how human life started on earth?
539691
WHEN ALLAH SEND ADAM(A.S) ON EARTH.
994441
Bacteria appeared on earth between 3.4 and 4 billion years ago. Precambrian evidence of filamentous bacteria-like structures, found making up fossilized sediments called stromalites, has been discovered in Australia and southern Africa. These fossils date back between 3.4 and 3.5 billion years old. Environmental conditions of earth 4 billion years ago were much different than those of today. It has been theorized that the atmosphere was a reducing atmosphere with intense lightning, tremendous volcanic activity, very little oxygen, intense ultraviolet radiation, and meteorite bombardment. These conditions made it impossible for any type of aerobic life to exist. The first cells may have originated by chemical evolution in an anaerobic environment.\n\nAbiotic Synthesis Theory of Life: A.I.Oparin postulated, in the 1920's, that primitive earth with its reducing atmosphere favored chemical reactions that produced simple monomers that eventually formed complex organic compounds necessary for life. Stanley Miller and Harold Urey tested this hypothesis by building an apparatus to simulate the conditions of the earth at that time.\nTheir experiments produced 20 amino acids and other organic compounds including: ATP, lipids, some sugars, and the bases of RNA and DNA. The main problem of organic synthesis is how did these molecules develop without the aid of enzymes to speed up the reactions? Sidney Fox, of the University of Miami, dripped a dilute solution of organic monomers onto hot sand, clay , and rock. The water vaporized and left behind polypeptides he called proteinoids. Clay was abundant in prebiotic earth. Clay has the ability to act as a substrate for this type of chemical reaction. The charged sites on the clay attracted monomers in such concentrations to bring them into close proximity for chemical binding. Once these organic compounds were produced, aggregates of these proteinoids self-assembled into small spheres called protobionts. These small spheres were capable of osmotic swelling and shrinking and even able to produce a membrane potential.\n\nRNA the first Genetic Material: Evidence to support the idea that RNA was the first genetic material includes: short polymers of self-replicating RNA have been abiotically produced in a test tube without enzymes. RNA has the ability to act as a catalyst to help make mRNA, tRNA or rRNA. The RNA folding is unique depending on its sequence. This along with mutations, creates a variety of closely related molecules. Through chance this self-replicating material was captured by the protobionts and the entire structure developed under the guide of natural selection.\n\nOther Origin Theories:\n\nPanspermia. Extraterrestrial organic compounds located on the surface of meteorites could well have contributed to the pool of material found on prebiotic earth. Modern meteorites have given up specimens of simple organic compounds such as amino acids.\n\nSome researchers believe that life began on the sea floor away from the harsh surface environments. The discovery of deep sea vents showed the scientific community that the materials needed for life to begin were present away from the harsh surface.\n\nJulius Rebek produced a simple organic molecule in 1991 that served as a template for self-replication. This discovery suggests that RNA was too complex to have come first and a much simpler self-replicating molecule preceded it.
247560
It depend if you are a religions person or believe in facts. Me, as a geologist I believe in facts and science.\nThe earth forms 4.6 billions years ago. How did we know? By using the radioactive decay method. \nNobody really knows how it form but you can get differrent references. Try historical geology books. \nEarth solidifies around 3 billion years ago, how? From the dated rocks namely Banded Iron Deposits. Life began at PreCambrain era. Meaning 512 millions years ago. Dinosaurs came to life at least 100 million years ago and died 65 miilion years ago because of  a comet hitting the earth.\nActually there are a lot more happend but for your satisfaction try to look for a Historical geology book. A very interesting book.
518764
Earth wasn't invented (at least not if you listen to common sense), it was created from abiotic (non-living) sources. It started when hydrogen and helium clouds turned into stars because of their gravitational force. These stars then developed other simple elements like oxygen, nitrogen and carbon (necessary for organic compounds) these brought about nebulas which made simple compounds. Eventually matter formed into large masses that became planets, comets, and asteroids.
1032657
Earth is special because it has water. Human life, or any other kind of life, is heavily dependent on water. If a planet has water than the chances are high that it will have life.
397661
Yes, I don't understand why people have such a hard time accepting this truth but yes, life began in Africa.  We are all descendants of Africans.
553451
Life exists almost everywhere on earth, and it has many forms.  Some of which are almost impossible to detect and it's debated whether they're actually "life" (like virii).\n\nIf it could be proven either way, I would bet my worldly posessions and my right arm that there is some sort of life beyond Earth.  They might not be carbon-based or water-based, but I am certain that there are objects out there that consume things, grow, reproduce, and possibly defend themselves or even have rational consciousness.\n\nAs for some alien being looking just like a human and living among us, that's a different story.  I can't see two independent strains of life coming out so similar, especially considering the variety right here on our little planet.  Either we'd all be from alien roots, or the "aliens" would have originated from earthly roots.
16197
God created man, in one sense, by bringing angels to the earth capable of taking on physical forms.  They disregarded their instructions to avoid cohabitation with the pre-human inhabitants of Earth.  They "ate the forbidden fruit", and mankind was the result.
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The earth has evolved geologically, chemically, and biologically.  Geologically:  When the earth formed, it was basically a molten mass.  It cooled, and settled into layers, with the densest layers in the center, and the least dense in the crust.  The atmosphere of the early earth was basically methane, ammonia, hydrogen, carbon dioxide, and water vapor.  The hydrogen escaped, the carbon of the carbon dioxide bonded with rock.I don't recall what happened to the rest.  But, when life began, it was life that found oxygen a poison.  However, when photosynthetic organisms appeared, they actually produced oxygen as a waste product.  Some forms of life evolved to be able to use the oxygen to permit them to more efficiently extract the energy from organic compounds.  As far as life itself is concerned, the first organisms, according to the current model, were extremophiles - they were one celled organisms living in extreme environments, such as the volcanic vents on the ocean floor.  Life gradually evolved from simple unicellular to more complex unicellular to multicellular.  Geologically, when the earth was new, there was very little land.  As a result of volcanic activity, grantic crust formed, which underlies the continents.  The continents, or rather the crustal plates on which they "float" have been moving since they formed due to convection currents within the earth's mantle.  So, the layout of the land forms has been changing, and with them, the ocean currents.  This has resulted in a gradual and constant change in climate.
1108935
Origins of life were initially suspcted to be of creation from God.\nThen the Theory of Evolution kicked in, suggesting all life came from a single cell.\nNow life came from a stone that banged into earth 4 billion years ago.\nBut are any of them true if we keep finding more truths. If breakthroughs always happen, wouldn't there be an endless amount of breakthroughs? So what we all know now is not the truth?\n\nThe origins of life on earth?\nDon't even think about it.
333564
If you look at the history of life on earth, there are several steps where things seem to be difficult. Life starting at all seems to have been relavtively easy. The earth cooled down enough by 3.8 billion years ago to have liquid water. By 3.5 billion years ago, there was bacterial life. So *at most* 300 million years was needed for this transformation.\n\nThe next bigstep was the transition from bacterial (call procaryotic) to cellular life with nuclei (eucaryotic life). This happened about 2 billion years ago and so took about 1.5 billion years to accomplish. At this time, cells also started producing oxygen, which lead to a massive die-off.\n\nAfter this, multi-cellular life appeared about 570 million years ago, so another 1.5 billion years after eucaryotic life. \n\nGiven the length of time needed for these transitions on earth, it appears that going from bacterial life to multi-cellular life was very difficult. After multi-cellularity was achieved, it only took about 570 million years to produce humans and technological life.\n\nSo my guess is that bacterial life is very common in the universe, but multi-cellular life is probably rather rare. There are other considerations about how long a technological civilization would last, but that is another issue.
485002
Could be both-God created aliens and the environment conducive to life, which and who in turn switched on life on earth.
251225
it was a ball of burning gas that seperated from the sun billions of years ago, got trapped in the suns gravity and began revolving around it, and in time it cooled down and formed the earth, but it was still too hot for life, it cooled more and more and the atmosphere shaped from the fumes rising from it, eventually it rained and made huge oceans on earth which later became the home for the first cells that later made all different living things.
912164
I don't really back this alien idea as most of our genes and DNA matches up with other animals etc on the planet so is that to say that aliens created everything?\n\nIf you mean did aliens just create humans then how can we explain all these matches with the existing life on Earth?
1057616
No one found life on Earth as life was made on Earth, we evolvolutionised from bacteria that was by nothing but infectious static.\nAliens found life on Earth and put you on it as everything that I know that is from this planet didn't come from another world we were made from the soil.
452046
The human population did NOT start out as two (this readily confirmed by analysis of genes found in different groups of humans across the globe).  Also, Earth is some 4.57 billion years old.  Additionally, humans have existed for several million years.\n\n\nOkay...I'll humor you...\n\n-a human generation is 20 years\n-there are only 300 generations in 6000 years\n-before healtcare each generation more or less had enough time to mature and then have offspring\n-human births are risky compared to other animals and can possibly kill the mother\n-average lifespans before healthcare is estimated 20-35\n-sexual maturity generally occurs between 12-14\n-lifespan has only started increasing since 1800 so that is 200 years or 10 generations\n-Therefore to get and maintain 6.5 billion each successive generation had to have an increase of 21,666,666.667 individuals or more per generation to get from 2 to the 6.5 billion in the necessary time AND maintain population size.\n\nTherefore it is NOT possible for humans to have started from a population of 2 and increase up to 6.5 billion considering all factors involved.
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The first living cells were (big word coming up) heterotrophic anaerobes. This meant that they were other feeders (fed on naturally occuring amino acids) without oxygen. It wasn't until later that photosynthetic (organisms able to use energy from the Sun) developed. \n\nhttp://www.windows.ucar.edu/tour/link=/kids_space/qlife_ani.html\n\nThere is still debate within the scintific community if viruses are actually living.  The need a living host in order to function and reproduce.\n\nhttp://www.beyondbooks.com/lif72/2c.asp