Just because we could possibly engineer and spread life to other planets does not imply that the same thing happened to earth 4 bl years ago... It only means that it COULD have happened this way.
And there's much research going on on abiogenesis.
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Methanosarcina acetivorans C2A
Species: M. acetivorans
Sowers et al. 1986
Methanosarcina acetivorans is a versatile methane producing microbe which is found in such diverse environments as oil wells, trash dumps, deep-sea hydrothermal vents, and oxygen-depleted sediments beneath kelp beds. Only M. acetivorans and microbes in the genus Methanosarcina use all three known metabolic pathways for methanogenesis. Methanosarcinides, including M. acetivorans, are also the only archaea capable of forming multicellular colonies, and even show cellular differentiation. As of 2006, the genome of M. acetivorans is the largest of all sequenced archaeal genomes.
In 2006, James Ferry and Christopher House discovered that M. acetivorans uses a previously unknown metabolic pathway to metabolize carbon monoxide into methane and acetate using the well known enzymes phosphotransacetylase (PTS) and acetate kinase (ACK). This pathway is surprisingly[according to whom?] simple, and has been proposed by Ferry and House as perhaps the first metabolic pathway used by primordial microbes.
However, in the presence of minerals containing iron sulfides, as might have been found in sediments in a primordial environment, acetate would be catalytically converted into acetate thioester, a sulfur-containing derivative. Primitive microbes could obtain biochemical energy in the form of adenosine triphosphate (ATP) by converting acetate thioester back into acetate using PTS and ACK, which would then be converted back into acetate thioester to complete the process. In such an environment, a primitive "protocell" could easily produce energy through this metabolic pathway, excreting acetate as waste. Furthermore, ACK catalyzes the synthesis of ATP directly. Other pathways generate energy from ATP only through complex multi-enzyme reactions involving protein pumps and osmotic imbalances across a membrane
Wiki, where any comedian can post his or her comedy............
Quote:I think, instead, that the fossil/genetic evidence points to a single source for present life forms.
From what I've read, that evidence is weak and relies primarily on a statistical guess... it is merely presumed to be more probable that the similarities in life forms are because of a single ancestor rather than parallel evolution. It could just be, however, that RNA and DNA are a natural consequence of the chemical structure of the universe that will form, again and again, given reasonably favorable conditions. Further, the extents of what constitutes favorable conditions keeps expanding rather than contracting. Until fairly recently, biologists never conceived of life thriving by deep ocean vents at near boiling temperatures without biological food or light, but it does quite well, thank you, without these niceties.
Chemosynthetic life, blood systems based on copper rather than iron (octopus), fungi, Archeabacteria (having no nucleus), and slime molds of the kingdom Protista all seem to challenge the "common descent" theories. Even within the common descent theory, there's a requirement that there was a rich world filled with rna-based life prior to dna life forms, and scholarly papers suggest that non-rna/non-dna life likley preceded those life forms including:
Robertson, MP; Joyce, GF (2012). "The origins of the RNA world". Cold Spring Harb Perspect Biol 4 (5). doi:10.1101/cshperspect.a003608. PMC 3331698. PMID 20739415.
Cech, TR (2012). "The RNA worlds in context.". Cold Spring Harb Perspect Biol 4 (7): a006742. doi:10.1101/cshperspect.a006742. PMC 3385955. PMID 21441585.
Today, there are several competing theories for how life arose on Earth. Some question whether life began on Earth at all, asserting instead that it came from a distant world or the heart of a fallen comet or asteroid. Some even say life might have arisen here more than once.
"There may have been several origins," said David Deamer, a biochemist at the University of California, Santa Cruz. "We usually make 'origins' plural just to indicate that we don't necessarily claim there was just a single origin, but just an origin that didn't happen to get blasted by giant [asteroid] impacts."
Most scientists agree that life went through a period when RNA was the head-honcho molecule, guiding life through its nascent stages. According to this "RNA World" hypothesis, RNA was the crux molecule for primitive life and only took a backseat when DNA and proteins—which perform their jobs much more efficiently than RNA—developed.
"A lot of the most clever and most talented people in my field have accepted that the RNA World was not just possible, but probable," Deamer said.
A New Physics Theory of Life
Why does life exist?
Popular hypotheses credit a primordial soup, a bolt of lightning and a colossal stroke of luck. But if a provocative new theory is correct, luck may have little to do with it. Instead, according to the physicist proposing the idea, the origin and subsequent evolution of life follow from the fundamental laws of nature and “should be as unsurprising as rocks rolling downhill.”
“You start with a random clump of atoms, and if you shine light on it for long enough, it should not be so surprising that you get a plant,” England said.
Popular hypotheses credit a primordial soup, a bolt of lightning and a colossal stroke of luck.
True, there is much going on in the field of abiogenesis, but it is more like comedy, than research. Why? because the simplest form of life has hundreds of thousands of lines of DNA code, believing that this could form at random, is no different from believing in the tooth fairy....
Interesting references you found, thanks.
Quote:“You start with a random clump of atoms, and if you shine light on it for long enough, it should not be so surprising that you get a plant,” England said.
That's my point. It might well be pretty much automatic given enough time and a reasonably tolerable environment.
Quote:Popular hypotheses credit a primordial soup, a bolt of lightning and a colossal stroke of luck.
And again, this is my complaint. That "colossal stroke of luck" sounds awfully much like the breath of god... a once-in-forever event, and I don't think it is, nor does Jeremy England.
Santa passing you over is he?
Try seeing the light.
I'm still baffled by your use of the word "arrogant."
Quote:I'm still baffled by your use of the word "arrogant."
What I think is arrogant is the premise that "oh we are SO special...."
When I was in grade school we were taught that there weren't any other planets in the universe... and life exists only here. That sounds awfully close to the Catholic church's old position that the earth was the center of the universe and exists only by divine grace. Like England, the presence and prevalence of life indicates to me that it is consistent with the physical laws of the universe; it works, it's efficient, and I don't believe in magic, so it must be, as was stated in that article, as likely as rocks rolling downhill. Granted it may take some time... but it might well be an automatic consequence of the structure of matter and energy.
other robust hypotheses have been proposed that do not require such a "colossal stroke of luck," including panspermia/transpermia
In 2013, the Atacama Large Millimeter Array (ALMA Project) confirmed that researchers have discovered an important pair of prebiotic molecules in the icy particles in interstellar space (ISM). The chemicals, found in a giant cloud of gas about 25,000 light-years from Earth in ISM, may be a precursor to a key component of DNA and the other may have a role in the formation of an important amino acid. Researchers found a molecule called cyanomethanimine, which produces adenine, one of the four nucleobases that form the “rungs” in the ladder-like structure of DNA. The other molecule, called ethanamine, is thought to play a role in forming alanine, one of the twenty amino acids in the genetic code. Previously, scientists thought such processes took place in the very tenuous gas between the stars. The new discoveries, however, suggest that the chemical formation sequences for these molecules occurred not in gas, but on the surfaces of ice grains in interstellar space. NASA ALMA scientist Anthony Remijan stated that finding these molecules in an interstellar gas cloud means that important building blocks for DNA and amino acids can 'seed' newly formed planets with the chemical precursors for life.
In March 2013, a simulation experiment indicate that dipeptides (pairs of amino acids) that can be building blocks of proteins, can be created in interstellar dust.
In February 2014, NASA announced a greatly upgraded database for tracking polycyclic aromatic hydrocarbons (PAHs) in the universe. According to scientists, more than 20% of the carbon in the universe may be associated with PAHs, possible starting materials for the formation of life. PAHs seem to have been formed shortly after the Big Bang, are widespread throughout the universe, and are associated with new stars and exoplanets