Wednesday 4 July 2012

Encore: Behe's mousetrap nemesis

[update 8 Jan. 2015] Many people find my interest in mousetraps odd. Björn Ostmann was one, now Micheal Weale also told me so via e-mail. Let me try to explain.

In a way it is odd, but it was Michael Behe, not me, who made it a famous example for irreducible complexity in his book Darwin's Black Box (first published 1996). His mousetrap model then gained some prevalence in the Intelligent Design controversy, because it could readily be understood by laypeople, who would not easily comprehend Behe's other, biological examples (e.g., blot clotting system, bacterial flagellum, Malaria resistance etc.). That's why I thought it natural to look into mousetrap designs and check whether Behe's claims are true for mousetraps in the first place. Otherwise, his conclusions from his favourite model for irreducible complexity would not be valid.

According to Behe, irreducible complexity is a simple concept. A thing that consists of several parts, but does not work if any one part is missing or broken, is irreducible complex. I accept that definition for mousetraps. Hence, mousetraps are irreducibly complex, no matter what other debaters say against this concept. Behe does not go wrong in devising a definition, he does so in what he concludes from it. He concludes that, because mousetraps are irreducibly complex, they can have no precursor that was working with one part less (false, see below), therefore, they can have no history (false, see below), therefore, they cannot evolve (depends on your concept of evolution). And as mousetraps are only a model, Behe maintains these claims for biological traits, also. But refuting them there is someone else's job.[end update]

Behe simply did not do his homework and check patents before making claims about mousetraps (Behe 1996, p. 39-42). Behe observed that a mousetrap does not work if any of its parts is lacking and therefore cannot have had a precursor made up of one part less.
Figure from US patent 528,671 by William C. Hooker
   A search for "animal trap" with a patents search engine can prove the opposite. The seminal patent (Hooker 1894), on which all current flat snap mousetrap designs are based, happened to have one part less—easily. The striker and spring of these traps were formed of one wire part. The figure on the right is from Hooker (1894), a top view on the platform with all the other parts mounted on it.  
    We are interested in the wire part that starts at #3, coils (#4), then runs into the striker (#2 and #8), runs through the coil, and ends at #5 behind the striker. Numbers 6 are fixtures. #14 with the strange exponent is the fixture for the holding bar (#9). Numbers 10, 11, 14, and 15 all belong to the catch with a notch for the bait. 

Behe (1996, p. 43) depicted the following mouse trap and observed:


Figure 2-2 from Behe (1996, p. 43)
"The mousetrap that my family uses consists of a number of parts (Figure 2-2): (1) a flat wooden platform to act as a base; (2) a metal hammer, which does the actual job of crushing the little mouse; (3) a spring with extended ends to press against the platform and the hammer when the trap is charged; (4) a sensitive catch that releases when slight pressure is applied, and (5) a metal bar that connects to the catch and holds the hammer back when the trap is charged. (There are also assorted staples to hold the system together.)" Behe (1996, p. 42)

Apart from usage (striker vs. hammer), these are the same trap functions carried by five parts. You can clearly see that spring and striker (hammer) are made of two parts, where Hooker (1894) used only one wire.

In Hooker's seminal patent spring and striker were made of one wire - two functions carried by one part!

That patent is 'ancestral' to all current flat snap traps. The reason for this is the huge commercial success it had. And the reasons for this in turn are probably threefold. It was small and, as the name 'Out O' Sight' suggests, could be placed where visitors and neighbors wouldn't see it. Hence consumers preferred (selected) it over the more monstrous alternatives of the time. It was cheap to produce in masses and good to package and ship, hence producers and traders preferred (selected) it. The flat surface, as you can see below, could be used for advertisement. This spandrel could be a reason why vendors preferred (selected) it.

Anyway, the direct precursor of Behe's mouse trap had one part less (!), was working perfectly (!), and was such a big commercial success that we today have a very large diversity of modifications of it - though most people don't notice the fine differences!

The reason why spring and striker were later made of separate wire parts are probably several. Firstly, it was easier for mass production and assembly. Secondly, the striker can be made of a harder alloy, the spring of a more flexible one if separate. The separation of spring and striker, however, was not patent-worthy because other traps (not flat) with separate spring and striker already existed in Hooker's days.

Vintage specimen of the real 'Out O' Sight.'


Hooker's patent is worth another footnote, because of thorough confusion of priorities. Here's what I wrote about it in a recent article in the journal Evolution: Education and Outreach. 

“William Chauncey Hooker (1894) patented a flat snap trap: “for catching mice and rats, a simple, inexpensive and efficient trap adapted not to excite the suspicion of an animal, and capable of being arranged close to a rat-hole” (quoted from the patent description). It allowed for mass production and went through many modifications (Drummond et al. 2002).

A safe to set modification of Hooker’s design was invented by John Mast (filed 1899, patented 1903): “The object of the invention is to provide means whereby traps of this class [flat snap traps] may be readily set or adjusted with absolute safety to the person attending thereto, avoiding the liability of having his fingers caught or injured by the striker when it is prematurely or accidentally freed or released” (also quoted from the patent description). The fact that Hooker sold his Animal Trap Company of Abingdon, IL, and it merged with the J. M. Mast Manufacturing Company of Lititz, PA, in 1905 (Drummond et al. 2002) may have contributed to a false attribution of priority to Mast (Hope 1996). Unfortunately, the misbelief in Mast’s priority is transmitted (e.g., Shanks and Joplin 2000).

Others falsely credit priority to James Henry Atkinson of Leeds, UK (e.g., Bellis 2009). His ‘Little Nipper’ received GB patent no. 27,488 in 1899 and has a treadle cut out of the whole width of the base. This increases the likelihood that the trap is sprung when a mouse only passes over it without being attracted to the bait. Another urban legend has Hiram Maxim, inventor of the machine gun, as inventor of the first, flat, snap mouse trap (‘Mousetrap’ by Wikipedia contributors, before I fixed it at January 6, 2010). In his memoirs, however, Maxim (1915) described his inventions as automatic cage traps. The resetting automatism of one was powered by a coiled spring made from the hoop of a skirt, that of the other was powered by the entering mice themselves.” (Dagg 2011)

P.S.: This mole trap is from a patent of Hooker (1879). All trap functions are carried by only two wire parts and the trap is reminiscent of John H. McDonald's suggestion for a reduction of complexity of mousetraps.

Figure from US patent 218,532 by William C. Hooker (1879).
References

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