The researchers suspect they were not meek. "We have no clue," said geobiologist Jochen Brocks of the Australian National University in Canberra, lead author of the study published in the journal Nature. The newly described fossils do not include the actual body of the organisms but rather their molecular remnants, leaving unclear their size, appearance, behavior and complexity - including whether they were all unicellular or some were multicellular. Eukaryotes today include fungi, algae, plants and animals, but none of those had yet evolved. They were gate-crashers in a world teeming with bacteria, simpler unicellular organisms lacking a nucleus. Eukaryotes possess a complex cell structure including a nucleus that acts as a command and control center and subcellular structures called mitochondria that power the cell. The newly identified fossils are of a rudimentary form of a steroid - a fat molecule that was an indispensable ingredient in cell membranes of pioneering members of a domain of now-dominant organisms called eukaryotes (pronounced yoo-KAR-ee-oats). These remains, researchers said on Wednesday, date to a time span during what is called the Proterozoic Eon that was crucial in the evolution of complex life but has been shrouded in mystery because of a spotty fossil record of the microscopic organisms that inhabited Earth's marine realm. WASHINGTON, June 7 (Reuters) - Fossil remains of a cell membrane component identified in rocks dating back about 1.6 billion years are opening a window into what scientists are calling a "lost world" of microscopic organisms that were the primordial forerunners of Earth's fungi, algae, plants and animals - including people.
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