posted on Mar, 25 2008 @ 07:37 PM
The oldest rocks which have been found so far (on the Earth) date to about 3.8 to 3.9 billion years ago (by several radiometric dating methods). Some
of these rocks are sedimentary, and include minerals which are themselves as old as 4.1 to 4.2 billion years. Rocks of this age are relatively rare,
however rocks that are at least 3.5 billion years in age have been found on North America, Greenland, Australia, Africa, and Asia.
New Haven, Conn. -- Yale scientists report they have synthesized molecules like those that probably gave rise to the earliest life forms on Earth
nearly 4 billion years ago, thus creating a biochemist's version of "Jurassic Park" populated by exotic molecular "fossils" that have long since
In the May 26 issue of the Proceedings of the National Academy of Sciences, the Yale biologists report the creation of one of these "fossils," an
unusual hybrid molecule made up of a scaffold from deoxyribonucleic acid (DNA) with chemical "scissors" attached to it.
Ronald R. Breaker, who created the first DNA enzymes in 1994 with colleagues at The Scripps Research Institute, said he "looted the tool box of
proteins" to get the amino acid "scissors," which destroy messenger ribonucleic acid (RNA) in humans and many other organisms. The feat was
accomplished using a technique known as test-tube evolution.
Breaker's tailor-made enzyme is the first known nucleic acid enzyme that uses an amino acid to trigger chemical activity, and it brings scientists a
step closer to finding the precursor of all life -- a single molecule containing both genetic code and an enzyme capable of triggering
"If we can raid a protein's tool box to take one of its favored chemical groups -- in this case, a key amino acid called histidine found in a
protein called RNase A -- then we should be able to raid the entire tool box and make use of anything we find there to make highly sophisticated DNA
or RNA enzymes," said Breaker, who collaborated with Yale postdoctoral associate Adam Roth.
Which Came First -- DNA, RNA Or Proteins?
The discovery provides important clues to the chicken-or-egg dilemma of which came first -- DNA, RNA or proteins. Most scientists agree life as we
know it cannot exist without DNA as the storehouse of genetic code, RNA as the genetic messenger, and proteins to carry out the chemistry of
reproduction. Can any one of these three key molecules have existed as the precursor of the other two, serving as both chicken and egg?
Evidence is mounting that "it was an RNA World at the dawn of life as the Earth began to cool," said Breaker, who added that he and his colleagues
can create dual-purpose genetic enzymes in the laboratory out of either RNA or DNA. "These genetic enzymes have the chemical sophistication, the full
catalytic ability, to do many of the fundamental reactions we see in biology today. I am confident one will be created soon that can replicate
He added that the new DNA enzyme he crafted destroys RNA with impressive efficiency at a rate 10 million times faster than it would decay naturally,
although the protein the enzyme mimics acts much faster still.
No naturally occurring DNA enzymes have been found to date, but such a discovery would not surprise Breaker. The discovery nearly two decades ago of
naturally occurring RNA enzymes, or ribozymes, earned Yale biochemist Sidney Altman and University of Colorado researcher Thomas Cech the 1989 Nobel
Prize in Chemistry. In separate experiments, Altman and Cech exploded the myth that RNA is merely a passive carrier of genetic code incapable of
triggering cell activity.
Referring to the dozen or more DNA and RNA enzymes created in his laboratory in recent months, Breaker said, "We believe these are like ancient
molecular 'fossils' that might have been found stomping around the planet -- or more likely floating in the seas -- during the Archean Era between
3.8 and 4 billion years ago."
RNA Identified As Strongest Candidate For Precursor To All Life
While the Yale biologists created the versatile protein mimic from DNA, Breaker theorizes that a similar enzyme could be created with RNA, which many
scientists believe is the strongest candidate for being the precursor of all other life forms. In addition to RNA's dual function as genetic molecule
and as enzyme, RNA serves important roles in all living systems as the carrier of genetic instructions from DNA and as the orchestrator of all protein
"This is exactly what you would expect if RNA invented these processes during the 'RNA World,'" Breaker said. "Because DNA is about a million
times more stable than RNA, DNA most likely evolved later as a safe storehouse for the genetic code first found in RNA. Similarly, proteins probably
evolved that were more efficient chemical catalysts, eventually driving most RNA enzymes extinct and relegating RNA to a more limited role."
The discovery that nucleic acids can raid the tool box of proteins means "the RNA World could have been a very sophisticated place," Breaker said.
"The earliest RNA could have had access to all of these chemical helpers now used by proteins. Instead of working from a very primitive palette,
varieties of RNA could have evolved that had a very rich chemical capability early on."
Now if the earth has been around for billions of years do you think it is possible that We might be getting a second chance and that maybe we have
evolved more than once?
Is it possible that at the begining of the planets birth Aliens could have introduced RNA or DNA to kick start life?
Are we a mixture of ET life? We could be the bastard sons of the universe
If you take all the probabilities and the even include planet X in this life would not be on this planet as it would get disturbed every 3-4K years
Maybe we are meant to be
I would like to discuss your views and opinions on the begining and what you all think...
A cool experiment for me would be if nasa dropped some dna on venus and see what happens