Unintelligent Design - The Late Devonian Mass-Extinction Or How Earth Is Badly Designed For Life

Artist’s impression of a Late Devonian landscape

Nicolas Primola

Fieldwork at Trail Island in East Greenland, near a Late Devonian rock outcrop.

Photo by John Marshall, University of Southampton

Study reshapes understanding of mass extinction in Late Devonian era: IU News

Way back 370 million years before the mythical 'Creation Week' the seas were full of life and angiosperm plants were rapidly replacing the tree ferns and other Tracheophytes and life was looking good, despite the fact that the single large landmass, Pangea, was on the point of breaking up.

Then something happened to cause another of those periodic mass extinctions that have punctuated Earth's long 'pre-Creation' history. What exactly it was has been the subject of ongoing debate by geologists, biologists and climatologists ever since evidence of it was found in the fossil record, particularly in Devonian rocks like those in Greenland.

But whatever the cause, it's not good news for creationists who have been duped by their cult leaders into believing Earth is fine-tuned for life by a designer god, and, by the circular reasoning that characterises creationism, therefore this fine-tuning 'proves' their designer god exists. A cynic might wonder, if faith is any good, why creationists are so desperate to find scientific 'proof' of their god that they perform all manner of ludicrous mental gymnastics and commit just about every logical fallacy in the book, to tell themselves and their target dupes that they have discovered it - and will be producing it any day now, real soon!

But that's by the by.

Sadly for creationists the evidence is that Earth is anything but finely tuned and perfect for life. The simple truth is that an Earth that was perfectly designed for life would never have extinctions, let alone mass extinctions like the ones that ended the Devonian and Cretaceous eras, and the one that's in progress right now. In fact, there would not even be biodiversity on such a planet because there would be no reason to adapt to adverse conditions because since these would not exist on a perfectly designed Earth, so life would not have progressed beyond the simplest of self-replicating molecules.

So, just for any creationists still under the delusion that Earth is finely tuned for life, here is a brief description of the Devonian and the mass extinction at the end of it:

Tell me all about the Devonian Era and the mass extinction that occurred at the end of it. The Devonian Era, spanning from approximately 419.2 million years ago to 358.9 million years ago, is a geologic period within the Paleozoic Era. It is often referred to as the "Age of Fishes" due to the diversification and dominance of fish during this time. The Devonian is divided into the Early, Middle, and Late Devonian periods.

Characteristics of the Devonian Era:

1. Diversification of Life:
   • Marine life continued to evolve, with the development of a wide variety of fish species. Jawed fish became more prevalent, and the first tetrapods (four-limbed vertebrates) began to appear.
2. Plant Evolution:
   • The Devonian witnessed significant developments in plant life, including the emergence of the first forests. Plants began to spread onto land, and early vascular plants evolved.
3. Continental Drift:
   • During the Devonian, the continents were grouped together in a supercontinent known as Gondwana. Over the course of the era, continents gradually drifted towards their current positions.

End-Devonian Mass Extinction:

The end of the Devonian was marked by a series of extinction events, collectively known as the Frasnian-Famennian (F-F) extinction event. This event occurred around 372 to 359 million years ago, near the boundary between the Frasnian and Famennian stages. It is considered one of the "Big Five" mass extinctions in Earth's history, although it is not as widely recognized as events such as the Permian-Triassic or Cretaceous-Paleogene extinctions.

Possible Causes of the End-Devonian Mass Extinction:

1. Climate Change:
   • Fluctuations in global climate, including changes in sea levels and temperature, have been proposed as potential causes. Climate shifts could have affected marine and terrestrial ecosystems.
2. Anoxic Events:
   • Anoxic (low oxygen) conditions in the oceans may have played a role. Reduced oxygen levels could have negatively impacted marine life, particularly organisms that rely on oxygen for survival.
3. Volcanic Activity:
   • Intense volcanic activity during the Devonian, particularly in regions like Siberia, could have released large amounts of volcanic gases, leading to climate perturbations and environmental changes.
4. Impact Events:
   • Some scientists suggest that asteroid or comet impacts might have contributed to the extinction, although direct evidence is limited.

Impact on Life:

The end-Devonian extinction event had a notable impact on marine life. While not as severe as some later mass extinctions, it led to the decline of many marine species, particularly among brachiopods and trilobites. Fish, however, largely survived, and the evolution of terrestrial life continued into the subsequent Carboniferous Period.

The exact causes of the Frasnian-Famennian extinction event are still a subject of ongoing research, and scientists continue to refine their understanding of the environmental changes that occurred during this critical period in Earth's history.

Now a group of geologists, oceanographers and climatologists led by Assistant Professor, Matthew S. Smart of Department of Earth Sciences, Indiana University Purdue University Indianapolis, Indianapolis, IN, USA. believe they have integrated the two main competing theories that seek to explain the mass extinction.

Briefly, the main competing theories are:

1. A period of large-scale volcanic activity threw dust high into the atmosphere, dimming the sun and causing global cooling (the result of the tectonic activity that caused and accompanied the break-up of Pangea).
2. A deoxygenation event caused by proliferating terrestrial plants and global warming. This sounds paradoxical because green plants like angiosperms and gymnosperms produce oxygen as a by-product of photosynthesis, however, warmer water holds less dissolved oxygen. Also, increased plant root penetration into the soil and into continental interiors made more nutrients available, so the theory is that increased nutrient-bearing runoff due to increased rainfall and plant root activity, caused marine algae to bloom and, when it died, their decaying bodies further deoxygenated the oceans causing a mass extinction of marine life, followed soon after by a collapse of terrestrial ecosystems and extinction of terrestrial plant and animal life.

The team's findings are published, open access, in the journal Communications Earth & Environment and are explained in an Indiana University news item:

The study is co-authored by School of Science at IUPUI faculty Gabriel Filippelli and William Gilhooly III. The lead author is Matthew Smart, an assistant professor of oceanography at the U.S. Naval Academy who was a graduate student in Filippelli’s lab at the time of the study.

The work is the first to unify two competing Late Devonian extinction theories into a comprehensive cause-and-effect scenario. Essentially, the group concluded that both events — mass volcanism and deoxygenation caused by land plants flushing excess nutrients into oceans — needed to occur for the mass extinction to take place.

The key to resolving this puzzle was identifying and integrating the timing and magnitude of the geochemical signals we determined using a sophisticated global model. This modeling effort revealed that the magnitude of nutrient events we were seeing based on the geochemical records could drive substantial marine extinction events, but the duration of the events required both factors — tree root evolution and volcanism — to sustain the marine conditions that were toxic to organisms.

Gabriel Filippelli, co-author
Department of Earth Sciences
Indiana University Purdue University Indianapolis
Indianapolis, IN, USA.

With experts in sedimentology, paleontology, geochemistry, biogeochemistry and mathematical modeling, the group literally dug deep to geochemically analyze hundreds of samples scattered across different continents. These include samples from Ymer Island in eastern Greenland, home of some of the oldest rock samples on the planet.

The process was highly interdisciplinary. This combined expertise created a rigorous approach to collecting the samples, correlating sequences in time, acquiring the chemical data and using geochemical models to test working hypotheses about the relative influences of biotically — plants — and chemically — volcanoes — driven triggers of mass extinction. Our analyses demonstrate that the influences are much more mixed than an either-or scenario.

William P. Gilhooly III, co-author
Department of Earth Sciences
Indiana University Purdue University Indianapolis
Indianapolis, IN, USA.

Throughout Earth’s history, there have been a series of biological innovations and geological events that have completely reshaped biological diversity and environmental conditions in the ocean and on land. In the Devonian era, a new biological strategy on land produced a negative impact for life in the ocean. This is a sobering observation when put in the context of modern global and climatic change driven by human activities. We have a lot to learn from Earth history that can help us think of strategies and actions to avoid future tipping points.

William P. Gilhooly III

Filippelli and Gilhooly said the study’s conclusion gives researchers a lot to consider. During the Devonian era, new biological outcomes on land produced negative effects for life in the ocean. In the present day, Gilhooly noted, activity like fertilizer runoff emptying into the ocean, combined with heating from fossil fuel combustion, are reducing oceans’ oxygen levels. The previous outcome of this similar scenario in the Late Devonian had catastrophic outcomes, he said.

Other contributors to the study were Kazumi Ozaki of the Tokyo Institute of Technology, Christopher Reinhard of the Georgia Institute of Technology, John Marshall of the University of Southampton and Jessica Whiteside of San Diego State University.

Abstract

The evolution and expansion of land plants brought about one of the most dramatic shifts in the history of the Earth system — the birth of modern soils — and likely stimulated massive changes in marine biogeochemistry and climate. Multiple marine extinctions characterized by widespread anoxia, including the Late Devonian mass extinction around 372 million years ago, may have been linked to terrestrial release of the nutrient phosphorus driven by newly-rooted landscapes. Here we use recently published Devonian lake records as variable inputs in an Earth system model of the coupled carbon-nitrogen-phosphorus-oxygen-sulfur biogeochemical cycles to evaluate whether recorded changes to phosphorus fluxes could sustain Devonian marine anoxia sufficient to drive mass extinction. Results show that globally scaled increases in riverine phosphorus export during the Late Devonian mass extinction could have generated widespread marine anoxia, as modeled perturbations in carbon isotope, temperature, oxygen, and carbon dioxide data are generally consistent with the geologic record. Similar results for large scale volcanism suggest the Late Devonian mass extinction was likely multifaceted with both land plants and volcanism as contributing factors.

Fig. 1: Study location.

a Location of the study site from which model data is derived (indicated by a red star). b Late Devonian (~370 Ma) paleogeographic reconstruction with the study location indicated by a red star as well as the relative locations of Late Devonian large igneous provinces (LIPs) indicated with orange triangles. LIPs include the Viluy LIP in Siberia, the Kola LIP in the Kola Peninsula and the Pripyat–Dnieper–Donets (PDD) LIP in East Europe. The base map was created using GPlates with reconstructions from ref. ⁸⁰. Locations of LIPs as described by Racki¹⁶.

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Fig. 5: Geographic distribution of Late Devonian phosphorus records.

Marine records (B–E) are shown in relation to the Heintzbjerg study site (A), indicated as red stars. Marine records include: (B) Steinbruch Schmidt, Germany; (C) Kowala, Poland; (D) Coumiac, France; and (E) H-32 Core, Iowa, USA. The Viluy large igneous province (LIP) is indicated by the orange triangle. The base map was created using GPlates with reconstructions from ref. ⁸⁰. Locations of LIPs as described by Racki¹⁶.

Smart, M.S., Filippelli, G., Gilhooly, W.P. et al.
The expansion of land plants during the Late Devonian contributed to the marine mass extinction.
Commun Earth Environ 4, 449 (2023). https://doi.org/10.1038/s43247-023-01087-8

Copyright: © 2023 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

It's only by ignoring the evidence such as this and the evidence of biodiversity all around them, combined with a lack of logical and critical thinking, that creationists can continue to cling to the absurd notion that Earth and life on it were magically created out of nothing just 10,000 years ago by a magician who perfectly designed it for life.

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