The other night I was watching a show on tv called Richard Hammonds Invisible Worlds (BBC). One of the topics he covered was gecko feet which was quite facinating. The following article goes into some detail of this amazing creature and his feet.
The best explanation seems to be that the geckos’ feet can exploit the weak short-range bonds between molecules. That is, they stick via van der Waals forces. But for such weak forces to work, there must be an enormous intimate contact area between foot and surface, so that enough individual weak forces can add up to a very strong force.
Under an electron microscope, researchers have found that the feet have very fine hairs (setae), about 1/10th of a millimetre long and packed 5,000 per square mm (three million per square inch). In turn, the end of each seta has about 400–1,000 branches ending in a spatula-like structure about 0.2–0.5 µm (microns—less than 1/50,000th inch) long. These spatulae can provide the necessary contact area.
This website has some good images of geckos’ feet.
With special instruments, a team of biologists and engineers from several American universities analysed a seta from the foot of a Tokay gecko (Gekko gecko). The foot pad has an area of about 100 mm2 (0.16 sq. inch) and can produce 10 newtons of adhesive force (enough to support two pounds). But they showed that an individual seta had an attractive force 10 times stronger than expected. In fact, one seta is strong enough to support an ant’s weight, while a million could support a small child—about 10 N/cm2, where 10 newtons is about the weight of 1 kg. So the gecko has plenty of attractive force to spare. This means it can handle the rough, irregular surfaces of its natural habitat.
Actually, the attractive force is far greater when the seta is gently pressed into the surface and then pulled along. The force also changes with the angle at which the hair is attached to the surface, so that the seta can detach at about 30°. These elaborate properties are exploited by the gecko’s ‘unusually complex behaviour’1 of uncurling its toes when attaching, and unpeeling while detaching. This all means that the gecko can not only stick properly with each step, but also avoid getting stuck, all without using much energy.
In his explanation of this marvelous feature of the gecko, Richard Hammond said that the gecko had to develop this toe curling ability in order to unstick its feet in order to be able to move. The use of the word develop makes it obvious that there are heavy evolutionary overtones that are assumed as the mechanism by which the gecko’s feet came to be.
Can anyone else see the disconnect here?
Evolutionary theory is a slow gradual process. Yet here we find three abilities associated with the geckos’ feet that have to present at the same time in order to work. If the hairs are present without the toe curling ability (which Richard is suggesting here), then the poor gecko will no be able to move and will quickly become a meal to the nearest predator. Without the self-cleaning ability, the geckos’ feet will quickly become non-functioning/useless. And why evolve toe curling as a precursor to hairy feet? To claim that this is the path taken, screams a designer at the helm realising that toe curling is needed to have occured before the hair. And when does the self-cleaning occur? These are not just singular variations in the DNA to change, say, regular toes to curling toes. According to evolutionary theory changes in anatomy like this would have to take many many mutations.
Even if it is reasonable to believe evolution started the ball rolling by giving the gecko a toe curling ability and the gecko was able to function/breed with this ability even though it serves no purpose, where are all the toe curling lizards that didn’t evolve further down the gecko path? There is no “Darwins tree” here whether alive or in the fossil record.
Rather than believe a complex unsubstantiated evolutionary story, a designer at the helm seems a much more simple and likely explanation for such an amazing creature.
