Posted on 03/20/2004 7:38:37 PM PST by Leroy S. Mort
Without the Moon, there would have been no life on Earth.
Four billion years ago, when life began, the Moon orbited much closer to us than it does now, causing massive tides to ebb and flow every few hours. These tides caused dramatic fluctuations in salinity around coastlines which could have driven the evolution of early DNA-like biomolecules.
This hypothesis, which is the work of Richard Lathe, a molecular biologist at Pieta Research in Edinburgh, UK, also suggests that life could not have begun on Mars.
According to one theory for the origin of life, self-replicating molecules such as DNA or RNA emerged when small precursor molecules in the primordial "soup" polymerised into long strands. These strands served as templates for more precursor molecules to attach along the templates, creating double-stranded polymers similar to DNA.
But the whole theory fails without some way of breaking apart the double strands to keep the process going, says Lathe. It would take some external force to dissociate the two strands, he says.
Doubling up
As an analogy, he points to PCR, the technique used to amplify DNA in the lab. DNA is cycled between two temperatures in the presence of appropriate enzymes.
At the lower temperature of about 50 ýC, single DNA strands act as templates for synthesising complementary strands. At the higher temperature of about 100 ýC, the double strands break apart, doubling the number of molecules. Lower the temperature, and the synthesis starts again. Using this process, a single DNA molecule can be converted into a trillion identical copies in just 40 cycles.
Lathe believes that thanks to the Moon, something similar happened during Earth's early years. Most researchers agree that the Moon formed five billion years ago from debris blasted off Earth in a giant impact.
A billion years later when life is thought to have arisen, the Moon was still much closer to us than it is now. That, plus the Earth's much more rapid rotation, led to tidal cycles every two to six hours, with tides extending several hundred kilometres inland, says Lathe. Coastal areas therefore saw dramatic cyclical changes in salinity, and Lathe believes this led to repeated association and dissociation of double-stranded molecules similar to DNA.
When the massive tides rolled in, the salt concentration was very low. Double-stranded DNA breaks apart under such conditions because electrically charged phosphate groups on each strand repel each other.
But when the tides went out, precursor molecules and precipitated salt would have been present in high concentrations. This would have encouraged double-stranded molecules to form, since high salt concentrations neutralise DNA's phosphate charges, allowing strands to stick together.
Unrelenting cycles
These unrelenting saline cycles would have amplified molecules such as DNA in a process similar to PCR, says Lathe. "The tidal force is absolutely important, because it provides the energy for association and dissociation [of polymers]."
Many researchers do not believe DNA and RNA were the first replicating molecules. Graham Cairns-Smith of the University of Glasgow, UK, thinks much simpler "genetic" material formed first, from the crystallisation of clay minerals.
But he says Lathe's idea deserves attention. "Whatever the replicating entities were that started the evolutionary process, it would be significant that they lived in an environment in which the conditions were changing."
If the theory is right, life could not have evolved on Mars, says Lathe. Phobos, the larger of Mars's two Moons, is so small that the tidal forces it generates are just one per cent of those generated by our Moon. "Even if there was water on Mars, life could not have evolved there because these polymers could not have replicated," he says.
Not only that, but also "To Serve Man...." (the cookbook!) [Twilight Zone?]
;-)
I always wonder what mystical mushroom people have to ingest to think that a physical copy or emulation of our consciousness would automatically be us. Excuse me, but the old body still dies. Living things already have the only kind of immortality avaliable to physical living things, and that would be children.
If you believe in a soul, that's fine with me, but I don't think God is going to be fooled by making physical copies of ourselves.
It's part of a greater question that I have an interest in: what will human beings be like 100, 1000 or a million years from now? We'll probably go through a lot of changes over the long-term, both mentally and (through bioengineering), physically. Humanity is on the cusp of an age that will probably see radical changes to the whole idea of what it means to be human.
When you look at how many insect species there are, you could hardly have any other result.
I agree with you. If one could transfer their consciousness, I think that person remains the same. However, a copy isn't the same, at least not in my mind. If someone were to copy me tomorrow then disintergrate the original, the rest of the world might not know the difference, but I (the I that exists right now) would be gone.
I was too specific. I should have been more generic.
If you were a program running in a computer, would you still like cheeseburgers?
The obvious trick is to shift the burden of proof the other way, but even that doesn't work.
Suppose that your neurons were gradually replaced by silicon designed to function as neurons, and to emulate the wetware for you. That is, instead of simply doing it in one fell swoop, your neurons are replaced one-by-one with chips, over some extended period of time, until there was eventually nothing left but silicon. Now, if you did such a thing, at no point would there ever be more than one "you" running around, so what happens then? Can you reasonably say that your consciousness has effectively been "transferred"?
Depends on what the computer environment was like. If it was set up in a way so that the transferred human consciousness perceived it as the "real" world, I would still have a love of (virtual) cheeseburgers.
In fact, I think any such artificial environment would need to be perceived by the transferred consciousness as the "real" world. I don't think a human psyche would survive sane and/or intact if it found itself in a pure computer environment.
Interesting scenario. If there was no break in the continuity of consciousness, then I think the being left at the end would be the same as the one at the beginning (well, except he'd have a head full of sand).
"We are Borg. Prepare for assimilation."
Why? What if each bit of silicon were designed to emulate the individual neuron it replaced, such that however the neuron behaved, the silicon perfectly replicated it? Not that there are no valid arguments to be made in favor of dying, of course, but one might imagine that silicon memories are much more "forgettable" than biochemical ones, if you should so wish it...
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