Origin of Life - Background Of The Origin Of Life, Theories Of The Origin Of Life, The "rna World" And The Origin Of Life
earth rocks billion acid
There is not direct fossil-like evidence of how life originated on Earth, the molecular processes that preceded the appearance of cells do not leave such tangible evidence. However, fossils of single-celled microorganisms are present in rocks 3.0–3.5 billion years old (with some scientific controversy over which rocks contain the oldest true bacterial fossils), and chemical traces in Greenland rocks establish that single-celled life existed as long ago as 3.8 billion years. As the Earth itself is approximately 4.6 billion years old, these data suggest that life evolved within 700 million years after the Earth formed. Experiments performed over the past 50 years suggest that many important ingredients of life, including amino acids and nucleic-acid bases (the molecular building-blocks of deoxyribonucleic acid [DNA] and ribonucleic acid [RNA]), could have formed abundantly under conditions that may have existed on the early Earth, and scientists conjecture that the presence of these molecules facilitated the formation of the first actual life.
Additional Topics
All cultures have developed stories to explain the origin of life. During medieval ages, for example, European scholars argued that small creatures such as insects, amphibians, and mice appeared by "spontaneous generation"—natural self-assembly of nonliving ingredients—in old clothes or piles of garbage. Italian physician Francesco Redi (1626?–1698) challenged th…
Most living cells today store genetic information in the long-ribbon-shaped molecules of DNA. The information stored in DNA's molecular components is transferred to another ribbon-shaped molecule, RNA, by a process termed transcription. Proteins, including enzymes, are then formed by cellular structures that translate the information on the DNA. The enzymes thus produced facilitate the bioc…
Radio astronomers have found that organic molecules (including amino acids), which might have played an important role in the formation of life, are present in dust clouds in outer space. Organic molecules are also known to be present in meteors that have fallen to Earth's surface. These observations provide further evidence that chemicals important for the genesis of life may have been pre…
Citing this material
Please include a link to this page if you have found this material useful for research or writing a related article. Content on this website is from high-quality, licensed material originally published in print form. You can always be sure you're reading unbiased, factual, and accurate information.
Highlight the text below, right-click, and select “copy”. Paste the link into your website, email, or any other HTML document.
User Comments