Evolutionary Creationism: A Christadelphian Perspective: Why David Pearce's "Evidence for Design" fails to disprove evolution

Saturday 25 January 2014

Why David Pearce's "Evidence for Design" fails to disprove evolution - 4

Pearce, having shown that he is poorly uninformed on the evidence for large-scale evolutionary change in the fossil record, then proceeds to invoke yet another creationist argument, the 'living fossil' as disproof of evolution:

"How is it that fossil bees, preserved in resin and claimed by the scientists to be many millions of years old, are recognisable as close relatives of our honey makers today? Or the squid-like nautiloid dug up when they were building the Channel Tunnel between Britain and France, which was said to have been more or less unchanged for 500 million years! Why was there no appreciable change over such a long period?"

Once again, Pearce ignores the fact that evolution refers to fact (common descent and large-scale evolutionary change) and theory (the modern evolutionary synthesis). Evolution, as a science with a historical elements also refers to historical path. Unsolved questions about the specific details of natural history do not make the considerable evidence for common descent vanish.

TR Gregory observes that:

In addition to its incarnations as a “fact” and a “theory,” evolution also can be discussed in a third distinct capacity, namely, as a “path” (Ruse 1997). Evolution as path deals with the factual details of life’s history, such as the degree of relatedness of modern species to one another, the timing of splits among lineages, the characteristics of extinct ancestors, and the major events that have occurred over the nearly 4 billion years of life’s saga. As an example, specialists including paleontologists and molecular systematists may investigate whether birds are the descendants of a lineage of dinosaurs (and if so, which one), when flight first evolved and what changes this entailed, and what the patterns of diversification of birds have been since the evolution of flight. Similar questions can be asked about each branch of the tree of life. [1]

I've mentioned repeatedly that questions about the details of how evolution occurred do not mean that the evidence for common descent somehow vanishes. Likewise, unsolved questions about the exact time lineages separated or the amount of morphological change that exists between contemporary species, and their remote ancestors do not mean that macroevolutionary change never occurred.

Pearce's insistence that 'living fossils' disprove evolution once more betrays his ignorance of the subject. Specifically, they show that Pearce thinks of evolution in terms of orthogenesis:

"Literally, the term means evolution in a straight line, generally assumed to be evolution that is held to a regular course by forces internal to the organism. Orthogenesis assumes that variation is not random but is directed towards fixed goals. Selection is thus powerless, and the species is carried automatically in the direction marked out by internal factors controlling variation." [2]

Orthogenesis was one of a number of alternative theories of evolution popular during the 'eclipse of Darwin' when natural selection fell out of favour during the late 19th and early 20th centuries, due in no small part to the lack of a decent theory of inheritance. Orthogenesis in turn was abandoned mainly from the palaeontologial evidence which failed to show the required patterns of linear change in the fossil record, but also due to the lack of a mechanism to explain how it could occur. Bowler notes:

...the supposedly linear trends were merely the paleontologists' oversimplified interpretation of insufficient evidence. It is easy to draw a straight line linking a few specimens, but further information usually shows that the evolution was in fact branching and irregular. Orthogenetic trends existed more in the minds of their exponents than in nature itself." [3]

By arguing that evolution has been falsified by the apparent lack of change in the fossil record, Pearce is thinking in terms of a discredited theory of evolution, one which ironically has been refuted by the fossil record to which he appeals.

Certainly, there are examples where there is little appreciable morphological change in the fossil record. One could argue that if their environment has not changed, they have not been subjected to much selective pressure, but this ignores non-adaptive evolutionary change from genetic drift. Explaining this has been the subject of ongoing scientific research. However, at the risk of repetition, this does not mean the evidence for common descent somehow goes away. It doesn't.

Pearce in fact overstates his case when he appeals to the alleged lack of change in bees and nautiloids. Take bees. Pionar and Danforth report the discovery of Melittosphex burmensis, a fossil bee dating from the Early Cretaceous (~100 million years ago). Melittosphex burmensis represents one of the earliest bee fossils, and is anything but identical to modern bees, showing as it does a mix of wasp and bee traits.

The forewing venation is typical of many small bees, with a distinct stigma, two submarginal cells, and a weakly arcuate basal vein (Fig. 1A), and is unlike that of any extant or fossil apoid wasps. The hindwing is not visible. The hind leg has an elongate, slender hind tibia [lacking distinct tibial spines characteristic of apoid wasps (Fig. 1A)], a narrow hind basitarsus [a characteristic of apoid wasps (Fig. 1A)], and a weakly developed basitibial plate. The hindleg strigil is absent (Fig. 1A). There are two hind-tibial spurs [as in most bees (1)]. The midtibia bears two spurs [a groundplan feature of apoid wasps (1) (Fig. 1A)]. The male specimen bears several pollen grains between the hairs on the first and second metatarsal segments and adjacent to the antennal cleaner on the left foretarsus. [4] (Emphasis mine)

This is not a modern bee, but rather a transitional form between bees and wasps:

M. burmensis exhibits traits unique to bees (branched hairs, absence of hind-leg strigil, and absence of hind-tibial spines) as well as groundplan features of apoid wasps (paired mid-tibial spurs and slender hind basitarsus). This mosaic of wasp and bee traits is to be expected from an early, transitional form that bridges the gap between extant bees and crabronid wasps. [5] (Emphasis mine)

That one of the earliest fossil bees is an unarguable transition between wasp and bee shows that contrary to Pearce's assertion, we do see evidence of large-scale evolutionary change in bees.

Science (2006) 314:614

Pearce's failure to reference his article makes it difficult to know what fossil he is referring when he speaks of

the squid-like nautiloid dug up when they were building the Channel Tunnel between Britain and France, which was said to have been more or less unchanged for 500 million years!

If he is going to make such claims, he needs to document them so that we can see whether he is referring to the primary literature or a popular science account, which often can distort the facts. Given his clearly documented ignorance of the fundamentals of evolutionary biology, Pearce has already lost the benefit of the doubt, and his claims need to be considered wrong until independently verified.

Nautiloids are a branch of the cephalopods, and a represented by the genera Nautilus and Allonautilus. Nautiloids have a long history, stretching back to the Cambrian around 500 million years ago. While they have not changed that much over this time, it is quite misleading for pearce to say that they have existed more or less unchanged for 500 million years:

Trilacinoceras

Source

Endoceras

Source

Endoceras lived in the Ordovician, and reached lengths of up to 3.5 metres, making them some of the largest nautiloids that ever lived. Compare it with the contemporary nautilus, here seen feeding on a red snapper, and it is easy to see that Pearce's claim that they have existed more or less unchanged for 500 million years is somewhat misleading, to say the least.