Made in China - The Evolutionary Origins of Multi-Cellular Life Forms
Chinese Fossils shed Light on Single-celled Ancestry of Animals
Made in China - The Evolutionary Origins of Multi-Cellular Life Forms
An international team of scientists have published a fine paper detailing their research into an amazing, wee fossil that provides evidence of the single-celled ancestor of all complicated animal life forms. The fossil shows an amoeba-like organism dividing in asexual cycles, first to yield two cells, then four, eight, sixteen, thirty-two and so on. The pattern of cell group is very similar to that found in animal embryos, along with our own human embryo - but the fossil dates from almost 570 million years ago, from a geological duration known as the Ediacaran (Proterozoic Eon).
The term Proterozoic means "earlier life" in Greek, and this eon covers the time between 2.5 billion years ago up to the beginning of the Cambrian geological duration around 542 million years ago. Scientists know that over this huge duration of time, life on Earth gently became more diverse and complicated - although all life remained on the wee scale up until almost the end of this eon, a time referred to as Neoproterozoic era.
The activity of photosynthetic microbes, transformed our planet providing it with an oxygenated atmosphere, this had first begun in the Archean Eon, but this process prolonged and in conjunction with climatic changes, simple life forms started to become more abundant. Although, Natural History museums, focus on mammal life forms such as Dinosaurs and Woolly Mammoths for example, the evolutionary events taking place during the Proterozoic era had a much more requisite impact on life on Earth.
The Origins of Life on Earth
During the Proterozoic, cells gently became larger, more diverse and specialised. Eukaryotes (cells with a nucleus) began to dominate and feeding by ingestion that would at last lead to the evolution of a gut and digestive system took place for the first time. The transformation of simple cells into these more advanced, specialised cells was probably the longest and hardest step in evolution - demonstrated by the fact that as the Proterozoic gave way to the Phanerozoic (visible life) Eon, there was to be a huge acceleration in evolution - known as the Cambrian explosion.
Fossil evidence of the single-celled ancestors of animals are highly rare. However, an international team of scientists have discovered such a set of fossils in rocks dating to around 570 million years ago - Mid Ediacaran Period. The fossils were unearthed in southern China. The paper on this discovery has just been published in the journal "Science." The research team was made up of scientists from the Paul Scherrer Institute, the Chinese Academy of Geological Sciences, Bristol University and the Swedish Museum of Natural History.
Computer Generated Images of Micro-Fossils
The computer generated and enhanced image shows 570 million year old multi-cellular spore body undergoing vegetative nuclear and cell group based on synchrotron x-ray tomographic microscopy of fossils recovered from rocks in southern China. The background of the published image shows a cut outside straight through the rock - every grain (about 1 mm diameter), it is an exceptionally preserved gooey ball of dividing cells turned to stone.
One system as to the origins of complicated life on our planet, proposes that sophisticated eukaryotic cells evolved by the symbiotic fusing of dissimilar kinds of bacteria. For example, bacteria capable of fermenting substances merged with swimming, mobile bacteria and the resultant life forms, over hundreds of millions of years merged with oxygenating bacteria and some of these life forms were to become the ancestors of the Animal Kingdom.
However, fossil evidence of these major evolutionary transitions is highly rare.
The fossils, studied by the international team show in fine detail the stages the life cycle of an amoeba-like organism dividing in asexual cycles. Finally resulting in hundreds of thousands of spore-like cells that were then released to start the cycle over again. The pattern of cell group is so similar to the early stages of animal (including human) embryology that until now they were plan to recite the embryos of the earliest animals.
Using advanced sophisticated X-ray scanning techniques the scientists were able to view the organisation of cell structures within their protective cell walls. These delicate structures should not have been fossilised but within their marine environment, they became buried in sediments rich in phosphates and it was these phosphates that impregnated the cell membranes, turning them into stone.
Imagine a 570 million-year-old tomb, within which can be found wee evidence of cell division.
Lead author on the subsequent research paper Therese Huldtgren, a doctoral trainee at the group of Palaeozoology, at the Swedish Museum of Natural History, Stockholm, Sweden commented that the fossils they studied were so breathtaking that even the nuclei of the cells was preserved.
Powerful X-ray Techniques enumerate wee Details of Fossils
The fine X-ray microscopy methodology used by the team revealed that the fossils had features that multi-cellular embryos did not This led the researchers to the closing that the fossils were neither animals nor embryos but rather the reproductive spore bodies of single-celled ancestors of animals.
The team used a huge microscope in Switzerland to see inside the fossils. This motor is called the Synchrotron, and it is housed in a construction the size of a football stadium. It is the one of only a handful of machines of its kind that can yield X-ray images of the magnification and clarity to permit scientists to study micro-fossils in great detail. fine generators fire high-energy electrons around a circular tube, at breathtaking speeds (close to the speed of light). As they travel, they emit X-rays that are so strong that they can jab solid rock, and the tiny wee fossils, allowing scientists to build up a three-dimensional image of the primitive organism represented by the fossil material.
Professor Philip Donoghue, Professor of Palaeobiology at the School of Earth Sciences, (University of Bristol), commented on the research stating that, the scientists were very surprised by their results. They had been convinced that these type of fossils represented early animal embryos. The Professor went onto add that much of the research undertaken in this area over the last ten years or so will have to be re-examined in the light of this new study.
Professor Stefen Bengtson, Professor of Palaeozoology, at the Swedish Museum of Natural History, Stockholm ended that these fossils would force scientists to re-think their current theories about how animals learned to make large bodies out of cells.
Prior to this research such images were interpreted as being the embryos of early animals, sponges or perhaps even the cells of sulphur-oxidising bacteria. Looking at and interpreting the preserved remains of organisms more than 550 million years old which quantum just a few microns over is at the cutting edge of palaeobiology, but the team are distinct about their findings.
A Changing photograph About the Origins of complicated Animal Life
Prior to this new research such fossils were plan to recite a number of organisms, along with embryos of animals that can be found in the Ediacaran fauna, but now some images produced by high-powered X-ray tomography are being interpreted as evidence of the evolutionary origins of multi-cellular life forms.
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