'Alien life' may be found on Earth

If we don't know what the mechanism of life's origin was
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how can we state:
All known life on Earth is descended from a common ancestor. We're all on the same tree
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What I got from the article is that we actually wouldn't know what to look for in the first place
 
Apache said:
Well two life or many more life forms could have formed at similar times in different parts of the earth, allowing for many millions of years of unimpeded development.... but it didn't happen.
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Maybe it did, but as evolution shows. Lifeforms evolve depending on their surrounding conditions. Even a 1% more intense environment for any one of those branches would have resulted in it being the dominant and more evolved branch a few million years later when the branches met as simple organisms. The dominant branch would have annihilated the weaker ones quite utterly.

Think about the size of predators and prey on large continents like Eurasia, America, Africa. They evolved bigger and stronger because of the size and space and stimuli . They had to evolve to handle a multitude of conditions. Then consider the tiny predators and prey on an isolated island. They are just as evolved, but they are specialised creatures. Adapted to survive in their specific tiny ecosystem. When pitted against the creatures of larger ecosystems, they would be completely annihilated. Thus ending their branch of life.
 
B.O.F.H. said:
Do you understand evolution?

Or do you favour creationism as an explanation for life in general?
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open-a-can-of-worms.jpg
 
McSack said:
how can we state:
What I got from the article is that we actually wouldn't know what to look for in the first place
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Dude, it's in our DNA. They look for repetitive overlapping sequences in the DNA.
http://astrobiology.nasa.gov/articles/evidence-for-a-new-root-of-the-tree-of-life/

Also, how do we know there wasn't life forms with different DNA sequences in the beginning that has subsequently died out because of competition. Just because current life forms share a common ancestor doesn't mean there weren't "other" life forms.
 
Lol I'm actually busy studying for my Archaeology exam so here's my input: it did happen. At the end of the Mesozoic era, dinosaurs became extict, and as a result of environmental changes and other factors, new life in the form of mammels started appearing, sparking the caenozoic era.

So in a way, it has already happened.
 
Apache said:
People believe that life started on earth on its own with no outside help, and then from this one life form all life came. So what the guy in the article is implying is that why did it not happen more then once.
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But it did?
 
RaptorSA said:
Dude, it's in our DNA. They look for repetitive overlapping sequences in the DNA.
http://astrobiology.nasa.gov/articles/evidence-for-a-new-root-of-the-tree-of-life/

Also, how do we know there wasn't life forms with different DNA sequences in the beginning that has subsequently died out because of competition. Just because current life forms share a common ancestor doesn't mean there weren't "other" life forms.
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Sweet jeezuz ... my eyes started bleeding 3 sentences into that link. Luckily I found some easier "enlightenment" on wiki
 
Sysem said:
Lol I'm actually busy studying for my Archaeology exam so here's my input: it did happen. At the end of the Mesozoic era, dinosaurs became extict, and as a result of environmental changes and other factors, new life in the form of mammels started appearing, sparking the caenozoic era.

So in a way, it has already happened.
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Dude we're talking Hadean here.

Also, mammals started waaaay back when the first reptiles appeared. You've heard about mammal-like reptiles right (http://www.nhm.ac.uk/nature-online/...ino-reptiles/mammal-like-reptiles/index.html)? They've been with Dinos ever since the first Triassic "dino" like reptiles appeared.
In fact, South Africa actually has a crapload of mammal like reptile fossils due to the fact that most of our Geological "top layers" washed out to the ocean millions of years ago, leaving us mostly with pre-mesozoic layers. Quite sad actually, now we're left with Dinos like Massospondylus and Algoasaurus... *yawn*
 
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Sysem said:
Lol I'm actually busy studying for my Archaeology exam so here's my input: it did happen. At the end of the Mesozoic era, dinosaurs became extict, and as a result of environmental changes and other factors, new life in the form of mammels started appearing, sparking the caenozoic era.

So in a way, it has already happened.
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I'm pretty sure he means life starting from scratch as it were. It's besides the point though. The Earth like conditions life arose from doesn't refer to Earth in it's present state. Life arose originally in an environment much different from today and then proceded to change the environment. In other words once you have life you won't have the conditions for life to arise for much longer, therefore different life forms are unlikely to arise spontaneously twice on the same planet unless life is wiped out and the Earths environment "regresses". Assuming that there are ideal conditions for life to arise of course.

That's the fundamental flaw in that argument. Don't expect it to loosen the dogs grip on its bone though. This thread will be pushing 20 pages by 5 o'clock.
 
Well there is hard evidence.

On one meteorite that landed on earth they found fossil evidence of living cells. This life would not have been created on earth.

So its alien life... and it was "created" independently of the life that was created on earth.
 
Nerfherder said:
Well there is hard evidence.

On one meteorite that landed on earth they found fossil evidence of living cells. This life would not have been created on earth.

So its alien life... and it was "created" independently of the life that was created on earth.
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Unless of course, we were seeded by wherever that meteorite came from!
 
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