Earth complex life origin of the new clue: ice age lead to multi-cell life appears

About 659 million years ago, the Sturtian ice age ended, the earth quickly warming, into the hot “greenhouse period.” During this period of 15 million years, phosphorus, oxygen and other multi-cell life required for the release of a large number of elements. Before the plankton appeared in large numbers and became a multicellular animal, the continent of the earth had gone through the process of fusion, division and reintegration. This timeline shows the relationship between the geochemical changes of the earth and the emergence of eukaryotes such as algae.

Dating back to 2 billion years ago, but until 500 million years ago, life was developed to the extent that it could be seen by the naked eye. One of the questions that has long been confused by biologists is how life has evolved from microbes into multicellular plants and animals and eventually dominates this blue planet? Now, scientists have analyzed the chemical traces of life left in the rock 1 billion years ago and found that it is likely that a severe ice age led to the emergence of multicellular life.

In an article published in the journal Nature, researchers carefully reconstructed the evolutionary timeline of life before and after the Snowball Earth period. About 700 million years ago, the earth had a severe ice age, known as the Sturtian ice age. About 659 million years ago, the end of the Sturtian ice age, the rapid warming of the earth, into the so-called “greenhouse period.” Then, the steaming earth went into the Marinoan ice age, and the ice and snow re-covered almost the whole earth. In the 15 million years between the two “snowballs”, new earth life began to emerge. Jochen J. Brocks, a geologist at the Australian National University, and colleagues analyzed the residual cell membrane traces in ancient rocks, hoping to determine the process of multicellular life. The cell membrane consists of lipids and their byproducts, which can be used as biomarkers as fossils of early microbes. By analyzing the chemical composition of these cell membranes, Brookes and his team found that new and larger marine planktonic algae were rapidly emerging in warm seawater after the Sturtian ice age. Some of these algae belong to eukaryotes, meaning that they have developed a nucleus – another necessary step in evolving multicellular life.

However, if the earth after the Sturtian ice age does not undergo major changes in geology and chemistry, multicellular life can not be further evolved. From the upper atmosphere to the dark and deep sea, the molecular composition of the earth must change.

Researchers point out that when the snowball Earth period ends, melted glaciers rapidly erode the continent and deliver large amounts of nutrients into the ocean. Filled with mineral ice and snow mud poured into the ocean, sink to the sea, while the carbon element fixed. Everything is really started at this time. “Such a large-scale reduction of carbon deposition must be balanced by the release of oxygen into the atmosphere, causing long-term oxygen production in the Neoproterozoic deep sea,” the researchers wrote in the paper. The earth, which had a very low oxygen content, was suddenly filled with oxygen – both the ocean and the atmosphere.

The rise in oxygen content raises a series of related events, including an increase in phosphorus content in water, which is the composition of DNA and the energy molecule-ATP Key component. Algae and other more complex forms of life began to appear, and during the life of the release of oxygen. With the algae differentiation, there have been other forms of life that eat algae. Over time, new predators who feed on these organisms have also evolved. More and more organisms die and sink to the bottom of the sea, so that more carbon fixes. As the researchers say, the Earth has developed a “more efficient bio-pump”.

This change from oxygen and phosphorus is unstoppable. Even after the Minoan Ice Age Earth, the tropical ocean surface is heated to 60 degrees Celsius, and algae can still find a living space in the poles and continue to evolve. The form of life we ​​know today seems to be between the snowball period and the greenhouse period and is constantly wandering in warm seawater. About 550 million years ago, the Earth’s climate gradually became more stable, with the head, tail and internal organs of the animals began to appear. Andrew Knoll, a geologist at Harvard University that did not participate in the study, said the results of the study would change the debate about the complex life of the Earth. The work of Brooks and his colleagues fundamentally shows that environmental change is the key to the evolution of life. If there is no oxygen in the ocean, animals can not appear on the earth.

This is also the reason why scientists have been concerned about the process of marine deoxidation in recent years. Due to climate change, as well as the transport of terrestrial nutrients, there are some areas of deoxidation in the ocean – known as the “death zone”. These areas will slow down or even stop the Earth’s bio-pump process. Earth is a huge geochemical machine, and many processes are running in millions of years. The chaos of these processes may completely change the face of the world. In other words, life on earth may flourish, such as when the oxygen content and phosphorus content in the ocean rise; and sometimes it may bring about the extinction of life. (Any day)

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