The first organisms that "breathed" oxygen appeared about 3.1 billion years ago, according to new scientific estimates. The new Israeli genetic analysis of several different families of microorganisms came to the rather unexpected conclusion that the use of oxygen by living microorganisms began nearly 600 million years earlier than the so-called "Great Oxygenation Event," which filled Earth's atmosphere with oxygen gas about 2.4 billion years.
The Israeli researchers, led by biochemist Dan Tawfik of the Weizmann Institute of Science, who made the relevant publication in the journal "Nature Ecology &Evolution", according to "Science", analyzed the genomes of 130 families of prokaryotic organisms, which they are today the descendants of the most ancient microbes, bacteria and other microorganisms on our planet. An evolutionary "family tree" was thus created using genes from about 700 enzymes, which either use oxygen or produce it. Then, using the "molecular clock" method, they made estimates of when each of these enzymes evolved.
Of the 130 families of microorganisms, 36 could be dated with a relatively high degree of accuracy, according to the researchers. As Dr Tawfik said, "We saw something quite impressive:a clear emergence of microbes that used oxygen 3 to 3.1 million years ago." 22 of the 36 families of microorganisms appear to have appeared right around that time, 12 later, and only two earlier.
The appearance of oxygen-using proteins (enzymes) marked a pivotal stage in the emergence of aerobic microbes, a transition from a previously essentially anaerobic world. Scientists generally agree that the early Earth's atmosphere and oceans lacked oxygen gas. However, there is some evidence that there was some oxygen relatively soon, as cyanobacteria - the early photosynthetic microorganisms - probably by 3.5 billion years ago had begun to release oxygen as a by-product, but did not use it themselves. The use of oxygen for "breathing" took a few more hundreds of millions of years.
The new Israeli study estimates - based on retrospective genetic analysis - that approximately 3.1 billion years ago, microorganisms appeared that began to "breathe" oxygen and use it for greater energy production. Presumably the ability to breathe/use oxygen evolved slowly, initially in small pockets, and gradually spread across the planet over the next hundreds of millions of years.
After the "Great Oxygenation Event" that followed, the environment of our planet began to transform dramatically and life experienced a real "explosion" thanks to oxygen. Thus there was the evolution of multicellular organisms and eventually of animals and humans. Other scientists, however, such as evolutionary biologist Patrick Shih of the University of California, Berkeley, appeared more cautious because the "molecular clock" method on which the genetic analysis and dating was based is still a developing science and therefore its conclusions have a degree of uncertainty. of doubt.
APE-ME