The Man In A Suit - Alien Evolution

[gumboot]

So where do elephants fit into your ideas?

I presume you're talking about the trunk? What about it?

ETA: it seems to me that any species that begins tool use is one which will potentially evolve toward greater tool use, and whatever appendage is used for that tool use can be picked up by natural selection and change over time in such a way that it may become better at that task.

Only where the appendage can be dedicated to tool use. If we take an elephant's nose, for example, it is used for a range of essential activities, including drinking water. This prevents the trunk becoming a dedicated tool device.

Crows, for instance, can make and use tools with their feet and beaks, they are not "bipedal with four limbs", but it's possible over deep time for the crow's beak to evolve into a more adept tool using appendage, were the selection pressures to happen to exist in the right way

Except that, like an elephant's trunk, a bird's beak has other essential uses which prevents it developing into a dedicated tool-user.

It's only once an animal has genuinely spare appendages dedicated to tool use that the animal will benefit from taking time and effort to manufacture tools to carry around with it.

 

[George 152]

While some octopi demonstrate remarkable intelligence, it's still not even remotely close to the sort of intelligence seen in great apes, let alone humans.

All animals other than humans seem to have hit a sort of cognition "ceiling" in their evolutionary path, stopping at what is, by human standards, a very basic level of intelligence.

Octopi certainly benefit from their intelligence, and they would irrefutably benefit enormously from even greater intelligence. Why hasn't it developed?

There seems to have been something special about our evolutionary position that enabled us to break through the ceiling.

If the Octopi lived as long as we do there is no reason as to why their intelligence couldn't match ours.
Dolphins use toys and tools

 

[gumboot]

Well, actually, we're locked into two pairs of limbs because that's what the first land vertebrates had, evolved from the pectoral and pelvic fins of lobe-finned fishes.

My understanding is that the earliest ancestors of tetrapods only had bones in the pectoral fins, not their pelvic fins. Maybe I'm mistaken.

But this limitation only applies to vertebrates on this planet. There's no convincing reason that land animals on another planet would have had to evolve from a vertebrate ancestor with four limbs.

I've explained why; it's a matter of efficiency. A second set of limbs offers a distinct advantage over one pair. A third doesn't offer a significant advantage over two.

Unless you happen to be an insect or a spider. Some arthropods have even more.

They only offer an advantage because they're so small. A high number of legs enables maneuverability in extremely rough terrain (such as walking up walls, etc). To a very small animal such as a spider or insect even relatively flat land is full of obstacles that are enormous relative to the animal (plants, rocks, etc).

 

[SezMe]

Do you have any links or references for that ? (because I don't think it's correct)

I second this question because I, too, don't think it is true. For example, processing of the signals sent from the retinas is done in several different parts of the brain which, in total, comprise about a third of the brain mass.

 

[The Shrike]

It's only once an animal has genuinely spare appendages dedicated to tool use that the animal will benefit from taking time and effort to manufacture tools to carry around with it.

Interesting idea, but how do you define "spare" limbs? I don't have to be using my hands every minute of the day to ensure my survival, so they are spare? How is that different from me not using my feet every minute of the day because I am often sitting down?

In which of the following Hominid genera would you consider the hands to be spare appendages?

Pan
Gorilla
Australopithecus
Homo
Ardipithecus

 

[Turgor]

Only where the appendage can be dedicated to tool use. If we take an elephant's nose, for example, it is used for a range of essential activities, including drinking water. This prevents the trunk becoming a dedicated tool device.

Do you use your hands when you drink water? If not, please describe the method you use to drink water.

 

[theprestige]

Ugh. This thread sums up everything I hate about Pop Evolution: Look at a single case of how things are, invent some plausible Just So Story of why, and promptly conclude that How Things Are is How Things Must Be.

 

[Guybrush Threepwood]

Do you use your hands when you drink water? If not, please describe the method you use to drink water.

He probably lies down by the stream and drinks directly from it, so should be put to death at once.

As for the rest of the OP I suspect alien intelligent life might be so different from us that we spend decades arguing about whether it really is alive or conscious, rather than going straight up to it and shaking hands while marvelling that they have seven fingers.

 

[dlorde]

I second this question because I, too, don't think it is true. For example, processing of the signals sent from the retinas is done in several different parts of the brain which, in total, comprise about a third of the brain mass.

The structural differences between human and other primate brains are relatively small, mainly consisting of greater numbers of cortical neurons. The assertion that the human brain is different in organization to that of any other animal is trivially true, but the difference is not significantly greater than one would expect, given the evolutionary relationships. See the summary to Myth #4 here.

Unless there is some well hidden research, I know of nothing to support McHrozni's assertion about significant differences in processing. If there is some, I'd be really interested to see it.

 

[dlorde]

Interesting idea, but how do you define "spare" limbs?

Quite; and what about the case of various monkeys, where use of a prehensile tail frees up the lower limbs for tasks other than hanging on?

 

[gumboot]

Interesting idea, but how do you define "spare" limbs? I don't have to be using my hands every minute of the day to ensure my survival, so they are spare? How is that different from me not using my feet every minute of the day because I am often sitting down?

The limbs have to be free to be dedicated to tool use, as I said. If the limbs are utilised for locomotion, you can't transport tools long distances, which discourages development of more complex tools.

In which of the following Hominid genera would you consider the hands to be spare appendages?

Pan
Gorilla
Australopithecus
Homo
Ardipithecus

Pan and Gorilla are quadrupeds, Australopithecus and Homo are bipeds, and Ardipithecus is thought to have been something of an intermediate between the two, I believe - with scientists suggesting it was a quadruped in the trees but had altered enough physically that it could travel short distances bipedal.

Or, in other words, only Australopithecus and Homo have spare limbs.

 

[gumboot]

Do you use your hands when you drink water? If not, please describe the method you use to drink water.

I can drink water with one hand, leaving the other free to carry my tools (that actually raises another point, while tool use only requires one limb, making tools requires two).

 

[gumboot]

If the Octopi lived as long as we do there is no reason as to why their intelligence couldn't match ours.

Do you mean an actual octopus, or a theoretical octopus-like creature?

Dolphins use toys and tools

Yes, they do.

 

[quadraginta]

While some octopi demonstrate remarkable intelligence, it's still not even remotely close to the sort of intelligence seen in great apes, let alone humans.

All animals other than humans seem to have hit a sort of cognition "ceiling" in their evolutionary path, stopping at what is, by human standards, a very basic level of intelligence.

Octopi certainly benefit from their intelligence, and they would irrefutably benefit enormously from even greater intelligence. Why hasn't it developed?

There seems to have been something special about our evolutionary position that enabled us to break through the ceiling.

Using homo sapiens is a relatively limited snapshot of evolutionary history to base such broad assumptions upon.

A couple hundred thousand years is an eye-blink to geological history. A very small one. There's an awful lot of hubris involved in assuming our eye-blink is somehow definitive.

 

[Roboramma]

I presume you're talking about the trunk? What about it?




Only where the appendage can be dedicated to tool use. If we take an elephant's nose, for example, it is used for a range of essential activities, including drinking water. This prevents the trunk becoming a dedicated tool device.

People use their hands to drink water too, and don't need to move and drink at the same time, so we (and an elephant) can put down our tools to drink and pick them up again when we leave

As I said, the same applies to an elephant

As to requiring two spare limbs to make tools: that's simply not true, your argument for requiring spare limbs only applies to having a limb to hold the tool during locomotion, to doesn't suggest that an elephant couldn't use it's trunk and feet to make tools (ever seen the video of the crow bending a wire into shape to get stuff out of a jar (something like that)? It uses it's beak to hold the wire and it's feet to help bend it in shape

Except that, like an elephant's trunk, a bird's beak has other essential uses which prevents it developing into a dedicated tool-user.

There's nothing in evolution that suggests an appendage can't be used for multiple purposes: I can use my mouth to eat and breathe, and manipulate tools (and I do)

It's only once an animal has genuinely spare appendages dedicated to tool use that the animal will benefit from taking time and effort to manufacture tools to carry around with it.

Aside from what I said above, you're clearly not considering all the possibilities: what about an animal with a pouch like a kangaroo? It could use it's feet to make and use tools and put them in it's pouch when it's on the move

 

[I Ratant]

One of the classic stories...
http://en.wikipedia.org/wiki/Mission_of_Gravity

 

[Reivax]

You may find this interesting. The idea that a dinosaur may have reached extreme intelligence if they were not wiped out.

 

[Delvo]

Alien life would still have to live with the same laws of physics and chemistry that we have, so evolution can be expected to follow some of the same tracks, especially in cases in which Earth lineages unrelated to each other ended up with similar traits.

Intelligence is useless to a life form that doesn't move around. For that matter, intelligence requires a brain, which is a development of the nervous system, and even THAT doesn't exist in life forms that don't move around. Movement favors bilateral symmetry and cephalization.

Because of a short oxygen supply compared to the atmosphere and a lack of workable building/toolmaking materials, it's not really plausible for a species to get technological if it lives under water. Also, a brain that's going to get technological has to have some minimum size that can't be a whole lot less than ours, because creating lots of complex interactions between neurons requires having lots of neurons to interact. So, let's bring our cephalized, bilaterally symmetrical critter out of the water and onto dry land and make it a size that can carry a suitable brain. Then something interesting happens with the limbs. The more a body is under the influence of gravity, whether because of coming on land or because of being large, the better it is to have a small number of large limbs instead of a large number of small ones. (That's not just a theory but an observation of what has actually happened separately in more than one case.) So a land animal big enough to have anywhere near the kind of brain we're looking for would probably have the minimum number of pairs of limbs it can get away with and still be functional on land. The same basic physical reason why we built devices with three feet or more, it wouldn't be very practical for an animal to have less than three limbs, at least not for animals that are just coming out of the water for the first time: it would be unstable when standing up and draggy if sprawling out. That makes the practical lower limit two pairs instead of one.

Re-orient the body and learn to balance on one pair while using the other pair for something else, and then, *POOF*, you've got what some might call a humanoid alien: two legs, two arms mounted higher up on the body, and a head on top... quite likely even breathing and eating through the same opening like us because of another established rule we know of in nature that old openings get hijacked for new functions more often/easily than new openings get created. Also, in a critter on the ground, eyes belong on top, so they'll probably be higher than the mouth even after the descendants are standing up straight later.

What that doesn't give any reason to expect the aliens to have in common with us is any of our particular proportions (ratios of sizes between one part and another), or ears on the sides of the head, or a nose like ours.

 

[GraculusTheGreenBird]

Well, except the assumption is that oxygen is needed for life underwater, which is pretty specific to metabolism of life on earth, and not even all earth life. Other planets could have completely different forms of life, completely different biology underwater, and plenty of materials available for tool making.

We also still have an anthropomorphic assumption that lighter fluids like gas is somehow necessary for life, which I dont think is true. It makes just as much sense for example, to think of an alien spacecraft filled with a dense liquid as it does with air, they are both self contained environments needed to protect the life from vacuum when travelling through space.

And regarding the earlier comment that animals will larger number of legs tend to be smaller, as their extra legs help them navigate more bumpy terrain, I don't really buy that. My understanding was that arthropods seem to have reached a size limit due to their respiration method, rather than anything else. There have been plenty of huge insects in the past, and we have large spiders and centipedes now.

Also, why do we assume that intelligence has to be embodied in a physically large form, or a size similar to ours? It seems that primates brains needed to reach a particular size to enable our intelligence to flourish, but under a different planetary biology, that size might be completely different.

So why not a hand size intelligent insect or fish equivalent, or organisms based around sets of three limbs? Seems just as likely to me.

 

[Delvo]

Well, actually, we're locked into two pairs of limbs because that's what the first land vertebrates had, evolved from the pectoral and pelvic fins of lobe-finned fishes.

My understanding is that the earliest ancestors of tetrapods only had bones in the pectoral fins, not their pelvic fins. Maybe I'm mistaken.

It was both. That's where our pelvises and legs came from. There's also a third pair of bony, muscular fins in at least some, behind the pelvic fins, called anal fins. (I'm skipping the lower caudal fins here because of structural differences from the three pairs.) But fish with all three pairs did not colonize land, or at least not with competitive success.

Similarly, in arthropods, the group that's most successful on land is the one with the fewest limbs (6), the second-most successful group on land has the second-fewest (8), and the third-most successful group on land, which is actually mostly found in water or going back & forth between land and water, has the third-fewest (10+). Of the two groups with the most limbs, retaining them on every segment, the one that came onto land has been the arthropods' least numerous, least diverse, and most ecologically restricted group (centipedes & millipedes), while the one that stayed in the water was the opposite of that until a mass extinction (trilobites).

The only molluscs to colonize land are molluscs with no limbs (snails & slugs, no octopuses or squid or nautiluses).

Among animals on land, even if you exclude vertebrates and just stick to arthropods, there's also an inverse connection between size and limb count, although it's looser than the above pattern.

The general rule is that the burden of supporting & propelling the body is inversely related to limb count; more burden calls for fewer limbs (at least down to 4 because 2 is a special case because it's less than the minimum for the tripod effect), whether the added burden happens due to coming out of the water or due to growing large. The reasons have to do with proportional surface area touching the ground and proportional limb size.

There's no convincing reason that land animals on another planet would have had to evolve from a vertebrate ancestor with four limbs.

I don't recall seeing it said that anything has to happen here. But there are good reasons to expect some outcomes be be more likely, and more common in the real universe, than others.

I presume you're talking about the trunk? What about it?

... If we take an elephant's nose, for example, it is used for a range of essential activities, including drinking water. This prevents the trunk becoming a dedicated tool device.

When we started using our hands for tools, we were also still using them for locomotion, maybe not when on the ground, but at least in trees. They were never spare. Their use just shifted, including a time that they were used for both functions. Tools may even have been what caused them to be diverted away from locomotion. Similarly, if we are to postulate something like alien elephants using their trunks (and presumably also tusks) for tools, then it makes sense to postulate that those would also end up serving two or more purposes for a while, possibly later to be followed by dropping the non-tool-related functions if there's a conflict.