Looks like a bullshit paper. This big question mark is: assuming life evolves on a suitable planet, what are the odds that something like an intelligent technological species would ever evolve? We only have one example: us. You can't extrapolate from that, so they just made up numbers.
Define "technological". We've recently accepted that there are several tool-using species other than us.
We have a head start on other apes, but they might catch up if we weren't in the picture. If octopi stopped dying so young, they might give us a run for our money. Orcas have fashion trends ("did you see Becky's dead salmon hat? I'm getting one of those!"). Mess with corvids at your own risk.
From a technological point of view, the main distinctive feature of humans has not been the use of tools, which is relatively widespread among animals, but the control of fire.
The control of fire is what has enabled humans to produce and use new classes of materials that all other living beings are unable to make, e.g. ceramics, metals, glasses, cements, thermoplastics and thermosets, various kinds of crystals, including semiconductors, etc.
These materials have been essential in the development of human technology during the last twenty thousand years.
All the other living beings can use only a limited range of materials, consisting of polymers that can be synthesized at ambient temperature and pressure (e.g. wood or horn or chitin), adhesives and the equivalent of sedimentary rocks (in various kinds of skeletons, most commonly made from composites of proteins or chitin with insoluble salts of calcium, strontium or barium, but also including those made of sedimentary glass, i.e. opal, like in sponges and diatoms). (Natural glass is either volcanic, made by rapid cooling, like most artificial glass, or sedimentary, i.e. opal deposited from a solution of silicic acid in water. Living beings can catalyze the latter reaction in order to make siliceous skeletons.)
So the myth of Prometheus was actually quite wise in comparison with many later attempts to define essential features of humans.
Any living beings that have remained confined to a water environment, like cephalopods, do not have any chance to develop a technology comparable to that of humans, because without being able to use fire they could not make metals and the other materials required for that. Being unable to create an advanced technology is not an obstacle to reaching a high intelligence, as high as that of humans. The humans of fifty thousand years ago were as intelligent as those of today (perhaps on average even more, as all the dumb ones died quickly), even if they did not have yet any technologies that could not have been developed by something like an octopus.
I'm trying to decide whether it would be possible for super-intelligent cephalopods to use underwater lava vents to refine metals. Would make a fun SF premise, but I take your point.
> From a technological point of view, the main distinctive feature of humans has not been the use of tools, which is relatively widespread among animals, but the control of fire.
> The control of fire is what has enabled humans to […]
… on Earth with an iron-nickel core and an oxygen rich atmosphere, with easy access to vasts of low energy density organic material (dead trees) and higher density energy source (coal). Either of the two can be literally picked up from the surface, which was even more important for ancient civilisations.
But mastery of combustion is just one successful path, not a universal prerequisite. What matters is access to controllable high energy densities and redox chemistry that can extract, shape and join structural and conductive materials. On many plausible worlds those needs could be met without fire. Fir instance:
1. Native metals and cold working – worlds rich in native copper, silver or gold from hydrothermal deposition or reducing atmospheres allow metal use with no smelting. Cold hammering, annealing on warm geothermal surfaces, and pressure-sintering can produce wire, sheet and simple tools. Meteoric iron is another route to early ironwork by cold forging.
2. Electrochemical extraction at ambient temperatures – acidic or chloride brines can leach Cu²⁺, Ag⁺, Zn²⁺ and similar ions that can be plated onto seed cathodes. Electricity could come from: a) galvanic piles built from naturally dissimilar minerals in a brine; b) tidal, wind or river generators driven by simple turbines; c) lightning harvesting into capacitors, then steady discharge into plating cells. This is essentially solvent-extraction and electrowinning without a firebox.
3. Solar furnaces without flames – on oxygen-less or thin-oxygen worlds with intense sun, arrays of polished stone, mica sheets or vitrified sand mirrors can reach smelting temperatures. Early optics need not be metallic – glazed ceramics and transparent minerals suffice – so a civilisation could jump straight to photothermal metallurgy.
4. Non-combustive chemical heat – highly exothermic mixtures – thermite-class reactions and metal sulphide or halide reductions – release smelting-grade heat once initiated. On halogen-rich worlds, fluorides or chlorides could be reduced by hydrogen or metals to yield both heat and purified product. This is chemistry as furnace.
5. Under-ice or ocean worlds – combustion may be impossible, yet hydrothermal chimneys deposit native metals and sulphides. Technology could develop around: a) ceramic and glassworking using geothermal heat; b) galvanic circuits using sulphide–metal couples in seawater for plating; c) arc heating from captured lightning or magnetospheric induction to melt and weld underwater.
6. Biological ore upgrading and metal precipitation – an interesting idea to entertain as microbial consortia already leach copper and gold on Earth at ambient temperatures. Projecting further, an alien biosphere could be domesticated to: a) acidify heaps and liberate ions from ore; b) reduce and precipitate metals onto templates for near-net-shape parts; c) grow conductive biomaterials that substitute for early copper wiring. Biometallurgy can start well below 100 °C and scale industrially.
We should also not entirely dismiss a possibility of material alternatives that postpone, or even replace, metallurgy – advanced ceramics, glasses, cements, laminated woods and fibre composites can carry a civilisation far – structural engineering, containers, even turbines and high-temperature reactors. Conductive paths can begin with graphite, sulphides and native copper; semiconducting minerals such as galena enable primitive electronics. Metallurgy may arrive later or remain niche.
None of the above is outside the constructs of the laws of physics and chemistry, and, most assuredly, the suggested alternatives are not crack pot theories or hard code science fiction – provided the local environment has favourable conditions that meet one or multiple criteria. Even more so if an alien civilisation had an earlier head start – modern humans have only been around for 200 thousand years circa (we won't include the earlier hominid forms), and if another civilisation could have started advancing «just» 1 billion years earlier, they would have had a luxury of progressing steadily even if at a slower pace.
To sum it up, none of the above requires fire for a hypothetical extraterristrial civilisation to advance. Fire was the proverbial low-hanging fruit and the path of the least resistance, so the early humans enthusiastically adopted it given that the terrestrial environment favoured and «encouraged» the use of fire, so to speak.
if you include the earlier hominid forms, of which they were able to continue interbreeding, then you’re talking about 600k to maybe (likely not) 1 mya!
The native metals are either too soft for being used for tools (Cu, Ag, Au) or too hard to be possible to forge (platinum-group metal nuggets, which were the material originally named "adamant" by the Greeks, before the Indian diamonds became known after the expedition in India of Alexander the Great).
Native metals have always been used only as jewels, before it became possible to melt them, in order to make hard alloys, e.g. copper-arsenic or copper-antimony, and later copper-tin.
The exception has been meteoric iron (i.e. Fe-Ni-Co-Ge alloy), which is hard enough to be useful (because it is an alloy), but that could never be an abundant resource. Moreover, meteoric iron cannot be forged without heating it. Cutting and polishing it like you do with stones is very difficult, but possible. However, such a method of using it does not provide the main advantage of metals, of enabling the creation of complex shapes by plastic deformation. Had it not been possible to forge meteoric iron by heating it in fire, nobody would have bothered with attempts to make knives out of it, instead of using stone tools.
Using concentrated light instead of fire would work, so such an invention could be imagined on a planet where the atmosphere could not provide fire, like on Earth. However this is not something that could be invented by aquatic animals, because they would have to invent first means to make chambers empty of water where materials could be heated in such a way. Such a succession of inventions, including adequate pumps, is extremely implausible because their utility would not appear until all the necessary techniques would exist. It would be far more plausible for aquatic animals to first develop means to live outside the water, and only then make such inventions, in an environment where they are much easier.
While there are bacteria that can reduce some metal ions, e.g. of copper, silver or gold, to the corresponding metal, they do not do this for producing a metal, but for removing poisonous ions from their environment by sequestering them into the insoluble metal. On Earth, living beings have either a complex structure or chemical versatility, never both. It seems likely that this constraint would also exist elsewhere, so one should not expect intelligent beings that are able to reduce metal ions into metals by their body physiology. In any case, the pure metals produced in this way, like also the native metals precipitated in abiotic conditions, are useless for making tools, without being able to heat them to high temperatures for making alloys and for controlling their polycrystalline structure. The same applies to metals that would be produced by electrolysis.
Fire using air is the source of heat originally used by humans on Earth. Any other available source of strong heat could have replaced it in the history of another planet. The point is that to ascend to the level of human technology any living being must acquire the capability of processing materials at temperatures very different from their ambient temperature. None of the techniques of producing metals at the ambient temperature is sufficient for being able to make useful things out of them. The same for other classes of materials, e.g. semiconductors or glasses.
One could imagine an extremely advanced technology where one would be able to make a big object by putting an atom after another in just the right place. That could work at ambient temperature and produce anything. Even if such a technique were possible, I find it impossible to believe that any living beings could become capable to develop it without first passing through the stage where a lot of material transformations can be made only at high temperatures and/or high pressures.
The plausible scenarios I have outlined concern the seeding and emergence of a civilisation in the absence of terrestrial fire – a detail that, whilst seemingly minor, is foundational to the argument. Given sufficient time, such a civilisation could, through alternative pathways, achieve technological maturity without reliance on combustion. That is the crux of the matter.
Moreover, fire – as it is understood on Earth – is not merely a product of an oxygen-rich atmosphere. It is inextricably tied to the cyclical processes of organic growth and decay specific to this biosphere. To assume that such a mechanism is universal is a failure of both imagination and scientific rigour. It is patently unreasonable to presume that alien worlds capable of hosting life would replicate the precise biochemical and atmospheric conditions of this planet.
One might as well expect a symphony to be performed identically by instruments fashioned from entirely different matter – and yet remain surprised when the melody diverges.
By this criteria - all papers that extrapolate are BS papers.
There’s a ridiculous number of stars in the sky - no matter how low you put the odds of intelligent life, you will still end up with more than 1 civilized species in the universe.
This is, at least for me, the primary utility of such extrapolations. And eventually - extrapolations will be tested.
Setting aside if its perfectly fine or not, its not the same as extrapolating from actual data (and no its not “perfectly fine” to completely make up a number and pretend like its science.)
