This is an image from the nation’s best selling high school science textbook by Miller and Levine. Note the language in the image: “with a beak designed to grip and hold tightly, like a pair of pliers".
Designed by whom exactly? God? Under the theory of Natural Selection, beaks are not ’designed’ by any engineer or carpenter. Beaks evolve, responding to selection pressures across many generations.
I think if I brought this example to the textbook authors they would likely admit they didn’t mean to use the word ‘designed’ or it was just a convinient expression. It is not the only use of the word ‘design’ in the text. Turns out according to the textbook authors geckos feet are "designed" to maximize surface area so as to scurry up walls. Very clever designer.
Is this a case ‘No Harm, no foul?”. I mean its probably ok if we use the word ‘design’ to stand in for the idea of evolution, right? It’s a little cumbersome when talking about a feature of an organism to each time say ‘the feature evolved due to selection pressure over many generations'.
But one problem with using ‘design’ as a pedagogical abbreviation for evolution, is evolution does not act like a human engineer. Birds actually do a lot more with their beaks than just break seeds. They also use beaks for grooming, fighting, courtship, feeding their young, singing, heat exchange and breathing. Selection pressure occurs on the structural feature in relation to the totality of those uses and their composite fitness in a given environment. We probably could make the beak stronger by filling the bird’s nares (nostrils) with bone but then the bird would need to find another way to breathe.
If we want to compare a beak with a human made artifact we could pick something like a Swiss-army knife. Anyone who has used a Swiss-army knife knows that each of the tools differs slightly from its stand-alone counterparts. The scissors have a small spring, the tweezers are tiny, the bottle opener works differently than its broader, stand-alone, ringed cousin, etc. The explanation for this design, of course, is that in addition to the scissors needing to be able to cut, they also need to fold back into a slim package and not disturb the co-inhabitants. These multiple constraints are similar to the multiple constraints a beak needs to fulfill for a typical bird.
The belief that a single feature must map to a single purpose in the way engineers usually think of design for simple objects tripped up many early naturalists who, for instance, thought that because an animal’s skin, fur or feathers could be useful camouflage that meant that all patterns and colorings must be about camouflage. This led to rather outrageous claims humorously documented by the late Steven Jay Gould such as that flamingos were well suited to blending-in during sunsets as naturalists struggled to reconcile facts with theory. As Darwin himself realized, some features of organisms are not functional for what we assume is their evident purpose: a peacock’s tail feathers do not aid in flight but peahens find them very becoming!
The French word bricolage or roughly translated, tinkering, has been offered as a better metaphor for how natural selection generates complexity. Natural selection is not an orchestra playing instruments designed solely for music, it is the percussion band on the street corner that uses spoons and bowls for its drums only later to use the same spoon and bowl to eat dinner.
Does this apparent nuance matter beyond teaching kids to be scientists? I think it does. Work from the behavioral economics literature suggests we can all fall into the fallacy of teleological or, in this case, design thinking when our cognitive resources are challenged.
Any time scientists find themselves thinking that a given 'adaption' is 'for' some narrow purpose I think they should pause and reconsider. Nature existed prior to our inventions and nothing binds it to our design processes.