It was not ‘oxygen’ that prompted the explosion of life evolution, disproving the theory of 70 years
It was not “oxygen” that prompted the explosion of life evolution, disproving the 70-year-old theory / Credit: Canva . Nazology Editorial Department
About 1 billion years ago, the previously single-celled organisms on Earth became multicellular, and during the Cambrian period, which began 542 million years ago, they became powerful predators.
For over 70 years, biology textbooks have attributed this dramatic evolution of multicellular animals to increased oxygen levels on Earth.
Even a relatively new textbook on biology states that “a rapid increase in oxygen concentration was behind the advancement of multicellular animals.”
In fact, it takes a great deal of energy to build the kind of tissues possessed by advanced multicellular animals, such as agile muscles, hard bones, and complex nervous systems, and must rely on the powerful burning power of oxygen to do so. because it was thought that no
However, in the papers published in the last few years, this common sense has come to be questioned.
This is because when we investigated the strata at that time, we found many minerals that were only formed under conditions of low oxygen concentration.
Researchers at the University of Copenhagen decided to look at oxygen levels in the Ediacaran period.
The Ediacaran Period is included in the Proterozoic Era and immediately precedes the Cambrian Period / Credit: Canva . Nazology Editorial Department
As shown in the figure above, the Ediacaran Period, which began 635 million years ago, was the period immediately preceding the Cambrian Period, and the Cambrian Explosion was preceded by an explosion of multicellular organisms known as the Avalon Explosion. era.
Due to the Avalon explosion, the creatures on Earth changed from being invisible to the naked eye to being large enough to be seen with the naked eye.
Many of the organisms born during this period are thought to have eaten microbial mats deposited on the seafloor, creating a calm ecosystem without predators.
If it is possible to investigate the oxygen concentration at that time, it should be possible to know how the advancement of multicellular organisms that occurred in the Ediacaran period was related to oxygen concentration.
For the investigation, ancient rock samples of the Oman Mountains were examined and minerals such as iron, molybdenum, thallium and uranium were investigated.
By examining the isotope ratio of iron and other minerals, it is possible to know whether oxygen was abundant or low at that time.
They found that during the Ediacaran period when multicellular organisms diversified, the oxygen concentration in the ocean did not increase, but rather decreased slightly.
Similar results were confirmed for minerals collected in Canada and southern China,At the time of Avalon’s explosion, the average oxygen concentration in the ocean was shown to be only 5 to 10 times lower than it is today (comparable to oxygen concentrations at twice the altitude of Mount Everest). I was.
This result puts an end to the 70-year-old theory that “high oxygen concentration is a condition for the evolution of multicellular organisms”.
Researchers say, “This means that the theory we have believed to be true since childhood is wrong. Textbooks will also need to be revised.”
But if so, why did organisms evolve so explosively despite the lack of oxygen?
