The Legend of the Sphex¹
For over a hundred years, the great golden digger wasp Sphex ichneumoneus has been a favourite species for ethologists² to study. The behaviour of this species is instructive in several different ways, and in this post we will try to take away a series of lessons.
A Curious Behaviour
The following passage is an excerpt from Intuition Pumps and Other Tools for Thinking, a collection of short essays by Daniel Dennett³;
When the time comes for egg-laying, the wasp Sphex builds a burrow for the purpose and seeks out a cricket which she stings in such a way as to paralyze but not kill it. She drags the cricket into the burrow, lays her eggs alongside, closes the burrow and flies away. In due course, the eggs hatch and the wasp grubs feed off the paralyzed cricket, which has not decayed, having been kept in the wasp equivalent of deep freeze.
Did you just go eeuw, gross? Anyone who reflects on this gruesome fact would begin to question the notion of a Benevolent Creator or Intelligent Designer. In the words of Charles Darwin himself -
I cannot persuade myself that a beneficent and omnipotent God would have designedly created parasitic wasps with the express intention of their feeding within the living bodies of Caterpillars.
This then, is the first lesson — the moral angle to the Legend of the Sphex. But in case the suffering of crickets and caterpillars doesn’t do much to shake our convictions, here’s something that relates to a thinking, feeling mammal — elephants who grow old enough, eventually starve to death because their teeth fall off. Couldn’t Nature have come up with a more dignified, more humane end to the life of such a magnificent creature? The logical answer is “No, because there isn’t anyone in charge or anyone to appeal to”. In the words of Richard Dawkins -
The universe that we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, no good, nothing but pitiless indifference
Creationists must invoke amazing powers of self-deception to rescue their moral intuitions from unpleasant facts such as these.
Competence Without Comprehension
Next we’ll look at another curious behaviour of the Sphex wasp, quoting from the same source -
The wasp’s routine is to bring the paralyzed cricket to the burrow, leave it on the threshold, go inside to see that all is well, emerge, and then drag the cricket in. If the cricket is moved a few inches away while the wasp is inside making her inspection, the wasp, on emerging from the burrow, will bring the cricket back to the threshold, but not inside, and will repeat the preparatory procedure of entering the burrow to see that everything is all right. The wasp never thinks of pulling the cricket straight in. On one occasion this procedure was repeated forty times, always with the same result.
An extremely clever and apparently well thought out strategy turns out on closer inspection to be completely hard-wired behaviour! The wasp seems to be simply executing a series of genetically programmed steps, with not an inkling of what it’s doing and why. In other words, a behaviour that seems impossible to accomplish without intent, purpose, and foresight is in fact achieved without any of these.
Why has the wasp not evolved a more flexible, dynamic routine? Because there is a cost involved, in terms of bigger brains which would need extra protein to grow and extra calories to run. Evolution has a pragmatic “if it ain’t broke don’t fix it” strategy where additional investments will only be selected for if they deliver enhanced survival or reproductive fitness. And a wasp in its natural environment doesn’t usually have to contend with biologists running scientific experiments!
Similar patterns have been observed in birds. Cuckoos lay their eggs in the nests of other birds (the “host”). The host keeps feeding the baby cuckoo though it “should” be obvious to it that the thing in their nest is not their own offspring. For one thing, the baby cuckoo is often larger than the adult host while still in the nest!
As usual, it’s complicated
While every scientist dreams of hitting upon a simple, neat hypothesis which explains all the facts, real world data seldom affirm such hopes. It turns out that only some Sphex wasps are rigid enough to get stuck in a loop⁴.
After two or three times, … she grabbed the prey’s antennae with her pincers and slid it into the hole. Now who’s the dummy?
This is our third and final lesson. Unfortunately, the anecdote of the Sphex wasp’s algorithmic behaviour became so popular among evolutionary biologists that the fact of the experiment not being replicable every time was almost forgotten. But scientists should be wary of over-generalizing from sparse evidence. “Never let the facts get in the way of a good story” is poor advice to give to a scientist and not something any rational person should endorse. It is in fact the very antithesis of Science.
Notes
¹ The title is inspired by the Riddle of the Sphinx: which creature walks on four feet in the morning, two feet in the afternoon and three in the evening?
² Scientists who study the behaviour of animals in their natural habitat
³ Dennett himself is quoting from The Machinery of the Brain by Dean Woolridge (1963)
⁴ This quote is from the work of Jean-Henri Fabre (1879) whom Dean Woolridge himself was quoting
