Many people have wondered why Darwin took so long to publish. He presents his essay of 1844 to the Linnean Society to show that his ideas have remained unchanged between then and 1858. But nobody really knows why he waited. Maybe we should be asking (as Dov Ospovat, an historian of science, has done) what would have been lacking if Darwin had, instead, published his essay in 1844.
In the 1830s, many biologists, including Darwin, adhered to a strict teleological explanation of the complexity of life on earth. That is, they believed that organisms are perfectly adapted to their environment. But what if the environment changes? According to Lyell, a change in the environment caused species to go extinct and be replaced by others. However, this notion left much unexplained. For instance, why arenΓÇÖt the same species found around the world in apparently identical climates? Why do some organisms possess rudimentary, or vestigial, structures? Why do flightless beetles have wings?
As Darwin began to think about transmutation, he came to the conclusion that as the environment changed, organisms would change as well. However, he initially thought that all change would be adaptiveΓÇöin order that organisms could remain perfectly adapted to their surroundings. In September of 1838, Darwin read MalthusΓÇÖs Essay on the Principle of Population and wrote in his notebook that the power of geometrical increase in population was ΓÇ£a force like a hundred thousand wedges trying [to] force every kind of adapted structure into the gaps in the economy of nature, or rather forming gaps by thrusting out weaker ones.ΓÇ¥
Although this insight led him to the idea of natural selection, it did not immediately lead him to give up on the idea that organisms are perfectly adapted to their environments. At this stage, he seems to have thought of the pressure of population as eliminating those that were not perfectly adapted. But by March 1839, Darwin was clearly thinking of variations simply as differences rather than adaptive improvements.
In his essay of 1844, Darwin still believed in perfect adaptationsΓÇöand malthusian population pressures provided a mechanism to explain how adaptations can be adjusted so that they remain perfect despite a changing environment. He believed that a change in the environment was needed in order to produce variation and, therefore, transmutation. One consequence of this idea is that species would only change if the environment changed.
By the time the Origin of Species was published, Darwin had realised that adaptation is not perfect, but relativeΓÇöin any population it is always possible to become better-adapted to the environment. Chance variations can occur at any time, and Malthusian population pressures can always lead to improvements in adaptations regardless of whether or not the environment is changing. However, in 1844, Darwin did not see any problems with his theory; he turned to other work to find evidence to support it.
