This article comes from the WeChat public account: SF Chinese (ID: kexuejiaodian), by SF.
It is generally believed that since life first appeared on Earth about 4 billion years ago, the process of life evolution has been very slow. For more than 3 billion years until 600 million years ago, Earth life has always existed in the form of microscopic, simple microorganisms that are invisible to the naked eye, while the history of complex organisms may be only 600 million years. However, a latest study may upset this timeline.
By|Georgina Rannard
Translated by|Wen Jing
Visual design|Li Mei
The Ediacaran period is the last era of the Precambrian. In the oceans of the Ediacaran period, large multicellular organisms have already dominated. The traditional view is that before the start of the Ediacaran period (635 million years ago), life on Earth has always been mainly small single-celled prokaryotes.
Recently, an international scientific research team published their latest research results in the journal Precambrian Research, stating that they have found some new evidence to support their view that the emergence time of complex life on Earth may be 1.5 billion years earlier than previously thought.
The research team unearthed some fossils in the rock strata in the Franceville area of Gabon, Africa, and based on these fossils, they reconstructed that about 2.1 billion years ago, the local environment was suitable for animal survival. Scientists believe that these animals lived only in the inland sea and showed no signs of activities on a global scale, and eventually all became extinct.
These ideas are very different from the traditional thinking, and not all scientists agree. Most geologists believe that complex life (such as animals) on Earth began approximately 635 million years ago.
This study has also intensified a long-standing controversy over whether these ancient sediments found in Gabon are really fossils. In order to avoid this controversy as much as possible in this study, the scientists also observed the rocks (surrounding rocks) around these sediments, trying to find evidence that there were essential nutrients such as oxygen and phosphorus for life in the seawater at that time.
The head of the new research, Professor Ernest Chi Fru of Cardiff University in the UK, said that if this new conclusion can be confirmed, then the life forms at that time should be similar to slime molds - a eukaryotic microorganism that reproduces by spores and is between animals and fungi.
And a professor at University College London who did not participate in this research, Graham Shields, has reservations. Shields said: I don't object to the idea that the nutrient content was high 2.1 billion years ago, but I don't think this can lead to the diversification of complex life. To prove the existence of diversified complex life at that time, more evidence may be needed.
Chi Fru said that their work helps to prove the idea that complex life may be earlier than previously thought. He said: Look, there are fossils and there is oxygen, indicating that the environment at that time stimulated the emergence of the first complex organism.
The idea that complex life may be earlier than previously thought may have first emerged about 10 years ago. At that time, scientists discovered a special sedimentary structure in Franceville and named it the Francevillian Formation according to the name of Franceville. The Chi Fru team said that the Francevillian Formation is composed of fossils, which can show that life at that time could swing and move by itself.
But not all scientists accept this explanation. In the new study, in order to find more evidence to prove their point of view, the Chi Fru team analyzed the sediment cores drilled from the surroun ding rocks. The results showed that before the appearance of the Francevillian Formation, a laboratory for breeding life had already formed here.
They believe that the reason why there are high levels of oxygen and phosphorus is that the two ancient continental blocks, the West African Congo Craton and the South American São Francisco Craton, collided underwater and triggered volcanic activities. The plate collision isolated a part of the sea area, forming a nutrient-rich shallow inland sea.
Chi Fru said that this protected environment has the conditions for photosynthesis, which in turn greatly increases the oxygen content of the seawater. He said: So, the seawater can provide enough energy to promote the growth of organisms and the emergence of primitive and simple animal-like life forms with complex behaviors, such as those found in the fossils of this period.
But Chi Fru also said that the isolated environment is also the reason for the extinction of this life form due to the lack of sufficient new nutrients to maintain the food supply.
A doctoral student at the Natural History Museum in London, Elias Rugen, did not participate in this research, but he supports some of the findings in this study. The occurrence of such high levels of marine carbon, nitrogen, iron and phosphorus cycling at this site is unprecedented in the history of the Earth, he said, However, it is still unshakable that complex life could not have emerged and thrived 2 billion years ago. But he added that such a conclusion also requires more evidence.
Chi Fru said: The scene we see through fossils is similar to that in the Ediacaran period 635 million years ago, which to a certain extent supports our view. And this study can help us understand where we all come from.