New ancient fossils (Introduction)

by David Turell , Monday, February 02, 2015, 20:08 (3369 days ago)

Large macroscopic fossils, undoubtedly multicellular but with no evidence of differentiation from 2 billion years ago.-http://blogs.scientificamerican.com/artful-amoeba/2015/01/29/two-billion-year-old-fossils-reveal-strange-and-puzzling-forms/-"This new collection of fossils (a “lagerstätte” in the bio-lingo) is called the “Francevillian Biota” and hails from the west African nation of Gabon. So far scientists have collected over 400 fossils in scores of new types from the 2.1 billion-year-old deposit, including several new types not shown in their original 2010 Nature paper describing the cache, according to a new paper published last summer in PLoS ONE. “[These fossils] appear to represent a first experiment in megascopic multicellularity,” the authors suggest. And by megascopic, they mean mega — the largest specimen is 17 cm (nearly 7 inches) long.-"The researchers who've studied the remains of these creatures know a few things about them — they lived on the quiet seabed of an oxygenated, shallow ocean — but beyond that, clues are few. After their death, they were buried by sediment and often preserved in the sparkly mineral pyrite (also called fool's gold; I wrote about some similarly fossilized crustaceans here) by the action of bacteria in what would ultimately become a dense black shale. In fact, it was the combination of these organisms' quiet neighborhood and conditions that fostered fast fossilization by pyrite to which the authors attribute their remarkable preservation.-"What makes these fossils extra-special is not that they were multicellular organisms, as they almost certainly were. It's that they are visible to the naked eye. Multicellularity has evolved many times in Earth's history, and this was likely not the first time. But it is the first that we know of that was big enough for human eyes to see unaided.-"So what might have encouraged this early flirtation with bigness?-"Immediately prior to their evolution, atmospheric oxygen spiked during the Great Oxygenation Event of 2.3 billion years ago, a result of the invention of photosynthesis by cyanobacteria and the running out of iron deposits with which to sop all the resulting oxygen up by rusting out (the genesis of the famous banded iron formations in Minnesota and Western Australia). This is consistent, the authors say, with the idea that more fuel in the form of oxygen allowed the evolution of bigger life forms. Aerobic respiration of the type made possible by oxygen yields 15 times more power than anaerobic respiration, and all this extra power could fuel bigger bodies, some have hypothesized."