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 Book: Rare Earth

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NoCoPilot

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PostSubject: Re: Book: Rare Earth   Sun Jul 15, 2018 10:41 am

Very true, Richard.  There may have been THOUSANDS of original ancestor cells, the so-called "Eve" cells.

But, they all used DNA....

Which means whatever process created them, created ALL of them.

This is just another example of the myopia of Earthlings.  We see life everywhere, so we assume life must be ubiquitous elsewhere in the universe.  We know all our life is DNA-based, so we assume all life everywhere will be DNA-based.  It's the Star Trek Bias: beings on other planets will be human-shaped, speak English, and maybe have blue skin. And Captain Kirk will nail 'em all.
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PostSubject: Re: Book: Rare Earth   Sun Jul 15, 2018 10:52 am

NoCo wrote:
...all life shares A) DNA and B) a lot of it
Not quite right. The article you referenced speaks only to current life forms. Go back to the earlier life and read bacterial DNA and human DNA Big differences.

NoCo wrote:
By extension, any life on other planets would have had to come from Earth.
Are you kidding me? You must be kidding me. Go on. Admit it. You're kidding me.
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PostSubject: Re: Book: Rare Earth   Sun Jul 15, 2018 11:01 am

I'm kidding.  Life happened spontaneously everywhere of course.

It only took root on Earth.

_Howard wrote:
Go back to the earlier life and read bacterial DNA and human DNA.  Big differences.

But they're both DNA....
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richard09

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PostSubject: Re: Book: Rare Earth   Sun Jul 15, 2018 6:39 pm

NoCoPilot wrote:
Very true, Richard.  There may have been THOUSANDS of original ancestor cells, the so-called "Eve" cells.

But, they all used DNA....

Which means whatever process created them, created ALL of them.

I think the process you're looking for is called "chemistry".

NoCoPilot wrote:
This is just another example of the myopia of Earthlings.  We see life everywhere, so we assume life must be ubiquitous elsewhere in the universe.  We know all our life is DNA-based, so we assume all life everywhere will be DNA-based.  It's the Star Trek Bias: beings on other planets will be human-shaped, speak English, and maybe have blue skin.  And Captain Kirk will nail 'em all.

Not quite. We need to unpack your assertions a little bit.

NoCoPilot wrote:
We see life everywhere, so we assume life must be ubiquitous elsewhere in the universe.

This isn't an assumption, it's a calculation. Given a planet in the Goldilocks zone (admittedly pretty rare, we've only discovered 55 of them so far), or a moon that generates similar environments (which suddenly multiplies possibilities for each star), on the one example we've been able to examine closely, we've observed that life appeared almost as soon as the surface cooled enough to form oceans and solid ground. Given that there are billions upon billions of stars in each galaxy, and billions upon billions of galaxies in the universe, the assertion that life is so vanishingly rare that it probably hasn't occurred anywhere else is ... absurd. Based on our understanding of the history of life here, it is fair to say that if we could suddenly take inventory of all the possibilities in our galaxy, we would expect at least 80% to exhibit only single-cell life, and most of the rest to be not much better. But at least a few will have progressed to seriously multi-cellular organisms. Once evolution kicks in, it's a ferocious driving force. Now, you may want to argue that technological intelligence is super-rare. Maybe the commonest "good" environments are water-worlds, and the top of the food chain resembles dolphins or Orca. Maybe some worlds have other physical parameters that will make technological development very difficult, so the top of the land-based food chain can never discover or work with electricity (say). I don't know - and neither does anyone else. But if you wanted to argue that humans are probably the only technologically advanced species in the galaxy, I'd concede that could be a valid opinion (with the only real evidence in its favor being the Fermi paradox). Trying to make the arguments in this book really strains credulity.

NoCoPilot wrote:
We know all our life is DNA-based, so we assume all life everywhere will be DNA-based.

Actually, this one burns my butt. I don't have the expertise to know if there may be any other possibility, but I'm sure curious. There were some stones that came down in India that exhibited some very orderly structures that looked like they might be created by life. The "scientific" analysis was that there was no DNA present, so therefore no life was involved. Say what? Suppose we get a sample of interesting-looking stuff from Mars. Is our analysis going to be "no DNA, so no life"? As Tank Girl said, "Are you sure?". Maybe RNA and DNA are indeed the shit, but I'd like someone to say why.

NoCoPilot wrote:
It's the Star Trek Bias: beings on other planets will be human-shaped, speak English, and maybe have blue skin.  And Captain Kirk will nail 'em all.

And this is just you being silly.
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PostSubject: Re: Book: Rare Earth   Mon Jul 16, 2018 5:04 am

richard09 wrote:
But if you wanted to argue that humans are probably the only technologically advanced species in the galaxy, I'd concede that could be a valid opinion (with the only real evidence in its favor being the Fermi paradox).
And I'll concede your argument (including the Fermi paradox...) is equally valid, given the absence of any data one way or the other.

This discussion has about run its course. We're arguing about angels on the head of a pin.

richard09 wrote:
I think the process you're looking for is called "chemistry".
Except it's more than "chemistry," a lot more. Chemists have been trying mightily, but have not yet figured out how to create RNA in the laboratory. This is still the Big Gap in our understanding of how life began. The Big Gap between organic compounds and life is still the domain of magic, or religion -- not science.

Regarding Martian crystals: probably not life. The environment they came from was not conducive, and -- if life on Earth is the model -- once life takes hold it infects everywhere.
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PostSubject: Re: Book: Rare Earth   Fri Oct 19, 2018 8:28 am

Donald Prothero, in "When Humans Nearly Vanished," wrote:
Once the concepts of neutralism, junk DNA, and the molecular clock had been established in the 1960s and 1970s, increasing numbers of analyses used molecular clock methods to determine the time of divergence of different lineages.  These studies often focused on the DNA of the cell nucleus, which has a relatively slow mutation rate. Then another surprising discovery was made: the mitochondria, the “power plants” of the cells of all animals, which produce energy, have their own, separate DNA. Later, it was established that this DNA is a relic of the days when mitochondria were free-living purple nonsulfur bacteria, which first lived symbiotically within the cells of animals and eventually developed into organelles in the cells. Even more interesting, not only is mitochondrial DNA different from that of the nucleus, but its molecular clock ticks five to 10 times faster, with about 0.02 substitutions per base (or about 1 percent of the total DNA) occurring every million years.  For this reason, it can be used to examine genetic divergences that have happened in the past few thousand to few hundred thousand years, in contrast to the millions of years necessary for similar changes in nuclear DNA.
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