I specifically stated that a billion was not meant to be an actual number. You aren’t getting that I’m not giving a high probability of identical coding. I’m giving an infinitesimally small probability of identical coding. Just one that’s slightly larger than other codings. We can all agree that, on earth only one set of codes made it, but the mechanisms that decided what those codes were are not random. As with every other complex living system, the rules of thermodynamics apply because at its heart it’s limited by standard rate laws.
The first coding would only have a few genes, maybe proto-genes. Maybe it has as little as two. That gives sixteen possibilities assuming all four codons existed, but only the best makes it. Now the next coding depends on what matches the first. Thousands of genes didn’t suddenly combine to form a self replicating entity. That is a ridiculous notion. It happened stepwise and thermodynamics guided it every step of the way.
Can you tell us if all bacteria and archaea are dietary items for other bacteria
and archaea? And even if they are, consider rabbits who are prolific even where they
are dietary items for perhaps dozens of predators, besides being suseptible to a few
microbe-borne perils as well.
Let me put it this way: although I can think of no good reason to think more than one
origin of life is unlikely, it obviously is unlikely, since it has had at least several 100
million years, and possibly several billion years to occur within a vast evelope about
12 miles wide covering the entire surface of the Earth.
I do not know, and I am not sure what difference it would make. The point does not
depend on new life being unpalatable to all preexisting life, but only unpalatable to
enough to have a good chance of survival.
Also NB being palatable to another organism does not necessarily mean the other
organism is life-threatening. There may be hundreds of millions of species who feed
off us with no ill effect.
The difference it makes is whether the precursors to a contemporary abiogenesis event can reasonably be expected to be left alone, to become a new form of life, or whether they’re just going to be hoovered up by one of Earth’s abundant incumbents, instead. We’re not talking about a life-form, we’re talking about the precursors.
Are you suggesting rabbits could spring into being from a soup of amino acids?
Because the reason rabbits reproduce and thrive despite intense pressure from their environment is intrinsically bound up in the 3.5-billion-year history of that selection pressure relentlessly winnowing out all but the very wiliest, fastest, and horniest of them. Rabbits are complex and highly-evolved animals in exactly the way that new life starting from scratch would not be.
However, I am still not sure what difference it would make if all amino acids
were palatable to one or more preexisting forms of life. Are any amino acids
in danger of being exhausted? Bear in mond there are perhaps tens of millions
of species alive now, and certainly many more than that historically.
No, I was using them as an example of a species able to fluorish despite having numerous predators.
Does evolutionary theory require or even suggest (1) that a new life form cannot possess formidable defences
or (2) that a new life form must be imperiled by preexisting life?
Pretty much, yes. A new life form, newly emerged from prebiotic soup, is bound to be extremely simple. It will have the ability to reproduce, and precious little else. Things will not start evolving defenses until natural selection has had a chance to kick in, and it won’t have a chance to kick in because the new form is almost certain to be outcompeted into extinction (which may or may not involve being eaten) by the much more sophisticated types of organism that are already around.
Again, pretty much yes. All life forms are imperiled by existing forms. Evolutionary theory is all about struggle and competition for resources. The extinction of less fit forms is the very motor of evolution by natural selection, and things that are newly emerged from prebiotic soup, that have not yet been subjected to the rigors of natural selection, will, virtually inevitably, be less fit than the organisms that are already around and are the products (humans and bacteria alike) of billions of years of selection.
Of course, this was not the case when life emerged for the first time. Then, there was no competition, so the first, primitive, self-replicating organism had the chance to spread itself until there were enough of it around for the process of competing against different variants of itself to get evolution going.
A highly evolved species able to flourish despite having numerous predators specifically because it’s been ruthlessly selected for survival in that environment.
The putative new life form would be struggling against this sort of established, extremely efficient competition/predation – by definition, without the advantage of eons of adaption for the struggle it is about to undertake.
After some thought, I think this question deserves an answer too:
That’s a good question. In theory, I suppose a randomly-put-together First Organism might possess an unusually strong defense of some sort, like, say, an impenetrable shell.
But the secret to long-term survival is not so simple. All currently-known multicellular life not only has formidable defenses (or adaptation strategies that serve the same purpose), but also is adept at changing those defenses, survival strategies, and adaptations, often with startling rapidity.
I’m currently reading The Genius Within: Discovering the Intelligence of Every Living Thing, and Dr. Vertosick emphasizes the adaptation of bacteria, viruses, and the immune systems of mammals. Interestingly, your immune system uses both sophisticated networking and a natural-selection-like pressure to rapidly evolve in response to pathogens (this is how vaccines work, among other things).
He says insects do not have such an immune system – an insect is born with the immunities he or she will have when at death – but insects substitute rapid cycling of large numbers of individuals to exploit natural selection in an analogous way, allowing the species to adapt to new pathogens even if individual bugs are not saved.
This is the context in which our putative armored First Organism would debut. Animals which might feed on it, discovering its impenetrable shell, will simply employ some other tool in their immense toolbox of physical and behavioral adaptations. They will flip it over and eat out the soft parts from underneath, or drop it on a rock, or lead an animal that CAN crush the shell over to it and pick over what that animal leaves behind, or any of a thousand other sophisticated strategies, while our First Organism is stuck with only one trick (so far).
I would say that, yes, all amino acids are exhausted, though what I mean is “already part of something living.” If you leave out a petri dish full of amino acids, it will be colonized by bacteria almost immediately, and they’ll consume every last useful resource within a matter of days (hours, if the conditions are right).
If life was going to spontaneously arise in an environment with existing life forms, it would really need to find some novel niche that was not already filled and there just aren’t many of those.
Not in any remotely plausible theory. In actuality it took many millions of years of natural selection to get from the first living things to multicellular organisms, and millions more after that to get to things with shells. There is really no doubt that the first living things upon which natural selection could get to work would have been extremely simple, perhaps little more than a strand or two of nucleic acid (or some similar, ancestor molecule) or of proto-protein, and would have been quite defenseless if there had been anything around to eat it or compete with it for resources.
This sort of very crude, fragile organism is the most you can expect to emerge from abiogenesis. All other features and abilities that living things have emerged from natural selection and that took not only time but competition. The fragile first organisms could survive only because there was nothing else there to compete with them. If any sort of new proto-life ever arose on Earth later, by abiogenesis, it faced ruthless competition from the already established and evolved life, and had virtually no chance to survive long enough to take hold.
I do not see why this should be a postulate of evolution. There are numerous
compunds which could be constituents of new life could which could be toxic
to many, most, or all forms of already existing life depending on the timeline.
Prior to the discovery of innoculation who imperiled smallpox microbes?
The first life necessarily did not need to feed on any other life. I do not
believe evolution has anything to say about when certain forms began to
feed on other forms. Could have been one generation, could have been
untold millions. Unless that is pinned down then the door is open for new
life to exist completely unthreatened by earlier life for a potentially very long time
Let’s get away from bunnies, and look at microbes, since newly evoled life would
be almost certainly miscroscopic.
I know little about the range of lifestyles adopted by microbes. You?
Are all microbes potential meals for at least one other microbe? Or do only some,
or very few microbes face predatory threat?
Also, microbes, being so simple, have great potential for rapid mutation and adaption.
Such considerations seem to me to offer grounds for arguing that new life would
not necessarily face significant existential threat, and I am not convinced a strong
case has been made for the inverse. This is especially true for the early era of
life on Earth, say “only” the first few 10s of millions of years, when the number of
competitors would have been much less.
This is interesting, but let’s stick with microbes as far as new life goes;
I would like to know more about the range range of vulnerabilites and defences
so far observed in them.
I guess it depends on how longwinded and tenuous a process is abiogenesis when it’s happening - if it’s slow and fragile, then it stands a poor chance of happening without being consumed, contaminated, trampled or disturbed by the busy and ubiquitous processes of existing life.
But, see, that’s part of the point everyone is making. If a brand-new microbe emerged, it would not be emerging into a world consisting of nothing but microbes, but rather into a world already populated at every size scale with hungry critters looking for lunch.
What don’t the bacteria consume, anything? Whatever they leave over might
be where to look for potential new life. Also, may the contents of your petrie
dish include a large measure of cyanide? Cyanide occurs naturally in many living
things as common as apple seeds. Some lucky new life form might possess a
predator-discouraging amount of cyanide in it system. And cyanide is not the
only toxin imaginable.
It occurs to me to mention at this point that it is by no means established that
all life must be carbon-based, despite carbon’s unique advantages.
Again, yes, this is possible, by pure chance, but it is not at all likely. What is certain is that new life, newly arisen by abiogenesis, could not have evolved any defenses (or other competitive strategies), because when it is brand new it has not had any chance to evolve yet. It is unlikely ever to get that chance.
Lots of things, including (but not limited to) the immune systems of humans (and any other animals it might try to infect). Inoculation does not create immunity out of nowhere, you know, I just gives a heads-up to the already existing immune system.
Anyway, smallpox is not a good analogy to the earliest life. It is a virus, and viruses, by their nature, cannot reproduce without having more complex organisms to infect. The first living things were not viruses. Whatever the first living things were like, we can be confident that things like them would not be able to survive (more than very briefly) on Earth today.
Feeding is not the only issue. Competition for resources is the key issue, and that, before the advent of photosynthesis (which is complex and necessarily takes along long time to evolve) mainly meant competition for energy rich chemical compounds. Established, evolved life would have a big head start on gobbling up any of them before any crude, fragile, newly abiotically synthesized life forms could get them.