Skip to main content

What Was the First Life on Earth?

What Was the First Life on Earth?

The earliest evidence for life on Earth arises among the oldest rocks still preserved on the planet.
Earth is about 4.5 billion years old, but the oldest rocks still in existence date back to just 4 billion years ago. Not long after that rock record begins, tantalizing evidence of life emerges: A set of filament-like fossils from Australia, reported in the journal Astrobiology in 2013, may be the remains of a microbial mat that might have been extracting energy from sunlight some 3.5 billion years ago. Another contender for world's oldest life is a set of rocks in Greenland that may hold the fossils of 3.7-billion-year-old colonies of cyanobacteria, which form layered structures called stromatolites.
Some scientists have claimed to see evidence of life in 3.8-billion-year-old rocks from Akilia Island, Greenland. The researchers first reported in 1996 in the journal Nature that isotopes (forms of an element with different numbers of neutrons) in those rocks might indicate ancient metabolic activity by some mystery microbe. Those findings have been hotly debated ever since — as, in fact, have all claims of early life.
Still, the fact that suggestive evidence of life arises right as the rock record begins raises a question, said University of California, Los Angeles, geochemist Elizabeth Bell in a SETI Talk in February 2016: Is the timing a coincidence, or were there earlier forms of life whose remnants disappeared with the planet's most ancient rocks?


These cone-shaped structures discovered in 3.7-billion-year-old rocks in Greenland, about the size of a quarter, may be fossilized colonies of microbes and the earliest fossils of life on Earth, researchers say.
Credit: Allen Nutman/Nature
The period that occurred before the rock record begins is known as the Hadean. It was an extreme time, when asteroids and meteorites pummeled the planet. Bell and her colleagues said they might have evidence that life arose during this very unpleasant time. In 2015, the research team reported discovering graphite, a form of carbon, in 4.1-billion-year-old crystals of zircon. The ratio of isotopes in the graphite suggested a biological origin, Bell and her colleagues wrote in the journal Proceedings of the National Academy of Sciences.
"There is some skepticism, which is warranted," Bell told Live Science. Meteorites or chemical processes might have caused the odd carbon ratios, she said, so the isotopes alone aren't proof of life. Since the publication of the 2015 paper, Bell said, the researchers have found several more of the rare-carbon inclusions, which the scientists hope to analyze soon.
From what is known of this period, there would have been liquid water on the planet, Bell told Live Science in an interview. There might have been granite, continental-like crust, though that's controversial, she said. Any life that could have existed would have been a prokaryote (a single-celled organism without membrane-bound nuclei or cell organelles), Bell added. If there was continental crust on Earth at the time, she said, prokaryotes might have had mineral sources of nutrients like phosphorus.
A different approach to the hunt for Earth's early life suggests that oceanic hydrothermal vents may have hosted the first living things. In a paper published in July 2016 in the journal Nature Microbiology, researchers analyzed prokaryotes to find the proteins and genes common to all of these organisms, presumably the final remnants of the Last Universal Common Ancestor (LUCA) — the first shared relative from which all life today descends.
The research team found 355 proteins shared by all archaeal and bacterial lineages. Based on those proteins, the researchers reconstructed a view of LUCA's genome, hinting that it lived in an anaerobic (oxygen-free), hydrothermal environment. If that's the case, Earth's first life (or at least the first life that left descendants) would have resembled the microbes that cluster around deep-sea vents today, the researchers said.

 

Comments

Popular posts from this blog

Shi Cheng, the lion city under water.

China's Atlantis: How the Lion City was purposely-flooded to make way for a power station but remains completely intact 130ft underwater after 50 years Shi Cheng was once centre of politics and economics in eastern province of Zhejiang Covered in water to build hydroelectric power station in 1959 and was forgotten Now divers want to use the metropolis as a tourist site and have gone to plan routes,   A maze of white temples, memorial arches, paved roads, and houses... hidden 130 feet underwater: this is China's real-life Atlantis. The so-called Lion City, tucked in a lake between the Five Lion Mountain, was once Shi Cheng - the centre of politics and economics in the eastern province of Zhejiang. But in 1959, the Chinese government decided a new hydroelectric power station was required - so built a man-made lake. Metropolis: Shi Cheng, dubbed Lion City after the Lion Mountains that surround it, has lain hidden under 131 feet of water since 1959 to generate ...

Who really discovered the Jackson 5?

Motown at 50: Myth-busting: Who really discovered the Jackson 5? By  Peter Lindblad (Universal Motown) Diana Ross is thought by many to have discovered the Jackson 5. But longtime Motown promotions man Weldon McDougal remembers it differently.Having just been bumped up to director of special projects at the label, McDougal was in Chicago making preparations for a Bobby Taylor and the Vancouvers show. They had a record out called “Does Your Mother Know About Me?” “So I [went] to Chicago [to] make arrangements at the club they were playing to take about four or five of the tables up front for VIP tables … things like that,” remembers McDougal. “Got it all situated so that when the main night came, which was a couple nights later, they would greet our guests.” There to handle everything on a Wednesday, McDougal found out the club was having a talent show that evening. The winner would open for Taylor two nights later. The Jackson 5 stole the show, and they re...