Evidence of the single-celled ancestors of animals, dating from the interval in Earth's history just before multicellular animals appeared, has been discovered in 570 million-year-old rocks from South China by researchers from the University of Bristol, the Swedish Museum of Natural History, the Paul Scherrer Institut and the Chinese Academy of Geological Sciences.
All life evolved from a single-celled universal common ancestor, and at various times in Earth history, single-celled organisms threw their lot in with each other to become larger and multicellular, resulting, for instance, in the riotous diversity of animals. However, fossil evidence of these major evolutionary transitions is extremely rare.
De fossielen:
The fossils, reported this week in Science, preserve stages in the life cycle of an amoeba-like organism dividing in asexual cycles, first to produce two cells, then four, eight, 16, 32 and so on, ultimately resulting in hundreds of thousands of spore-like cells that were then released to start the cycle over again. The pattern of cell division is so similar to the early stages of animal (including human) embryology that until now they were thought to represent the embryos of the earliest animals.
Het onderzoek:
The researchers studied the microscopic fossils using high energy X-rays at the Swiss Light Source in Switzerland, revealing the organisation of the cells within their protective cyst walls. The organisms should not have been fossilized -- they were just gooey clusters of cells -- but they were buried in sediments rich in phosphate that impregnated the cell walls and turned them to stone.
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Bron: Artikel van University of Bristol (met korte video)
