Oxygen and the Cambrian: in the pre-Cambrian (Evolution)

by David Turell , Tuesday, October 18, 2022, 16:31 (765 days ago) @ dhw

DAVID: What I note is the Ediacaran period is from 635 million to 541 million years ago. All it produced are strange, stalked animals with no motility. 410,000 year later the Cambrian starts in full bloom with all sorts of motile animals appearing in rapid succession. Not your view at all.

dhw: I’m getting confused, because I don’t know what exactly is supposed to be the significance of the 410,000-year transition period. Perhaps you would explain what you think your God did during that time.

That period is the time between the last Edicarans and the first Cambrians. God designed the Cambrians.

dhw: Meanwhile, in my effort to gain a bit of enlightenment, I’ve found these two interesting articles. The first concerns a research project (the bolds are mine):

Co-Evolution of Life and Environment During the …
https://www.frontiersin.org/research-topics/31295

(It’s …..During the Ediacaran-Cambrian Transition)

QUOTES: The Ediacaran-Cambrian transition is a crucial time interval for the evolution of animal life on Earth. Throughout this interval new ecosystems formed and novel bodyplans proliferated.. At the end of the Ediacaran there was a significant extinction event, though some forms including tubular fossils and acritarchs survived into the Phanerozoic. Substantial environmental and geological change also occurred during the Ediacaran-Cambrian transition, including, possibly, increasing oxygen levels, along with other chemical changes in the oceans. All of these events were accompanied by the proliferation of metazoan phyla in the early Cambrian, which were at least partially triggered by the significant environmental and geological changes at the Ediacaran-Cambrian transition, but in turn themselves influenced sedimentary environments and ocean chemistry.

Though a large number of studies of the biotic and abiotic changes, and their relationship, during this interval have been conducted, questions remain and new data are continually being gathered. Thus, here we call for more studies with the purpose of expanding understanding of this key time period in the history of life and its environmental and geological context.

The link between “novel bodyplans” and environmental conditions is always a feature, and so it would seem that the process of innovation had already begun during the transition period. However, it was interrupted by a significant extinction event, and the process began again in the early Cambrian. We therefore have proliferation during the 410,000 years of changing conditions, and further proliferation during the early Cambrian. The “extinction event” interrupted what would otherwise have been a continuous process, but interestingly we come now to the second article:

Paleontologists Find Evolutionary Link between Ediacaran and …
https://www.sci.news/paleontology/ediacaran-early-cambrian-metazoans...

Paleontologists Find Evolutionary Link between Ediacaran and Early Cambrian Multicellular Animals

QUOTES: Paleontologists have described the first three-dimensional preservation of soft tissue in Namacalathus hermanastes, a skeletal metazoan (multicellular animal) that lived some 547 million years ago (Ediacaran period) in what is now Namibia, and established a strong evolutionary link between Ediacaran and early Cambrian metazoans.
Prior to the new study, it had proven difficult to trace links with earlier animals because their soft tissues — which provide vital clues about the animals’ ancestry — almost always break down over time.

They found that Namacalathus hermanastes was an early ancestor of species that appeared during the Cambrian explosion/b]. Among them are types of prehistoric worms and mollusks.
“These are exceptional fossils, which give us a glimpse into the biological affinity of some of the oldest animals,” Professor Wood said.
“They help us trace the roots of the Cambrian explosion and the origin of modern animal groups.”

dhw: We have the usual clear explanation of why fossils are so rare, but if we have a strong evolutionary link between Ediacaran and Cambrian animals, who knows what other links might have come into existence during the period of transition? There’s no answer to that question, but research is ongoing, and so we should NOT jump to the conclusion that species sprang from nowhere without any precursors.

Finding one link does not explain the vast array of new phyla appearing so suddenly. A small link is not a gap buster.