That’s true now, but it wasn’t true at the beginning. We have no idea how many starts life had that failed or were out competed. We don’t know how resolved the DNA structure was when something we would call life came about. We are pretty certain chirality was resolved long before life began, but that’s pretty simple to explain.
Aargh, that was responding to smeghead.
I’m not clear on what you want out of this line of argument.
Is it possible to win the lottery on the same day you give birth to quadruplets at precisely 08:09:10 on 11-12-13? Sure, it’s possible.
Is it possible that some form of protolife evolves multiple traits simultaneously in a hostile, competitive, nutrient-poor environment, leaping past what took 500 million years of evolution under more favorable conditions the first time? OK, sure. It’s possible. No one can say it’s not.
But we can say that we see no evidence it has ever happened in the past and that we have been unable to make it happen intentionally, let alone on accident.
I do not see why it would be unlikely, given how many different toxins there are, not all of which have (yet) been observed in living things.
And speaking of evolution, dietary needs also evolve, correct? The requirements of every living thing are the result of 100s million years of evolution, right? The ability to recognize edible material ought to be included in the evolutionary process. If so, a brand new form of life might be be unrecognizable as a potential food item, hence not tempting.
Good rejoinder, but by “imperiled” I meant “preyed upon by.” Since the smallpox virus cannot exist out side the human body a better example would bacteria living outside animal bodies, say tetanus. Who has ever eaten tetanus, in the wild?
Any reason new life might not closely resemble viruses?
Even now habitat and resources support 10s of millions of species, with few under any pressure of non-human origin. I therefore disagree resource shortage is likely have been an issue at any time in the planet’s biogenic history.
My objective throughout has been to argue against the plausibility of earlier life posing an insurmountable predatory challenge to the survival of newer life.
Newer life need not have leapfrogged anything like 500 million years, although, given the phenomenal potential of the Earth’s biosphere, it might leapfrog even more than that.
I agree there is no evidence of more than one origin of life, and I tend to believe there has in fact been only one origin.
Interesting…so why is the blue-green algae still around? It is identical to the variety that was around a billion years ago.
This is the ‘why are there still monkeys?’ argument.
Theyte not* identical to their ancestors.
I know this isn’t what you meant, but there is one sense that it is plausible, or even very likely. The very first evolved life was likely fragile and may not have even survived the environment, let alone other life. So there may have been several false starts before life really got a foothold and survived. No one knows, for instance, if life existed prior to the Late Heavy Bombardment, or if it did, if it survived the experience.
In other words, the successful fourth origin of life may be us.
Scientists state all life is related. If this is so then it means one of two things. Life started at one time and then conditions changed that prevent any other forms of life commencing or whenever life commences it must follow the same rules.
My question is “Why does life not spontaneously reappear some where on earth?” This of course would be a different type of life present on earth now!
Most likely because before it can get beyond the crude precursors of life, it gets eaten or whatever it needs to sustain itself gets eaten. Against critters with more than a billion years headstart on evolution, it’s a toddler thrown into a shark tank.
EDIT: I think there was a recent thread on this, actually…
Tell that to the sulfur-based life forms growing around the steam vents at the bottom of the ocean.
Since a similar thread was active only two days ago, I have merged the two threads.
Colibri
General Questions Moderator
The “sulfur-based” organisms on the ocean floor aren’t actually sulfur-based, at least not in the sense that we’re carbon-based. They’re carbon-based, too, and use the same DNA with the same genetic code that we do. It’s just that some of the things (but not even all of them) we use oxygen for in our biochemistry, they use sulfur. We share a common ancestor with them, even though we’ve obviously gone different ways in the billions of years since that common ancestor.