- Despite lack of observational basis, Darwin proposed Universal Common Descent (UCD) saying: “Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed“. He also said elsewhere (referring to UCD): “…the littlest creature (or four or five of them)…” With his remarks, Darwin left the door open to creation (“life was first breathed”), but since then, Neo-Darwinists have rejected creation and replaced it with belief in undirected abiogenesis while maintaining belief in UCD.
- UCD is incompatible with the current view of Earth as just an ordinary planet circling an ordinary star located nowhere special inside an ordinary galaxy. If Earth is “nothing special” and abiogenesis is an ordinary “arising” of life from non-living matter, spontaneous abiogenesis would be a trivial common occurrence here on Earth as well as throughout the Universe, and we would have many “trees of life” instead of one. However, until now, all abiogenesis experiments have failed to produce life, spontaneous generation has been rejected, and the Fermi paradox stands, all these keeping the single “tree of life” and UCD hypothesis still alive and still inexplicable.
- Conditions for starting life should be similar to those required for sustaining it. The Big Bang model mandates a beginning of life. Furthermore, once started life must be sustained by the same or very similar environment. And since life is being sustained now on Earth, abiogenesis should be ongoing contrary to all observations to date. Tidal pools, deep sea hydrothermal vents, and the undersurface of ice caps have been hypothesized to originate abiogenesis due to their persistent energy gradients, but no abiogenesis or its intermediate phases have been observed around these sites. Given these, the only methodological naturalistic alternative is ‘limited window of opportunity for abiogenesis which suggests primordial life substantially different than all known forms of life, and perhaps originating on another planet followed by panspermia. However, this alternative defies Occam’s razor and the absence of supporting evidence including the earliest ever known fossils (stromatolites) that are of commonly occurring cyanobacteria rather than of alien origin.
- Universal Common Descent requires an inexplicable biologic singularity. All known forms of life are based on the same fundamental biochemical organization, so either abiogenesis happened only once or it happened freely for a while but then it stopped when the ‘window of opportunity’ closed and only one organism survived to become the Last Universal Common Ancestor (LUCA) of all existing life on Earth. However, these two biologic singularities should be unacceptable given the lack of evidence and the assumption of continuity in nature. Furthermore, the second scenario requires two discontinuities: one for the cessation of abiogenesis and the second one for the bottleneck leading to LUCA.
- In conclusion, UCD hypothesis leads to a number of bad and very bad scenarios: a) Earth is “nothing special” should lead to a “forest of life” rather than a single “tree of life” and to ubiquitous abiogenesis (unobserved); b) Alien life plus panspermia is refuted by the Fermi paradox and oldest known stromatolites fossils; c) Single event abiogenesis is an unsupported and therefore unacceptable singularity; d) ‘Window of opportunity’ abiogenesis followed by LUCA bottleneck is even less acceptable double-singularity. And this brings us back to Darwin’s “open door” to creation, perhaps the most rational alternative that fits all biologic observations.
Con: Maybe abiogenesis is happening a lot. I think the already existing life would dispose of it quickly though.
Pro: if so, 1. We should be able to duplicate abiogenesis in the lab; 2. We should see at least some of the intermediate abiogenesis steps in nature; 3. Existing life can only process what looks like food. Cellulose is a well known organic material that cannot be broken down by a lot of organisms and is known to last as very long time in dry conditions.
Just a few comments:
1.Observation. We observe that living beings originate through procreation of other living beings. We also observe that offspring are not identical to their parents. Although we haven’t clearly identified the origin of new species this way, this is arguably because we haven’t yet built up a documented track record over long enough time to observe this.
If there is no UCD, all species were created out of thin air. This has never, ever be observed. Not one single time.
I would argue that in terms of observation, the UCD model is far better supported than the special creation model.
2. is pure speculation.
3. Conditions for starting life. This is simply incorrect. We know that the conditions on Earth were very different several billions of years ago than they are nowadays. It is certainly feasible that the conditions back then were more conducive to the origin of life than they are now, and that as conditions slowly changed over time, life has adapted to survive under the new conditions. This also goes a long way to counter your point 4.
5. The opposing hypothesis to UCD is multiple special creation. There is exactly zero observational evidence for this, there is not a single scientific model for how this could possibly happen, and this model demands an incredibly unlikely scenario where, within the limits of fossil preservation, successive created species look exactly as if they are related through common descent. In comparison with UCD, this hypothesis is worthless.
You might want to google for observed speciation.
One thing is different after the Origin Of Life: Now there is life. Such as bacteria.
Every time an interesting stew of chemicals gets together, and something might be possible, guess what? Bacteria move in, grow there, and eat the interesting chemicals. Result: fat and happy bacteria, and no additional origin of life.
This is not a new point of mine — it was even mentioned by Darwin.
This is a false assertion. Common genes are evidence for this. Genes shared between chimps and rats and not mice and humans are evidence for this. Genes shared between Zebra fish and humans and not humans and mice are evidence for special creation.
Not at the genetic level.
Good grief, Bill. You can construct a phylogenetic tree just from comparative anatomy. Linnaeus did this. You can construct a phylogenetic tree just from comparing DNA sequences. Here is a paper with quite a few citations.
The two trees look remarkably similar. That’s consilient evidence for you.
Where we have additional evidence where common descent has occurred they look almost identical. You need to explain the differences not just “remarkably similar”.
I was actually referring to paleontological systematics.
Well, that’s an active avenue of scientific research. But you agree that the two trees are “almost identical”? And still not good enough? Yet ID doesn’t even offer a testable hypothesis? Dawkins called this virtuoso believing.
In this case the trees are fine. They are missing a key element and that is a hierarchal structure at the gene and morphology level. Where you can independently show common descent (you from your parents) the trees are not hierarchal.
Seriously, Bill, I have no idea what this sentence means.
Strictly speaking if that situation was as you are assuming it to be (which I doubt), it would not be evidence for special creation, but it would certainly count heavily against the way we think that evolution works at the level of vertebrates. I doubt that the case is as clear as you think it is though.
1. To properly evaluate the claim, we’d have to know how those authors counted those “shared” genes, and whether they’re really talking about strict presence absence of, say, a gene family, or if they refer to differences in number of members in a family.
2. To properly evaluate the claim, we should have complete, high-quality, genome sequences for all organisms. If the differences you claim are small, then it’s very possible that the “missing” genes are in sections that failed to be sequenced in one organism or another.
3. The search for missing/present genes should proceed cautiously. Annotation quality varies from author( to author. Thus, it is possible that “missing” genes, are not missing, just not annotated. The opposite can also happen: bad annotations making something to be a gene that’s not actually a gene.
4. Viral insertions happen. So, viruses of the same kind might insert themselves after speciation has occurred and thus introduce what would look like the “same genes” in ways resembling patterns like those you claim.
5. All of the above also means that the claim needs quantification. If half our genes were shared with zebra fish, not not with chimps, then we’d be talking about something seriously wrong with the way we think that evolution proceeds in vertebrates.
6. Special creation is about religious fantasies, which is why it cannot be taken seriously.
So, errors can occur. We know that eukaryotic genomes are far from complete. There’s many human genomes deposited in databases, yet there’s no truly complete human genome available. For chimps, rats, and mice the databases are much poorer. Errors in annotation are bound to happen because the algorithms to detect genes do not always work well. The resulting annotations require lots of revisions on the part of authors, and even those revisions might fail due to limited knowledge. Gene families vary in copy numbers even within a single species population. Thus, an analysis depending on counting copies of gene families will have a biological reason to produce patterns like those you mention, and still not count as a problem for our understanding of vertebrate evolution.
So you have shown scientifically that special creation is about religious fantasies. Brilliant 🙂 I look forward to your academic work falsifying the bible.
In all seriousness, I do think your above claim about re testing is important and a solid argument from you.
It is so by definition. Where else but from religion would we get such wording as “special creation”?
I don’t need to falsify the bible to understand that it’s written by people whose limitations in knowledge mirror those of the peoples and times when it was written.
I’m not sure I understand what you’re asking. Do you think anything I wrote is false? For example:
1. Do you think that all those genomes are of high-quality, rather than fragmented and of varying quality?
2. Do you think that software for finding genes in genome sequences is robust and entirely accurate? To answer that take into account that the training of the software is done with experimentally confirmed genes, and that those genes might be low-hanging fruit, and that even those genes end up being poorly predicted. There was a famous article about the enormous disagreement between the public and “business” human genome projects due solely to differences in gene prediction recall. There was differences in 50% of the annotations. It must have improved ever since, but still far from perfect.
3. Do you think viral insertions don’t happen?
4. Do you think copy number variation doesn’t happen?
5. Do you think that gene counting cannot mean different things to different people?
6. Do you think your claims would hold regardless of what’s meant when talking about “shared” and “non-shared” genes?
I mean, I like understanding things. I like making sense of things. So, I approach things first by checking how things were done, and what’s meant by the wording. Do you think it is not important to know such things? That we should make grandiose claims in ignorance? Wouldn’t lack of checking be a bit counterproductive to your beliefs if you’ve misinterpreted something?
Sal presented a huge claim about domains based on data that clearly showed him wrong, and then cited articles, that also already showed him to be wrong, to support his position. Do you think making claims that shallowly is good for the IDiot community? That we’d think that we should take their claims seriously when they cannot even read?
So you have defined it as true 🙂
I don’t think you can support this claim but good luck.
We don’t expect perfect concordance. Each tree is inferred from a limited amount of data. Particular characters can be misinterpreted, changes between the same bases in a DNA sequence (or amino acids in a protein sequence) can occur in more than one place on the true tree, by accident. We can computer-simulate these processes, and see how much noise this causes in an estimate of the phylogeny. In simple cases, we can even do statistical calculations as to how much difference to expect between trees inferred from different regions of the genome.
It’s a whole field, usually called statistical phylogenetics.
I already did. But you don’t need to believe me, you can check those articles yourself (go to the other thread and check my comments and Sal’s linked articles for starters).
ETA: Ups! Now I see that what you meant was that I gave you a solid answer. See? We need to read carefully. I messed up big time, and now I apologize. Sorry.
No problem. I am interested your genetic recombination claim. I hope you develop it.
1. Bacteria divides every 20 minutes while humans every 20 years. We should have observed new bacteria species all the time. And even animals would be all in transition all the time.
2. How so? It’s like you’re saying “it rains today so it’s ok to expect it won’t rain again”.
3. What about stromatolite fossils? That shows statis, not what you imagine.
4. Then why a “tree of life” and not a “forest of life”?
5. There is no one opposing hypothesis. Can’t argue based on “this is the only way”.
You obviously didn’t read the Pro-Con notes. Try again.
Not this topic, but it is quite common to have two incorrect methods leading to the same false interpretation.
Thanks for the interest. You might want to start here, and then there. Not that developed, but you might get the main point.
Yes Darwins idea rejected out of hand common design before it made a claim of observation leading to a conclusion of common descent.
It was failed reasoning and poor science. Still is eh.
There is never a reason to imagine a unlikely concept of common descent based on grouping traits in bodyplans.
God could make a general plan with segregated plans and a plan of biology to preserve itself by changing bodyplans.
1. Actually, new bacteria species are being discovered on a regular basis.
2. Conditions on the early Earth were wildly different from today, e.g. there was no or little free oxygen in the atmosphere. Whatever the processes were that gave rise to life, they may be incompatible with the current conditions, so this argument fails.
3. Stromatolites were once abundant but are now very rare, so they are not exactly thriving. They were in fact material in changing the composition of the Earth’s atmosphere.
4. Competition between life forms?
5. Not sure what you mean. There exist, and have existed, numerous different species. Unless they originate through common descent, they must have popped out of nothingness. Is there another possibility? UCD wins hands down as the best available scientific hypothesis.
You’re absolutely right, the point was made in your Pro-Con notes, where it is the only convincing point.
In context it doesn’t look as if Darwin proposed anything despite lack of observational basis, since he mentioned several observations already in 1960, and extended the number of observations later on, as can be seen in 1872.
ETA: I hadn’t looked into Darwin’s “Origin” for quite a while. I find it beautiful.
Charles Darwin: a man before his time?
Perhaps his life ran backwards, and eventually he became a monkey.
Ups! 1860! but I should have mentioned the one in 1859.
“With his remarks, Darwin left the door open to creation (“life was first breathed”), but since then, Neo-Darwinists have rejected creation and replaced it with belief in undirected abiogenesis while maintaining belief in UCD.”
Undirected abiogenesis can be researched. Creationism can’t. It’s as simple as that.
“UCD is incompatible with the current view of Earth as just an ordinary planet circling an ordinary star located nowhere special inside an ordinary galaxy. “
Since nobody is suggesting that earth is “just” an ordinary planet, your point is moot.
“However, until now, all abiogenesis experiments have failed to produce life, spontaneous generation has been rejected,…”
Since no abiogenesis experiments have attempted to produce life, your logic fails.
“Conditions for starting life should be similar to those required for sustaining it.”
Why must this be so? Human life starts in a liquid environment in the absence of an nitrogen/oxygen atmosphere, but it certainly can’t be sustained without one.
God could do anything.
1. Correction: new bacteria species are being NAMED, not discovered. LTEE started with eColi and still produces eColi. Nothing else.
2. Point 3. in the OP: “Conditions for starting life should be similar to those required for sustaining it”. Else life doesn’t survive. Plus no proof whatsoever for your imagined scenario.
3. Don’t matter “rare” or “thriving”. They lived, live, and never changed – goes to show “no evolution”.
4. Are you asking me? This is Noah’s Ark all over again. Only you claim this extreme bottleneck (one LUCA!) to be a random event? As explained, this is an impossible double-singularity (option d).
5. Yes, there is another possibility, Intelligent Design. First off nothing EVER “pops into existence”. Second, UCD is not at all scientific (zero proof Darwin brain-fart).
1. Is there anything that cannot be “researched”? And “researched” means what exactly?
2. Perhaps you’ve lived all your life in a cave?
3. See 2.
4. Hence “similar”. Let’s try both and see no abiogenesis in either. Oh wait, they’re already trying both. And no luck. Ever.
And “evolution” nothing. Exactly right.
God could do anything in making a biological physics plan. before/after the fall.
in fact thats what one would have to do to let it run itself. just like in physics. Why not??
So likeness in biology is predictable from a God concept. A randomness is not predictable from a God concept.
1) research means mechanisms proposed, tested, evidence gathered, lather, rinse, repeat. How do you propose doing this for “god-did-it”?
2) No. I have heard many of the arguments. When people say that earth is an ordinary planet circling an ordinary star they simply mean that, given the billions of galaxies and billions of stars, it is unlikely that earth is any more exceptional than any other planet. All we can say is that the earth has the characteristics necessary for earth life to survive. And if we find life on another body, that body will have the characteristics necessary for its life to survive.
3) Perhaps you can link to a research paper that claims that its goal is to produce life. That would be an interesting read.
4) Are you suggesting that an aquatic environment is similar to a terrestrial environment?
1. How can you name new bacteria if you haven’t discovered them first? Genuinely curious…
2/3. There is a lot of evidence for lack of oxygen on early Earth. Geochemical data, isotope data. Life could arise in one form, change the environment simply by existing, and evolve to keep up with the changes.
4. No, I wasn’t asking you, I was making a suggestion.
5. I don’t understand you alternative model. How does the ID manifests itself? If new species don’t originate from descent with modification, where do they come from? You say that they don’t pop into existence. You also say that they are not related to ancestors of a different species. Whence then do they come from? Say, at time X, species A does not exist. At time A+delta, it does exist. What, according to your scientific model, physically happened to bring species A about?
There is tons of scientific work done on UCD, as I’m sure you will know. A lot of it is discussed in this forum. In contrast I have never seen any scientific work done on special creation. If it exist, can you give a link? And I am not asking for work that claims to put UCD in doubt, I am asking for work that researches special creation. Thanks in advance.
1. No, it isn’t.
2. Even if it were, that wouldn’t mean that there’s no UCD.
3. Ordinary and extraordinary are judgement calls. For some, Earth being one among billions of planets might be extraordinary compared to trillions of planets that might not be like Earth. For others that would not be extraordinary.
Several layers of misconceptions here.
1. If Earth is nothing special, again, a question of perspective and preferences, it doesn’t follow that life should arise willy-nilly all over the place.
2. Abiogenesis could be “trivial,” another one that’s a question of perspective, and still end up, after lots of competition and random events, with UCD.
3. UCD refers to life on Earth alone. Of course there’s no reason for life in other galaxies to have common ancestry with life on Earth.
So far no experiments have attempted to produce life. They’ve all been about figuring out if different conditions produce complex chemicals from simpler ones, figuring out the behaviour of self-assembling/self-replicating chemicals, etc.
Failure to do something doesn’t mean that it doesn’t or didn’t happen. We cannot produce a solar system. That doesn’t mean that the solar system didn’t have a beginning.
Of course! We cannot expect complex life to arise without progenitors, which is why we understand that life, at its origins, must have been much simpler.
Moved 3 comments to guano.
It’s about the content/abuse ratio, folks.
1. I have no problem with research and have not asked for a description. Sure you can study creationism as in Lemaitre validating the Book of Genesis.
2. So now you think “Earth as just an ordinary planet”?
3. Miller–Urey, etc. Do some research
4. Yes. Not identical but more so than Mars.
1. You can rename a subgroup. The point was not about a new outdoor discovery but about new bacteria species in the lab, from same ancestor. This we don’t see although we should given how fast they reproduce.
2/3 “Evolve” in one generation? Regardless, obligate/facultative an/aerobic bacteria are all common. Demonstrate experimentally your abiogenesis scenario.
5. It can be special creation the way we make a phone or car. It can be some guided biologic descent. We don’t know. What we DO observe is that abiogenesis is not happening and organisms do not transmutate in other species. We don’t measure value of scientific work in “tons”. Not this topic, but you can say Big Bang confirms the Book of Genesis.
Anyway, do you understand why the UCD assumption creates a bigger dilemma?
1. Yes it follows. “drake equation”
2. Already discussed. See paragraph 4. in OP
3. There would be many trees of life on Earth. Again, see and understand 4.
4. Miller Urey etc, but those grapes were sour.
5. Yes. But default assumption should be “not happening” if it never happened.
No it doesn’t “think instead.”
Not discussed. Paragraph 4 is about “singularities.” I wrote “competition and random events,” which do not require singularities. To understand what I meant you’d have to learn to think first, which is plainly impossible for you to do, then read about coalescence, as well as about random events and power-law distributions, which requires some mathematical literacy. So I’m not wasting my time explaining any of it to you.
No there wouldn’t. Life in other galaxies cannot result in many trees of life on Earth. Read and understand some basic logic.
Miller-Urey was about complex chemicals from simpler ones, as I just said. Learn to read for comprehension.
However, we know it must have happened. Some idiot who can barely think, and against all odds, made this very point:
See? It happened. Life had a beginning.
That just doesn’t follow. It’s not the same for life to start as for life to be sustained.
If you say so.
Again, this doesn’t follow.
Since the first claim is a non-sequitur, this is nothing but a claim based on a non-sequitur.
But life is not absent from any of those places, which makes it a tad difficult to say that they’re the very same environments as those where life originated. Right? There’s at least one, but very important, difference: there’s life!
This is a nested non-sequitur. That doesn’t follow either. There might have been a limited window of opportunity, but that’s not the only option. It’s one of many.
You didn’t need all those non-sequiturs to get here. Of course original life must have been very different to current life forms. We’re talking about abiogenesis. Today’s life is bounded to progenitors. That could not have been the situation at the beginning. Dah!
Oh! How awful that must be. Occam might get angry.
I would have agreed with this one, were it not for the following part.
You should really take a few courses on logic. Well, not that you’d be able to follow them.
1. The earliest fossils doesn’t mean the same as the original life. Get that? Let me repeat: earliest fossils doesn’t mean original life. Life could have started millions of years before there was any organisms that could leave evidence in the form of fossils.
2. Can you point to the genetic/molecular studies demonstrating that those stromatolites were produced by “commonly occurring” cyanobacteria?
3. How could you possibly determine if the organisms leaving those stromatolites were or were not from an alien origin? I think they were not from alien origin, but I doubt that anybody has evidence one way or another.
4. Furthermore, logically, if life came by panspermia to Earth, which I doubt, whether those stromatolites were formed by “commonly occurring” cyanobacteria or “uncommonly occurring” ones, they’d still be of alien origin.
1. What is the difference between a ‘new subgroup’ and a new species? Please clarify your terminology. Can you also point me to where biologists claim that bacterial evolution happens so fast that we should already have seen new species evolve in the Lenski experiments? I don’t think that anyone has made that claim, making your objection irrelevant.
2/3. Where does this ‘one generation’ come from? Clearly, oxygenation of the Earth’s atmosphere by organic activity would have taken a long time, many, many generations. Some bacteria thrive in oxic conditions and others in anoxic ones. So what? Life adapts to ecological niches.
5. What scientific evidence is there that species have been assembled like phones or cars? Is there any actual evidence of this at all? Where are the scientific hypotheses of this theory? What scientific research has been done on this idea? If there isn’t any, why is that?
Moreover, this idea leads to many further questions: where was this assembly done? By whom? Who built the assembly plants? Where did these builders themselves come from? Doesn’t this just displace the original question to the next level, one that is even more problematic because now you don’t just have to explain the origin of very simple organisms, but of very complicated ones that can design and build assembly plants for life. In what way does this advance our understanding?
I am intrigued by ‘some guided biological descent’ – are you saying that you accept that some evolution is possible by descent with modification (leaving aside the cause of the modification)?
The amount of scientific research, and how often it is cited, is certainly an indicator of the impact of the work. Low-value work tends to disappear whereas fruitful work gets picked up and expanded by others, often leading to further discoveries and better theories. This is how science has advanced over the centuries. Shoulders of giants and all that.
And no, I don’t see how UCD creates a bigger dilemma. Not for science, at least. The alternative isn’t even in the running, because there is no way of formulating special creation or divine intervention in scientific terms. I can see that for some believers there might be a religious dilemma. I am not really qualified to argue about that.
I wonder how many of the IDcreationists who claim that scientists have “failed” to create life in the Miller-Urey experiments have even read the original papers. I mean, the objective and motivation of the experiments are stated outright in the beginning of the introduction and abstracts. You can’t somehow fail you realize what the intention of these experiments were.
They can be found here: Stanley L. Miller (1953):A production of Amino Acids under Possible Primitive Earth Conditions. Science, New Series, Vol.117, No. 3046 (May 15, 1953), pp. 528-529.
Stanley L. Miller (1954): Production of Some Organic Compounds under Possible Primitive Earth Conditions.
Now, here’s the hilarious irony. If the experiments had succeeded, contrary to expectations, in actually synthesizing living organisms from nonliving systems, IDcreationists would have claimed these organisms were intelligently designed and didn’t originate “naturally”. That’s what they claim happens in things like evolution simulations, and not to mention evolution experiments using artificial selection (because the simulation, like the experimental protocols, are designed, so must the results be considered “designed” apparently).
Yet when the experiments, which again aren’t even intended or expected to mimick the origin of life, therefore “fail” to create life, IDcreationists insist this constitutes a failure of “abiogenesis”/evolution/naturalism/atheism/etc.
It’s having your cake and eating it too all the way down. There’s isn’t an argument against abiogenesis, or evolution, that doesn’t ultimately rest on a hypocritical double standard.
There is also the irony that the (so far) failure to create life in the lab is actually an argument against ID rather than in favour of it. Unless humans aren’t considered intelligent, I suppose.
Rumraket and faded_Glory,
Those are excellent points. If I do an evolutionary simulation and it fails to achieve improvement in fitness, I bet it will immediately be accepted by ID types / creationists as proving the ineffectiveness of natural selection. But if it succeeds in improving fitness, it will be declared to be an example of ID.
Heads: we lose, tails: they win.
Simple denials without logical support are worthless. What’s the point?
a. If starting life conditions are not similar, then life starts and dies immediately over and over. Even live birth is ‘similar’ – same pressure, temperature, chemical needs, etc. Note ‘similar’ is not ‘identical’.
b. “have been hypothesized” – not my claim. Yet no abiogenesis seen. Same conditions / “no life” (sterile) can easily be duplicated in the lab. Guess what? No abiogenesis!
c. If no ‘limited window of opportunity’ then window still open, then why no abiognesis observed today?
d. Yet there’s zero evidence for “life must have been very different to current life forms”.
1. Yes, “doesn’t mean” but a very strong evidence. There’s zero evidence for something entirely different prior.
2. “genetic/molecular studies” on fossils? Mad dogs should attack the original studies if unhappy: “Some represent now-extinct bacteria and microbes from a domain of life called Archaea, while others are similar to microbial species still found today. ” https://news.wisc.edu/oldest-fossils-found-show-life-began-before-3-5-billion-years-ago/
3. Point is they do not look at all alien – see 2. Also 3.5 billion yrs doesn’t leave a lot of time for alternative (desperate) scenarios
4. Panspermia is “refuted by the Fermi paradox ” – see bad scenario b.