【古生物学】地球の初期生物の多様性

Evidence of microbial activity in and around hydrothermal vents at least 3,770 million years ago is reported in Nature this week, which could represent some of the earliest life on Earth.

Some of the earliest habitable environments may have been hydrothermal vents beneath the oceans. To search for signs of life in these settings, Matthew Dodd and colleagues analysed jasper rocks from the Nuvvuagittuq belt in northeastern Canada that are interpreted as being from ancient hydrothermal vents. Previous studies have provided estimations of the age of the Nuvvuagittuq belt, ranging from around 3,770 million to 4,290 million years old. The authors observe tubes and filamentous structures preserved in these rocks that resemble similar structures attributed to bacterial life seen in other seafloor hydrothermal environments. Additional features preserved in these rock, such as iron oxide granules and carbonate rosettes, are indicative of biological activity, the authors add.

These findings complement a recent report in Nature about stromatolites - geological structures made by microbial colonies - from 3,700-million-year-old rocks in Greenland. Stromatolites formed in the sunlit surface waters of the sea; signs of life from hydrothermal vents show that even at this early date life had colonised the sea from its surface to the depths.