Friar Broccoli wrote:

On Aug 14, 1:06 am, John Harshman <jharshman.diespam...@pacbell.net>
wrote:

Friar Broccoli wrote:

On Aug 13, 8:38 pm, John Harshman <jharshman.diespam...@pacbell.net>
wrote:

K_h wrote:

Fermi's paradox suggests that there are little or no other intelligent
civilizations within the Milky Way galaxy.  On the other hand, intelligent
life should exist on a substantial fraction of planets with life because
natural selection broadly increases intelligence with time.

 .

Does it? News to me. What evidence do you have that this is the case?

 .

There has been an increase in the intelligence of a broad range of
species on earth with time.

Has there? What broad range, exactly? And if natural selection
broadly increased intelligence with time, we would expect all
species to be undergoing this push, wouldn't we?

 I don't see how this follows at all.  I would expect different
 species to adopt widely differing strategies depending on
 circumstances.  In plants, intelligence would be a complete
 waste of resources.  Others like Starfish and Jellyfish have
 used other strategies to ensure they can navigate and persist in
 their environments without needing intelligence.

Exactly. So the blanket statement that there's been an increase in a broad range of species, because natural selection selects for intelligence, is wrong. Natural selection occasionally selects for greater intelligence, sometimes for lesser. There is no general pattern.

 Brains are one method for allowing adaptive behaviour which in
 turn allows creatures to harvest an often wide range of
 resources, while avoiding a wider range of dangers in an
 increasingly complex environment. (Not all species need or use
 this strategy, just as not all use hard parts, or get really
 big or whatever.)

However, there is no general striving, even among those with brains, toward human-level intelligence. That's my point.

Yet we see that brains exist only in a small subset of species
within one restricted clade (Metazoa), and that, depending on
how you define the word, complex brains exist only in a small
subset of those (which I will choose to interpret here as
Cephalopoda and Gnathostomata), and that particular complex
ones exist only in a small subset of those (Aves and
Mammalia), and that only one species has human-level
intelligence, and from observing usenet, that only rarely.

It's hard to consider this a general trend. Similar results
could be achieved by random diffusion starting at a barrier,
with a great deal of variance in the intelligence of the
extreme tail.

 But you don't appear to be arguing a diffusion model.  When we
 had this same discussion (with respect to the broader measure
 complexity - of which intelligence is a subset) and I pointed
 out that trees had added complexity; you asserted that that
 increase had ended in the Permian.

 (that discussion was here:
 http://groups.google.com/group/talk.origins/msg/dd0e90c2d77de083)

 So you appear to be arguing that such characteristics pop (rather
 slowly) into existence and then remain static for the rest of
 time.  Your entire model bears an eerie similarity to an Old
 Earth Creationist model.  Are Pagano, Martinez, and Pitman
 starting to wear you down?

I agree that the random diffusion model is only a first approximation, and it doesn't really work that way. Sometimes there are big innovations, though not at any predictable rate; perhaps "chaotic" is a better model than "random".

 And even if you are arguing a diffusion model it plainly
 doesn't fit some obvious facts:

 Assuming that brain size as shown in the fossil record is an
 adequate surrogate for intelligence (admittedly it is far from
 perfect):

 If we consider the starting gate for the dinosaurs was the
 beginning of the Triassic and the gate for modern mammals the
 beginning of the Paleocene then mammals today are
 proportionately at the Middle Jurassic, but the brain to body
 ratio of the average large mammal vastly exceeds anything the
 dinosaurs produced then or at any other time in their history.
 And with the exception of the Ratites we don't (as far as I
 know) see any large small-brained reptile-like land animals
 competing with us.

 Furthermore, our own recent evolutionary history in no way
 matches a diffusion model.  Something caused a spike in primate
 brain size about 15 million years ago, and then we saw an even
 more dramatic spike during the last 3 million years.  I know a
 few theories about what drove the latter spike, and while I
 don't have the slightest idea, which, if any of them are "true"
 it is clear from the abrupt change in slope of the curve that
 something was DRIVING that increase.

All more or less true. There was a big increase in mean mammal brain sizes (controlled for body size) sometime in the Oligocene, if I remember, usually interpreted as an arms race between predators and prey. And there have been several episodes of brain size increase in various primates. Obviously it's not really diffusion, though it resembles diffusion in gross characteristics. Even in diffusion, if you want to predict what particles will be in the right tail tomorrow, which will be further right than the right tail today, you say that some of the particles in the right tail today are going to make up that new right tail. The animals with the biggest brains today are likely to be those with the biggest brains tomorrow, and some may be bigger than they are today. But in fact the impetus toward bigger brains, even in primates, seems a rare thing, because the conditions favoring human-level intelligence are rare, even in primates.

 Now returning to the specifics of which groups have done well
 in the brain game, it appears to me that we have enough data
 points to show an increase in brain size with time:

1- Metazoa/multicellars - begin with no nervous system
    Obviously intelligence depends on the development of
    multicellularity but that seems to be an inevitable outcome
    of evolution given enough time.  You said further down that
    it occurred at least five times.

"Inevitable" is too strong a word. For one thing, on earth it seems to have crucially depended on the evolution of eukaryotes, which of course happened only once, and after several billion years of evolution. It may be that the most probable outcome is single-celled prokaryotes forever.

 Brain development began in three separate lines of multicellular
 animal:

2a - Cephalopoda (squids, octopuses)
2b - Gnathostomata (jawed vertebrates)
2c - Arthropod (crabs and insects)

Why 2c? They have no more complex brains than most non-gnathostomes. There seems to be a level of brain power beyond which it's unlikely to go, and the ancestral bilaterian may have had that sort of brain.

 Your paragraph above mentions aves (together with mammalia) as
 achieving exceptional levels of intelligence, but I know of no
 work suggesting that birds are smarter than crocodiles, or
 sharks (which have a brain/body ratio similar to mammals), or
 octopus.

No? My understanding is that modern birds have unusually large brain/body ratios for archosaurs. Sharks are another possible addition to the list; hadn't considered them.

 So in my book we see significant advances in intelligence in
 at least five group lines:

3a - Cephalopoda(squids, octopuses)

 And within Gnathostomata:
3b - Sauropsida/reptiles (Crocodiles)
3c - Chondrichthyes (Sharks)
3d - Aves (birds)
3e - Mammals (John Harshman)

Aren't 3b and 3d the same instance, even if you accept 3d? Now in fact I'd say that within gnathostomes we have no particular increases in brain power between the root and Sauropsida. So we should leave 3b out. Still 4, though.

 Since Sauropsida began evolving about 300 million years ago and
 Aves about 150 million years ago and modern mammals began
 seriously diversifying 65 million years ago, we know that the
 enhancement of intelligence (or its surrogate - brain size) has
 been more or less continuous since the Cambrian although
 probably not in all the reference groups over the entire
 period.

I would deny that claim. There is no particular increase in brain size in Sauropsida.

 So it seems to me that we have passable physical and
 inferential evidence for a steady increase in brain size and
 intelligence over time, as well as a plausible model
 (adaptation to an increasingly complex and competitive
 environment) to explain why it occurred.

I don't think so. We have a few episodes of brain size increase in a few groups, some of those episodes building on previous episodes. We find ourselves in a group that has gone through more such episodes than any other group, but it's always a small subset of each group that undergoes a new episode, with the possible exception of the Oligocene arms race in mammals.

 Once again, I will ask you for evidence that the self-evident
 and expected pattern is not (more or less) the one I am
 describing.  Can you do any better than:

   "I'm wary of claims that anything is self-evident, and
    attempts to push the burden of proof onto the negative."

Sure. If the pattern were of a general increase in brain size in animals in response to an environment of increasing complexity, we would expect such increases to be broadly distributed over most or all groups. Instead we get occasional bumps in a few groups. (And I see no sign that arthropods are more clever now than in the Cambrian.) We certainly see no trend, even in the groups that have received these bumps, toward human-level intelligence.

It's very hard to generalize from a single example, which is what all these probability calculations have to do. And clearly the diffusion model is wrong in detail. We have two main departures: pre-adaptation and incumbency.

Some innovations are impossible except in a background of particular, previous innovations. So we can't talk about intelligence until we have a multicellular animal with a nervous system. Human-level intelligence must arise through a series of adaptations of varying probability. We couldn't possibly have expected it to happen until the evolution of bilaterians. Which happened only once, and so may be considered unlikely by the only guide we have. After that crucial event, it took another half billion years or more to get us; again, doesn't seem a likely thing.

Incumbency would argue in the opposite direction. Perhaps the presence of a group with a particular innovation fills up that slot and prevents any other group from achieving it. This certainly happens sometimes. Maybe the otters are just raring to start chipping stone tools, but we keep them from it. This too seems unlikely, since we are only a recent development, and otters have had plenty of time to try it before we showed up. Hey, we've only been in the Americas for 15,000 years or so. Where are the American intelligent species? So incumbency, in this case, doesn't seem to be a credible factor.