I believe it did happen more than once. The reason why life on Earth has developed into such complexity is that the primordial soup, where life developed out of, has been cooking undisturbed from events like supernovae and such that would have wiped out everyhing (Earth istself as well as the whole solar system) nearby. Life could develop over several billion years, and cosmic events like asteroid impacts didn’t wipe out all of life. Remaining life startet over again.
If life developed on another planet with similar features like earth, it could have been wiped out by a nearby supernova, by a collision between two planets and similar events, before it got any more complex.
Life has to start pretty simple. Chains of very basic molecules, that kinda self replicate. Those molecules would be tasty nutrients without any evolutionary self defense mechanism. So anything like that would be immediately eaten by the stablished life forms. No chance for enough self replication to evolve into anything.
Our current life tree have had many million years of evolution, we all are perfect killing machines. No proto life have a chance.
Were perfect. The conditions on earth back when life first appeared were very very different than they are now.
As for how many times it may have happened, there’s no way to know, only that it happened at least once (edit: unless it happened elsewhere and came here somehow).
deleted by creator
I don’t have the answer but what an interesting question!
For all we know it did. We believe that the Earth is 4.5 billion years old but it’s estimated that conditions suitable for life only appeared about 200 million years after that. Since the oldest fossils we’ve found are 3.7 billion years old, there is a 600 million year gap between when we think life could have formed and out earliest records of it.
There is every possibility that life formed multiple times in different environments on Earth in those first few hundred million years and then been wiped out by one of the frequent cataclysms that ravaged the early Earth. We have no way of knowing though. If life formed around a volcanic vent and then got wiped out by a meteor impact there would be no evidence it ever happened. Even if such life was wiped out by a climatic shift or something like that, there still wouldn’t likely be much evidence left if any right now. The Earth’s surface has been changed so much in the last 3.7 billion years, there are very few areas older than that where such fossil records from before that could be found.
And there’s a good chance that other life would be chemically or structurally similar, so without DNA evidence we’d confuse it’s fossils with others (see Prototaxites).
Also, maybe life does reoccur relatively frequently, but is killed by existing bacteria, viruses, bacteriophage… again, for being too chemically/structurally similar to the existing life.
Isn’t there evidence mitochondria took a different evolutionary path before they were captured by cells?
There are also a few other really weird cellular-scale life forms I forget the names of that could be different evolutionary paths. Though I’d think the seeming hegemony of life comes from life competing in the same environments and either killing off or adapting to/with other evolutionary chains like with mitochondria. It surely wouldn’t take billions or even millions of years for microscopic life to spread across Earth, so there’s been plenty of time for any different upstarts to mix or kill off each other.
First of all I love this question. My suggestion is that you shuffle a deck of cards, flip them over and note their exact order, then shuffle again and note the order again then keep shuffling and checking the order until the deck resets to the original shuffled order. It’s gotta happen eventually, but it might take you a while. In fact a lot of people have studied that very specific problem and there’s actually really good odds that every shuffled deck you’ve ever held has been the only deck of that order in history. So, yes, it almost certainly has happened somewhere, but good luck finding it.
It’s like when playing the lottery, if you say you’re picking all your numbers in a sequence, like 1,2,3,4,5 and 6. People will tell you’re crazy because sequences like that “never” happen. But the same is true for every other combination of numbers too. The sequence just makes it clearer how unlikely you are to ever pick the winning numbers.
52!
80658175170943878571660636856403766975289505440883277824000000000000
https://czep.net/weblog/52cards.html
I was fascinated for a couple years, back when flash player was coming to an end. I built a deck of cards in AS3 with the original goal of a simple single player blackjack. This was introductory research I came across that has held a fascination for me ever since.
It’s gotta happen eventually, but it might take you a while.
A while is a great euphemism here… A deck of 52 cards (poker playing cards) has so many potential orders that it is said that each time someone shuffles a deck nowadays, it’s really likely to get a deck order that has never been gotten before!
That’s exactly what they just said.
Found it! It had actually just fallen into the couch cushions.
There are more combinations in a deck of cards than atoms on earth.
But since we’re talking about early life forming (actually chemical replicators, much simpler than a virus) let’s use the card shuffling odds, but decks of cards are being shuffled in billions or trillions of places on early Earth every second for millions of years. Even a very low odds of finding a working sequence of molecules will be found geologically quickly given the amount of times done over area and time. We’re pretty sure now that life began very soon once the Earth cooled down enough to allow it. What took much longer was the more complex forms of life like viruses and single cells, then even longer for multicellular.
What’s more fucked is the “perfect container” thought experiment with infinity.
Take for an example an apple, you put it in your “perfect container” that nothing can pass thru. This is a hypothetical, it doesn’t exist.
What happens to the apple?
Fucking everything. It will rot and degrade, eventually breaking down to fundamental elements, but all the energy/matter to make an apple is in there. On an infinite timeline that stuff will go thru every possible permeation. Including an exact and perfect copy of the very same apple. Even if it takes billions and billions of years.
Maybe at some point in the middle. You get an orange.
no because entropy.
an apple is more like an ice sculpture. energetically far from equilibrium. once reduced to a puddle, the molecules will never spontaneously rearrange into the sculpture. It will just be a puddle. the molecules, yes, will constantly rearrange, into also, a puddle.
there has to be a force to act on them to push them out of equilibrium.
life is a state of matter held far from equilibrium.
life is a state of matter held far from equilibrium.
Way too early for this shit.
life is a state of matter held far from equilibrium.
Way too early for this shit.
Blame plants. Get back at them by smoking/ drinking some of them.
*permutation
Life could be forming again RIGHT NOW, but there’s already pretty well established life here already that could stamp the upstart out.
Behold ty he Life equation. And by extention also the Fermi paradox.
It almost certainly did…
But conditions on Earth were “perfect” for life to exist because this is where all the life we’ve ever seen evolved.
If conditions on Earth was different, life would have evolved differently and people would still say conditions were “perfect” it’s survivorship bias.
So earliest life likely sprung up with some pretty fundamental differences, and whatever evolved best hung around.
We can see modern versions of this when extremophiles overlap due to changing conditions. Life forms that have been isolated thousands (sometimes millions) of years. Or even just the life that exists in deserts for the brief period there’s puddles after a rain.
Earliest life was probably just a bunch of isolated pockets, who were eventually able to evolve and spread out from the extreme environments they came from. Sometimes they take over and spread, others they die out and only the ones that stayed in their extreme environment survives.
As an aside, see also Silurian hypothesis
“While we strongly doubt that any previous industrial civilization existed before our own, asking the question in a formal way that articulates explicitly what evidence for such a civilization might look like raises its own useful questions related both to astrobiology and to Anthropocene studies.”
For over three billion years, all we know of the evolution of life is from the chemical signatures it left behind, and from the genetic information of the surviving descendants. From that we can conclude that all current life arose from a common origin roughly coinciding with the first chemical signatures of living activity, and the most parsimonious explanation is that life arose on earth only once. But it’s also plausible that some of that early chemical activity was produced by forms of life that arose independently, but were displaced by ours before the emergence of multicellular organisms.
Keep in mind that the conditions before life formed were quite different than the conditions once it had already been established. Once life exists, there is a competition for resources. Fewer building blocks will be just floating around and available for spontaneous development of new life and a new replicator will be unlikely to survive in an environment filled with far more sophisticated replicators that have had a head start.
The conditions are perfect for life to thrive, and especially to evolve, we’re not so sure about forming.
Actually, I’m pretty compelled by the hypothesis that Mars actually had the perfect conditions for life to form. With less of an ocean covered surface, regular rain, and constant meteor showers. Such meteors would form holes lined with random chemicals, which then get filled with water, forming a puddle. If one puddle doesn’t have all the necessary components to form life, another likely will. That seems to me like a much better scenario than a sparsely diluted ocean on Earth.
Then whatever life originated on Mars might have been thrown into space by one of those meteors, and by chance, fell on Earth. There’s actually evidence that such interplanetary matter transfer is possible, and has happened. That would explain why we only know of a single common ancestor, the only one that arrived here.
I think OP’s question still holds, even if you think all of that happened. If there was so much life on mars and so much ejecta, why didn’t multiple (differently structured, eg not DNA) rounds of life get formed on mars and transplanted to earth? Why 1x?
Mitochondria don’t use DNA, so that particular detail has already been confirmed. Doesn’t mean they came from Mars, or weren’t from the same precursor to DNA-based cells, but it’s still interesting!
We can’t know that didn’t happen. We just know that only one life form succeeded, it is very possible that others were pushed to extinction because of that.
Then you get back to every other response on this thread, it probably did happen more than once.
I’m not convinced it’s only happened once.
A new bacterium could have been created in the ocean yesterday. How would we ever know?
Assume you mean from simple building blocks instead of evolving from the reproduction of other bacteria, we could know if there were ever enough of this new bacterium for us to find and isolate it.
For one thing, if it didn’t come from other living things it would not share the genetic code. Almost all organisms on earth use exactly the same translation of RNA codons to amino acids. The few exceptions are changes of just a couple of codons which had fallen to very low frequencies in the hosts’ genomes.
That universal code is one of the reasons we know all life discovered to date evolved from a common ancestor.
A new bacterium, if it evolved convergently to use DNA and RNA and a 3 letter code (a big if), would not use the same translation as modern life. Even if there is some bias towards specific codons, the chance of the same core code happening twice is astronomically low.
