I have been assessing (in the last few posts) Dinesh D'Souza's claim that the "single invariant trajectory" (from simple to complex) of the history of life on Earth is evidence of evolution. I have argued that it is only superficially true, and also that the claim as given represents circular reasoning. I intend to demonstrate a better--non-evolutionary--reason for even a superficial increase in complexity. But before I do that, I want to clarify the degree to which the evolutionary story is falsified by the actual fossil record. That is, I don't wish to leave my readers with the wrong impresssion that the trajectory that so impresses D'Souza is real.
According to Darwin's theory--and its modern synthesis--life is expected to have originated once, and that origination (from inorganic chemicals) would have been gradual, taking place over a long time and being completed rather late in Earth's history. Once that origin took place, life itself is expected to have evolved gradually, with increasing complexity the steady trend. While some pauses might be acceptable under this naturalistic scenario, no breaks or interruptions (at least none that would involve starting over) in this upward trend are predicated.
None of these expectations match the history of life on Earth as recorded in the geologic and fossil records. Instead, life originated early, suddenly, and repeatedly. Indeed, life is evident in the earliest rocks found. Fossils of living things trace back to 3.85 billion years ago, and rocks that are even earlier than this contain carbon signatures that indicate organic processes. These early life forms lived throughout a period when heavy bombardment by extraterrestrial objects was common, when Earth's habitability was in continual flux. Life did not arise once, but over and over again. Moreover, this early life was ubiquitous and diverse. There was not just a single form of bacteria, but a number of different ones, some that were chemoautotrophic in various ways and some that were photosynthetic. What's more, the simplest early life was every bit as complex as (and indistinguishable from) single-celled organisms alive today.
Nearly 90% of Earth's history is filled with nothing more than single-celled organisms (we'll see in the next post why this is true). The first significant move towards greater complexity was a sudden leap (some 530 million years ago) during what is called the Cambrian explosion. There was nothing gradual about this burst of life. Rather, life went from single-celled (and conglomerates of largely undifferentiated cells) to multicellular organisms with fully developed tissues, tissue systems, organs, and organ systems in a period of just a few million years. Long known form the Burgess shale of British Columbia, these Cambrian fossils have been greatly augmented in recent years by findings from Chengjiang, China. It is now recognized that virtually all the extinct and extant animal phyla sprang suddenly into existence in this late and brief period of Earth history.
Even in the recent 10% of Earth's history--a period from which the fossil record is much more complete and easily discerned--there have been major extinction events that contradict evolutionary predictions. The best known are those that ended each of the three dinosaur eras. Most people are aware of the meteorite collision (on the Yucatan Peninsula and in adjacent waters) that brought an end to the Cretaceous and caused the extinction of the last dinosaurs, but similar events are known to have wiped out first the dinosaurs of the Triassic and then the subsequent dinosaurs of the Jurassic. In each case, new life forms (completely unlike those wiped out) arose to fill the planet anew.
At whatever scale one chooses to examine the record of life on Earth, one sees not the gradual and steady increase in complexity that evolutionists (and D'Souza) pretend is the case. Rather, life always appears suddenly, fully-formed, fully-adapted for the conditions of that time, and as part of full ecologies. Preceding such appearances are large gaps devoid of anything that might constitute evolutionary precursors, and all of the evidence conspires to demonstrate that these gaps are actual (not the result of imperfections in the record). Moreover, following the sudden appearance of any group or species, its tenure in the fossil record is always characterized by stasis and not (as expected by evolutionary theory) change.
In other words, when D'Souza appeals to an invariant single trajectory in the history of life on Earth, he is merely parroting evolutionists, whose claims represent what their theory would require but not what the actual fossil evidence shows.