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Cambrian Explosion Blues

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Cambrian explosion

What else is new in the campaign to explain the Cambrian explosion in Darwinian terms, despite the evidence? An article in The Australian says, “Fossils found in Gabon rewrite timeline of life on Earth,” as if finding earlier complexity is going to help the evolutionary story.

Fossils discovered in west Africa have pushed back the dawn of multicellular life on Earth by at least 1.5 billion years, scientists believe.

Just how complex the newly discovered organisms are is sure to be hotly debated.

But there can be no doubt that the creatures unearthed from the hills of Gabon, visible to the naked eye, have upended standard evolutionary timelines.

“The cursor on the origin of complex multicellular life is no longer 600 million years ago, as has long been maintained, but more like 2.1 billion years,” said Abderrazak El Albani, a researcher at the University of Poitiers and lead author of the study. [Emphasis added.]

The fossils, appearing to represent colonial organisms, vary from 12 centimeters to five inches. What are they? Ediacarans? The cookie-shaped fossils certainly don’t represent anything familiar, and the authors don’t draw any connections with what came later.

Up to now, conventional scientific wisdom held that the planet was populated only by single-celled microbes until the so-called Cambrian explosion, a major surge of biodiversity that began some 600 million years ago [actually, more like 530 million or 540 at most].

Ever-more complex life forms emerged rapidly from there, eventually creating an evolutionary tree with homo sapiens atop one of its branches.

“Multicellularity represents one of the principle thresholds in evolutionary history,” Philip Donoghue and Jonathan Antcliffe from the University of Bristol said in a commentary, also in Nature.

But the new organism, which appears to have lived in colonies, shows that the drive toward complexity began much sooner.

The article also claims that these organisms had a membrane-bound nucleus protecting its chromosomes! This announcement cannot help the Darwinian story. Earlier complexity, with no affinity to what followed, does not fit what Darwin had in mind. Perhaps the dating of the strata is wrong. If not, it looks like a proverbial Precambrian Rabbit that will have “upended standard evolutionary timelines” until the Darwin damage control committee can come up with a new story.

Fast-forwarding to the Ediacaran era, NASA put out another positivist spin at Astrobiology Magazine about the enigmatic animals that flourished before the Cambrian explosion:

Microbial mats that existed on sea floors prior to the “Cambrian explosion” provided the foundation for early animal life to arise, new research looking at trace fossils of that early life has found.

When Charles Darwin wrote On the Origin of Species and for decades thereafter, scientists ascribed the beginning of animal life to the Cambrian, eventually pinned to about 540 million years ago when trilobites and other multicellular organisms emerged in a relatively short timeframe.

In recent years, however, astonishing complexity has been discovered in the period right before the advent of the Cambrian explosion, revising the scientific view of the origins of the most complex, multicellular life on Earth.

“By the time we get to the Cambrian — which has much more familiar organisms — a lot of the evolution had already happened on Earth,” says paleobiologist Mary Droser at the NASA Astrobiology Institute at the University of California, Riverside.

Droser presents a queer idea that microbial mats caused animals to appear.

The range and diversity of microbial mats that served as the foothold for Ediacara biota would prove even more pivotal to the ecology of these ancient habitats. The mats offered an alternative path from the free-floating lifestyle of microscopic algae and bacteria as something for the new and enterprising species to attach to or feed from on a shifting seafloor. The stability and environmental complexity provided by the sticky mats made the extensive seafloor habitable.

In this magical world, microbial mats made animals evolve, and the animals returned the favor:

The appearance, diversification, and evolution of Ediacara biota are inextricably linked to these mats. Researchers have found that with the rise of complex animals comes advancements in the microbial mats themselves, revealing the ecological interplay between the species, Droser says.

And so, the story goes, the evolving life could ride out the storms and exploit the shared benefits they provided each other. “Earth’s first vertebrates, mobility, early mollusks, skeletons, plant-like reproduction and population struggles such as competition over resources and space, which are all vital components of modern animal ecosystems today” were just a matter of time.

What is her evidence for this tale? Droser only presents Dickinsonia, Spriggina, and various “evolutionary dead ends” with no clear connection to the twenty new phyla appearing in the Cambrian explosion.

“We would argue that the beginning of animal life as we know it begins in the Precambrian,” says Droser. “By the time that you get to the Cambrian, all of the major groups are established.

What? There’s a blatant falsehood for you Where are her arthropods? Where are the ctenophores? echinoderms? brachiopods? Where are bilaterian animals with eyes, guts, and articulated limbs? Her only empirical evidence for this claim is an inference from patterns in microbial mats that might indicate mobility of some Ediacarans like Dickinsonia and Spriggina. “Sprigginia [sic] fossils are some of the most complex fossils found in the Ediacaran period,” she says enthusiastically. “Vaguely resembling soft-bodied trilobites, Sprigginia has a head-like region and repeating segments running the length of its body.”

This greatly overstates the evidence. They are not true segments, and a head-like region is not a head. Meyer dealt with Spriggina in detail in his book (pp. 82-85), quoting numerous authorities such as Conway Morris, Valentine, and Erwin who do not believe a connection exists with any Ediacaran animal to the Cambrian biota. In fact, as Meyer explains on page 86 and following, the Ediacarans themselves exploded onto the scene. Most paleontologists believe the Ediacarans went extinct before the sudden appearance of twenty new animal phyla in the Cambrian. The NASA astrobiologists make a fake bridge across the divide that cannot hold the weight of all the new body plans needing to get across.

Ironically, another entry in Astrobiology Magazine undermines the “oxygen theory” for the rise of Cambrian animals.

A study by University of California, Berkeley geochemists presents new evidence that high levels of oxygen were not critical to the origin of animals.

The researchers found that the transition to a world with an oxygenated deep ocean occurred between 540 and 420 million years ago. They attribute this to an increase in atmospheric O2 to levels comparable to the 21 percent oxygen in the atmosphere today.

This inferred rise comes hundreds of millions of years after the origination of animals, which occurred between 700 and 800 million years ago.

Basically, animals already had arrived before dissolved oxygen was sufficient to contribute to the “emergence” of animals. So much for that explanation.

Photo: Dickinsonia, by Verisimilus at English Wikipedia [GFDL, CC-BY-SA-3.0 or CC BY 2.5], via Wikimedia Commons.