I have been exploring the many fruits of theistic evolution. An argument which is being bounced around at the moment and one that I am interested in is the question of whether we were actually inevitable. It’s a kinda design argument I guess. That once life on this planet had formed were we an inevitable route for evolution or should we count our lucky stars that we are here.
Its something I picked up on while reading research by Conway – Morris and his team into the Burgess Shale.
Morris has a big disagreement with Gould over the Shale. Gould sees the event as a one off freak. So many diverse phyla occurring in such a short space of time that if we were to re-run the tape of evolution the outcome would be completely different. Morris on the other hand thinks there are a lot more similarities then are given credit for and that the process of evolution has a nack of singling on a certain function to overcome a problem. Such as the many different lines of creatures who have evolved wings, eyes etc. With evolution grouping so regularly and following the same compact lines was it inevitable that we would evolve as an almost set solution.
The burgess shale is the main point of argument for this at the moment. After the explosion the similarities in the process are clear. Here is a large extract on an article by Morris
Looking back at the Cambridge group's classifications of the Burgess Shale, undertaken many decades after Walcott's pioneering work, my colleagues and I can see that we made some mistakes. Too often, we thought we had stumbled across yet another novel body plan (phylum, if you will), and in a few crucial instances, we did not realize that seemingly unrelated fossils were actually fragments of a single organism. With the benefit of hindsight, we can see that we had exaggerated the diversity of these supposedly bizarre fossils and needed to reconsider their evolutionary relationships. Recent discoveries in southern China (Yunnan) and northern Greenland (Peary Land) have provided links that join several of these previously unconnected fossils and establish them in recognizable phyla.
Let's begin with the animal Wiwaxia. In Wonderful Life, it is described as "another Burgess oddball, perhaps closer to the Mollusca than to any other modern phylum ... but probably not very close." Ironically, the first breakthrough in establishing Wiwaxia's affinities came from a postgraduate paleontologist at Harvard who was inspired by Gould's lectures a decade or so ago. This young researcher, Nick Butterfield, managed to extract pieces of scalelike armor from the fossilized creature. When Butterfield studied their microstructure, he noticed immediately that it was the same as that of the chitinous bristles (chaetae) that project from the bodies of such modern annelids as earthworms. His conclusion, published in 1990, was that Wiwaxia was not a mollusk at all but an annelid. Yet this was what Walcott had claimed in 1911. In at least this case, Butterfield concluded, Walcott was not "shoehorning" bizarre animals into familiar phyla, as Gould had charged; Walcott had got
it right the first time.
Another recent discovery, in which I was fortunate to play a role, sheds further light on the place of certain Burgess animals in evolutionary history. On July 9, 1989, I was with a team in northern Greenland, collecting at a site containing fauna from Sirius Passet, a regional variant of the Burgess Shale. It was our first day at the site, and almost immediately we found an extraordinarily complete fossil of a halkieriid--an armored slug with a trig shell at either end. We wondered whether this organism--with such a weird anatomy, apparently so different from any other animal's--represented yet another new phylum. But that was only at first sight. Until then, halkieriids had been known only from the evidence of isolated scales; with our discovery of this and other complete specimens, however, we were able to confirm that the creature was in reality closely related to Wiwaxia.
In making that connection, we were moving toward resolving a fundamental problem in evolution: How are body plans constructed, and how do new phyla actually emerge? To get from halkieriids, well represented as Lower Cambrian fossils, to Wiwaxia, which thrived in the Middle Cambrian, there is no need to postulate macroevolutionary jumps or some sort of genetic revolution. The halkieriids are not only older than Wiwaxia but also clearly more primitive. In life, halkieriids crawled across the seabed, their scales forming a beautifully arranged protective armor. Wiwaxia looked somewhat similar, but as Butterfield showed, its scales evolved into chaetae. So is Wiwaxia an annelid? It is really amatter of definition, but in my opinion, Wiwaxia is a member of the annelid stem group—a creature still in the process of becoming an annelid. Once scrutinized, the wiwaxiids and the halkieriids, despite their seemingly great differences, are closely related. They may be connected by two simple steps: the scales of halkieriids are transformed into wiwaxiid chaetae, and lobate, leglike extensions develop so that the style of locomotion changes
from crawling to a kind of stepping.
In recent years, the techniques of molecular biology have profoundly influenced
paleontology in ways that hear on Gould's premise that the Burgess Shale was a seemingly inexplicable explosion of hundreds of bizarre life-forms, unrelated to anything familiar. One major surprise concerns the evolutionary position of the phylum Brachiopoda, a group with bivalved shells. Molecular data, quite unexpectedly, shows brachiopods to he closely related to annelids. Functional morphology also indicates that the shells of brachiopods must have originated as two separate valves; clams, in contrast, derived their familiar double shells from an ancestor with a single plate, across which developed a narrow zone of weakness, which became the hinge. Projecting from the margin of both valves of a brachiopod are delicate, chitinous bristles--identical to those of annelids Halkieriids also have two prominent shells. In the pre-brachiopods, I believe, the two shells were probably close to each other, back to back. To produce a true brachiopod, all that was necessary was to fold one shell beneath the other. And, interestingly, exactly this process can he seen in the embryological development of certain primitive, living brachiopods. So what was once a worm is transformed into a bivalved animal, the familiar brachiopod. Nor does the story finish here. If the scales of halkieriids can become chaetae, surely they can also evolve into the structurally identical chitinous bristles of a brachiopod.
Of course, the origin of brachiopods is not so simple, but such transformations are
functionally plausible and historically believable. Although constrained by genetic
possibilities, they are products of convergent evolution. Similar environmental selection pressures, acting on differing anatomies, can create convergent or parallel adaptations.
New discoveries and interpretations have altered our view of arthropod evolution as well. The biggest surprise is Hallucigenia, exemplar of the bizarre. Or is it? Recent finds from the Chinese deposit of Chengjiang reveal that my original reconstruction of this odd-looking, spiky animal had but one simple mistake: I had envisioned it upside down. Hallucigenia (a name coined by a colleague and me in an attempt to capture its dreamlike appearance) may still look strange, but with new discoveries, especially from southern China, Hallucigenia is now seen to belong to a group of primitive arthropods. And what about the famous Anomalocaris, another of Gould's star oddballs? "Nothing ... about Anomalocaris suggests a linkage with arthropods," he writes. Now we know better. The discovery, in different species, of lobopod-like legs and jointed appendages along the length of the body not only establishes a link between Anomalocaris and the more primitive Hallucigenia but also is crucial for understanding the appearance of the first arthropods--a group that would
eventually radiate into crabs, spiders, and the millions of species of insects.
So the Burgess creatures do not form an exception to the orthodox mechanisms and
patterns of evolution, as I believe Gould has implied. The new evidence suggests that not only did the sheer number of species increase since the Cambrian (as nearly everyone agrees), but, more significantly, the total number of phyla has been maintained and has not, contrary to what Gould has written, shown a catastrophic decline. But now we come to the most egregious misinterpretation of the Burgess Shale in Gould's book—a conclusion drawn not from the evidence of paleontology but from Gould's personal credo about the nature of the evolutionary process.
Gould sees contingency--evolutionary history based on the luck of the draw--as the major lesson of the Burgess Shale. If you rerun the tape of evolution, he says, the results would surely come out differently. Some creature similar to Pikaia, a small eel-like animal with a rudimentary head, may have survived in Cambrian seas to become the ancestor of all vertebrates. If it hadn't, Gould says, perhaps other--entirely different--major animal groups would have evolved instead from one of the Burgess Shale's other "weird" body plans. Such a view, with its emphasis on chance and accident, obscures the reality of evolutionary convergence. Given certain environmental forces, life will shape itself to adapt. History is constrained, and not all things are possible.
To understand how creatures that are descended from very different groups can evolve similar forms and functions, consider that dolphins, which evolved from doglike mammals, are shaped like fish because there exists an optimal shape for moving through water--a classic example of convergent evolution. Or consider another example: both placental mammals and marsupials produced a large, saber-toothed carnivore on separate continents. If such a quality as intelligence can arise both in human beings and in the octopus--an eight-armed sea animal without a bone in its body--then perhaps there is a course and a direction to evolution that would be achieved despite diverse anatomical starting points.
Contingency or no, I believe that a creature with intelligence and self-awareness on a level with our own would surely have evolved--although perhaps not from a tailless, upright ape. Almost any planet with life, in my view, will produce living creatures we would recognize as parallel in form and function to our own biota. But first, life must arise, and we have no idea how rare an event that might be. If we are honest, despite our exciting fancies about extraterrestrials, we must admit the real possibility that life arose but once, and that we are alone and unique in the cosmos--with an awesome and, to many, unanticipated role as stewards of all other living things. But were we to let evolution take another route than it did, why not grant (as Gould will not) that another kind of being would have evolved to fill our special place in nature?
I found the position interesting. Any thoughts?
Regards
Beef
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The design argument in Theistic Evolution.
) then would intelligence have arisen in the reptillian world instead. Is it the fact of it that is 'programmed' in, or the actual specific lifeform.
