“The great tragedy of Science – the slaying of a beautiful hypothesis by an ugly fact.“
Thomas H. Huxley (1825 – 1895)
English biologist; supporter of Darwin;
father of Aldous & Julian Huxley.
In the lead up to this, the 200th anniversary year of Darwin’s birth, I’ve attended my fair share of evolutionary research seminars. Surprisingly, few presented alternative hypotheses, or better yet, multiple alternative hypotheses. In fact, rarely was a specific evolutionary hypothesis enunciated. And when one was, the speaker usually failed to point out what critical experiment or observation could falsify it. Admittedly, these talks were directed toward a general, non-specialist audience. But many of those in attendance were students and this “omission” seemed like a missed didactic opportunity. Moreover, Evolutionary Theory is championed (all too often in courthouses in the United States) as a true science (as opposed to Creation “science”) because its hypotheses are falsifiable. So where are all these falsifiable hypotheses????
My undergraduate Invertebrate Zoology professor, Demerest Davenport emphasized (i.e. drummed it into our skulls) that adaptive questions can be addressed using “Strong Inference”. He had us all read the 1964 SCIENCE article of that name, by John R Platt1. At the time I was not especially impressed because it sounded like what we had been taught in General Biology and General Chemistry and had already accepted as standard operating procedure. In his recent blog, Massimo Pigliucci2 suggests that the main point of Platt’s article was to explain why the “soft sciences” (including the evolutionary sciences) were less successful than the new (at the time) “hard sciences” like molecular biology and modern physics. I am not sure I agree with Pigliucci’s hard- vs soft-science dichotomy (perhaps that is a discussion for a later blog). In any case, as a young scientist, my take home message was that “Strong Inference” could be applied to all kinds of questions and that it should have been applied more often than it had. Perhaps, that is still so today.
“In its separate element, strong inference is just the simple and old-fashioned method of inductive inference that goes back to Francis Bacon. The steps are familiar to every college student and are practiced, off and on, by every scientist. The difference comes in their systematic application. Strong inference consists of applying the following steps to every problem in science, formally and explicitly and regularly:
1) Devising alternative hypotheses;
2) Devising a crucial experiment (or several of them), with alternative possible outcomes, each of which will, as nearly as possible, exclude one or more of the hypotheses;
3) Carrying out the experiment so as to get a clean result;
1′) Recycling the procedure, making sub-hypotheses or sequential hypotheses to refine the possibilities that remain; and so on.”1
The advantage of testing a main hypothesis against multiple, alternative hypotheses is that it protects the scientist against what T.C. Chamberlin called over “affection for his intellectual child”:
“The moment one has offered an original explanation for a phenomenon which seems satisfactory, that moment affection for his intellectual child springs into existence and as the explanation grows into a definite theory his parental affections cluster about his offspring and grows more and more dear to him….There springs up also unwittingly a pressing of the theory to make it fit the facts and a pressing of the facts to make them fit the theory….”1
A Beautiful Hypothesis
Dr Stephen Colbert (Hon DFA) has pointed out, sometimes you have to think with your gut. And evolutionary theory can generate some great gut-worthy hypotheses that simply “feel” right. Here is an example: You all know “Why” the giraffe has a long neck? As long ago as Lamarck, the explanation has been “to get to the top of the acacia tree to reach the tender, most nutritious leaves'” Darwin and Lamarck may have differed in their notion of “How” the giraffe acquired its long neck but they would have agreed that it was advantageous in competing for food. We’ll call this the Interspecific Foraging Competition Hypothesis (IFCH). Soon after Darwin and Wallace proposed Natural Selection theory, the IFCH had become the accepted explanation for the giraffe’s long neck.
Now you have to admit that the IFCH is a beautiful hypothesis. It just feels right (sensu “Truthiness”). It just makes sense. It fits (with Darwinian natural selection).
Why ruin it by testing it?
An Ugly Fact
Why? Because there might be a better explanation. One obvious test of IFCH is to determine how giraffes actually USE their neck? In 1996, Robert Simmons and Lue Scheepers decided to do just that, and in their review of the literature, Simmons and Scheepers found that giraffes don’t use their neck in a way consistent with the IFCH — they tend to spend most of their time foraging at about shoulder height even when food is scarce and competition high. Now you could attempt to “save” the beautiful hypothesis by special pleading, or by suggesting that all of the many studies cited by Simmons and Scheepers “missed” something. Of course, then you would be reduced to simply refuting ugly facts. However, if there were plausible alternative hypotheses, then those could be explored and perhaps we can reject the IFCH without feeling empty-handed. The irony of the story of the giraffe’s long neck is that Darwin had developed another theory (Sexual Selection Theory) that could have been used to generate plausible alternative hypotheses to IFCH (although he didn’t know it at the time, he came close when he recognized that male giraffes use their long necks to swing their heavy skulls and stubby horns as weapons). But the rest of Simmons and Scheepers story will have to wait until next time.
Tom Nolen is an evolutionary biologist with an interest in sexual selection, as well as the neural basis of communication and sensory function. He is the chair of the Department of Biology at SUNY New Paltz and a founding member of the EVoS program there. While he mostly studies insects, snails and jellyfish, he has been known to observe the occasional Hominin, being one himself.
Citations (Read these before posting comments –start by Googling the authors)
- Platt, JR (1964). Strong Inference: Certain systematic methods of scientific thinking may produce much more rapid progress than others. SCIENCE 146(3642), pp: 347-353.
- Pigliucci, M (2009). Strong Inference And The Distinction Between Soft And Hard Science. http://www.scientificblogging.com/rationally_speaking/strong_inference_and_distinction_between_soft_and_hard_science cited on the web, May 31, 2009.
- Chamberlin, TC, cited in Platt (1964) above.
- Simmons, R and Scheepers, L (1996). Winning by a neck. Sexual selection in the evolution of giraffe. American Naturalist. 148(5), pp: 771-786.