On Thursday, September 27, 2018 at 2:36:27 PM UTC-6, Chris L Peterson wrote:

On Thu, 27 Sep 2018 13:17:48 -0700 (PDT), Gary Harnagel
wrote:

On Thursday, September 27, 2018 at 8:04:27 AM UTC-6, Chris L Peterson wrote:

On Thu, 27 Sep 2018 05:27:17 -0700 (PDT), Gary Harnagel
wrote:

I suspect that ALL life will have the same DNA.

That seems unlikely. We have created alternate forms of DNA in the
lab, using different bases than A, G, T, C, and U. And which code
differently. I can believe we might see similar genetic chemistry, but
many different bases and coding.

That depends on what one's assumptions are.

I'm making no assumptions.

Of COURSE you are, and so am I.

Only pointing out, as a matter of fact, that there are other nucleic acid
chemistries possible. The details of our particular genetic system developed
out of evolutionary processes.

But WHERE did those processes occur?

It seems extremely unlikely that the same one would develop even under
identical conditions. Similar, sure. Most life will probably be based
on the same basic chemistry. But the details are likely to be very
different.

ONLY if life actually developed independently here.

Some guesses are better than others. I think it's very arrogant to
believe that nobody's out there, and it's even more arrogant to believe
they haven't been around longer than we have.

Life, yes. Technological life, maybe no. We appear on the verge of
destroying ourselves, and that may be the norm for technological
species. They may not get much older than us.

There's always a distribution when you have a "norm" and all that's
necessary is a survivor out in the sunny side of the bell curve.
Given the age of our galaxy at nine billion years (and it has
incorporated stars far older than that - there is a red dwarf only
150 LY away that is estimated to be 14 billion years old). So that
one survivor can spread its DNA over the whole galaxy in a few million
years.

Life has been present on Earth for 3.5 billion years. It only became
complex multicellular life in the last 600 million, and a species
capable of becoming technological only developed in the last 2
million. And on average, species only survive for a few million years
before they go extinct.

You're comparing humans with nonhuman species. That may be a BIG fallacy.

So even if life is common (which I think likely), technological life may
be very rare.

Rare, yes, but nonexistent, no.

And then we need to consider why it would even want to spread itself over
the galaxy,

“The universe is a pretty big place. If it's just us, seems like an awful
waste of space.” -- Carl Sagan

even assuming it somehow survived its own ability to control nature.

Not a big assumption considering the millions of suitable planets.