Bronze-level articleAbiogenesis

From RationalWiki
Jump to: navigation, search
One of our pieces on

Biology

Icon bioDNA.svg
The science of life
Biology articles

Abiogenesis is the process by which a living organism arises naturally from non-living matter, as opposed to biogenesis, which is the creation of living organisms by other living organisms. Scientists speculate that life may have arisen as a result of random chemical processes happening to produce self-replicating molecules. One of the popular current hypotheses involves chemical reactivity around hydrothermal vents.[1][2] This hypothesis has yet to be empirically proven although the current evidence is generally supportive of it. Give those crazy scientists a half billion or so years to play,[3] though, and they might do just as well as nature once did!

Contents

[edit] History: spontaneous generation

Before recent centuries, it was widely believed that abiogenesis happens all around us, that many individual present-day organisms had originated from nonliving matter. Frogs and mice seem to come from mud, and maggots from rotting meat. In this form, abiogenesis is more usually called "spontaneous generation".

In the ancient Greco-Roman world, it was advocated by some notable philosophers, like Aristotle (History of Animals, Generation of Animals). Their medieval successors also advocated it, pointing to parts of the Bible that seem to support it, like Genesis 1:20. In 1648, Jan Baptista van Helmont proposed this recipe for mice[4]:

... if a foul shirt be pressed together within the mouth of a Vessel, wherein Wheat is, within a few dayes (to wit, 21) a ferment being drawn from the shirt, and changed by the odour of the grain, the Wheat it self being incrusted in its own skin, transchangeth into Mice: and it is therefore the more to be wondered at, because such kinde of insects being distinguished by the Signatures of the Sexes, do generate with those which were born of the seed of Parents: That from hence also, the likeness or quality of both the seeds, and a like vitall strength of the ferments may plainly appear: And which is more wonderfull, out of the Bread-corn, and the shirt, do leap forth, not indeed little, or sucking, or very small, or abortive Mice: but those that are wholly or fully formed.

But in 1646, Sir Thomas Browne published a book Pseudodoxia Epidemica ("Vulgar Errors" or "Popular False Beliefs"), in which he expressed skepticism about a variety of common beliefs, including spontaneous generation. Alexander Ross wrote a response to him[5], which included

He doubts whether mice can be procreated of putrifaction. So he may doubt whether in cheese and timber worms are generated; Or if Betels and wasps in cowes dung; Or if butterflies, locusts, grashoppers, shel-fish, snails, eeles, and such like, be procreated of putrified matter, which is apt to receive the form of that creature to which it is by the formative power disposed. To question this, is to question Reason, Sense, and Experience: If he doubts of this, let him go to Ægypt, and there he will finde the fields swarming with mice begot of the mud of Nylus, to the great calamity of the Inhabitants.

Some years later, Francesco Redi became doubtful of the spontaneous generation of flies, so around 1668, he did some classic experiments in which he showed that keeping flies away from rotting meat keeps maggots and flies from appearing in it[6]. However, he still thought that spontaneous generation happens in some other circumstances. Though spontaneous generation was soon discredited for macroscopic organisms, it still seemed true of microscopic "animalcules". But even there, spontaneous generation was gradually discredited by Redi-like experiments, with Louis Pasteur delivering the final blow in 1861.

Still to this day, however, there are cranks who insist that spontaneous generation happens. Wilhelm Reich, for example, saw micoscopic vesicles he called "bions" which he claimed could organize themselves into full-blown amoebas. (He rejected the notion that he was merely reconstituting amoebic cysts, because he didn't believe in the "air infection" hypothesis.)

[edit] Evolution and abiogenesis

Often brought up in the origins debate is how evolution does not explain the origin of life. Let's get something abundantly clear: abiogenesis and evolution are two completely different things. The theory of evolution says absolutely nothing about the origin of life. It merely describes the processes which take place once life has started up. There may also be multiple pathways to producing naturally occurring "life". Depending, of course, on the definition of life. This is something that Ben Stein is apparently willfully ignorant of.

An objection to the distinction is that it is goalpost moving but this would only be true if evolution at some point did try to explain the origin of life and then people moved away from it. This is not the case at all. Evolutionary theory started with the observation of the mutability of species - a property that only exists once life has begun, indeed later definitions of "life" have often used the ability to evolve as a key component. This, of course, has been known for some time as animals and crops have been selectively bred for thousands of years. Later, the idea was refined by Charles Darwin in the form of natural selection, where nature provides the selection criteria to drive evolution. At no point was evolution, nor natural selection, about explaining the origin of life.

One objection is that explaining the origin of life is a natural extension to what evolution has to explain. In fairness this is true, and theories surrounding abiogenesis often use natural selection as a jumping point for how organised molecules could themselves develop further (thus making such molecule groups "alive" by the definition discussed above). But whether evolution and natural selection can explain this stage in the development of life is absolutely irrelevant to its validity to living creatures post abiogenesis. A common analogy to the fallacy of rejecting evolution due to it not explaining the origin of life is that gravity doesn't explain the origin of life. Another might be that it is akin to confusing a university's admission process with grading, advancement, and graduation once students are admitted.

[edit] Artificial abiogenesis

In the 1950s, several experiments by Stanley Miller and Harold Urey verified that the natural formation of amino acids, components of DNA, and other organic compounds out of inorganic materials was possible under the atmospheric conditions of Primordial Earth. Le-Chatelier's principle states that protein synthesis is not possible on water since it requires a condensation reaction. The UV radiations from the Sun would've made it impossible on land. Today, it is generally accepted that Abiogenesis happened in neither land nor oceans, but a combination of both, in mud. Also, the primordial Earth conditions are now thought to be different than those at the time of Miller's experiment, which makes it outdated. "Many scientists now suspect that the early atmosphere was different from what Miller first supposed. They think it consisted of carbon dioxide and nitrogen rather than hydrogen, methane, and ammonia. That's bad news for chemists. When they try sparking carbon dioxide and nitrogen, they get a paltry amount of organic molecules - the equivalent of dissolving a drop of food colouring in a swimming pool of water. Scientists find it hard to imagine life emerging from such a diluted soup" (National Geographic, "The Rise of Life on Earth", March 1998, p.68). There have been, however, more successful, newer experiments based on these conditions. There is only one major problem with Miller's experiment: "How do you make polymers? That's not so easy." (Earth, "Life's Crucible", February 1998, p.34)[7]

[edit] Lipid Magic

In 1965, Alec Bangham was the first to discover the autocatalytic properties of phospholipids.[8] How you can prove this aspect of nature and disprove the creationist version of the second law:

  1. Get a glass of water.
  2. Get a yolk of an egg.
  3. Put the egg yolk in the water.
  4.  ????
  5. Profit!!!!

What actually is happening: the amphipathic lipids arrange themselves based on their interaction with water molecules. It may not be the most extravagant example, but it does show spontaneous order.

Pier Luigi Luisi has shown that vesicles made of these lipids can grow by incorporating new lipids, and can make new vesicles leading to a primitive replication.

[edit] Other

In 2001, Louis Allamandola demonstrated that organic material can be synthesized in deep space using a "Chill vacuum chamber"--a lot of biomolecules: nitriles, ethers, alcohols, ring-like hydrocarbons, and others.[9] [10]

In a complementary experiment, Jennifer Blank at Lawrence Berkeley National Laboratory discovered that: "Through subsequent chemical analysis, the team discovered that the initial amino acids in the mixture had linked together to form peptides, from which proteins can be formed." [11]

In 2010, Craig Venter and his colleagues inserted a wholly artificial chromosome into a bacterial cell and created the first artificial life form (a.k.a. "dial-a-genome").[12] While it may seem like artificial abiogenesis, it nevertheless involved some major cheating: the artificial chromosome was constructed using gene sequences of an existing organism.

In 2011, Lee Cronin at the University of Glasgow is trying to start an evolutionary process in polyoxometalate-based "cells".[13]

[edit] Creationists and abiogenesis

Certain creationists correctly point out that abiogenesis must have taken place at some point to begin the process of evolution. They then attempt to use this premise to "disprove" evolution, claiming that Louis Pasteur had conclusively refuted it. However, he only showed that it is not a typical present-day occurrence even for the simplest of free-living organisms.

Creationists also like to rebut abiogenesis by pointing out seeming prebiotic environments where it does not happen, like in their Peanut Butter Argument[14]. However, the most suitable environment has been the subject of active research, like that of Günter Wächtershäuser with his hypothesis of an iron-sulfur world of hydrothermal vents.

Another creationist statement often made is that evolution is abiogenesis; this is simply ignorance of scientific terminology. Evolution is the gradual change of organisms over time, whereas abiogenesis is the start of life itself. The creationists may also be projecting their belief in separate creations onto mainstream biologists.

Yet more creationist illogic is, "Scientists can't explain the origin of life, therefore it must have been God and specifically the God I believe in." (Protestant version, Roman Catholic version according to choice)

[edit] Oil

See the main article on this topic: Abiotic oil

Oil is now understood to be biogenic in origin, not abiogenic. A hypothesis that oil was abiogenic in origin was popular in the Soviet Union until the 1980s. The abiogenic origin hypothesis proposed that oil formation results from chemical reactions taking place within the earth, and that oil is thus continually replenished and not a fossil fuel. A few ( notably astronomer Thomas Gold until his 2004 death, and Jack Kenney) have continued to promote the abiogenic origin hypothesis.

[edit] Understanding of origin sciences by the wider community

Many people don’t understand origin sciences. This is caused by a couple of factors.

  1. Religious views can get in the way of wanting to understand abiogenesis, preferring explanations involving a miraculous event.
  2. Comprehending that unlikely does not equal impossible and, furthermore, that, given sufficient time and opportunity the unlikely becomes likely, is difficult for many non-specialists to understand[15], and harder yet for the wilfully ignorant and the scientifically handicapped. Furthermore there is but a small field of scientists who are sufficiently trained in chemistry and geology to be able to properly review abiogenesis. There is, however, a dedicated society to studying the origin of life.[16]

[edit] Journals

[edit] Specifically for origins of life research

  • Origins of life and evolution of the biosphere [17]

[edit] Other journals

  • The journal of molecular evolution[18]
  • The journal of molecular biology[19]

[edit] See also

[edit] External links

[edit] Footnotes

  1. http://www.newscientist.com/article/mg20427306.200-was-our-oldest-ancestor-a-protonpowered-rock.html
  2. http://www.youtube.com/watch?v=U6QYDdgP9eg
  3. Because that's roughly how long it took to form those initial molecules after things cooled down a bit.
  4. Ortus Medicinae, Chapter 19, http://www.nightenlight.com/higher-worlds-visited/rsc/john-baptista-van-helmont/oriatrike-or-physick-refined-001-030
  5. Arcana Microcosmi, Book 2, Chapter 10, Heading 5, http://penelope.uchicago.edu/ross/index.html
  6. Experiments on the generation of insects - Francesco Redi - Google Books
  7. http://www.issol.org/miller/miller1953.pdf
  8. http://www.fasebj.org/content/24/5/1308.full
  9. http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=N0233842AH&q=Organic+Synthesis+in+Simulated+Interstellar+Ice+Analogs&uid=790860697&setcookie=yes
  10. http://www.mendeley.com/research/organic-synthesis-simulated-interstellar-ice-analogs/
  11. https://www.llnl.gov/str/September02/pdfs/09_02.1.pdf
  12. Researchers Say They Created a ‘Synthetic Cell’, The New York Times
  13. http://www.newscientist.com/article/dn20906-lifelike-cells-are-made-of-metal.html
  14. http://www.godtube.com/view_video.php?viewkey=ab476a318839606743bd
  15. at least those who don't follow science topics
  16. http://issol.org/
  17. http://www.springer.com/life+sciences/journal/11084
  18. http://www.springer.com/life+sciences/cell+biology/journal/239
  19. http://journals.elsevier.com/00222836/journal-of-molecular-biology/
Personal tools
Namespaces

Variants
Actions
Navigation
Community
Tools
support