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Originally, life evolved from non-living matter. Why is life only generated from other life nowadays, and why doesn't it evolve from inanimate matter, like it did originally billions of years ago, when life evolved on Earth?

Maybe I should reword this further. Living organisms reproduce other living organisms but the first living organism came from non living material or chemicals. So could life be created in a laboratory as it originally was ? Originally the process leading to a life form took one billion years, so would this be the answer to my question that it takes too long and that is why it is not being repeated again ?

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  • $\begingroup$ Welcome to Biology SE and thanks for your interesting question! I edited your question slightly to improve readability. Please feel free to roll back. $\endgroup$ – AliceD Jan 7 '15 at 1:31
  • $\begingroup$ Thanks Chris for finding my question interesting and for rewording it to improve it's readability. I am looking forward to reading answers to this question . $\endgroup$ – Peter U Jan 7 '15 at 1:45
  • $\begingroup$ Szostack from Harvard in this video The Origin Of Life on Earth discusses various fundamentals to prebiotic biophysics that might provide insights although no definitive. $\endgroup$ – Cymatical Jul 7 '17 at 5:42
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Abiogenesis, the development of living things from non living matter, is not something we know much about, since it happened about 4 billion of years before we were around and haven't reproduced it in the lab. My guess is that it's not easy. However, the Miller-Urey experiment and others have told us something about abiogenic production of organic compounds.

The first living organism on Earth ( Let's imaging some self-replicating RNA ) was probably very inefficient, copied itself slowly and made a lot of errors. At the time it could survive because there wasn't any competition. However, as time went on some of these copies were more efficient and copied themselves more quickly, outnumbering the original sequences and driving them into extinction. Wait another 3.5 - 4 billion years and you have modern life.

If abiogenesis were to occur on Earth today, the resulting organism would likely be inefficient like the first organism. However, now it would face immense competition from very efficient modern organisms and would probably be eaten.

This is speculation, but I assume that any new type of life on Earth would be carbon based, since organic carbon based building blocks are abundant. If anything, abiogenesis might be easier on modern earth than early earth because the starting materials (nucleotides, amino acids) are readily available, but competition from modern life and reactive oxygen in the atmosphere would hinder any new abiogenesis.

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  • $\begingroup$ Interesting note about reactive oxygen there at the end — indeed, the Great Oxygenation Event, when oxygen began to be present in the atmosphere, was one of the most significant extinction events in the history of life on Earth. $\endgroup$ – augurar Jan 8 '15 at 2:42
  • $\begingroup$ @augurar I never thought oxygen would be that reactive until I started doing LC-MS and kept finding stuff 16 or 32 mass units too heavy, even after keeping them at -20 in the dark. $\endgroup$ – user137 Jan 8 '15 at 4:58
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There are two questions here:

  • Why does life only generate life?
  • Why doesn't life continue to be generated on Earth?

The first one is easy. We don't only generate life. If that were true, it might be illegal to flush toilets. Life forms of some kind would occupy all the space in our atmosphere. Babies - or some living things - would rise up from our graves. Conceivably none of the millions/billions of people who have died from the beginning of history (and well before that) would be dead. Add to that animals, and everything in the other Kingdoms included in Life, and there would be nothing left perhaps except for life. To be honest, life generates heat, death and simple substances much more commonly than it generates life.

If you mean, why does like produce like (in your case, a life generates a similar life form*, that's because of genetic material. New life is based on the genetic material of the preceding life form. People don't give birth to zebras, zebras do. When the genetic material is damaged enough, we give birth to a non-viable or diseased child. If a mutation is favorable, it is (under the right circumstances) spread through an advantage. An example of this is the appearance of lactase, an enzyme which allows adults to derive continued nutrition from animal milk.

As to your second question: why doesn't life continue to be generated on Earth? Are you 100% sure that it isn't happening? How would you recognize a life form foreign to our own? How many different kinds of life can evolve under the same planetary conditions, the same planetary element ratios, etc.? If a very rudimentary silicon-based life form evolved in, say, the last 2,000,000 years, would you know how to look for it? In other words, are you defining life only as we now know it - a carbon based, DNA-propigated form?

Furthermore, if a non-carbon based life form could only evolve on this planet to a very basic, simple level, would you give credence to it as a newly evolved "life" form? Intelligent life is rare. I would guess that very simple life forms are far less rare in the Universe.

How would you classify (or explain) the chemosynthetic bacteria that oxidize sulfur instead of oxygen?

I realize that there are a lot of questions here and not many answers. But part of finding an answer is asking the right questions.

The Origins of Lactase Persistence in Europe

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    $\begingroup$ By question (1) I think the PO means why life is only generated by living organisms. In other words, there is only a single question I guess. $\endgroup$ – AliceD Jan 7 '15 at 4:58
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    $\begingroup$ @ChrisStronks - I do tend to take people at their word... $\endgroup$ – anongoodnurse Jan 7 '15 at 5:00
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    $\begingroup$ Asking good questions is an art. $\endgroup$ – AliceD Jan 7 '15 at 5:01
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    $\begingroup$ I think this is mostly answering another question than what is being asked (especially looking at the original formulation by the original poster), and the second part of the answer, which is more relevant, is mostly speculation. LUCA is also an accepted and well-supported concept, and if you are challenging that all life on earth has a common ancestor you need to back this up by references (I'm not sure that you are though?). $\endgroup$ – fileunderwater Jan 7 '15 at 9:57
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    $\begingroup$ Chemosynthetic bacteria are a poor example. All known life shares certain characteristics, in particular the same system of mapping DNA codons to amino acids (the genetic code). In fact, almost all species use the exact same mapping from codons to amino acids, with minor exceptions. If a life form were discovered that did not have DNA or transcribed it differently, that would be a good reason to suspect an independent origin. $\endgroup$ – augurar Jan 8 '15 at 2:53
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Abiogenisis, where imperfect micelles (spheres) of hydrophobic carbon chain formatiions leads to potentials for capturing and mixing elements and molecules forming peptides, polypeptides and protiens that can then catalyze enzymes to patterns to the micelle to a cell of sorts.

Was it inside a terrestrial micelle that life formed or Did amazing spiraling symetry of life get help or even need it from galactic wave patterns, crystal energy of minerals or was it just a mixing up microscopic pieces of Pythogerian parts and geometry.

Either and anyway, given low energy potentials needed for effeciency of a new life form, unless it was non carbon based, it would have practically zero chance of survival where energetic mass of life that already exists just chews it up and mutates spin offs. Only a dynamic shift in genetics as we know it would allow us to detect divergent life.

That said, got to love the ugly waterbear.

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    $\begingroup$ It would be great of you added some references to support your response! $\endgroup$ – Bez Jan 7 '15 at 18:34
  • $\begingroup$ Check out iBiology playlist on Youtube to get you started Bez. $\endgroup$ – Cymatical Jul 7 '17 at 5:15

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