Darwin revolutionised biology, indeed no-one else has ever had such an impact on the field. But science doesn’t simply stop and applaud its heroes for a job well done. It is the nature of science and scientists to test people’s ideas, reject them if they fail these tests, update them when new evidence comes along. Darwin’s theory is no exception, in fact if anything, because it was so important and novel, it was tested more rigorously than most theories have been. For many years Natural Selection was very unpopular and our understanding of Evolution is still changing. Biologists continue to ask questions and test new and old ideas, and more and more details are made clear in the process. After 150 years of testing and updating, how do Darwin’s ideas seem now?
What Did Darwin Get Wrong?
Inheritance
Perhaps Darwin’s only major failure was that he didn't understand inheritance correctly. He proposed his own theory of inheritance, called Pangenesis, but it was based on scant and unreliable evidence and has long been rejected. In his publications he often talks about the inheritance of acquired characteristics, or evolution by ‘use and disuse’ – the famous example being that blacksmiths (who have big muscles) would pass on their bulk to their children.
Part of Darwin’s genius however was to realise that not understanding inheritance wasn’t a problem for his theory of natural selection. He had proof from his work on domesticated animals and plants, and from his reading and communication with other scientists, that characteristics can be, indeed are, inherited. This was enough to build his theory. In On the Origin of Species Darwin leaves inheritance largely as a ‘black box’.
Had things gone slightly differently Darwin could have heard the answer, for only two years after Darwin’s death Weismann published his correct “Germ-Plasm” theory, and during Darwin’s own lifetime Gregor Mendel had published the results of his experiments on crossing peas which began the field of genetics. Combining Darwin’s theories of evolution with Mendel’s genetics and Weismann’s Germ-Plasm theory was the most important breakthrough in biology since Darwin published The Origin. The discovery of DNA and it’s structure and method of replication was the next great update, opening doors to whole new fields of research and a whole new world of evidence for evolution.
Species, Speciation & Evolution In Action
Darwin was very clear about how natural selection operated to drive the evolution of a species. He was less clear on what a species was and how speciation occurs. Work in the first half of the twentieth century built on Darwin’s best guesses and improved our understanding of speciation.
Darwin also considered evolution to act too slowly to be observed; he was wrong. We now have many examples where we have documented the evolution of a population of animals or plants within a human’s life time. You can read more about this in the case studies section.
The Fossil Record
Darwin had little faith that the fossil record could provide any proof for his theory. Many anti-evolutionists ask “where are the intermediates in the fossil record?” seemingly confident in the lack of examples. The truth is the fossil record is very incomplete, but we have many, many examples of fossils which provide proof of evolution. We have fossils of unicellular organisms that are estimated to be over 3 billion years old, we have fossils which document the origin of animals, we have fossils of whole groups of now extinct organisms such as trilobites and dinosaurs, and we have sequences of fossils through which we can trace the evolution of major groups of plants and animals: tetrapods from fish, birds from dinosaurs, humans from more ‘ape-like’ ancestors. The fossil record, even though it is incomplete provides masses of evidence for evolution by natural selection, and absolutely no evidence for any alternative explanation!
Darwinian Evolution: Fact, Theory Or Fiction?
Darwin’s key theories have been rigorously tested and debated for 150 years. No other set of ideas in biology or, probably, elsewhere has been studied so intensely. We now know far more than Darwin did about the history of life on earth, and the processes which shape it. Throughout this website we refer to Darwin’s theory of evolution. A theory is a framework or explanation which explains relevant observations and makes testable predictions. The evidence supporting Darwin’s theory is overwhelming. So too is the lack of evidence for any alternative. This website only scrapes the very surface of the massive bulk of evidence.
After 150 years of research we can safely say that Darwin’s theories of evolution, common descent, multiplication of species, natural selection and sexual selection are facts. Nice one Darwin!
Written by Stephen Montgomery
References & Further Reading
Evolution: The History of an Idea
by Peter Bowler, University of California Press: 1983
The Evolution of Darwinism
by Timothy Shanahan, CUP: 2004
This Is Biology
by Ernst Mayr, Harvard University Press: 1997