Task1. Read this article about the earliest creatures on Earth.

Fossil: Evidence Points to Early Life Forming on Deep-Ocean Floor

June 2000

An Australian geologist has reported finding fossil evidence for the existence of heat-loving microorganisms that lived near submarine hot springs about 3.2 billion years ago, some 2.7 billion years earlier than previously believed. The microbes lived under extreme conditions of heat and darkness near volcanic vents on the deep-ocean floor where sunlight could not penetrate.

The researcher’s findings could lend support to the theory that life on Earth first originated on the deep-ocean floor in extreme heat, rather than in warm pools of water on the surface of Earth as many scientists have long conjectured. According to this theory, the earliest creatures derived their energy through a process known as chemosynthesis by metabolizing inorganic chemicals such as sulfur, rather through the process of photosynthesis, which converts sunlight into energy.

Geologist Birger Rasmussen of the University of Western Australia in Nedlands reported the discovery in a letter in the June 8, 2000, issue of the journal Nature. Rasmussen described finding threadlike microorganisms in a volcanogenic massive sulphide, a type of metal deposit of volcanic origin that is usually formed on the seafloor, in a region known as the Pilbara Craton in northwest Australia. The volcanic rock deposits in this region date from the Archean Eon, a period that lasted from 3.8 billion years ago to 2.5 billion years ago. The Pilbara Craton region and a rock formation in South Africa are the only two places in the world where rocks from the Archean Eon are known to have preserved fossils.

The fossilized filaments were 1 to 20 mm (0.04 to 0.8 in) in length and only a thousandth of a millimeter in diameter. Rasmussen based his finding of a biological origin on the filaments’ wavy form, uniformity in length, and similarity to other known fossils of microorganisms from the Archean Eon. He also found that the filaments were completely dissimilar to threadlike structures that are known to be of nonbiological origin.

By analyzing the chemical composition of the rock in which the microfossils were found, Rasmussen concluded that the ancient microbes inhabited a world where the temperature was near 100°C (212°F). This temperature is similar to that near hydrothermal vents (hot springs) found today on the floor of the Pacific and Atlantic oceans. Rasmussen noted other similarities between the fossilized microbes and the microorganisms that live near present-day hydrothermal vents and derive their energy from chemosynthesis. Scientists first discovered these vents in 1995 and were amazed to find a diverse marine community living under such extreme conditions.

In a commentary in Nature on Rasmussen’s article, geologist Euan Nisbet of the University of London in England wrote that “although Rasmussen’s work does not show that deep-water hydrothermal life came before photosynthetic life, it does lend circumstantial support to the argument that steps in the early history of life took place around hydrothermal systems.”

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