Some say the world will end in fire, Some say in ice

September 18, 2009 4:45 AM

If there was an extinction event that wiped out a significant amount of species on Earth, including humanity, would there be enough time on our planet's timescale for complex, conscious beings to evolve again and escape the Sun's eventual stellar evolution into a red giant?

I came across two papers [1] that when coalesced make me think that there won't be enough time, but I'm looking for other sources (books, papers, websites) that tie together several scientific views (astronomical, biological, etc.) of the fate of life on Earth and the Earth itself. Bonus points if you provide an explanation or information that contradicts what I've read so far. Thanks.

[1] The first paper states that in approximately one billion years the oceans will evaporate and the Earth will be unliveable. So, one billion years doesn't seem like much time compared to the 3 to 4 billion years it took life to evolve (again, assuming the unlikely chance of an extinction event). The second paper states that intelligent life is an evolutionary aberration, and unlikely to happen again.

posted by ollyollyoxenfree to science & nature (10 comments total)

I suppose it would depend what scale the 'extinction event' was. If most life died out then the Earth would likely settle into a long bacterial era. Perhaps an extinction event on this scale would leave few valuble eco-niches in its aftermath. A smaller scale event, that perhaps just manage to kill off all humans, might leave larger niches open for life to fill.

What I find more interesting would be the consequences of an extinction event if, say, a few humans did manage to cling on. Perhaps a thousand humans in a remote mountainous region managed to irk out an existence for the thousand years or so after the catastrophe. The Earth would be theirs for the taking. Our genes would expand in ways they never will given the restrictions our current environment places on us. Give that thousand strong human sub-group a billion years and they might very well become humans 2.0.

It's an odd question because of how much it leaves out. What is intelligent life anyway? Do we class that on how much we can do or how well at surviving we are? I'd rather be a cockroach or a worm when the asteroid impacts. Life for them has a much more open, and flexible, horizon.
posted by 0bvious at 5:23 AM on September 18

The big dinosaur extinction event was about 65 million years ago wiped out a significant number of species. At the time our ancestors were small animals. 500 million years ago our ancestors were worms. So unless the extinction event wipes out everything more complicated than a worm, it would seem to be possible for intelligent species to evolve to a technologically advanced state in under a billion years.
posted by justkevin at 5:25 AM on September 18 [3 favorites]

You might see if those papers that concern you are cited, each citation being either a refutation or implicitly an acceptance.

I think it's generally felt that human intelligence is mostly a feature of sexual selection, like a peacock tail. Yes, peacocks are quite unique, but most all birds have tails that are suboptimal for flight, due to similar pressures. But otoh you might not get birds either after a serious extinction. So I doubt you can meaningfully discuss this without first building some solid model for various critical steps in human evolution.

Btw, I don't think an extinction event is actually all that unlikely, although simple eukaryotes might survive most strikes. Your time might be better & more profitably spent doing scientific research or engineering. Carbon nanotubes might be helpful for building space elevators. etc.
posted by jeffburdges at 5:28 AM on September 18

Intelligent life isn't just "a matter of time" or something like that. It could happen really rapidly, or it could fail to happen in 100 000 billion years on a planet with life and a sun that lasts that long. There are no endpoints in evolution.
posted by carmen at 6:10 AM on September 18

Intelligent life may have taken 3.5 billion years to evolve from simple bacteria but given an extinction of 90% of life it would still be likely that another intelligent species would evolve much sooner than that. Much of the time period of the past 3.5 billion years was harsh and tumultuous. Earth has "mellowed" out since then with a relatively more stable environment. Also given that more complex life forms survive the extinction then it is very likely to get another intelligent life-form before doomsday.
posted by JJ86 at 6:17 AM on September 18

I'd say depending on your definition of "intelligent," it's quite likely. Culture and capacity for tool use appears to have evolved independently in at least two unrelated animal families in the last 65 million years.

But there is a big fallacy behind this question and some of the answers that evolution favors more intelligence and more complexity. Sometimes it does, sometimes it doesn't.
posted by KirkJobSluder at 6:45 AM on September 18

Also, by most estimates, we are in the middle of a mass extinction event that got rolling during towards the end of the last glacial maximum.
posted by KirkJobSluder at 6:48 AM on September 18

The question that I think we must ask now is, "Will humanity be part of this mass extinction event?"

Inquiring minds, indeed.

Cheers.
posted by PROD_TPSL at 7:17 AM on September 18

Piling guess upon guess really just makes worse guesses. We've got the lifetime of the sun pretty well nailed down but all else are just huge contingencies. There really aren't any useful data that can be brought to bear on this question.

There also seems to be an implicit assumption that you need intelligence as we construe it as necessary to extra-solar travel. To put this in Gary Larson terms, the fish must consider insects to be quite intelligent to not only leave the water but fly through the air, too. But this also assumes that there is reproductive profit to be gained from leaving a dying star, but evolution is not predictive and the energetic costs of interstellar travel are so great that it probably is an "unreachable realm of design space" as Dawkins might say. Put more directly, it is a particularly human vanity that anything should go to such extreme efforts to preserve its descendants against a threat that will be eons in the happening.

Your question also seems to imply that human-like intelligence should or should want to get of the earth which the universe neither requires nor desires; it also neglects the highly-intelligent slime molds on Klatu-5 which are not in any looming danger of their sun dying anytime soon.

I'm guessing what underlies your question is the futurist desire for a DNA diaspora that will allow earth's descendants to see the universe out to its eventual heat death. It is a nice - if provincial - concept, but the universe is pretty indifferent to the idea. I'd put my money on the robots we'll build in the next millennium as having the best chance of making it off-world. Maybe they'll accidentally carry some spores on them.

(Yes, I have probably stepped outside the bounds of your question, but the question was pretty unbounded to begin with.)
posted by fydfyd at 7:21 AM on September 18

Would there be enough time for sentience to evolve again? Probably.

Would they have the resources to escape Sol's tertiary phase? Probably not; we have done most of the fossil fuel and mineral extraction already. If we don't make it off-world, no terrestrial sentient species will.
posted by infinitewindow at 7:32 AM on September 18