What type of biological life will more than likely be found on other planets?

Because I choose to do it step by step.

I tend to highly agree with this statement, but as I thought about it more I am not so sure. My thoughts are that we do not know what we don't know. If the life evolved on a planet similar to ours I think this is very likely.

Even though its a bit of a misnomer, I added that "highly" evolved qualifier to supply some implicit assumptions that we're dealing with an environment that would foster a lot of change in the inhabiting species. It'd be a bland discussion to consider a planet where only simple bacteria evolved. I assumed we're more along the Star Trek line here where we're talking about species that would be interesting to us as humanoids.

But there is the rub. We have no idea of what alien life could be like. Is bilateral symmetry a result of unique circumstances in the evolution of life on this planet?

I think that bilateral symmetry did evoke an important advantage that has been utelized ever sense it emerged. I don't think there are any species that subsequently lost it. And, again considering things that would be interesting to us as humanoids, almost all of the Animals exhibit bilateral symmetry.

I think there is a very high likelihood that other life out there exhibits bilateral symmetry, but am very open to the idea that we may find something that utterly astounds us and falls completely outside of any of our expectations.

See, I just don't thing we find some really wacky alien that lacked any symmetry and was just totally bizarre in that regard (at least, talking about something on par with the Animal clade). I'd expect symmetry.

To put it simply, with the knowledge we have I think you are correct. It is what we don't know that is the wild card.

Sure, but what kind of enviroment could exist that would favor assymetry and still push towards something like Animals?

See, I just don't thing we find some really wacky alien that lacked any symmetry and was just totally bizarre in that regard (at least, talking about something on par with the Animal clade). I'd expect symmetry.

Don't you think this is because of the bias you have from the world you live on and the life you see around you? I would expect symmetry also because that is how we know and expect life to be, but would not be surprised if there was life that did not exhibit bilateral symmetry.

Sure, but what kind of enviroment could exist that would favor assymetry and still push towards something like Animals?

That is my point. We do not know what we don't know. Until we actually have contact with alien life, we have no idea what the circumstances are of its evolution. We can imagine lots of scenarios and there are a lot of scenarios we would not imagine, because there maybe some things out there outside our ability to currently imagine.

You're just wasting time and bandwidth by limiting it to one step per post. You can make multiples steps per post and still maintain the slow progress of a step by step discussion be going like this:

If you accept "A"
And you accept "B"
and you accept "C"

Then we can conclude "Z".

That way, the responder can just interject wherever they disagree, either A B or C, and you can move right along with the discussion. That's way better than limiting it to a single step per post, which doesn't provide any benefit over that anyways, as it avoids wasting time and space.

Hi, Jar.

jar writes: Could hominids have expanded into ice age areas without clothing or fire?

I don't know. At first glance, I would have to say that it doesn't seem like they could. But, from my understanding of the evidence, they very well might have.

Hominins (Homo heidelbergensis and Homo antecessor) are known from Europe from around a million years ago, which is at least half a million years before use of fire became very widespread.

And, I have no idea whatsoever when clothing was invented, but, if Wikipedia's article on clothing is to be believed, clothing is very likely less than half a million years old.

So, neither of these seems particularly strongly tied to either the first wave of hominin expansion (ca. 1.5 million years ago) or the recent wave of Homo sapiens expansion (ca. 50,000-100,000 years ago).

Don't you think this is because of the bias you have from the world you live on and the life you see around you?

Its based on my understanding of how life evolves and how environments impact that evolution.

I would expect symmetry also because that is how we know and expect life to be, but would not be surprised if there was life that did not exhibit bilateral symmetry.

I don't doubt that there will be other types of symmetry, and even species that are assymetrical, but I thinks its likely that the kinds of species that are interesting for this kind of discussion, i.e. Animal-like ones, will exhibit specifically bilateral symmetry.

That is my point. We do not know what we don't know. Until we actually have contact with alien life, we have no idea what the circumstances are of its evolution. We can imagine lots of scenarios and there are a lot of scenarios we would not imagine, because there maybe some things out there outside our ability to currently imagine.

Sure, its possible. But the kinds of enviroments that foster the kind of evolutionary change required for Animal-like species to emerge would also favor bilateral symmetry, in my opinion. We can get into the specifics of the reasons for my opinion, which deal with the early evolution of eukaryotes, but I'm gonna go get some lunch right now.

Really?

So do you think humans could have survived in Siberia without fire or clothes?

Other species have, for example mammoths did well from arctic conditions to equatorial jungles, but the reason was unrelated to intelligence but rather fat and hair.

Is it not human technology that allowed modern humans (Sapiens and Neanderthal as well as a few other candidate) to expand into climates like the arctic or ice age Europe, Asia and North America?

Hi, Catholic Scientist.

CS writes: I think that bilateral symmetry did evoke an important advantage that has been utelized ever sense it emerged. I don't think there are any species that subsequently lost it

Echinoderms reverted to radial symmetry: the larvae are still bilateral, but the right side is absorbed back into the animal, and the left side develops into the radial animal we know (starfish, sea urchin, etc).

Hi, Jar.

jar writes: So do you think humans could have survived in Siberia without fire or clothes?

No, I don't. But, you didn't say "humans" or "Siberia": you said "hominids" and "Ice Age areas." The only hominin I know of from Siberia is the Denisova hominin from around 40,000 years ago, which is well after the invention of both fire and clothing. So, yes, I agree with you that humans were probably able to reach Siberia largely because of fire and clothing.

But, as I already pointed out, hominins apparently expanded into other areas (even cold areas, like Europe) long before they had clothing or control of fire. That tells me that fire and clothing are not the only drivers of hominin expansion. Fire and clothing certainly don't explain how hominins expanded into tropical Asia, Australasia or Central America.

Remember, my argument is that the key to human expansion is the ability to invent new technology and new tactics to meet new challenges in new environments. So, in some cases, like Siberia, clothing and fire were the key to success in their new home; in other cases, new tool-making techniques were the key (e.g. Clovis); in other cases, it was discovery of new types of food (e.g. fish on the sea coast, fruit in the jungle, horses on the steppes, etc.); in yet other cases, it was rafts or canoes (e.g. Indonesia).

Humans were successful in so many different environments because we could change our technology and our lifestyle to match whatever environment we expanded to. We could do that because we are intelligent.

But Ice Age does not mean tropical.

But the expansion into North and Central America definitely depended on clothing and fire.

And I agree that human expansion was the result of human technology, but that human technology is not just the result of intelligence.

That's why I want to move slowly so that we don't end up running in circles.

I don't doubt that there will be other types of symmetry, and even species that are assymetrical, but I thinks its likely that the kinds of species that are interesting for this kind of discussion, i.e. Animal-like ones, will exhibit specifically bilateral symmetry.

There is a fair amount of life that is not bilateral symmetrical.
http://en.wikipedia.org/wiki/Symmetry_in_biology
Radial symmetry animals include starfish, jelly fish andsea anemones.

Flatfish and gastropods would be the most common assymetrical organisms. I guess I could imagine more life forms, even intelligent, that resemble snails and slugs. So we have right here environments that would help produce a non bilaterally symmetrical animal.

Can you envision where we may find life that is non animal or plantlike? Maybe a combo or something completely different?

Hi, Jar.

It seems to me that, if you're not in total control of the flow of discussion, then we can't get anywhere. I'm perfectly happy letting you dictate the conversation, but, like Catholic Scientist said, it's kind of frustrating for me. To me, it doesn't seem like this is particularly complicated, but you keep getting lost at every step.

Look at this:

jar writes: But Ice Age does not mean tropical.

I don't understand where this comment is coming from.

My point was pretty simple:

1. Humans expanded into both cold regions and tropical regions.
   
2. Humans developed some technologies to help them survive on the cold steppes.
   
3. Humans developed other technologies to help them survive in tropical rainforests.

So, we were able to develop two different tool sets for two different environments.

Are you with me so far?

Edited by Blue Jay, : "list" code

Sure, but again, it is still only marginally relevant to the point I am trying to make, so please humor me and walk along slowly.

As I mentioned several times, human expansion was the result of human technology, but that human technology is not just the result of intelligence.

There are other species that developed intelligence, perhaps even more intelligence than humans, but did not develop the culture of transfer of technology and knowledge over generations and outside of the immediate group or tribe.

That last paragraph I think is the key.

It's possible based on what little I've learned that some cephalopods may well be as intelligent, maybe even more intelligent than humans, be more dextrous, able to solve problems, but because they have very short lives and live in the water, web almost certain to never develop anything like the culture of technology and knowledge accumulation and transfer common to humans.

Hi, Jar.

jar writes: Sure, but again, it is still only marginally relevant to the point I am trying to make, so please humor me and walk along slowly.

And, the frustrations continue to mount. I understand that you have a point that you really want to get across, but, in order to get there, you have just kind of deflected all the counter-arguments I have been making. I thought the whole point of a slow-walk process was to isolate the point of disagreement and deal with it.

Now, how about a substantive response to my counter-argument? Intelligence makes it possible for us to invent new technologies to deal with new challenges in new environments. That's how humans have adapted to every environment on the planet.

jar writes: There are other species that developed intelligence, perhaps even more intelligence than humans, but did not develop the culture of transfer of technology and knowledge over generations and outside of the immediate group or tribe... ...It's possible based on what little I've learned that some cephalopods may well be as intelligent, maybe even more intelligent than humans, be more dextrous, able to solve problems, but because they have very short lives and live in the water, web almost certain to never develop anything like the culture of technology and knowledge accumulation and transfer common to humans.

I'm sorry: I don't buy this. I'll grant that cephalopods are very intelligent, but there's no evidence that their cognitive abilities are comparable to ours.

But, I'm perfectly willing to grant that technological development is also strongly limited by the environment, and that land is a better habitat for technology than sea. But, I'm not sure what the point is: even on land, only the one species with the highest intelligence was able to develop technology. So, clearly, intelligence is the real limiting factor here.

But the kinds of enviroments that foster the kind of evolutionary change required for Animal-like species to emerge would also favor bilateral symmetry, in my opinion. We can get into the specifics of the reasons for my opinion, which deal with the early evolution of eukaryotes,...

My intuitive opinion is that symmetry is a response to gravity and results in the ability to balance and motivate more easily. That and the need to triangulate for vision and hearing. These conditions should be universal.