BBC Nature - History of life on Earth What Happened Before the Beginning? Every cosmologist and astronomer agrees: our Universe is 13.7 billion years old. Using cutting-edge technology, scientists are now able to take a snapshot of the Universe a mere heartbeat after its birth. Armed with hypersensitive satellites, astronomers look back in time to the very moment of creation, when all the matter in the Universe exploded into existence. It is here that we uncover an unsolved mystery as old as time itself - if the Universe was born, where did it come from? The big bang theory holds that the entire universe was once packed tightly into an unimaginably dense and tiny space, known as a "singularity." But what brought about that big bang? Successfully answering the question of what existed before the big bang would require bridging the gap between the so-far mutually incompatible worlds of relativism and quantum mechanics. This is the fourth episode. Watch the full documentary now
Fossil of ancient multicellular life sets evolutionary timeline back 60 million years -- ScienceDaily A Virginia Tech geobiologist with collaborators from the Chinese Academy of Sciences have found evidence in the fossil record that complex multicellularity appeared in living things about 600 million years ago -- nearly 60 million years before skeletal animals appeared during a huge growth spurt of new life on Earth known as the Cambrian Explosion. The discovery published online Wednesday in the journal Nature contradicts several longstanding interpretations of multicellular fossils from at least 600 million years ago. "This opens up a new door for us to shine some light on the timing and evolutionary steps that were taken by multicellular organisms that would eventually go on to dominate the Earth in a very visible way," said Shuhai Xiao, a professor of geobiology in the Virginia Tech College of Science. The discovery sheds light on how and when solo cells began to cooperate with other cells to make a single, cohesive life form.
Did a hyper-black hole spawn the Universe? The event horizon of a black hole — the point of no return for anything that falls in — is a spherical surface. In a higher-dimensional universe, a black hole could have a three-dimensional event horizon, which could spawn a whole new universe as it forms. It could be time to bid the Big Bang bye-bye. Cosmologists have speculated that the Universe formed from the debris ejected when a four-dimensional star collapsed into a black hole — a scenario that would help to explain why the cosmos seems to be so uniform in all directions. The standard Big Bang model tells us that the Universe exploded out of an infinitely dense point, or singularity. But nobody knows what would have triggered this outburst: the known laws of physics cannot tell us what happened at that moment. “For all physicists know, dragons could have come flying out of the singularity,” says Niayesh Afshordi, an astrophysicist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada. On the brane Model discrepancy
Timeline: The evolution of life By Michael Marshall There are all sorts of ways to reconstruct the history of life on Earth. Pinning down when specific events occurred is often tricky, though. For this, biologists depend mainly on dating the rocks in which fossils are found, and by looking at the “molecular clocks” in the DNA of living organisms. There are problems with each of these methods. Modern genetics allows scientists to measure how different species are from each other at a molecular level, and thus to estimate how much time has passed since a single lineage split into different species. These difficulties mean that the dates in the timeline should be taken as approximate. 3.8 billion years ago? This is our current “best guess” for the beginning of life on Earth. At some point far back in time, a common ancestor gave rise to two main groups of life: bacteria and archaea. How this happened, when, and in what order the different groups split, is still uncertain. 3.5 billion years ago 3.46 billion years ago
Big Bang According to the Big Bang model, the universe expanded from an extremely dense and hot state and continues to expand today. The graphic scheme above is an artist's concept illustrating the expansion of a portion of a flat universe. The Big Bang is the scientific theory that is most consistent with observations of the past and present states of the universe, and it is widely accepted within the scientific community. It offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background, large scale structure, and the Hubble diagram.[3] The core ideas of the Big Bang—the expansion, the early hot state, the formation of light elements, and the formation of galaxies—are derived from these and other observations. As the distance between galaxies increases today, in the past galaxies were closer together. Overview Timeline of the Big Bang The earliest phases of the Big Bang are subject to much speculation.
Commonly found fossils | National Trust Belemnites 'If you find a bullet-shaped fossil you could well have found the remnants of an ancient squid. These fossils are called belemnites.' says our wildlife and countryside officer Pete Brash. Ammonites 'Ammonites look a lot like coiled snail shells, but they were actually sea predators,' says our expert Rod Hebden. The ammonite was a tentacled sea creature that lived between 400 and 66 million years ago, similar to today's nautilus but more closely related to octopuses and squid. Ammonite fossils can be found in Dorset, and you can see two polished ammonites at Arlington Court, in Devon. Devil’s Toenails (Gryphaea) Although these commonly found fossils look like the claw of an ancient animal or, indeed, a devil, they were created from oysters that once lived on shallow sea beds. They are between 200 and 66 million years old, relics of a time when what is now the land in Britain was covered by the sea, and are particularly common on the coast of Yorkshire. Sea sponges and sea urchins
Australia's fossil past Australia, the world's oldest visible geology Ediacara fossils from the Flinders Ranges. Photograph courtesy of the Australian Heritage Council. A fossil is the impression of a living organism that has been preserved. Fossils are preserved in substances such as sediments, coal, tar, oil, amber, or frozen in ice. As well as body fossils, which are actual skeletal remains, there are impressions of soft animals, plants and footprints which have been left as mud hardened. Large numbers of fossils indicate that an enormous number of plants and animals have lived on Earth since life evolved more than 3,500 million years ago. Because of its relative isolation over millennia, Australia has a rich, unique fossil record, dating from approximately 3.2 billion years ago, close to when the Earth was stabilising its formation. Fossil sites Riversleigh, north-west Queensland, one of the most important fossil sites in the world. Australia has the world's best example of dinosaur tracks. Palaeontologists
Fossils, Rocks, and Time: Fossil Succession If we begin at the present and examine older and older layers of rock, we will come to a level where no fossils of humans are present. If we continue backwards in time, we will successively come to levels where no fossils of flowering plants are present, no birds, no mammals, no reptiles, no four-footed vertebrates, no land plants, no fishes, no shells, and no animals. The three concepts are summarized in the general principle called the Law of Fossil Succession: The kinds of animals and plants found as fossils change through time. When we find the same kinds of fossils in rocks from different places, we know that the rocks are the same age. How do scientists explain the changes in life forms, which are obvious in the record of fossils in rocks? Scientific theories are continually being corrected and improved, because theory must always account for known facts and observations. The study of fossils and the rocks that contain them occurs both out of doors and in the laboratory.
Evolution and the Fossil Record by John Pojeta, Jr. and Dale A. Springer Dating the Fossil Record (Previous Page || Next Page) The study of the sequence of occurrence of fossils in rocks, biostratigraphy, reveals the relative time order in which organisms lived. Although this relative time scale indicates that one layer of rock is younger or older than another, it does not pinpoint the age of a fossil or rock in years. Determining the age of a rock involves using minerals that contain naturally-occurring radioactive elements and measuring the amount of change or decay in those elements to calculate approximately how many years ago the rock formed. About 90 chemical elements occur naturally in the Earth. To help in the identification and classification of elements, scientists have assigned an atomic number to each kind of atom. Although all atoms of a given element contain the same number of protons, they do not contain the same number of neutrons. Potassium (atomic number 19) has several isotopes. (Previous Page || Next Page)
600-Million-Year-Old Embryos Found By William J. Cromie Gazette Staff Embryos of relatively advanced animals, together with plants similar to modern seaweeds, have been found in rocks almost 600 million years old by Harvard scientists. The discovery moves the bottom line of animal life tens of millions of years back in time and dramatically clarifies our view of the evolutionary history of Earth. Most of today's animals can be traced back to fossils about 540 million years old. But now, beautifully preserved three-dimensional embryos and seaweeds have been dug from a phosphate mine in southern China by Andrew Knoll, professor of biology, and graduate student Shuhai Xiao. "It's amazing that the embryos are so similar to modern ones," Knoll comments. Bilateral animals have bodies in which the left and right sides are mirror images of each other. "The algae are similar to red, brown, and green seaweeds you can find along shallow coastlines today, although they are smaller in size," notes Xiao. Mining History Reading the Rocks
New 600-Million-Year-Old Fossil is the World's Oldest Sponge We shared a common ancestor with SpongeBob SquarePants hundreds of millions of years ago, though exactly how long ago has been up for debate. Now, analyses of a newly discovered 600-million-year-old fossil suggests that sponge-like animals predate the Cambrian by 60 million years. And if an advanced sponge-like form was already around during the Precambian period, that means that similarly advanced fossils of our (very early) ancestors from that long ago are also waiting to be found. The findings were published in Proceedings of the National Academy of Sciences this week. Previous studies have suggested that the last common ancestor shared by animal sponges and almost all other animals—called eumetazoans, which includes people and clams alike—existed more than 200 million years before the Cambrian period began around 541 million years ago. Named Eocyathispongia qiania, the fossil animal is just 1.2 millimeters wide and 1.1 millimeters tall.