I think to even start answering what alien life would look like would require you to figure out which alien environments could have life evolve on them. We know that there are other Earth-like worlds out there, so we could focus on those and ignore ice worlds, ammonia worlds, moons orbiting gas giants etc even though these could well evolve alien life as well. But then if you look at the history of the Earth, there have been many different periods where completely different life evolved. The first primate-like creature was tiny and appeared just before the KT Impact event that wiped out the dinosaurs. So even if we found another planet exactly like Earth, you couldn't assume that it would have human like aliens. Or even if they had evolved in the past whether they were still alive.

(November 26, 2018 at 7:43 am)Mathilda Wrote: I think to even start answering what alien life would look like would require you to figure out which alien environments could have life evolve on them. We know that there are other Earth-like worlds out there, so we could focus on those and ignore ice worlds, ammonia worlds, moons orbiting gas giants etc even though these could well evolve alien life as well. But then if you look at the history of the Earth, there have been many different periods where completely different life evolved. The first primate-like creature was tiny and appeared just before the KT Impact event that wiped out the dinosaurs. So even if we found another planet exactly like Earth, you couldn't assume that it would have human like aliens. Or even if they had evolved in the past whether they were still alive.

Excellent points. Because even if we found a ‘twin Earth’ (and we haven’t, regardless of what appears in popular journalism), there’s simply no way of knowing that evolution would follow the same paths as it has on Earth.

Given the staggering variety of life here (a rose looks nothing like a rhinoceros), speculating about extraterrestrial life is just that - speculation.

Boru

(November 26, 2018 at 3:06 pm)BrianSoddingBoru4 Wrote:

(November 26, 2018 at 7:43 am)Mathilda Wrote: I think to even start answering what alien life would look like would require you to figure out which alien environments could have life evolve on them. We know that there are other Earth-like worlds out there, so we could focus on those and ignore ice worlds, ammonia worlds, moons orbiting gas giants etc even though these could well evolve alien life as well. But then if you look at the history of the Earth, there have been many different periods where completely different life evolved. The first primate-like creature was tiny and appeared just before the KT Impact event that wiped out the dinosaurs. So even if we found another planet exactly like Earth, you couldn't assume that it would have human like aliens. Or even if they had evolved in the past whether they were still alive.

Excellent points. Because even if we found a ‘twin Earth’ (and we haven’t, regardless of what appears in popular journalism), there’s simply no way of knowing that evolution would follow the same paths as it has on Earth.

Given the staggering variety of life here (a rose looks nothing like a rhinoceros), speculating about extraterrestrial life is just that - speculation.

Boru

But Protistas have microscopic life that take on the function of plants, animals, and fungai, only they're not related to any of those things beyond them all being eukaryotes. I think we'd find plants, animals, and fungai on an alien world, based on that.

(November 26, 2018 at 10:08 pm)Mechaghostman2 Wrote:

(November 26, 2018 at 3:06 pm)BrianSoddingBoru4 Wrote: Excellent points. Because even if we found a ‘twin Earth’ (and we haven’t, regardless of what appears in popular journalism), there’s simply no way of knowing that evolution would follow the same paths as it has on Earth.

Given the staggering variety of life here (a rose looks nothing like a rhinoceros), speculating about extraterrestrial life is just that - speculation.

Boru

But Protistas have microscopic life that take on the function of plants, animals, and fungai, only they're not related to any of those things beyond them all being eukaryotes. I think we'd find plants, animals, and fungai on an alien world, based on that.

I think life on other planets with conditions and chemistry broadly similar to earth probably will evolve organisms broadly similar in form and physical construction to bacteria and archea. But the structural and metabolic chemistry may well be very different.

But beyond simple prokaryotic like cells, I think any entirely independent line of evolution, even if it takes place in environment and chemistry similar to earth, would result to more complex cells or organisms that are quite different in all ways, including metabolism, structure, manner of reproduction at cellular level, from those on earth.

I think evolution of eukaryotic cells was a difficult and highly contingent step. I think the current majority view is eukaryotic cells formed by process of endosymbiosis of two or three different types of bacteria or archea cells. If I am not mistaken, all eukaryotic cells appear to descend from a common eukaryotic ancesters, implying the successful phylogenies resulting from endosymbiosis event occurred relatively few times in the history of life on earth and may be a difficult thing to pull off. That implies the biochemistry of all eukaryotic organisms on earth, including plants, animals and fungi, all depended heavily on the contingent circumstances of a singular or a comparatively small handful of particular endosymbiotic events.

This implies to me that if we were to wind the clock back on earth to before the first eukaryotic cell, and let time run forward again in its normal way, similar eukaryotic cells capable of leading to our complex animal, plants and fungi may not have a high chance of arising again even on earth.

So I suspect life on other planets, even if the physical and chemical environment were very like those on earth, would be unlikely to follow similar divisions as life on earth even at the most basic level of fundamental cell structure and organization.

At work.

Just think.

Worlds where spiders, scorpions and the like develope hinged and efficient 'Book' lungs and so are not just limited by amospheric properties.

Or where crustaceans such as the 'Land frab' and such evolve much earlier and become one of the dominant land based competitors.

Amonites learn to chemically crack water. Keeping the hydrogen in their shells to become fierce aerial predators.

The mutation that allows for placentas never happens and so Marsupials continue to dominate the wilds.

(November 27, 2018 at 4:08 pm)Peebo-Thuhlu Wrote: At work.

Just think.

Worlds where spiders, scorpions and the like develope hinged and efficient 'Book' lungs and so are not just limited by amospheric properties.

Or where crustaceans such as the 'Land frab' and such evolve much earlier and become one of the dominant land based competitors.

Amonites learn to chemically crack water. Keeping the hydrogen in their shells to become fierce aerial predators.

The mutation that allows for placentas never happens and so Marsupials continue to dominate the wilds.

 

I think because we live in the Phanerozoic eon in the history of earth, We tend to think of alien life as some outlandish variation of the Phanerozoic world on earth. But life on earth lived 7 times as long the Proterozoic eon as in our own Phanerozoic eon. So I think it is not more likely, and more interesting to consider, that ancesters of higher life on alien worlds branched off from their equivalent of our main line of evolution way back in mid or even early Proterozoic.

At work.

Was just fantasizing.

Tilobites filling the ecological nitch of Cheetas. Carapace and claws clickety, clacking as they chase down their prey.

For my alien life I'm going to focus on alien intelligent life that is at least at our level of intelligence and civilization building.

First you gotta have limbs that can manipulate objects in your environment.
You gotta have some kind of eyes to see your environment.
You gotta be able to move around in your environment.

I'm thinking octopus like creatures that evolved and changed to survive on land.

question to all.

We came out of the water, developed 4 legs for mobility, then only used 2 as we stood up.
Why couldn't we develop a bigger brain whilst running faster on 4 limbs? Too run away faster? (An evolutionary advantage.)

(December 1, 2018 at 10:52 pm)Rahn127 Wrote: For my alien life I'm going to focus on alien intelligent life that is at least at our level of intelligence and civilization building.

First you gotta have limbs that can manipulate objects in your environment.
You gotta have some kind of eyes to see your environment.
You gotta be able to move around in your environment.

I'm thinking octopus like creatures that evolved and changed to survive on land.

I suspect majority of higher life that would reach the level of development suitable for creating and supporting civilization will be aquatic.

The reason is life and complex life are much more likely to evolve and be found in aquatic environments. And marine environment potentially offer vastly more developmental space than land environments.

If my guess is right, then I wonder if the difficulty with making fire and smelting metal in water means most civilization are barred from proceeding down the technical path not by cognitive deficiency, but by inability to leverage energy sources to save labor and provide spare capacity for technical development.