Science issues

Teaching evolution
Author: Peter Campbell

Evolution by natural selection is fundamental to biology. It provides vital insights into major concerns such as agriculture and human health, and can lead to practical solutions. It also explains human origins and connects us with other forms of life on earth. All young people, as part of their preparation for modern life, should learn about these ideas at school.

Given its importance, how then should we introduce evolution by natural selection? What is most likely to engage interest and develop understanding?

At primary school, pupils learn about the variety of life and begin to learn about classification. At KS3 they develop that knowledge and begin to learn about ecological relationships, inheritance and selective breeding.

A conventional approach at KS4 is to begin with Darwin, a man with a beard who lived in the 19th century. While learning about his ideas, pupils may also be taught about how Darwin came to publish On the Origin of Species and the public debate which followed. This approach must seem distant, dull and formulaic to many students.

Would it not be better to begin with the present?
• Molecular biology now provides an alternative route to understanding the evolution of species and their classification. Similarities and differences in DNA between species show sometimes surprising connections in the tree of life.

• Antibiotic-resistant bacteria are becoming a real threat to public health. International travel and commerce makes outbreaks of new strains of ‘flu and other infectious diseases a greater threat.

• ‘Evolutionary medicine’, a new branch of medicine, studies contests between the body's defences and pathogens. It also explains why some people are prone to certain medical conditions as a result of evolutionary selection.

• Juries and judges routinely accept DNA evidence in criminal cases. DNA evidence is also used to determine paternity and to identify people at risk of genetic diseases.

• Understanding the link between geology and fossils is enabling scientists to make new finds of 'transitional' fossils, filling in the fossil record of evolution.

• Embryology shows many similarities in the way that apparently different species develop.

• Human activities and climate change are driving some species to extinction. There are interesting examples worth studying such as icefish, which lost their haemoglobin in oxygen-rich Antarctic water and will not survive as ocean temperatures rise.

Today the evidence for evolution is overwhelming. I accept that not all of these ideas are accessible at GCSE level. But a careful selection of them could provide a much more motivating introduction for most students to the subtle ideas associated with evolution by natural selection, which need careful explanation. The huge computing power used to sequence genomes and accompanying challenges of data storage too would interest many students, and may even suggest career options for some.

A more contemporary introduction to evolution could also provide insight into how evidence and explanations interact, or how scientists work and communicate. Arguably, getting across the nature of science is of equal importance when teaching evolution, for waiting in the wings are dogmatic creationists with no respect for evidence.

Can we afford to miss conveying the excitement of science, evolution as understood now and in recent decades? Why not leave Darwin's fascinating story as a mere footnote, to be pursued at A-level and beyond?

References
Sean B Carroll (2008) The making of the fittest. London: Quercus
Brian & Deborah Charlesworth (2003) Evolution: A Very Short Introduction
Donald Prothero, ‘What missing link?’ New Scientist, 1 March 2008
Neil Shubin (2008), Your inner fish. London: Allen Lane

Comment

Your Comments

Thu, 13 March 2008 : Dean Madden

Pete is correct and I've read the books he refers to and agree about the importance of DNA evidence. Bravo. I can't really understand why on earth it took so long for curriculum/textbook etc people to realise that DNA evidence for evolution was important (the first papers on this appeared in the 1960s). Comparative sequence data, both of DNA and proteins, have only been available comparatively recently, but it's still amazing that there was this bloody great elephant standing in the room, so to speak, and so few people seemed to be aware of it. As some of you know we're working on post-16 materials for this, to be sent to all UK schools free-of-charge next year (bookmark this spot: www.dnadarwin.org). To that end, we're currently working on some introductory exercises to introduce the bioinformatics stuff (principles of phylogeny, sequence alignment etc). It looks, at this stage, as if it wouldn't make much sense unless you understood the basic principles of variation, natural selection and inheritance, as well as something about DNA and proteins. So, I may change my mind, but I suspect that kids would benefit from understanding Darwinian evolution (a bit) first before encountering the DNA evidence. Then again, the Nuffield way of doing things would be to present the evidence: biogeography, fossils, molecular evidence and so on -- then to derive a theory to account for this, which might also work. The problem with all this 'new' stuff is often that people get tied up with the details and can't decide what's vital and what can be left out. It needs some really careful thinking about what people need to know, understand and so on. I think it could easily work at GCSE if you did it the right way. BTW: I quite like Darwin, and I wouldn't want to leave him out, bearded Victorian or not. I know Nuffield currently objects to these people -- I had to delete a picture of Buchner from a Nuffield prac. recently as Sarah C. didn't like him -- but that's just sexist beardism, and is actually a rather old-fashioned view. (Not that I would ever wish to disagree with Sarah, really.)

Thu, 13 March 2008 : Ralph Levinson

Peter You make some very interesting, important and detailed points. I agree with you on almost everything although there are some small differences. First evolution is fundamental to an understanding of modern biology and indeed as genomics and modern biology advances there is more and more compelling evidence in favour of natural selection as the theory which underlies evolution. It also helps us explain how natural life is organised and supposedly anomalous organisms such as aquatic mammals, lungfish and flightless birds. I think your approach is right although evolution ought to be the default discourse at Key Stage 4, in other words, how does evolution explain the compelling phenomena you mentioned rather than these phenomena being illustrative of evolution. But I do want to raise the issue of creationism and the problematic wording of ‘dogmatic creationists with no respect for evidence’. We have to accept that the majority of the students we teach, and possibly a small minority of science teachers, are in fact covert if not overt creationists. I think it is a danger to see them as the enemy. On the contrary creationism could be welcomed as a challenge to natural selection because it would encourage students to think about the role of evidence and inference in constructing scientific theories. If we take the literalists first, ie those who say the Earth is 5 000 years old then it could be very helpful in a scientific context to formulate this statement as a hypothesis. If it is true what evidence would be consistent with this theory and what evidence would refute it.? What kinds of arguments do we use to examine the evidence? This seems to be a helpful challenge in digging a bit deeper into the nature of science. Then there are the so-called ‘intelligent designers’ who oft-quote the perfectly formed cilia and the wondrous eye. How can such intricate mechanisms with mutually supporting structures have evolved? Well, in fact there are more than enough examples in nature and the fossil evidence supplies many more. But it does seem to be to be useful to be able to meet that challenge. Whether such approaches convert any students, I have no idea. Probably not immediately but it might give pause for thought and reveal what science is really about. I am certainly not advocating teaching creationism. What I am suggesting is that we take care over our reaction to its introduction in a lesson and instead meet it as a test to promote the fact of evolution and the theory of natural selection.