beausoleil

One point often raised is that eyes have been developed many times in the fossil record, whereas human-style intelligence has occurred only once. This is taken as evidence that development of intelligence is not favoured in itself but requires an unusual combination of other factors (capacity for speech of some sort, dexterity, social organisation) before it instills a competitive advantage. I have read that, in general, there doesn't seem to be any tendency towards larger brains as creatures evolve.

If the author is 'confusing' difficult with unlikely (can't see I understand where the problem is with this in the context, actually). he seems to me to be in good company. It's become almost a truism in the astrobiology community that life must be likely to arise in circumstances similar to the early Earth because in the geological record it seems to have arisen quite quickly after the end of the cataclysm.

Jayhawker Soule

It strikes me that few things are as tenuous as something which is "almost a truism in the astrobiology community". I still vote with Mayr. If asked to guess, I would guess that life is ubiguitous and intelligent life inordinantly rare.

beausoleil

I can think of lots of things more tenuous, actually, since astrobiology is now a well defined research area. Not that I'm here to defend it, particularly.

As an example, I don't think I've read a discussion of the Drake equation recently which doesn't invoke the argument that life arose quickly on the Earth in support of the idea that life will be ubiquitous where the conditions are similar.

I think the argument that, where a species has the prerequisites for development of intelligence, intelligence will arise quickly, is analogous to that argument outlined above linking the speed of life's origin to its likelihood. I wondered if someone would like to expand on what the problem is. It seems quite reasonable to me to argue that something that happened in a relatively short amount of time is relatively likely to happen in similar circumstances. For instance, is the argument that if life hadn't got started quickly we wouldn't be here to study it's origin?

In fact I'm not in disagreement with what you say about the relative likelihoods of life and intelligence, though I think the evidence is more entangled than people generally accept.

Later - This is what I was hoping to see the reasoning behind:

"This seems like bad science and worse logic. It only begins to make sense if you view evolution as goal-seeking."

[ June 21, 2002: Message edited by: beausoleil ]</p>

ishalon

there's other alternatives...

ishalon

since someone mentioned eyes earlier; i read somewhere about how eyes appeared to have evolved separately in several areas... does anyone know examples of these?

[edit] i find it very unlikely that all eyes would evolve in twos, and with the same basic structure though.

[ June 20, 2002: Message edited by: ishalon ]</p>

elwoodblues

Get thee some Dawkins. It'll do you a world of good.

One of the last sane

Sphenodon punctatus has three eyes, although one is covered in skin, and some early reptilian fossils show the same characteristic.

ishalon

probably, ive just had limited time recently. but now... SUMMER

What type of animal is sphenodon punctatus? interesting, though...

Queen of Swords

Regarding eyes, check out Wayne Barlowe's Expedition for a description of (hypothetical alien) creatures who have evolved without eyes.

tronvillain

While basic life may be relatively common given the correct conditions, it seems likely that complex life is extremely rare and intelligent life even more rare. Once you have intelligent life, what are the chances of developing a civilization capable of sending significant signals or proves out into the galaxy?

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