|Feature Article - August 2011|
|by Do-While Jones|
An article in Nature about the mole’s thumb reminded us of the classic evolutionary fairy tale about the panda’s thumb.
A current article about the mole’s thumb caught our attention because it reminded us of the classic evolutionary argument about the panda’s thumb. So, before we examine the mole’s thumb, let’s review the panda’s thumb argument.
More than 30 years ago, Stephen Jay Gould wrote a classic column for Natural History magazine which later became the title essay for a collection of his columns published in book form. That classic essay claimed that imperfection is a better argument for evolution than perfection is.
The message is paradoxical but profound. Orchids manufacture their intricate devices from the common components of flowers, parts usually fitted for very different functions. If God had designed a beautiful machine to reflect his wisdom and power, surely he would not have used a collection of parts generally fashioned for other purposes. Orchids were not made by an ideal engineer; they are jury rigged from a limited set of available components. Thus, they must have evolved from ordinary flowers.
Thus, the paradox: Our text books like to illustrate evolution with examples of optimal design--nearly perfect mimicry of a dead leaf by a butterfly or of a poisonous species by a palatable relative: But ideal design is a lousy argument for evolution, for it mimics the postulated action of an omnipotent creator. Odd arrangements and funny solutions are the proof of evolution--paths that a sensible God would never tread but that a natural process, constrained by history, follows perforce. 1
This is a philosophical, not scientific, argument. It’s based on how Gould thinks God would do things. He thinks that God, unlike modern engineers, is not smart enough to employ reusable components in His designs. He thinks God would “reinvent the wheel” with each new creation. We don’t care to debate or speculate upon how God would, or should, do things. We merely point out his argument is based entirely upon what Gould thinks God would do.
Which brings me to the giant panda and its "thumb."
Giant pandas are peculiar bears, members of the order Carnivora. Conventional bears are the most omnivorous representatives of their order, but pandas have restricted this catholicity [universality] of taste in the other direction--they belie their order by subsisting entirely on bamboo. 2
We can’t help but digress for a moment to point out the arbitrary nature of the biological classification system.
The modern biological classification system is a hierarchical structure with levels (top to bottom) named Kingdom, Phylum, Class, Order, Family, Genus, and Species. That is, several similar species are grouped into a genus. Similar genera are grouped into a family. Similar families are grouped into an order, et cetera.
What is it that makes living things similar? It’s an arbitrary decision made by someone who thinks he is smarter than you.
All members of the order Carnivora are carnivorous. That is, they are all exclusively meat eaters, EXCEPT for those members that are omnivorous or vegetarians (like pandas) which are placed in that order because they obviously belong there.
Evolutionists generally believe that the most similar creatures have the closest common ancestor. Therefore, the biological classification system reveals “the tree of life.” Creatures in a particular order should be more like other creatures in that same order than creatures in a different order (because they inherited most of the same traits from a closer common ancestor). DNA of creatures in the same order should be more similar than DNA of creatures in different orders (because they inherited their DNA from a closer common ancestor).
If the theory of evolution were true, then it would be relatively easy to classify living things, and the DNA comparisons would always confirm the relationships. The problem (for evolutionists) is that it is really hard to come up with classification criteria that work all the time. That’s why biologists ignore their own rules (when it suits their purpose) and put herbivores (vegetarians) and omnivores (which eat plants and animals) in the carnivore (meat eating) category.
Gould was at the zoo one day, and observed some pandas eating bamboo.
I was amazed by their dexterity and wondered how the scion [descendant] of a stock adapted for running could use its hands so adroitly. They held the stalks of bamboo in their paws and stripped off the leaves by passing the stalks between an apparently flexible thumb and the remaining fingers. This puzzled me. … So I counted the panda's other digits and received an even greater surprise: there were five, not four. Was the "thumb" a separately evolved sixth finger? 3
He did some investigation, and learned this:
The panda's thumb is not, anatomically, a finger at all. It is made from a bone called the radial sesamoid, normally a very small component of the wrist. In pandas, the radial sesamoid is greatly enlarged and elongated until it almost equals the true digits in size. … The panda's, thumb comes equipped not only with a bone to give it strength but also with muscles to sustain its agility. 4
The panda's true thumb is committed to another role, too specialized for a different function to become an opposable, manipulating digit. So the panda must use parts on hand and settle for an enlarged wrist bone and a somewhat clumsy, but quite workable, solution. 5
Notice how Gould’s belief in evolution twisted his observation. Initially, when he was watching the pandas eat, he was “amazed by their dexterity” because they did it “so adroitly.” But when he came to believe that the thumb is just an accidentally enlarged bone that happened to be useful, their table manners were “somewhat clumsy.”
Ironically, just after finishing the first draft of this essay, I received the (then) current issue of New Scientist in the mail which said,
Even so, Gould harboured grave doubts about the ability of science to remain free from social pressures and bias. 6
The article was about a 19th century scientist named Morton who had measured the skulls of 670 people of various races and made some conclusions about the comparative intelligence of those races based on brain size. Gould thought that Morton’s racial views had unconsciously affected his measurements. But when Lewis actually measured the skulls in Morton’s collection (which Gould had not done), he found that Morton had accurately measured the skulls, and that Gould’s suspicions about the measurements were racially biased.
Some commentators have observed that Gould may have proven his own point about bias being inevitable in science, but with the bias merely being his own rather than Morton's. 7
This explains Gould’s changing description of the panda’s dexterity from “adroit” to “clumsy” to support his evolutionary conclusion.
The Panda’s Thumb argument is entirely philosophical, and isn’t even consistent. Gould says that if God had created the panda, He would have given it a better thumb for eating bamboo. But the panda has a perfectly good built-in wrist bone knife that slices bamboo with amazing ease, as if it were specially designed for that exact purpose. But Gould says it really is somewhat clumsy because it must have evolved by accident. How can you argue with inconsistent “logic” like that?
Because the panda’s thumb is such an evolutionary icon, this headline in Nature drew our attention:
How the mole got its “thumb” 8
That headline sounds like a Rudyard Kipling “Just So Story.”
The Just So Stories for Little Children were written by British author Rudyard Kipling. They are highly fantasised origin stories and are among Kipling's best known works. … The Just So Stories have a typical theme of a particular animal being modified from an original form to its current form by the acts of man, or some magical being. For example, the Whale has a tiny throat from a swallowed mariner who tied a raft in there to block the whale from swallowing others. The Camel has a hump given to him by a djinn as punishment for the camel refusing to work (the hump allows the camel to work longer between eating). The Leopard has spots painted on him by an Ethiopian (after the Ethiopian painted himself black). The Kangaroo gets its powerful hind legs, long tail, and hopping gait after being chased all day by a dingo, who was sent after the Kangaroo by a minor god whom the Kangaroo had asked to make him different from all other animals. 9
The Just So Stories were published in 1902, and were clearly influenced by Darwin’s incorrect belief that acquired characteristics could be inherited.
According to last-month’s highly respected, peer-reviewed scientific journal, here’s the Just So Story of how the mole got its thumb.
Almost all land vertebrates have five fingers, but moles flout this rule. On top of their five digits, the creatures have co-opted a wrist bone to evolve a pseudo-thumb that increases hand-surface area for digging. 10
The journal makes no mention of a minor god whom the Mole had asked to make him different from all other animals. But, then, the mole isn’t different because the panda has a similar protruding wrist bone which acts like a thumb.
The fact that the wrist bone exists and is useful is not evidence that it evolved for that purpose. (Nor is it evidence that it was intentionally created by a supernatural power for that purpose.)
Here’s the part that should cause a problem for evolutionists: Moles are not closely related to pandas, but they both have protruding wrist bones which serve a useful purpose. Such unique characteristics are generally considered (by evolutionists) to be evidence of a close common ancestor.
To make things worse for evolutionists, other creatures closely related to the mole don’t have this kind of “thumb” because they don’t have the gene for it.
Marcelo Sánchez-Villagra at the University of Zürich in Switzerland and his colleagues tracked key molecular markers in embryos of the Iberian mole (Talpa occidentalis) and the North American least shrew (Cryptotis parva), a close relative that lacks the long, sickle-shaped bone. They found increased expression of Msx2, a gene that promotes digit development, in the area of the developing mole paw in which a wrist bone becomes elongated. The gene product was absent from this region in the shrew.
The pseudo-thumb is not technically a sixth digit, because it comes from a wrist bone, and develops later than the five true digits. 11
This is inconsistent with the evolutionary assumption that the most closely related individuals should have the most similar physical characteristics and the most similar DNA.
The Iberian mole has the Msx2 gene which causes an elongated wrist bone. The closely related North American least shrew does not have that gene, nor does it have an elongated wrist bone. But the giant panda, which is not closely related, does have the elongated wrist bone.
Your friendly neighborhood evolutionist will probably say this is an example of “convergent evolution.” In other words, the fantastically improbable mutation happened twice, independently, in distantly related animals. That’s a cop-out.
For more detailed data about the classification of pandas, moles, and shrews, see the on-line supplemental information at Mole's Thumb Supplemental Material
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Gould, Natural History, November, 1978, “The Panda's Peculiar Thumb”, http://www.stephenjaygould.org/library/gould_panda%27s-thumb.html
6 DeGusta and Lewis, New Scientist, 23 July 2011, “Taking the measure of Gould’s skulls”, page 24, https://www.newscientist.com/article/mg21128225-900-goulds-skulls-is-bias-inevitable-in-science/
8 Nature, 14 July 2011, How the mole got its ‘thumb’, page 142, http://www.nature.com/nature/journal/v475/n7355/full/475142c.html
10 Nature, 14 July 2011, How the mole got its ‘thumb’, page 142, http://www.nature.com/nature/journal/v475/n7355/full/475142c.html