Scientists claimed they discovered 3.5 billion-year-old fossils in Western Australia about 40 years ago. According to a new research, these rocks did indeed contain biological life, making them the earliest fossils yet discovered. The study was published in the journal Nature.
The rock formation where the fossils were found contains many layers that record different times in the planet's history. The layer that contained the fossils was about 530 million years old and had layers of bacteria living in mud pools. These bacteria used carbon dioxide and water molecules to build complex organic compounds that they stored inside their cells until they were buried by more sedimentary material. Scientists think that over time, some of these organisms may have been able to reproduce using their descendants as seeds, starting the first phase of evolution on Earth.
Although scientists have known for quite some time that ancient microbes existed, this new discovery shows that they were much more evolved than previously thought. A team of researchers led by Peter Ward of the University of California, Berkeley, found the fossils while searching for evidence of how early plants acquired nutrients from the surrounding environment. They used magnetic particles attached to the bacterial cells' surfaces to trace their path through the sediment after they died. The results showed that most of the bacteria lived in clusters that appeared to be connected to each other and to larger structures such as grains of sand.
The earliest forms of life According to a December 2017 investigation, 3.465 billion-year-old Australian Apex chert rocks once harbored microbes, the earliest direct evidence of life on Earth. The finding of microbial mat fossils in 3.48 billion-year-old sandstone in Western Australia was disclosed in a 2013 paper. The new discovery extends the record of life on Earth by about 700 million years.
Modern bacteria have a typical size of 5-250 microns (μm), or 0.00005-0.25 inches. The 3.4 billion-year-old microfossils were smaller than this, with some measuring only 1 μm across, or 200 times thinner. They also lived in clusters rather than as single cells.
The researchers found the evidence in the form of spherules, which are hollow bubbles formed when gas bubbles within the water phase of a sedimentary rock dissolve and are replaced by minerals from dissolved particles in the surrounding environment. Microbes use this process to create protective shells that allow them to survive in extreme conditions. Sponges, corals, sea lilies, and puffballs are all composed of dead bacterial cells joined together with polysaccharides (complex sugars) into an organic matrix.
Bacteria are responsible for many important processes in nature. They decompose toxic chemicals such as mercury and arsenic, produce several important nutrients, and help control disease-causing organisms.
According to a December 2017 investigation, 3.465 billion-year-old Australian Apex chert rocks once harbored microbes, the earliest direct evidence of life on Earth. The research was conducted by scientists from the University of California, Berkeley, the University of New South Wales, and the Chinese Academy of Sciences.
The discovery was made possible through the application of high-resolution X-ray microscopy, which allowed the researchers to see the internal structure of the fossils for the first time. It revealed that the ancient microbe-laden rocks were composed of small spherical particles about 1/4 of a millimeter in diameter that were attached together with polysaccharides rather than minerals. These particles may have provided a favorable environment for the early evolution of cells.
The study also found chemical signs of life in the form of simple organic molecules in the same 3.48-billion-year-old rock sample. This is the oldest evidence of life discovered so far in Australia. Previously, the record holder for Earth's oldest fossils was 3.54 billion years old and they belonged to bacteria.
Dr. Lee Spitzer, one of the authors of the study, said that they are now trying to determine if these organisms were able to reproduce like modern ones do.