(Phys.org)—A team of chemists working at the MRC Laboratory of Molecular Biology, at Cambridge in the UK believes they have solved the mystery of how it was possible for life to begin on Earth over four billion years ago. In their paper published in the journal Nature Chemistry, the team describes how they were able to map reactions that produced two and three-carbon sugars, amino acids, ribonucleotides and glycerol—the material necessary for metabolism and for creating the building blocks of proteins and ribonucleic acid molecules and also for allowing for the creation of lipids that form cell membranes. Chemistry in a post-meteoritic-impact scenario. A series of post-impact environmental events are shown along with the chemistry (boxed) proposed to occur as a consequence of these events. a, Dissolution of atmospherically produced hydrogen cyanide results in the conversion of vivianite (the anoxic corrosion product of the meteoritic inclusion schreibersite) into mixed ferrocyanide salts and phosphate salts, with counter cations being provided through neutralization and ion-exchange reactions with bedrock and other meteoritic oxides and salts. b, Partial evaporation results in the deposition of the least-soluble salts over a wide area, and further evaporation deposits the most-soluble salts in smaller, lower-lying areas. c, After complete evaporation, impact or geothermal heating results in thermal metamorphosis of the evaporite layer, and the generation of feedstock precursor salts (in bold). d, Rainfall on higher ground (left) leads to rivulets or streams that flow downhill, sequentially leaching feedstocks from the thermally metamorphosed evaporite layer. Solar irradiation drives photoredox chemistry in the streams. Convergent synthesis can result when streams with different reaction histories merge (right), as illustrated here for the potential synthesis of arabinose aminooxazoline at the confluence of two streams that contained glycolaldehyde, and leached different feedstocks before merging. Credit: (c) Nature Chemistry (2015) doi:10.1038/nchem.2202 Read more at: http://phys.org/news/2015-03-chemists-riddle-life-began-earth.html#jCp
extract: The chemists with this new effort believe they have found a way to show that all three arguments are both right and wrong—they believe they have found a way to show that everything necessary for life to evolve could have done so from just hydrogen sulfide, hydrogen cyanide and ultraviolet light and that those building blocks could have all existed at the same time—in their paper, they report that using just those three basic ingredients they were able to produce more than 50 nucleic acids—precursors to DNA and RNA molecules. They note that early meteorites carried with them ingredients that would react with nitrogen already in the atmosphere, producing a lot of hydrogen cyanide. By dissolving in water, it could have very easily come into contact with hydrogen sulfide, while being exposed to ultraviolet light from the sun. And that, they claim, would have been all that was needed to get things going. Read more at: http://phys.org/news/2015-03-chemists-riddle-life-began-earth.html#jCp Abstract A minimal cell can be thought of as comprising informational, compartment-forming and metabolic subsystems. To imagine the abiotic assembly of such an overall system, however, places great demands on hypothetical prebiotic chemistry. The perceived differences and incompatibilities between these subsystems have led to the widely held assumption that one or other subsystem must have preceded the others. Here we experimentally investigate the validity of this assumption by examining the assembly of various biomolecular building blocks from prebiotically plausible intermediates and one-carbon feedstock molecules. We show that precursors of ribonucleotides, amino acids and lipids can all be derived by the reductive homologation of hydrogen cyanide and some of its derivatives, and thus that all the cellular subsystems could have arisen simultaneously through common chemistry. The key reaction steps are driven by ultraviolet light, use hydrogen sulfide as the reductant and can be accelerated by Cu(I)–Cu(II) photoredox cycling. Read more at: http://phys.org/news/2015-03-chemists-riddle-life-began-earth.html#jCp
The same way all other attributes of life came into being. Chromosomes mutate, resulting in an offspring being slightly different from its parent. In rare instances, the difference gives the offspring a slight survival advantage, so it has a good chance of reproducing and propagating the new DNA. Many of the "lower" animals have primitive brains and central nervous systems, such as the octopus. This bequeaths them with at least a small, limited ability to think, reason and make choices. So "intelligent life" is not limited to our own close relatives: the other chordates (mammals, birds, reptiles, amphibians, fish and cartilaginous fish like eels and rays). The entire chordate brain evolved from the olfactory lobe: the tissue that analyzes odors that come in through the nose or a similar organ. The primitive fish had only one sense: smell. This was the most important one, because it allows them to find food, so it was the first one. Random mutations occurred at a very slow rate (as they still do today) and eventually more brain tissue developed, giving the animal the ability to make decisions about which smells would be more profitable to chase after. Eyes and other sense organs also developed the same way, taking millions of years for the mutations to reinforce each other. The brain itself continued to enlarge (again the result of mutations), giving the more intelligent creatures an advantage in finding food, evading predators, and out-competing the less intelligent creatures. Mutations occur all the time, the result of everything from cosmic rays to a cell damaged in a fight or accident. If these mutations take place in the reproductive system, they may be propagated to the creature's offspring. 99.999999 percent of the time, mutations are NOT helpful. The creature may die before reaching breeding age, but even if this does not happen, its offspring with the mutation may not survive. It's rare for a mutation to occur that is advantageous, but when this happens, it may be passed down to the offspring, giving the next generation a slight advantage in survival. The new creatures may be stronger, faster, smarter, better camouflaged, able to digest more food, etc., so they will be more likely to survive than the offspring of the creatures without the mutation. A mutation may occur in any part of the body: limbs, eyes, skin, bones, organs.... or the brain. So long as the reproductive cells carry the mutation, it will be passed down to the next generation... although only about 1/2 of the time because every animal inherits half of its DNA from its mother and half from its father. This is just as true for a mutation that results in a slightly different foot shape, as it is for one that results in a slightly bigger brain... which is the basis for higher intelligence. Many kinds of animals exhibit behavior which we would regard as "intelligent," even though they don't have a brain or a central nervous system. Many insects, for example, make some amazingly clever decisions. Intelligence is not only found in the higher animals with brains and a central nervous system. There are electric signals passing through the organs of flies and spiders, and perhaps even worms. So it's very difficult to draw a line and say, "All animals on this side of the line have intelligence, and all the others do not." It's impossible to track these mutations because they happened so slowly. For example, it took 100,000 years for the black bear to mutate into the polar bear, and there is very little difference between them. They can still mate with each other and produce offspring.
