cambrian

Earlier Burgess-Shale-Type Fossils Found in Greenland

Graham Budd has been critical of associations between Ediacaran fauna and Cambrian animals, and has also debunked alleged Precambrian animal ancestors such as Vernanimalcula (Stephen Meyer, Darwin’s Doubt, pp. 85, 90-91). Budd also was in attendance at the Darwin-doubting Altenberg 16 conference in 2008 (p. 292), confessing that the fossil record tells little about the origin of biological forms. This Cambrian expert from Uppsala University has a new paper in Geology describing new exquisitely-preserved fossils of the Burgess Shale type, but earlier. Along with lead writer Ben Slater, Graham Budd’s team unveils photographs of tiny but exquisite parts of arthropods, worms and other animals that burst into appearance in the Cambrian Explosion. What’s amazing is that these fossils were collected not in Canada or China, but in the northern reaches of Greenland.

The location, called Sirius Passet in Peary Land in the far north of Greenland, has been known as an early Cambrian fossil site, but it lies close to a geological fold belt. Having been heated to 200° C or more by metamorphism, most of the fossils at Sirius Passet have suffered thermal alteration and are difficult to interpret. Not far to the south, however, the team found sites in the same formation that escaped most of the alteration. News from Uppsala University describes how they found a “treasure trove of highly detailed fossils” of the Burgess Shale type.

The ‘Cambrian explosion’ of animal diversity beginning ~541 million years ago is a defining episode in the history of life. This was a time when the seas first teemed with animal life, and the first recognisably ‘modern’ ecosystems began to take shape.

Current accounts of this explosion in animal diversity rely heavily on records from fossilised shells and other hard parts, since these structures are the most likely to survive as fossils. However, since most marine animals are ‘soft-bodied’ this represents only a small fraction of the total diversity.

Rare sites of exceptional fossilisation, like the world-famous Burgess Shale, have revolutionised palaeontologists understanding of ‘soft-bodied’ Cambrian life. Because of the special conditions of fossilisation at these localities, organisms that did not produce hard mineralized shells or skeletons are also preserved. Such sites offer a rare glimpse into the true diversity of these ancient seas, which were filled with a dazzling array of soft and squishy predatory worms and arthropods (the group containing modern crustaceans and insects). [Emphasis added.]

Also important is that these fossils date earlier than the Burgess Shale by 10 million years (518 million instead of 508 million), and yet are recognizable as the same animals. This indicates that the Cambrian animals had a global distribution at the time they were fossilized. The same animals are found many thousands of miles apart on three continents.

Instead of the large, articulated fossils from China and Canada, those at the Greenland sites are made up of tiny fragments. So rich were the deposits, they often found 100 specimens in a 50-gram sample.

A team of palaeontologists from Uppsala (Ben Slater, Sebastian Willman, Graham Budd and John Peel) used a low-manipulation acid extraction procedure to dissolve some of these less intensively cooked mudrocks. To their astonishment, this simple preparation technique revealed a wealth of previously unknown microscopic animal fossils preserved in spectacular detail.

Most of the fossils were less than a millimetre long and had to be studied under the microscope. Fossils at the nearby Sirius Passet site typically preserve much larger animals, so the new finds fill an important gap in our knowledge of the small-scale animals that probably made up the majority of these ecosystems. Among the discoveries were the tiny spines and teeth of priapulid worms — small hook shaped structures that allowed these worms to efficiently burrow through the sediments and capture prey. Other finds included the tough outer cuticles and defensive spines of various arthropods, and perhaps most surprisingly, microscopic fragments of the oldest known pterobranch hemichordates — an obscure group of tube-dwelling filter feeders that are distant relatives of the vertebrates. This group became very diverse after the Cambrian Period and are among some of the most commonly found fossils in rocks from younger deposits, but were entirely unknown from the early Cambrian. This new source of fossils will also help palaeontologists to better understand the famously difficult to interpret fossils at the nearby Sirius Passet site, where the flattened animal fossils are usually complete, but missing crucial microscopic details.

The photos of the small carbonaceous fossils (SCFs) in the paper show exquisite details of identifiable Burgess Shale type animals. Pieces of trilobite cuticles were also found. Trilobites are among the most complex of Cambrian animals, possessing articulated limbs, eyes and multiple body systems for locomotion, digestion and survival. The authors seem most excited about finding the earliest pterobranch hemichordates (a type of filter feeder known in the Burgess Shale), recognizing that the worldwide distribution indicates an even earlier origin. The paper says,

Our report of early Cambrian pterobranch fragments confirms this hypothesis [of early origin], and their potential affinities to Graptolithina also suggest that the divergence and radiation of the pterobranch clades containing cephalodiscids and graptolites had a somewhat deeper, early Cambrian origin.

Nowhere do they suggest evidence for evolution or transitional forms. On the contrary, these new fossils confirm the picture of abrupt appearance and stasis. The best the team can say is that this fossil site offers “new insights” into the fossilization process and may “reshape our view” of this ‘episode’ known as the Cambrian explosion:

“The sheer abundance of these miniature animal fossils means that we have only begun to scratch the surface of this overlooked resource, but it is already clear that this discovery will help to reshape our view of the non-shelly animals that crawled and swam among the early Cambrian seas more than half a billion years ago,” says Sebastian Willman, researcher at the Department of Earth Sciences, Uppsala University.

Marshall Is Back

In 2013, U.C. Berkeley paleontologist Charles Marshall published a critique of Darwin’s Doubt in the journal Science that Stephen Meyer considered the first critical review to actually address the main argument in the book: the inability of standard evolutionary mechanisms to explain the origin of morphological novelty in the Cambrian period. Meyer wrote a four-chapter response to Marshall in the follow-up book, Debating Darwin’s Doubt (2015).

Late last year, Marshall wrote an article in Science (November 29, 2017) called “A tip of the hat to evolutionary change,” in which he reviewed another paper in the same issue that claims to reveal “an unexpectedly simple pattern of driver action in peak evolutionary success.” That paper by Žliobaitė et al concludes from the fossil record of herbivorous mammals that species rise toward success and decline toward extinction in a “hat shape” graph (thus his title).  In passing, Marshall admits that “one of the challenges of studying evolution … is the hierarchical structure of the evolutionary process.” What drives innovation: abiotic (environmental) processes or biotic processes, like competition? How do they work together? How simple is the rise to “evolutionary success”?

Though only peripherally related to evolutionary processes in the Cambrian explosion, Marshall’s article shows what he thinks these days about the origin of biological novelty. Old-fashioned Darwinian competition is a driver of extinction, he agrees, but what drives innovation?

The results of Žliobaitė and colleagues’ work also provide insight into the drivers of evolutionary innovation. The authors’ data for North America and Europe show that, although both biotic and abiotic factors contribute roughly equally to genus origination rates, neither contribution is statistically significant. As the authors note, this provides evidence that evolutionary innovation is not driven by biotic or abiotic external changes. Instead, the data support the idea that evolutionary innovation is influenced by intrinsic factors — the less-predictable origin of the ‘right’ variants at the right time, able to exploit either existing or new resources.

This statement indicates that nothing much has changed in his thinking. It appears Marshall still has no better tool for innovation than lucky mutations that just happen to arrive at the right time to be exploited. How this solution can possibly address the “hierarchical structure of the evolutionary process” leading to body plans with hierarchical levels of morphological innovation seems lost in academic jargon and generalizations.

The Greenland fossils are observational facts. Graham Budd’s team in that cold, remote, northern wasteland could look at those cold, hard facts under a microscope, seeing complexity that shouldn’t be there by any unguided natural process. If Charles Marshall had a better mechanism for innovation than sheer dumb luck, he has had years to announce it. Until and unless he does, Meyer’s thesis remains unchallenged: only intelligent design can account for the functional hierarchical organization revealed by the Cambrian animals.

Photo: Location in Greenland where fossils were found, by John S. Peel, via Uppsala University.

Source: Evolution News