Geckos and Design

My Radio silence ends with Brian Thomas’ latest DpSU, Scientists Discover New Clue to Geckos’ Climbing Ability.

Northland Green Gecko (Naultinus grayii), Orana Wildlife Park, Christchurch, New Zealand.

Geckos can run just as easily along a wall or ceiling as they can across a floor. This is due to special pads on their toes, which can even grip glass. No man-made adhesive technology comes even close to functioning as well as gecko feet. And after years of research, the last missing puzzle piece to gecko foot design has apparently been found.

Is it a ‘clue,’ or the ‘last missing puzzle piece’? Mixed metaphors aside, the reader is immediately confused as to whether we now know everything there is to know about Gecko feet. I would say a) almost certainly no, and b) whether or not it has is irrelevant for my purposes here. Anyway, poor headline writing and/or poor writing generally. Not a good start.

The paper that this is in reference to is Direct evidence of phospholipids in gecko footprints and spatula–substrate contact interface detected using surface-sensitive spectroscopy, in the Journal of the Royal Society Interface. From the abstract:

Detailed studies have revealed that geckos are ‘sticky’ without the use of glue or suction devices. Instead, a gecko’s stickiness derives from van der Waals interactions between proteinaceous hairs called setae and substrate. Here, we present surprising evidence that although geckos do not use glue, a residue is transferred on surfaces as they walk—geckos leave footprints. Using matrix-free nano-assisted laser desorption-ionization mass spectrometry, we identified the residue as phospholipids with phosphocholine head groups…The presence of lipids has never been considered in current models of gecko adhesion. Our analysis of gecko footprints and the toe pad–substrate interface has significant consequences for models of gecko adhesion and by extension, the design of synthetic mimics.

“Matrix-free nano-assisted laser desorption-ionization mass spectrometry”? Sounds almost as if that came from something like the Star Trek Random Technobabble Generator. And to think I wondered what the appeal of chemistry was…

What’s Mr Thomas’ argument today then? First, he makes as if to go down the “learning from the designer” road. As well as the ‘synthetic mimics’ mentioned above, B.T. alludes to an unrelated paper in nature that describes “self-repairing slippery surfaces” inspired by pitcher plants. However he suddenly changes tack on the next paragraph, arguing instead the (equally fallacious) “all-or-nothing programming/system/design” one:

As remarkable as its phospholipids are, a gecko requires much more than that to get around the way it does. Gecko locomotion is an all-or-nothing system. For example, these lizards need curved toe pads. If their toes were flat, the entire surfaces of their feet would adhere, and the geckos would not be able to lift their legs. But because of the curved shape, only a portion of the footpad contacts the substrate at any one time. By rolling their toes, geckos can quickly and repeatedly remove and replace their feet as they walk or run.

So, we have two characteristics that a Gecko needs to have to walk on your ceiling. The others that he lists are “integrated neuromuscular coordination,” “peculiarities in skeletal arrangement,” and “keratin hairs.” Without these five things, according to Mr Thomas, “geckos would become easy prey as they vainly stumbled about in an imaginary evolutionary past.”

Not necessarily. Without those five a Gecko would indeed have trouble getting electrocuted by your ceiling light-fittings, that doesn’t mean that it would have been incapable of surviving at all. You take a less-distinctive lizard (Geckos are lizards, right?) which can survive perfectly well as it is. Maybe the climate changes, and a desert becomes more forest-like. It becomes advantageous to have certain skeletal mutations so as to climb over vegetation in search of food – flat, ground-hugging feet are no-longer in vogue. And so on – these traits are perfectly able to be built up sequentially, and certainly they could evolved via that much more likely route of a number of characteristics improving concurrently. While on the way the proto-Gecko may not be able to do all the things the modern Gecko can do – just as the modern Gecko can’t do the things a hypothetical future-Gecko could – there is no reason to suppose that the route is impossible.

I mean to say, even if one of the mutations necessary for the ‘creation’ of the Gecko as we see it today was, in fact, harmful at first – and I haven’t exactly been presented with the evidence that this is the case – it could still take hold in the population. In other words, there is no problem to Gecko evolution. Therefore, the following is incorrect:

The only possible means to achieve such all-or-nothing systems is through intentional creation. And although producing the remarkable “superhydrophobicity” found in the gecko and pitcher plant is clearly a challenge for intelligent people, and impossible for unintelligent nature, it is no problem for an all-wise Creator.

My chemistry teacher goes around saying that we’re all just a bag of chemicals for a reason. Organic chemicals do things – over time natural selection favours the ones that do things that are actually helpful.

I’d give this DpSU a 2/10 – seriously, he had a in the order of a fortnight off and this was the best he could come up with? Honestly…

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