidence that existed at that time because he used them as aids in arriving at the ages of rocks, although Lyell himself believed in special creation.
The fact that the Earth was now possibly hundreds of millions of years old, rather than merely thousands, created an intellectual environment that was more open to acceptance of the idea that new species can gradually evolve from old ones, because that needed long time spans too.
Darwin (and also Wallace) had a Gestalt-type switch when he was struggling to find the mechanism that causes species to evolve in a way that seemed to indicate directionality. The trigger was Thomas Malthus’s Essay on the Principle of Population (1798) that argued that populations would grow exponentially, except for the fact that they encounter limited resources that restricts growth because of starvation and premature death. This gave Darwin the idea that natural selection could serve as the mechanism he was looking for. In The autobiography of Charles Darwin 1809-1882 (Nora Barlow (ed), 1958, page 120), he describes his epiphany in ways that suggest a Gestalt-type switch:
In October 1838, that is, fifteen months after I had begun my systematic enquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The result of this would be the formation of new species. Here, then, I had at last got a theory by which to work. (my italics)
Darwin and Wallace saw that if there are variations, then it makes sense that some variations are more likely to survive to adulthood and produce more offspring than others. If this advantageous property is heritable and passed on to its offspring then, over time, that particular variation will dominate the population. And by a very long series of such small changes, new species would emerge.
Once Darwin saw the world in this new way, there was no going back. And the rest, as they say, is history.
I have argued that the kinds of switches in viewing the world that Darwin and Wallace experienced are like Gestalt switches in perception. When one changes one’s perspective, suddenly things fall into place and new patterns emerge. What seemed inexplicable, mysterious, and even impossible before suddenly seems clear and even obvious. And once the new way of seeing things is pointed out to others, they immediately see it as obvious too. As Thomas Huxley said after learning how the theory of evolution worked, “How extremely stupid not to have thought of that!” As a result, the new view spreads like wildfire.
But even when told what to look for, not everyone makes the switch. There are some people who never see the new pattern, either because of a rigidity of attitude or, as we will see in the next posting in the case of evolution, because they do not want to see the new pattern because they cannot bear to give up the old one. For them the duck remains a duck and they never see a rabbit.
Next: The mental block of creationists
POST SCRIPT: Well, that didn’t take long!
On Tuesday, I wrote about the atheist billboard campaign in Ohio, putting up three billboards near Cleveland, Columbus, and Cincinnati. Some godly people in the Cincinnati area have already taken offense and threatened violence, requiring the billboard to be moved to another location.
See here for more details.