Friday, October 27, 2006

Ponds, not oceans, the cradle of life

Another rediscovered gem from my pile of unclassified science journal photocopies!

There is a major problem with origin of life theories which assume that life began in the ocean (e.g. "deep-sea thermal vents and tidal pools," etc).

[Graphic: Reflections From a Warm Little Pond, NASA]

And that is, "a spherical membrane called a vesicle that could enclose self-replicating chemical chains ... When sodium chloride or ions of magnesium or calcium [i.e. salts] were added the membranes fell apart" and "Earth's early oceans were 1.5 to 2 times as salty as they are today":

"The cherished assumption that life emerged in the oceans has been thrown into doubt. New research shows that primitive cellular membranes assemble more easily in freshwater than in salt water. So although the oldest known fossil organisms were ocean dwellers, life may actually have developed in freshwater ponds. Most theories on the origin of cellular life presume that the first step was the formation of a spherical membrane called a vesicle that could enclose self-replicating chemical chains - the ancestors of modern DNA. The idea is that the ingredients for simple membranes were all present on the early Earth, and at some point formed vesicles spontaneously in water. It seemed most likely that this took place in the sea rather than freshwater, largely because of the sheer size of the oceans. With their unique chemistry, deep-sea thermal vents and tidal pools are generally believed to be the most likely sites. Now research by graduate student Charles Apel of the University of California, Santa Cruz, suggests that this is wrong. Apel and his colleagues were able to create stable vesicles using freshwater solutions of ingredients found on the early Earth, but not salty solutions, they will report in a future issue of Astrobiology. `When sodium chloride or ions of magnesium or calcium were added the membranes fell apart,' Apel says. This happened in water that was less salty than the oceans are today. ... Geologist L. Paul Knauth of Arizona State University points out that Earth's early oceans were 1.5 to 2 times as salty as they are today, making it even more unlikely that viable cells could have arisen there. Giant salt deposits called evaporites that formed on the continents have actually made the seas less salty over time. `No one in their right mind would use hot seawater for laboratory studies of early cellular evolution,' says biochemist David Deamer of the University of California, Santa Cruz, who is reporting the work with Apel. `Yet for years we have all accepted without question that life began in a marine environment. We were just the first to ask if we were really sure of that.' `This is a wake-up call,' says mineralogist Robert Hazen at the Carnegie Institution of Washington. `We've assumed that life formed in the ocean, but encapsulation in freshwater bodies on land is appearing more likely.' The finding would not have surprised Charles Darwin. Over a century ago he speculated in his personal letters that the origin of life was `in some warm little pond with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc. present." (Kaplan, M., "Ponds, not oceans, the cradle of life," New Scientist, 9 May 2002)

But as the article says, "It seemed most likely that this took place in the sea rather than freshwater, largely because of the sheer size of the oceans," presumably meaning that in an entire ocean there is a greater likelihood that all the biochemical building blocks (amino acids, nucleic acids, fatty acids, etc) would be in it.

However then the problem is that the very size of the ocean means that there is proportionately less likelihood that the building blocks would all be together in the same place at the same time, as this somewhat humorous quote by complexity theorist Stuart Kauffman illustrates:

"Further, it was supposed, simple organic molecules in the atmosphere, along with other more complex ones, would be expected to dissolve slowly in the newly formed oceans, creating a prebiotic soup. From this soup, it was hoped, life would somehow form spontaneously. This hypothesis continues to have many adherents, though it suffers from considerable difficulties. Chief among them is the fact that the soup would be extremely dilute. The rate of chemical reactions depends on how rapidly the reacting molecular species encounter one another-and that depends on how high their concentrations are. If the concentration of each is low, the chance that they will collide is very much lower. In a dilute prebiotic soup, reactions would be very slow indeed. A wonderful cartoon I recently saw captures this. It was entitled `The Origin of Life.' Dateline 3.874 billion years ago. Two amino acids drift close together at the base of a bleak rocky cliff; three seconds later, the two amino acids drift apart. About 4.12 million years later, two amino acids drift close to each other at the base of a primeval cliff. ... Well Rome wasn't built in a day." (Kauffman, S.A., "At Home in the Universe: The Search for Laws of Self-Organization and Complexity," [1995], Penguin: London, 1996, reprint, pp.34-35. Ellipses original).

But then there is also a problem with a smaller freshwater pond (apart from the fact that in nature fresh water without dissolved salts in it is extremely rare to non-existent-especially if it was supposed to include all the other biochemical building blocks!) in that the likelihood that it would have all the building blocks in the one pond is astronomically unlikely.

Indeed if life originated in a freshwater pond (or anywhere) then it would have to be the functional equivalent of a laboratory that our advanced 21st century technology has yet to demonstrate it can build (since modern science has still yet to synthesise a living cell from non-living chemicals).

Origin of life theorist Robert Shapiro gives an illustration of what a fully naturalistic assembly of life in such a "Darwin Pond" would involve and concludes, "Different accounts leading to the origin of the replicator could be constructed, ... but all would share the same general defects": 1) "Many steps would be required which need different conditions, and therefore different geological locations"; 2) "The chemicals needed for one step may be ruinous to others;" 3) "The yields are poor"; 4) "with many undesired products constituting the bulk of the mixture"; 5) "It would be necessary to invoke some imagined processes to concentrate the important substances and eliminate the contaminants" and therefore 6) "The total sequence would challenge our credibility, regardless of the time allotted for the process" (my emphasis):

"Once, a long time ago when the earth was quite young, a group of high mountains rose above the ocean, forming a large island. It was volcanic, somewhat like a Hawaiian island of today, for continents as we know them had not yet formed. Because of the height and extent of these mountains, and because of the prevailing wind and weather patterns, a variety of climate zones existed on the island. Thunderstorms were frequent on the rainy side, where it was always cloudy. In the high altitudes, near the mountaintops, the rain froze, and the precipitation came down as snow or hail. The atmosphere was reducing, and these conditions favored the formation of hydrogen cyanide in the discharges. The rain and snow were rich in this chemical. Large glaciers descended from the highest peaks. At their base, in the summer season, lay a number of partly frozen alkaline lakes. Hydrogen cyanide collected in them, and reacted with itself extensively, until the time came when the lakes froze solid in the winter. When warmer weather resumed, the lakes thawed in part and the reaction started again. In one very important year, however, spring did not return. The climate in the highlands had taken a turn for the worse. More snow fell at the mountaintops and the glaciers advanced, pushing the frozen lakes down the mountain. The flow path of one glacier led it away from the wetter side of the island toward a central plateau, which was geothermally active. In this more temperate climate the glacier tip melted, and the hydrogen cyanide reaction mixture flowed into a boiling acidic spring. Such boiling springs exist today in areas like Yellowstone Park and Iceland. Bacteria, which belong to the same broad class as the methanogens, are able to grow there. In the early days that we are considering, of course, no life existed, but over the course of an hour the boiling acid converted a small amount (about 0.1 percent) of the solids that the glacier had brought into adenine. The acid would eventually also have destroyed the adenine, but before that could happen the spring waters flowed into a broader stream. In doing so, they passed over some alkaline soils which neutralized them. It seldom rained in this broad plateau area, and when it did, it fell in the form of sunshowers, rather than thunderstorms. The rays of the sun caused formaldehyde, rather than hydrogen cyanide, to be formed. The formaldehyde rain flowed in tiny streams into a geologically different, but also geothermally active, part of the central plateau, which contained boiling neutral pools, thick with suspended minerals. As each formaldehyde stream flowed into a boiling mineral pool it was converted into a complicated mixture by a process called the formose reaction. The sugar ribose formed a small part of this product. Moving waters carried the mixture down the length of the pool over the next several hours, allowing enough time for the change to be completed. At this point the product flowed out of the hot pool and was swept downstream by a rapid icy brook. This escape was fortunate, as the ribose would have decomposed if it had remained too long in the pool. The adenine and ribose streams merged in the central plateau, but they could not yet form adenosine. They needed a hot environment and the presence of sea salt for that purpose. Happily, a precipitous waterfall took them almost to sea level, on the hot, day side of the island. Time was of the essence, as the sugar was not stable and was being lost. At the base of the waterfall, the stream widened to form a broad delta. The waters flowed over a variety of different types of rock and mineral formations. At some point they entered a tidal pool which had been cut off from the sea at low tide. Minerals lining the pool had a special affinity for both adenine and ribose, and retained them, while most of the other substances were swept away as the tide filled and drained the pool. It was a very hot day. The sun evaporated the remaining water in the pool and heated the adenine and ribose in the presence of salt, converting them in part to the nucleoside adenosine. As this was happening, a violent storm occurred far out at sea, creating large waves. The tides returned to the tidal pool in a rush, sweeping out its contents and transporting them farther inland. They were deposited in a nearby pond, which we name Darwin Pond. This was to be the chosen site for the origin of life. No sooner had the adenosine reached Darwin Pond when successive waves, each flowing from a different direction, brought in: supplies of the other nucleosides needed to make RNA. Had these chemicals only been human, they would have embraced at the joy of their first meeting, and in anticipation of the glorious future that lay ahead of them. They would then have taken turns, each describing the marvelous and different series of events that had led to its own creation. We must not inject our own feelings into the story, though. Let nature continue the synthesis. Phosphate was needed for the conversion of nucleosides to nucleotides. Several geologists have contended that phosphate was not readily available on the early earth, and only increased in concentration in the waters gradually, as appropriate rocks weathered. Darwin Pond, however, was one of the few choice locations blessed with the right kind of mineral; it already had abundant phosphate. Thus, when the continuing heat wave evaporated the pond almost to dryness, the nucleosides were converted to nucleotides. This process was aided by an additional catalyst which was found in the minerals lining the pond. The nucleotides now needed to combine, to form the replicator. This process was helped greatly by the presence of certain chemicals called amines which were brought in by another temporary flood. The amines would have been unwelcome earlier in our account, as they would have interfered with several earlier steps. The climate now stabilized. Days were as hot as before, enough to dry up the pond. Each night, however, winds brought in enough moisture to form a thin liquid film at its bottom. These alternative periods that and moisture afforded the nucleotides a chance to come together in various ways and then to break apart again. One evening, by chance, the replicator was formed. It took charge immediately, assembling other nucleotides into copies of itself, more rapidly than they could come apart. Life had been created and evolution could begin .... Different accounts leading to the origin of the replicator could be constructed, using other experiments published in the literature. Some would be less spectacular than the above one, but all would share the same general defects. Many steps would be required which need different conditions, and therefore different geological locations. The chemicals needed for one step may be ruinous to others. The yields are poor, with many undesired products constituting the bulk of the mixture. It would be necessary to invoke some imagined processes to concentrate the important substances and eliminate the contaminants. The total sequence would challenge our credibility, regardless of the time allotted for the process." (Shapiro, R., "Origins: A Skeptic's Guide to the Creation of Life on Earth," Summit Books: New York NY, 1986, pp.182-185).

Yet because he is a scientific materialist, Shapiro thinks the equivalent of this must have happened somehow. And scientific materialist say that we creationist/IDists are the `true believers'!

Stephen E. Jones, BSc (Biol).


Genesis 8:1-5. 1But God remembered Noah and all the wild animals and the livestock that were with him in the ark, and he sent a wind over the earth, and the waters receded. 2Now the springs of the deep and the floodgates of the heavens had been closed, and the rain had stopped falling from the sky. 3The water receded steadily from the earth. At the end of the hundred and fifty days the water had gone down, 4and on the seventeenth day of the seventh month the ark came to rest on the mountains of Ararat. 5The waters continued to recede until the tenth month, and on the first day of the tenth month the tops of the mountains became visible.

2 comments:

Mark said...

Great post Steve. It seems that although time passes, the old old story gets told and retold. It must have happened because why else are we here?

Stephen E. Jones said...

Mark

Thanks for your comment and Good to hear from you again.

And thanks for putting that link to CED on your ID Network Australia page (http://www.idnet.com.au/).

If one rules out Intelligent Design apriori, the only option left for the origin of life (and the origin of *everything* else) is unintelligent processes.

So no matter how improbable it seems, unintelligent processes simply *must* have created life (note the sub-title of Shapiro's book, "... the *Creation* of Life on Earth"), because we are here!

BTW apologies for the delay in moderating your comment. I had given Blogger my email address to notify me when there were comments awaiting moderation, but on just now checking it was not there. I have now redone it and checked that it *is* there.

Stephen E. Jones