"Today's Spiral Galaxies Were Once the Ugly Ducklings"Short version of the article: There were a whole lot more "peculiar" galaxies 6,000,000,000 years ago than there are now. Right around that time, apparently, something happened and the universe started having a whole bunch of spiral galaxies like the one we're in.
Space.com (February 8, 2010)
"Beautiful spiral galaxies grew out of odd shapes that astronomers say were the ugly ducklings of the early universe.
"It's long been assumed that galaxies grow over time, and shapes change. But the main construction phase for many modern galaxies was thought to have occurred close to the beginning of time, the first few billion years after the theoretical Big Bang 13.7 billion years ago.
"Contrary to this conventional view, nearly half of the spiral galaxies of today, like our Milky Way, had peculiar shapes just 6 billion years ago — more recently than had been thought, the study found.
"If confirmed, the finding highlights the importance to many galaxies of collisions and mergers in the recent past. It also provides clues for the unique status of our own galaxy, the Milky Way, researchers said in a statement...."
"...Although our own galaxy is a spiral galaxy, it seems to have been spared much of the drama; its formation history has been rather quiet and it has avoided violent collisions in astronomically recent times. However, the large Andromeda Galaxy from our neighbourhood has not been so lucky and fits well into the 'spiral rebuilding' scenario. Researchers continue to seek explanations for this."
Except that ours seems to have had less of the violent activity that normally happened.
By coincidence(?), our sun and Earth formed roughly 4,500,000,000 years back - after the spiral-making events had started.
Maybe it really was a coincidence, with no cause-effect linkage. Or, maybe (really, at our current level of ignorance, this is all pretty much speculation) the universe hadn't gone though the processes it takes for sticky stuff on a wet ball of metal and rock to grow from things wriggling in tidal basins to us - until fairly recently.
With a 1,500,000,000 year lag time, there'd still be room for some seriously old races to be around.
Who knows, maybe that fellow in the magazine was right: and we haven't met E.T. because everybody dies off. Right after reaching the awful, terrible, wasteful and (here comes a frightfully important word) unsustainable level we awful, terrible, wasteful humans are at.
I'm not all that worried, myself. But then, I'm aware that human beings stopped being "sustainable" on Earth when some maniac got the idea of poking seeds in the ground and waiting for them to grow into plants we can eat.
The way I figure it, we're at least 1,000 times over the absolute maximum sustainable limit of this planet. That's assuming that homo sapiens sapiens is strictly and only an opportunistic omnivore, with adults weighing somewhere between a hundred and a hundred and fifty pounds.
Anyway: That article on galactic evolution was interesting.