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Primordial Soup: Interview with Stanley Miller
An anonymous reader writes "Stanley Miller's classic 'primordial soup' experiments showed that 13 of the 21 amino acids necessary for life could be made in a glass flask. For its fifty-year commemoration, Miller is interviewed today and reflects on what Carl Sagan
called 'the single most significant step in convincing many scientists that life is likely to be abundant in the cosmos.'"
Primordial Recipe: Spark and Stir
Date Wednesday, May 14 @ 00:48:06
Topic Extrasolar Life
No single experiment, according to Carl Sagan, has done more to convince scientists that life is 'likely abundant in the cosmos' than the work fifty years ago by then graduate student, Stanley Miller. This week celebrates his milestone publication, and Astrobiology Magazine interviewed him about his work and reflections today.
Primordial Recipe: Spark and Stir
by Astrobiology Magazine staffwriter
Fifty years ago on May 15, 1953, a University of Chicago graduate student, Stanley Miller, published a landmark two-page paper in Science magazine. He considered if amino acids could be made from what was known about the early Earth's atmosphere. Could the building blocks of life be cooked up?
"... some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity etc...", Charles Darwin, on the origins of life in tidal pools
Credit:Smithsonian
Miller began his paper:
"The idea that the organic compounds that serve as the basis of life were formed when the earth had an atmosphere of methane, ammonia, water and hydrogen instead of carbon dioxide, nitrogen, oxygen and water was suggested by Oparin and has been given emphasis by Urey and Bernal. In order to test this hypothesis..."
When Miller first presented his experimental findings to a large seminar, it is reported that at one point, Enrico Fermi politely asked if it was known whether this kind of process could have actually taken place on the primitive Earth. Harold Urey, Stanley's research advisor, immediately replied, saying 'If God did not do it this way, then he missed a good bet'. The seminar ended amid the laughter and, as the attendees filed out, some congratulated Stanley on his results.
Although Miller had submitted his paper in mid-December 1952, one reviewer did not believe the results and delayed its publication until May 15th. Later Carl Sagan would do many experiments varying the chemical percentages, but described the Miller-Urey experiments as "the single most significant step in convincing many scientists that life is likely to be abundant in the cosmos."
Early Earth: Flash in a Flask
Even today, only a few definitive things are known about what the Earth might have been like four billion years ago. It is thought that the early sun radiated only 70 percent of its modern power. No free oxygen could be found in Earth's atmosphere. The rocky wasteland lacked life. Absent were viruses, bacteria, plants and animals. Even the temperature itself is uncertain, since three schools of thought today maintain that the Earth could have been alternatively frozen, temperate or steamy.
Charles Darwin imagined life springing from a temperate world, with small ponds or runoff channels. Compared to diluted chemistry in a vast ocean, repeated evaporation and refilling have possible advantages, to find just the right concentrations somewhere so that biochemistry could begin. Glaciers, volcanoes, geysers and cometary debris potentially resupplied this primordial pond with both energy and more complex organic compounds. That is a scenario requiring relatively temperate starting conditions, and more extreme possibilities are also in the mix.
If the early Earth was a cauldron of volcanic activity, then seepage of acidic gases and heating might have circulated vital compounds to the surface. These vents may have been underwater, and precursors to biochemistry like acetic acid may have become reactive in combination with carbon monoxide. Alternatively, if the early Earth lacked any greenhouse of blanketing carbon dioxide, life could still have begun in a ball of ice. When combined with water, even a thin atmosphere of organics (formaldehyde, cyanide and ammonia) can create some building blocks of life (such as the amino acid, glycine). Thawing this 'snowball Earth' could then be triggered by a chance collision with large comets or meteors.
Terrestrial options for ea
from October 1996: Exobiology interview
On a related note: exobiology vs astrobiology? which do people prefer? (The definitions are in the links)
Suicide Booth: You are now dead! Thank you for using Stop and Drop, America's favorite since 2008.
Racemic mixtures are not decompsed anything. They are mixtures of "mirror-image" molecules. A completely racemized mixture is one with equal numbers of "left" and "right" members. Presence of both will not prevent you from using one or the other.
Look at you set of hands, one is racemic "left" and the other is racemic "right". You have a completely racemized mixture of hands. This does not deny you use of your left hand.
If amino acid procduction is industrial, usually you get (depending on the process) a mixture of the two racimic (D and L) formations that an amino acid can take. They are mirror images of each other.
Why is this important, well on planet Earth, almost all amino acids involed in life are of type L. (Metorites and non-living processes contribute the majority, if not all, of the D racemes discovered today)
Why only L-amino acids? Today we do not "know" with 100% certainty, but the theory is a living system, for whatever reason, started producing L-amino acids, which unbalanced the ratio. Other living systems (or perhaps the same one) which harvestd these L-amino acids survived and thrived in this L-amino acid rich environment while those that required D-amino acids may have never existed or may have died out due to competition.
Replies to several different posts (sorry for the lack of attribution): /Ah, but does he mention that his amino acids... /broke down as fast as they were made (in a /carefully customised device, not in the wild), /and were completely racemised at formation? Or /that no evidence of a reducing atmosphere exists?
/Also Miller had to create a "trap" to collect the /amino acids being formed to protect them from /breaking down again. What would the comparable /"natural" trap be?
/As a student of Biological Anthropology, I have /had the oppertunity to take a history of /biological anthropology in which Miller was /mentioned. Interesting guy, but the theory is not /supported any more except by the few staunchest /researchers. In other words, this is pop science. /It survives in text books (like many other /evolutionary inaccuracies that nobody seems to be /willing to update). In truth, the experiment did /not conclude much. In short, the amino acid /theory in reality did not produce very much at /all
Amino acids tend not to break down much. They are exceedingly stable once made. Those that happened to wander back into the electric current might have suffered, but the majority would have stayed safely in solution. The chemical reaction was proceeding in the gas phase; the products were sequestered in the water.
The products are racemic amino acids. Several plausible hypotheses have been put as to how it happened that the L amino acids became predominate: circular dichroism in natural radiation, preferential decompostion of D 14C labeled amino acids, etc.
We don't know all that much about the exact composition of the atmosphere at every time in the earth's history, but the fact that high-energy processes can give amino acids from simple precursors trumps all nit-picking.
The natural trap would be water. High energy events are always happening in the atmosphere (lightning, UV rays, cosmic rays). Lighting blasts convert nitrogen to nitrates. Roughly 10% of the nitrate in soil comes from nitrogen transformed by lightning, and the nitrates are trapped by water. The point to take home from the Miller experiment is that the small, high-energy intermediates formed by these processes can combine to form biologially complex building blocks.
This is just wrong. The conclusion drawn from the results of the experiment was revolutionary. It is of at least on the scale of Wohler's synthesis of urea, a biochemical, from "dead" cyanogen and ammonia.
If Slashdot were chemistry it would look like this:Cadaverine
Actually, I seem to recall that the way that hypotheses operate is by being proven wrong. Empirical evidence can stack up for years in favor of a hypothesis, but a single test that shows it doesn't work under one of the given conditions disproves it.
I will refer you to this site, which has a handy breakdown of the scientific method for you. Note in particular the bit that says "Experiments are useful in disproving hypotheses. Hypotheses cannot be proved."
The God argument is a problem for scientists *precisely* because it's not disprovable. (Note that that does not mean it's true by default, it means that there is no way to test whether or not it is true.)
Next: I don't recall bringing up the age of the earth, but since you ask, there are many ways of measuring the age of geological structures, and thus the earth.
- radiometric dating. This method relies on the radioactive decay of an unstable type of atom (parent isotope) within the rock into another type of stable atom (daughter isotope). In a certain period of time, called the half-life, half of the parent isotopes will have decayed into daughter isotopes; in an additional, equivalent period of time, half of the remaining parent isotopes will have decayed, and so on. The length of the half-life, which can be measured, varies for different isotopes. By measuring the ratio of parent to daughter isotopes, the time that has elapsed since decay began can be calculated; this is equivalent to the age of the rock.
- fission track dating. Certain minerals in rocks contain small amounts of uranium which decay radioactively by the splitting apart of the atomic nucleus (nuclear fission). The two fission fragments produced are highly energetic and highly charged, and they produce a linear trail of radiation damage in the surrounding crystals of the rock. This trail is known as a fission track. Fission tracks can be enlarged by chemical etching until they can be observed and measured under a microscope. The number of tracks is proportional to the time since they started to accumulate, and to the amount of uranium in the rock. The amount of uranium present can be determined by irradiating the rock with neutrons to produce a second set of fission tracks. The ratio of the original tracks to the new ones gives a measure of geological age.
- amino-acid racemisation. The method relies on the fact that molecules of amino-acids, the building blocks of proteins, occur in two different forms that are mirror images of each other. These two forms are referred to as left-handed and right-handed. In living organisms, only left-handed amino acid molecules are present, but once the organism dies they slowly convert to their right handed form. Simultaneously, the right handed forms produced slowly convert back to left handed forms, until an equilibrium is reached (half left handed and half right handed), at which point the ratio remains constant. The time taken to reach equilibrium is known, so by determining the ratio of right handed to left handed forms it is possible to estimate the time elapsed since the organism died.
see the Museum of Victoria's site for more detail. You may also like to check out the Age of the earth FAQ, or that bastion of all wisdom - google.I used to have a better sig than this, but I got tired of it
> Oh, you think your position is so secure. "Every test designed to disprove the theory has failed". What are you talking about? Evolution is not scientific.
All you're doing is showing the better-informed part of the public that your denial of evolution is based on complete ignorance of what it is all about.
If you understood the theory of evolution at the "read one book on it" level you would be able to make a long list of conceivable falsifying observations.
> Tell me how you know the earth is so old (4.5 billion last time I heard). This is not a rhetorical question, I want an answer - and not about space. I'm talking about the earth
Try talkorigins.org for an introductory-level answer. Notice also that it was the first thing to pop up when I typed "age of the earth" into google and clicked the submit submit button.
Sheesh, evil *and* a jerk. -- Jade
It should be no surprise at all that the mixture was racemic. The reason only Creation "scientist's" websites say anything about it is because they are the only ones that think it has any relevance.
As for breakdown, they did break down quickly, that was in the original publications of the experiment.
The "break down as quickly as they are made" is a half truth. At the gas-liquid interface, this is true. The amino acids did break down very rapidly. However, a fraction of the products became dissolved in the liquid soon after formation, and were preserved. This caused a gradual buildup of product.
There is a reason for everything. Sometimes that reason just sucks.
---The 'monkeys on typewriters ending up with war and peace' flies in the face of reason, IMHO, and yet it is a crutch and fundamental pillar of evolutionary theory, attractive because one can always simply require the disbeliever to roll the dice a trillion more times or so.---
If your only idea of how evolution or the various theories of abiogenesis work is just "rolling the dice" then you're already tripped yourself up. The whole point to both these theories is that there are some natural MECHANISMS that produce organized results. Not just chance assembleges at all: it's the particular principles of chemistry, and later, genetics, that actually induce certain things under certain conditions, leading to other inducements, often in a feedback loop.
---consider this: they have never discovered fossilized remains of an inter-species mutation; e.g., a creature evolutionarily between A and B.---
Oh for goodness sake: did you think you could dazzle the boards with such a well-refuted lie? Even the very suggestion shows that you are not hip to the way in which evolutionary theory destroyed the very idea of "kind" whereby we could say that a creature is "between" two "other" kinds. Our idea of "kind" is simply our eagerness to pretend that what we see today represents a bunch of stable and eternal Platonic forms from which any deviation from is some sort of mutant. But ALL species alive today are potentially intermediate forms to something in the future, and their ancestors WERE intermediate forms between them and something even earlier. Worse, the idea of "intermediate forms" is doubly misleading, because it implies that any given direction is "going somewhere," transitioning between one discrete thing and a new, pre-defined goal. But the theory of evolution is NOT suggesting that in the least. There is no discrete goal that something is somehow knowingly "transitioning" towards.
Even if all that were not the case, we DO have plenty of fossils which demonstrate the sorts of big-scale "transistional forms" that you're asking about (ones that just happen to strike us as grossly "in-between" two sorts of creatures we are comfortably familiar with today because they share certain large and obvious features: but in reality, are ONLY "in-between" from our present perspective, not in any real sense). Talk origins has a whole listing of them.
..broke down as fast as they were made (in a carefully customised device, not in the wild), and were completely racemised at formation? Or that no evidence of a reducing atmosphere exists?"
I think you should take a look at the article. The "carefully customised" device is incredibly simple, consisting of 2 flasks, a hot plate, an electrical sparker, a water condesor, and some glass tubing. That's it. It could be further simplified to remove the heater, as all this does is to make more vapor available in the 2nd flask containing the sparker--you could envision a simpler setup that is put into a window so sunlight evaporates the solution to make it more available to the spark chamber (closed loop, naturally, so no gas actually escapes the system). Actually since then the whole thing would run at a lower temperature you could omit the condensor and the little bend in the glass tubing (the "trap") leaving you with a flask on the bottom with your solution, connected by a single length of glass tubing to a second flask on top with the attached two bits of wire and battery, the whole thing sitting in the window. Sunlight hits the bottom flask, causing evaporation which rises up to the top flask, which sparks, condensate builds up in the top flask and over time falls back into the lower flask or sticks to the interconnecting glass tubing. Slowly you would use up your initial reagents leaving you with a complex mixture with among its components a collection of biologically relevant molecules. Total list of materials for the apparatus: 2 flasks, two feet or so of glass tubing, say a foot of copper wire, and a car battery--even simpler than the original. l'm fairly sure this would work similar to Miller's initial experiment, albeit much slower mainly due to the lower temperature. You should remember that his experiment produced an abundance of multiple different biologically relevant molecules in only a week. The point is: this experiment is incredibly simple, not "carefully customized". All that it was meant to show was that under conditions that at the time were thought to be similar to those on a prebiotic earth you could produce a host of biologically important compounds from even simpler compounds thought to be abundant using energy sources that would be available: heat, light, lightning. At this the experiment, one of many under a great variety of conditions--see his website for a starting point--succeeds at marvelously. Others have already answered your other complaints so it is pointless to repeat their statements here.
To form life that's exactly like we know it may require specific combinations. But if you define life to be a self-sustaining chemical process, then there can be many ways that life could have arisen, other than the way it happened to on Earth. Read Kauffman's work on autocatalytic networks.
Really? Present the probability calculation. Kauffman's work, for instance, suggests that autocatalytic networks are almost inevitable given nothing but a sufficient diversity of chemicals, and some time. (I believe he has also estimated the time necessary for a given diversity.) I personally don't think we know nearly enough to be able to say with confidence what the probability was. But it's far from obvious that it was "overwhelmingly improbable".
This is wrong. The whole point of natural selection is that it is an extremely powerful organizing force. There is also self-organization (which ties into the above-mentioned work by Kauffman).
Don't be ridiculous. Peanut butter doesn't have a sufficiently complex chemical mix, nor physical conditions similar to the arisal to life on the early Earth; opening a jar of peanut butter has nothing to do with what might produce life. (Not to mention that "billions of times a year" is "essentially never", for the chemical processes we're talking about -- compare how many reactions take place in a single test tube.)
This might be the most absurd strawman argument I've yet seen from a creationist.
This is also false.
There were a lot more trilobites then there ever were T-Rexes, and conditions were often better to preserve them.
Actually, you would expect the heavier organisms to sink to the bottom first. However, it is not true that bottom-dwelling sea creatures are always on the bottom.
The top of Everest