Florid or falsifiable? The use of metaphors in science.

Metaphors can be a mixed blessing in science. Some are incredibly illuminating, some (which presumably seemed insightful when conceived) act to befuddle an argument. However, usually they seem to serve as something in between – a useful label, a good hint and the start of a discussion.

Of course, boiling down an entire scientific argument or idea to a single phrase is tricky. Science, as with most of life, is more nuanced than a few words designed to catch the attention. This week I watched online as Denis Noble talked at the International Union of Physiological Sciences Congress in Birmingham about how neo-Darwinism has got evolution wrong. It’s a shame that his view of all of modern evolutionary biology seems so heavily based on The Selfish Gene, a book that is now over 30 years old. One argument in Noble’s lecture, a well-mused motif in the philosophy of biology, was that genes cannot be selfish. I’m not going to even try to get into that discussion here, but it illustrates clearly how a simple metaphor doesn’t always beget a simple interpretation.

The best-known metaphor in my sub-field, the comparative and evolutionary study of culture and traditions, is the ‘ratchet effect’. It was coined by Mike Tomasello and colleagues about twenty years ago to describe how, through being able to accurately learn from others, human culture gets more and more complex and diverse. In other animal species individuals may learn socially from one another and, in some cases, have simple traditions that last multiple generations. Human culture is different, though, we don’t just follow traditions, over generations we build on them. We work together to produce hugely complex technologies, institutions and rituals. We accurately learn from others, copying their every move, trying to understand their motivations and goals. As a result human culture, with its cumulative improvements accurately passed on over generations, simply dwarfs the traditions of other species.

So why the ‘ratchet’? Well, the reason that it was invoked was to describe a system where changes keep being made, the gear keeps moving round a bit further, never slipping back, each click dependant upon the last. Each human generation builds upon the knowledge and experience of those before it, tweaking and combining ideas to make new, more complex, more rewarding ones. Let me be clear, it is a metaphor of mechanism and not determinism – no-one is arguing that it reaches a final point or that some populations are further round the ratchet than others. It’s not the same ideas that each generation in each population is racheting, but across the world there’s a steady rattle as new rituals, technologies, techniques and traditions are built on the back of older ones.

It’s a neat metaphor, nicely characterising how human culture is always moving. Sure, it’s not perfect. As with every scientific metaphor, it hides some of the complexities of the idea and there is a chance that it could be misinterpreted, but I like it. For an concept about how technologies (and other traditions) change, it seems apt – something I’m sure the authors knew when they penned it.

I can’t help thinking that some people worry too much about the specific etymology of scientific metaphors, placing too much emphasis on a catchy phrase, rather than the ideas behind it. On the other hand maybe there’s merit to that, the way someone describes their idea probably gives a good clue to their thinking. And, of course, if it gets people discussing an idea, it’s probably done its job.


Dean LG, Kendal RL, Schapiro SJ, Thierry B and Laland KN (2012) Identification of the Social and Cognitive Capabilities Underlying Human Cumulative Culture. Science, 335 (6072) 1114- 1118
Tomasello, M (1999) The Cultural Origins of Human Cognition. Harvard University Press, London
Webcasts from IUPS 2013 available on Congress website


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