It is hardly surprising to find that Charles Darwin’s On the Origin of Species was voted the most influential academic book of all time. His book changed our perception of humanity and its relationship to the natural world in ways that are simultaneously inspiring and disturbing. It presents two major challenges to the traditional view of the world as a divine creation. The most basic is the demonstration that all species – including humanity – have to be seen as products of a natural system of evolution. All species are related to one another as end-points of the branches in the great tree of life.
This vision challenges the conventional view that humans stand above nature by virtue of a unique spiritual capacity. In Darwin’s worldview we may be more advanced than the other animals by virtue of our mental and moral faculties, but we are part of the same web of relationships and subject to the same natural laws. This message is coming home to us ever more clearly as we find that our efforts to control nature all too often disrupt its operations in ways that may eventually challenge the future of life on earth.
This then points to the second, equally controversial thesis of Darwin’s book. The reason why evolution is an ever-branching tree rather than a simple line of progress leading up to the human race is that it operates by the process he called natural selection. Populations change because some individual variations work better in the environment to which they are exposed than others. If the environment changes, then the population will adapt as those best able to cope with the change outbreed the others. The variations themselves show no apparent purpose (today we explain them as the result of genetic mutations – copying errors in the transmission of information coded into the DNA). They are not totally random and modern biologists are beginning to understand the developmental constraints that play some role in directing the production of new characters. But as Darwin himself well appreciated, these influences are no more pointing toward some transcendental goal than are the variations themselves. We are not the intended outcome of the process because it has no predetermined goal. Neither the process nor the multiplicity of its products can reasonably be seen as the working out of a plan imposed by a benevolent Creator.
Some who find the basic idea of evolution acceptable would prefer to see the process as the unfolding of a divine plan. Darwin would have none of this. Nature shows too many signs of imperfection and short-termism for there to be such an overarching design. Every species is left to face the challenge of an ever-changing environment as best it can. We are now capable of changing the environment ourselves rather than merely adapting to it. But here again Darwin’s message leads us toward the challenges of the modern world as we find it increasingly difficult to see an unambiguous course of progress in human affairs. We are on our own and cannot seek for guidance in nature, except through the warnings it offers as we attempt to shape it to our own ends.
Charles Darwin’s ‘On the origin of species’ was voted the most influential academic book ever written to mark the inaugural ‘Academic Book Week’ in 2015.
Peter Bowler FBA is a fellow of the American Association for the Advancement of Science and a corresponding member of the Académie Internationale d’Histoire des Sciences. He was President of the British Society for the History of Science 2004-6.