Please note: This did NOT occur 7000 years ago! And it did NOT occur 4.5 BILLION years when the earth (and no rational person disputes this) was formed! So these beginnings of life have NOTHING to do with any of the popular mythology associated with origins of life!! The earth and the universe had existed for billions of years before life began and before life became multicellular.
"More than 500 million years ago, single-celled organisms on Earth's surface began forming multicellular clusters that ultimately became plants and animals. Just how that happened is a question that has eluded evolutionary biologists."
sciencedaily.com
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sciencedaily.com
Chinese Fossils Shed Light On Evolutionary Origin of Animals from Single-Cell Ancestors
ScienceDaily (Dec. 22, 2011) — 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.
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.
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.
Lead author Therese Huldtgren said: "The fossils are so amazing that even their nuclei have been preserved."
Co-author Dr John Cunningham said: "We used a particle accelerator called a synchrotron as our X-ray source. It allowed us to make a perfect computer model of the fossil that we could cut up in any way that we wanted, but without damaging the fossil in any way. We would never have been able to study the fossils otherwise!"
This X-ray microscopy revealed that the fossils had features that multicellular embryos do not, and this led the researchers to the conclusion that the fossils were neither animals nor embryos but rather the reproductive spore bodies of single-celled ancestors of animals.
Professor Philip Donoghue said: "We were very surprised by our results -- we've been convinced for so long that these fossils represented the embryos of the earliest animals -- much of what has been written about the fossils for the last ten years is flat wrong. Our colleagues are not going to like the result."
Professor Stefan Bengtson said: "These fossils force us to rethink our ideas of how animals learned to make large bodies out of cells." |
