Monday, May 18, 2009

Getting closer on solving the origins of life question

When arguing against evolution, many often evoke the unsolved mystery of the origins of life on Earth. Yes, it is a difficult problem, but it is a highly risky move, to say the least, for those looking for a divine miracle to put all their chips on this question. The same happened with the origins of the Earth and the Solar System back in the 18th/19th centuries. For a while this was considered as an unsolvable problem - outside the domain of science. Laplace's "nebular hypothesis" was deemed fanciful with some of the opposition directed specifically at its exclusive reliance on natural mechanisms to explain the origins of the solar system. Well...today, the formation of the Earth and the solar system is relatively well understood and no one brings up a direct supernatural explanation. God (of the gaps) has now moved to other unexplained places: a) the origin of life, b) the origin of consciousness, and c) the origin of our universe (yes - "ours". If there are other universes, then we'll move God (of the gaps) at the beginning of the multiverse).

Thus, it was fantastic to see this story about a breakthrough in RNA research that may bring us closer to understanding the origin of life:
An English chemist has found the hidden gateway to the RNA world, the chemical milieu from which the first forms of life are thought to have emerged on earth some 3.8 billion years ago. He has solved a problem that for 20 years has thwarted researchers trying to understand the origin of life — how the building blocks of RNA, called nucleotides, could have spontaneously assembled themselves in the conditions of the primitive earth. The discovery, if correct, should set researchers on the right track to solving many other mysteries about the origin of life. It will also mean that for the first time a plausible explanation exists for how an information-carrying biological molecule could have emerged through natural processes from chemicals on the primitive earth.
RNA has been a long suspect for this line of work:

Scientists have long suspected that the first forms of life carried their biological information not in DNA but in RNA, its close chemical cousin. Though DNA is better known because of its storage of genetic information, RNA performs many of the trickiest operations in living cells. RNA seems to have delegated the chore of data storage to the chemically more stable DNA eons ago. If the first forms of life were based on RNA, then the issue is to explain how the first RNA molecules were formed.

For more than 20 years researchers have been working on this problem. The building blocks of RNA, known as nucleotides, each consist of a chemical base, a sugar molecule called ribose and a phosphate group. Chemists quickly found plausible natural ways for each of these constituents to form from natural chemicals. But there was no natural way for them all to join together.
Well...here is a palusible way to get them to join naturally:

Instead of making the starting chemicals form a sugar and a base, they mixed them in a different order, in which the chemicals naturally formed a compound that is half-sugar and half-base. When another half-sugar and half-base are added, the RNA nucleotide called ribocytidine phosphate emerges.

A second nucleotide is created if ultraviolet light is shined on the mixture. Dr. Sutherland said he had not yet found natural ways to generate the other two types of nucleotides found in RNA molecules, but synthesis of the first two was thought to be harder to achieve.

If all four nucleotides formed naturally, they would zip together easily to form an RNA molecule with a backbone of alternating sugar and phosphate groups. The bases attached to the sugar constitute a four-letter alphabet in which biological information can be represented.
Neat! Oh...and a 19th century bearded-dude may have been right about this one too:

If Dr. Sutherland’s proposal is correct it will set conditions that should help solve the many other problems in reconstructing the origin of life. Darwin, in a famous letter of 1871 to the botanist Joseph Hooker, surmised that life began in some warm little pond, with all sorts of ammonia and phosphoric salts.” But the warm little pond has given way in recent years to the belief that life began in some exotic environment like the fissures of a volcano or in the deep sea vents that line the ocean floor.

Dr. Sutherland’s report supports Darwin. His proposed chemical reaction take place at moderate temperatures, though one goes best at 60 degrees Celsius. “It’s consistent with a warm pond evaporating as the sun comes out,” he said. His scenario would rule out deep sea vents as the place where life originated because it requires ultraviolet light.
Very cool stuff. Read the full article here. Also see Carl Zimmer's excellent explanation here: In the prebiotic kitchen. While we are on the subject, also check out this conversation between Paul Davies and Richard Dawkins as part of the Origins symposium. Much of it is focused on biology and origins of life issues and Paul asked some excellent questions. My favorite is towards the end, when he asks if its possible that Lamarckian evolution (instead of Darwinian evolution) may be dominant on another planet. Richard's answer was no. But I think it would be very cool to imagine the resultant diversity and how it would differ from here on Earth. A perfect premise for a sci-fi novel. Here is the video of the talk:

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