Cambrian Explosion: from Ediacaran to Cambrian timed (Introduction)

by David Turell , Tuesday, June 07, 2022, 00:36 (691 days ago) @ David Turell

Very new studies of the Cambrian gap:

https://salvomag.com/article/salvo61/a-biological-big-bang

"New high-resolution age data narrows the date range for the paleon-tological event known as the Ediacaran-Cambrian transition to 410,000 years. A period of 410,000 years seems a long time to most people, but to scientists who study Earth's history and life, it's a mere moment. Discovery of a novel life-form that appeared within such a "moment" in the earliest days of the Cambrian era carries profound implications. When viewed in light of the measured "molecular clock" rate, this new finding presents a serious challenge to the commonly accepted story of life's slow, gradual development by natural processes alone.

***

"The Cambrian explosion, more than a half-billion years ago, saw the rapid appearance of mostly marine phyla, the first creatures to possess skeletons, digestive tracts, circulatory systems, and complex internal and external organs. They appeared very soon after sufficient oxygen became available in Earth's atmosphere and oceans to make their existence possible.

***

"The fossil record indicates that Ediacaran animals were the first to appear on Earth. They are characterized by tubular and frond-shaped filter feeders. The record also shows that Ediacaran fauna experienced a sudden mass extinction event. What followed almost immediately was the explosive appearance of vastly more complex Cambrian animals.

"Diazhao Chen's team, using the uranium-lead method, determined that the base portion of the Liuchapo Formation dates back 542.1 ± 5.0 million years.2 Using this same method, the mid-upper portion of this formation measured 542.6 ± 3.7 million years old.3 Five years later, Can Chen and his colleague Qinglai Feng refined this measurement (using a weighted-mean approach to measuring the uranium-lead zircon age) to demonstrate that the lower part of the Liuchapo Formation indeed marks the Ediacaran-Cambrian boundary.4 Their analysis reveals the boundary date to be 540.7 ± 3.8 [±6.6] million years ago. (The unbracketed error bar is the probable statistical error. The bracketed error bar represents the probable systematic error.)

"Ulf Linnemann and a team of fourteen geochemists provided an even more precise date for the end of the Ediacaran and the launch of the Cambrian. The team found a composite geological section of the Ediacaran-Cambrian boundary in southern Namibia. This site allowed for biostratigraphic as well as chemostratigraphic analysis, bracketed by radiometric dating.5 Their measurements constrained the date for the Ediacaran-Cambrian boundary to no earlier than 538.99 ± 0.21 million years ago and no later than 538.58 ± 0.19 million years ago.

"The Linnemann team's date indicates that the Ediacaran-Cambrian boundary is 2 million years more recent than the dates proposed by Diazhao Chen's team and by Can Chen and Qinglai Feng. Though different, it is considered consistent, not discrepant, in that the three dates all agree within the error bars of each. What their findings more notably reveal is the brevity, or narrowness, of that boundary. According to the Linnemann team's measurements, the faunal transition from Ediacaran to Cambrian biota appears to have occurred within a time frame of a mere 410,000 years.

***

"The mid-Cambrian, 520–535 million years ago, is where paleontologists have discovered the greatest number and diversity of Cambrian species. It is this epoch that has the richest, most extensive fossil beds. Increasingly, however, paleontologists are discovering phyla they thought originated in the mid-Cambrian actually being found in the early Cambrian deposits.8

"These discoveries demonstrate that during the Cambrian period the diversification of higher taxa occurs before that in lower taxa. As paleontologists Douglas Erwin, James Valentine, and John Sepkoski have observed, "The major pulse of diversification of phyla occurs before that of classes, classes before that of orders, and orders before that of families."

"The transition from Ediacaran to Cambrian phyla in less than 410,000 years challenges all current and as yet conceivable naturalistic models for the evolution of life. Such a period would be far too brief for the extinction of one phylum and the appearance of a new one, let alone several. The differences between one phylum and another are not minor, and the observed processes by which current models propose that these changes occurred are too slow to account for them.

***

"The obvious challenge for naturalistic models for life's history is to explain why the fossil record, especially the record for the Cambrian animals, shows the exact opposite of what the naturalistic models predict. New phyla appear first, not last. These phyla appear suddenly and without direct evolutionary precursors. Astronomers have noted that many Cambrian phyla appear the moment oxygen in Earth's atmosphere reaches the minimum level (10 percent) necessary for these phyla to survive."

Comment: in the Grand Canyon each lower (older) layer is precisely next to the one above. Nothing inbetween So where are dhw's wished for tranitionasl forms? The Edicarans are very well known by now. They are animals that have no resemblance to the Cambrians, whose crazy abrupt appearances have more complex before simpler forms! That's reversed evolution! Contrary to accepted Darwin theories, which are slowly dying away.