Marduk

"A thought occurs to me: what sort of signal would aliens have to be sending out for SETI to pick it up? "

A very strong intentional one aimed in our direction in a certain frequency band, no chance of picking up Alien TV or radio signals.
"Now Live from Onxyz Super Blrzxt! *^#^@ Radio! all music all the time!"

Jayhawker Soule

It happened once - I know of no evidence of Cretacious engineering or Triassic art. That it "happened in a relatively short amount of time" is, it seems to me (1) subjective, and (2) irrelevant. The very same thing might be said of the platypus.

beausoleil

Seems to me you're missing the point of my question.

Firstly, the relevant timescales for the origin of life in the context of the Drake equation are obviously determined by the rates at which physical conditions on planets change. For instance, the Earth looks capable of supporting liquid water for 5-6 Ga at least. In this context, the evidence for life within at most 100 Ma of the end of the lunar cataclysm suggests it emerged quickly. Scientists argue from this that, given appropriate circumstances, life is quite likely to emerge on a timescale short in the context of a planet's existence.

Your comment about human emergence from hominids suggested you had grounds for not accepting such reasoning. I wondered what they were.

Jayhawker Soule

Perhaps. Or, perhaps I'm simple unwilling to accept the burden of proof for your existential claim, i.e., the claim that the likelihood of the evolution of intelligent life is somehow proven by the emergence of simple lifeforms.

I stated earlier: "I would guess that life is ubiguitous and intelligent life inordinantly rare." Obviously, I take no issue with the suggestion that "life is quite likely to emerge on a timescale short in the context of a planet's existence".

What was the reasoning given for asserting that intelligent species are the likely result or the intended consequence of this unbiquity of life? The planet apparently had a very bad day about 65MY ago. Had that not occurred, who or what do think would be conversing on the web?

beausoleil

Here's your original post

I think we're clearly talking at cross purposes. The quote you've selected from the link only says there is a significant chance that humanoid apes will evolve into humans (or some equivalent process with other pre-intelligent species) based on the fact that it happened 'quickly'. You then say this is bad science and poor logic. But your most recent post seems to be talking about the likelihood of intelligent life arising from primitive life, which is something completely different. The link in question also highlights the development of precursors to intelligent life (bacteria -> humanoid apes) as the rate limiting factor in the development of intelligence. So it seems to me your criticism is unjustified.

The whole point of the article, in fact most scientific discussions of Fermi's paradox, is to discuss why intelligent aliens or their probes aren't here. Is the hurdle something we already cleared or is there some regularly occurring consequence of intelligent life's developing that we still have to face (massive wars, environmental disaster and so on). Or are creatures smart enough to colonise the galaxy also smart enough to see some hidden disadvantage we don't yet perceive?

"It seems more likely that an implausible evolutionary jump (or possibly the emergence of life in the first place, if Mars life turn out to be a chimera) could account for the ten or twenty orders of magnitude of improbability that need to be explained." as the author says.

Jeremy Pallant

One other issue with regard to alien civilisations is a matter of timing. This planet has suffered asteroid impacts that have essentially reset the evolutionary clock. Suppose the dinosaurs hadn't been wiped out 65 million years ago. They might have developed human-level intelligence. Perhaps if they had, we might have communicated with alien species far, far earlier. Miss that opportunity by a few million years, the theoretical alien civilisation might have died out, and we humans, many millions of years later would never know that another sentient species existed.

In other words, it is entirely possible that many alien civilisations might have evolved, even in this galaxy, but because that evolution took place earlier or later with respect to our civilisation, it is entirely possible that we would never know about them. Of course, if a space-going civilisation evolved a few million years earlier than ours, and is now undetectable, that would imply that civilisations do eventually self-destruct; go extinct. We will not know, of course, until we get out there and find the evidence of their existence.

On the other hand, we humans could be the first sentient species to arise in the universe. I have a very rudimentry understanding of stellar evolution, so bear with the mistakes I will inevitably make over the next few sentences.

As I understand it, all the elements in our solar system were birthed in stars. The earliest stars could not have produced these elements, but later generations could have. Based on this limited comprehension of mine, it is my understanding that our solar system, with its elements neccessary for life, developed as soon as was theoretically possible. So, we could be the first sentient species in the universe.

Now, feel free to rip me apart.

HomerOfBorg

They probably exist somewhere but I'm speculating that we and they are very rare due to the inhospitable nature of the universe. As has been stated, I suspect life's bell gets rung a little too often (astronomically speaking):


<a href="http://news.bbc.co.uk/hi/english/sci/tech/newsid_1975000/1975354.stm" target="_blank">Cosmic catastrophe 'a certainty'</a>

Jayhawker Soule

The criticism may well be unjustified. If so, I apologize - I'm certainly no expert when it comes to any of this stuff.

I believe what the author says about 'precursor' is that "the situation is more undecided". I certainly cannot argue with this. But, what this means, is that everything which follows is equally undecided. It's as if we were attempting a meaningful discussion about your ability to plant the flag properly at the peak of Mt. Everest while noting that your ability to get to the peak in the first place is "more undecided".

The author says: The author's 1st stage is "more undecided", while, presumably, the 2nd stage is not only 'less undecided", but easy. What determined the partition between these two stages? Why start with erectus and 2MYA? The earliest known hominid, Ardipithecus ramidus dates to 4.5MYA, and I suspect that this date will be pushed back with new discoveries. How much more or less "undecided", how much less or more "easy", is the path from ramidus to the paleontologists who study him? Shall we declare the path from ramidus to erectus "easy ...because it took such a short time"?

Forgive the play on words, but what on earth does time-span have to do with ease or probability? Every case of speciation, every case of descent with modification, took place in a "mere twinkle" of time given the age of the earth. The author seems to present us with a kind of Zeno's paradox run in reverse: "Moving from 'Z' to 'Y' must be easy because it happened so quickly, and moving from 'Y' to 'X' must be easy because it happened so quickly, and ..., and moving from 'B' to 'A' must be easy because it happened so quickly, therefore ..."

There is, of course, a problem with this analogy, in that ever step is conditioned by its history. I do not, however, believe this defect makes my concerns any less compelling. How many hominid species have been identified? How are they distributed over time? How does their appearance correlate with weather patterns? What other causal changes were taking place in their respective environments? How did the various species interreact? There is a book by Stanley titled "Children of the Ice Age" which links the advent of man with the physical uplifting of Panama. I haven't a clue if Stanley is correct, but your author's contention that 'it is highly probably that it will happen again because it happened once very quickly' makes sense to me only if you posit a goal-seeking evolution, i.e.: homo sapien sapien is meant to be, and will happen, if only the process is given sufficient time. Again ...
... is, to the best of my knowledge, faulty logic applied to a one-time event (unless, of course, you rid the term "easy" of its implication of "likely" -- an act which would render the statement irrelevant).

[ June 23, 2002: Message edited by: ReasonableDoubt ]</p>

braces_for_impact

The original intent of this thread seemed to me to be the compatability between atheism and the possibility of life on other planets. (Or, more correctly in my mind, acceptance of evolution and the possibilty of life on other planets.)

In any case, yes, if evolution and abiogenesis were true we would expect to find life on other planets. How rare intelligent life may be is another speculation. How compatable is theism with life on other planets? How about christianity in particular? What would the pope say about aliens landing on earth? Or Jerry Falwell for that matter? (Talk about making a bad impression, I could just see those missionaries now!)

As someone else suggested, seems like an awful waste of space for a god to make an entire universe for little 'ol us. On the other hand in regards to christianity, does Jesus have to die on every planet with intelligent life on it? (I can see that getting rather old REAL fast) or do alien civilisations somehow know of this "ultimate sacrifice" Jesus made here in this little corner of the galaxy? Any thoughts?

beausoleil

I think the the author's idea is that the development of intelligence conveys an advantage (and so is favoured) only in highly specialised circumstances. For instance, the precursor species needs to have the potential to develop precise communication skills and good digits to manipulate tools. Of course there are also more fundamental things like the development of complex cells allowing complex organisms, perhaps oxygen breathing for efficient energy utilisation.

His model (and other people's) is that, once these properties or potential properties are assembled in one species, selection will generate an intelligent descendant on a short timescale. The assembly, however, relies on a number of 'bottlenecks' - chance assemblages of properties that are statistically unlikely even over geological time. The evidence advanced elsewhere for such a model is that, apart from our line, evidence for increasing brain to body-mass ratios in the record is absent while other features, such as eyes, have arisen many times. In essence that's why he makes the distinction he does - he's saying that the 'bottlenecks' - the statistical 'waiting points' - are before some ancestor of modern humans.

The Fermi 'paradox' suggests that intelligent life doesn't usually get to the state of building Von Neumann probes within the time during which a planet can support life. In contrast, our planet has got to us well within that timescale. So it seems our planet is atypical and most do not pass the bottlenecks as fast as evolution did here. Either that or there are bottlenecks in the future we have yet to face.

Or look at it another way - for us to be here our planet's evolution made some developments much faster than was likely by chance alone, but there's no reason to think those advances were in the development of us from other primates. (Note that there's no assertion that evolution was directed or guided here - our presence 'selects' a record in which those advances were made quickly from those of all the available planets.) People often single out the evolution of eukaryotes as one, for instance.