And yet, a research team at the University of Leeds supported by the Universities of Lyon, Exeter and UCL, has found evidence that early animals evolved on Earth in response to wildly fluctuating atmospheric oxygen levels, and in particular during the period following the 'Great Oxidation Event' which occurred some 2 billion years ago when the cyanobacteria evolved photosynthesis and began polluting the atmosphere with the process's waste product, oxygen.
In between, that and the third step about 200 million years ago when atmospheric oxygen reached todays level, there was a second step during the 500 million-year long Neoproterozoic Era which began about 1 billion years ago. Until now, what happened during that period when early forms of animals appear in the fossil record, was something of a mystery. It was during this era that the earliest multicellular life forms, Ediacaran biota, made their appearance.
As the Leeds University News release explains:
The question scientists have tried to answer is - was there anything extraordinary about the changes to oxygen levels in the Neoproterozoic Era that may have played a pivotal role in the early evolution of animals – did oxygen levels suddenly rise or was there a gradual increase? Fossilised traces of early animals - known as Ediacaran biota, multi-celled organisms that required oxygen - have been found in sedimentary rocks that are 541 to 635 million years old. To try to answer the question, a research team at the University of Leeds supported by the Universities of Lyon, Exeter and UCL, used measurements of the different forms of carbon, or carbon isotopes, found in limestone rocks taken from shallow seas. Based on the isotope ratios of the different types of carbon found, the researchers were able to calculate photosynthesis levels that existed millions of years ago and infer atmospheric oxygen levels. As a result of the calculations, they have been able to produce a record of oxygen levels in the atmosphere over the last 1.5 billion years, which tells us how much oxygen would have been diffusing into the ocean to support early marine life. Dr Alex Krause, a biogeochemical modeller who completed his PhD in the School of Earth and Environment at Leeds and was the lead scientist on the project, said the findings give a new perspective on the way oxygen levels were changing on Earth.Technical details are given in the abstract to the open access paper in Science Advances:Fossil record of early animals from Mistaken Point Ecological Reserve in Canada.
Credit: Dr Emily. G. Mitchell – University of Cambridge.The early Earth, for the first two billion years of its existence, was anoxic, devoid of atmospheric oxygen. Then oxygen levels started to rise, which is known as the Great Oxidation Event.
Up until now, scientists had thought that after the Great Oxidation Event, oxygen levels were either low and then shot up just before we see the first animals evolve, or that oxygen levels were high for many millions of years before the animals came along.
But our study shows oxygen levels were far more dynamic. There was an oscillation between high and low levels of oxygen for a long time before early forms of animal life emerged. We are seeing periods where the ocean environment, where early animals lived, would have had abundant oxygen - and then periods where it does not.
Dr Alex Krause, lead author
School of Earth and Environment
University of Leeds, Leeds, UK.The findings – “Extreme variability in atmospheric oxygen levels in the late Precambrian” – are published in the journal Science Advances.This periodic change in environmental conditions would have produced evolutionary pressures where some life forms may have become extinct and new ones could emerge.
[the oxygenated periods expanded what are known as] habitable spaces [parts of the ocean where oxygen levels would have been high enough to support early animal life forms.]
It has been proposed in ecological theory that when you have a habitable space that is expanding and contracting, this can support rapid changes to the diversity of biological life.
When oxygen levels decline, there is severe environmental pressure on some organisms which could drive extinctions. And when the oxygen-rich waters expand, the new space allows the survivors to rise to ecological dominance.
These expanded habitable spaces would have lasted for millions of years, giving plenty of time for ecosystems to develop.
Dr Benjamin Mills, co-author
School of Earth and Environment
University of Leeds, Leeds, UK.
AbstractIn other words, extreme fluctuations in a key environmental factor was the backdrop for the radiation of different body plans as those forms which gave the species a greater advantage came to dominate as the developing ecosystems created more niches for them to occupy. It is entirely predictable therefore that there would be a rapid evolutionary radiation both in adaptation to specific niches, but also in the ability to evolve in response to these changes - the evolution of evolvability.
Mapping the history of atmospheric O2 during the late Precambrian is vital for evaluating potential links to animal evolution. Ancient O2 levels are often inferred from geochemical analyses of marine sediments, leading to the assumption that the Earth experienced a stepwise increase in atmospheric O2 during the Neoproterozoic. However, the nature of this hypothesized oxygenation event remains unknown, with suggestions of a more dynamic O2 history in the oceans and major uncertainty over any direct connection between the marine realm and atmospheric O2. Here, we present a continuous quantitative reconstruction of atmospheric O2 over the past 1.5 billion years using an isotope mass balance approach that combines bulk geochemistry and tectonic recycling rate calculations. We predict that atmospheric O2 levels during the Neoproterozoic oscillated between ~1 and ~50% of the present atmospheric level. We conclude that there was no simple unidirectional rise in atmospheric O2 during the Neoproterozoic, and the first animals evolved against a backdrop of extreme O2 variability.
Krause, Alexander J.; Mills, Benjamin J. W.; Merdith, Andrew S.; Lenton, Timothy M.; Poulton, Simon W.
Extreme variability in atmospheric oxygen levels in the late Precambrian
Science Advances; 8(41), eabm8191, DOI: 10.1126/sciadv.abm8191
Copyright: © 2022 The authors.
Published by American Association for the Advancement of Science. Open access
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
There are no crumbs of comfort for Creationists in these findings nor any evidence that the TOE is incapable of explaining the facts. Indeed, the TOE is the only explanation capable of explaining them and the facts are entirely at odds with what Creationist cult dogma requires its dupes to believe.
The history of oxygen in earth's prehistoric times is fascinating but very controversial and inconclusive. Different scientists believe very differently. Some scientists think that planet earth had abundant, breathable oxygen as far back as 1.8 billion years ago during the mid Precambrian era, while others think the Precambrian era was mostly anaerobic to hypoxic. Some scientists believe that planet earth became breathable with a 21 percent oxygen content during the Carboniferous period, between 350 million to 320 million years ago during the Paleozoic era. We don't really know.
ReplyDeleteThe only thing that's certain is that the early earth was not a paradise at all, but a gehenna, or hell, with a suffocating, unbreathable, toxic atmosphere with carbon monoxide, sulfur, methane, carbon dioxide, and ammonia. Boiling mud pools, active volcanoes, and geysers proliferated, and earth's surface was frequently pelted by meteors from space. The temperature was thousands of degrees hot. A human would suffocate and incinerate to death in seconds under these horrific conditions during the Precambrian era. This argues against Intelligent Design and argues against Benevolent design. As a matter of fact, this is stupid design and malevolent design. What a STUPID, cruel, disgusting, pointless, wasteful way to run a creation. This is just idiotic for any creator to design such a screwed up world. It's a huge embarrassment.