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Dissent on Drake

Centauri Dreams‘ recent post on the Drake Equation triggered a broad range of response, both in comments and back-channel e-mails, the latter of which produced a note from Kelvin Long quoting a rather controversial position on Drake by one leading scientist. Here it is. See if it raises your hackles:

“I reject as worthless all attempts to calculate from theoretical principles the frequency of occurrence of intelligent life forms in the universe. Our ignorance of the chemical processes by which life arose on earth makes such calculations meaningless.”

The words are Freeman Dyson’s, from his essay “Extraterrestrials” in Disturbing the Universe (Harper & Row, 1979), a book I re-read every few years as much to admire the author’s rhetorical skills as to draw again on his insights. Kelvin has differing views on Drake and so do I, but I’m going to quote Marc Millis’ reaction to the Dyson statement, reflecting as it does an approach toward scientific method that I share. Marc writes:

“On Dyson’s views of ‘meaningless’ calculations, I have to agree somewhat if the sole purpose of those calculations is the answer. If, however, the purpose is to increase our wisdom from attempting to solve such seemingly impossible questions, then I vehemently disagree. The value gained in taking the time to think these things through and understand all the factors involved is much greater than the cost of doing the calculations. The improvements in the human condition come not just from what we achieve, but what we learn along the way.”

To which I’ll add that what we learn along the way is often surprising and sometimes turns back around to affect what we can achieve in new directions. Widen this out to the field of interstellar propulsion and a further thought arises. Achieving a particularly ambitious goal, such as one day developing a way to travel faster than light, may or may not be possible. But if decades and even centuries of applied study demonstrate that it is not, that result will not be a failure. We will have learned from it essential facts about the nature of the universe, and that in itself is what science, ever widening its range, properly sets out to do.

Comments on this entry are closed.

  • Tibor February 7, 2009, 11:10

    I share Marc’s view. The gain from the Drake equation is “being on the way” – and it is huge.

    To my mind the problem is if we take the result of a Drake calculation as a “real” hint with respect to the number of intelligent life forms in the space-time volume looked at. This is simply not solid enough. Beginning at the very choice of the factors to be included into the equation through the uncertanities of each of the numbers, there is no firm ground to declare any number or number range – other than the trivialities – to be better than others or to be “best”. There are too many assumptions we have to make.

  • Mark Phelps February 7, 2009, 11:52


    I rather think that Dyson may be playing the foil,does not one of Clarke’s Laws
    have a statement about elder scientists?


  • kurt9 February 7, 2009, 14:36

    Dyson made these pithy comments back in 1979, a time when we were clueless about how life could have emerged on Earth. I think he was right. To a certain extent, I think he’s still right today.

    We have several good ideas about how life emerged on Earth, but nothing definitive. I just read Nick Lane’s book “Power, Sex, and Suicide” about mitochondria and its role in biological processes. The merger that lead to cells containing mitochondria was the basis for all eukaryote cells and complex life. Apparently this happened only once in the history of the Earth. If Lane’s argument is true, and he gives a very compeling argument in his book, it is likely that the Earth is the only planet in the galaxy that has complex life. A lot more research is needed in this area to get credible answers.

    The development of eukaryote cells is only the first of several hurtles that separate us from bacteria. I think big brains are unlikely too. We pay a price for our big brains. They take up 20% of our metabolism. They also require an unusually long gestation period (9 months) as well as maturation period, 25% of the lifespan. It remains an open question if big brains are as durable as wings. Until we settle space in a sustainable manner, I consider wings to be the winner.

    Then there is the issue of plate tectonics. I think plate tectonics are necessary for the emergence of complex life. I also think plate tectonics are rare (this is testable by studying Mars). If so, then this is further argument against the wide-spread existence of complex life.

    Kepler is a step in the right direction. However, terrestrial exo-planets must not only be detected, but must be characterized as sufficient resolution as to determine of there is a biosphere. I’m not sure how large or sensitive of telescope and instrumentation one needs to do this. I would think the presence of significant oxygen in a planetary atmosphere is a tell-tale sign of a biosphere. Oxygen gas is reactive. So, it has to be continuously replenished. After all, the Earth didn’t get its atmospheric oxygen until photosynthetic life had been pumping it out for millions of years.

    My gut instincts tell me that complex life, let alone intelligence, is rare in the universe.

  • andy February 7, 2009, 14:53

    There’s nothing particularly sacred about the Drake equation. It was a notable early attempt at estimating radio-SETI’s probability of success, that’s all. To think it states anything about the diversity of extraterrestrial life is to misunderstand its purpose.

  • David February 7, 2009, 20:36

    kurt 9 is very right on the eukarote issue Of course we just dont know what other life could be like. Maybe Mars will yeild something and our plaet searches may turn up something very interesting Full speed ahead BUT dont be disappointed of life isvery rare

    A BIG origin of life problem that I have worked on is the merger of the information system and metabolism …..

    BTW On seaparate Issue the Semate took out 6.5 Billion extra for NASA but that could easily be added back in the budget this summer so Marc and those in the deep space and proplusion efforts Fight for some of that!

  • john February 8, 2009, 1:18

    Question- If life is so common in the universe,why hasn’t it developed independently many times on earth? As far as we know all life on earth evolved from a common ancestor.

  • andy February 8, 2009, 10:42

    I guess it’s harder for abiogenesis to operate when there’s an existing biosphere that can eat up the pre-biotic stages before they get very far.

  • James M. Essig February 8, 2009, 17:01

    Hi Paul;

    I also share your opinion as well as that of Mark Millis regarding the meaning, purpose, and value in studying the Drake Equation and the various factors that comprise the function. It is interesting to note that some additional factors regarding the possible number of interstellar civilizations include natural extinction events such as supernova, natural pandemic or pathogenic outbreaks on the home planet, the destruction of one civilization by another more advanced civilization, and perhaps others.

    I would imagine that due to any moral code or federation like ethics that perhaps interstellar space faring civilizations would have, a factor involving a complete irradication of one species by a more technological species would likely be close to one if not very close to one. Since supernova are rare, any associated supernova caused death of a civilization would likely also be close to one or very close to one. Since we have not observed too many species on Earth become completely extinct from a natural pandemic, the would be natural pandemic factor would seem to be close to one also.

    Studying each of the traditional variables or factors within the Drake equation includes the study of subfactors or subvariables of each of the traditional factors. Such studies can perhaps nail down more accurate or more plausible values for the number of ETI civilizations within our galaxy, and by corollary, the number of such civilizations within the visible universe.

    The Drake equation, although a relatively simple product of factors is nonetheless a profound development that has given us more tools for which to analyse the probability of ETI civilization per unit of number of star systems within a statistical sample.



  • Ronald February 8, 2009, 17:40

    Ref. kurt9 and David: yes, I also think that the biggest biological challenges by far are the immense gap from abiotic chemistry to the first living cell and from single cell to multi-cellar complex life. All other evolutionary steps after that pale in comparison, as the evolutionary explosion in the late Precambrian/early Cambrian (and ever since) has also shown. Life appeared on earth rather quickly (within a few hundred million years), but the first 3 billion years it (probably) exlusively consisted of microbial life.

    Purely going by (very deficient) earthly statistics, therefore, it is quite well possible, first of all, that many potentially suitable planets in our galaxy do not possess life at all (yet) and, secondly, that even of all ‘living’ planets 80-90% may possess only microbiological life.

    Regrettable in a way, but on the other hand, as I have argued before, it also offers great opportunities for future human settlement and dispersal of (adapted) earthly life, in combination with terraforming (to the extent necessary). And without too many of the ethical problems surrounding the colonization of living planets.
    BTW, what would be the ethics regarding settling a planet with only limited microbial life in relation to human survival?

  • Ronald February 8, 2009, 17:43

    multi-cellar => multi-cellular, of course.

  • Adam February 8, 2009, 18:55

    Abiogenesis might have needed gases and UV levels that aren’t present in sufficient amounts today – hydrogen, methane etc. Extrapolating from the present to the deep past is usually a bad move.

  • amphiox February 8, 2009, 21:22

    john, all surviving life on earth descended from a common ancestor. That last universal common ancestor was not the first organism to come into existence. On the contrary, when it was alive, it had many contemporaries. Earth was already teaming with microbial life at that time. But none of those organisms gave rise to lineages to survived all the way to the present day.

    In all likelihood, primordial earth saw multiple independent abiogenesis events occuring in a variety of environments. Modern organisms are descendants of the most successful one. The others died out.

  • David February 9, 2009, 0:43

    Dont worry Adam we will have some more methane pouring out of the arctic
    Jim Essig mentions several threats I would add asteroid and Climate -those are the only realistic near term threats But both may als preclude a lot of life from developing -Many of our exoplanets have wild climates

    Ronald makes some excellant points We need intersteallar travle regardless
    I have been so stymied on abiogenesis I have worked on it with 2 excellant molecular biologists One who is now focused with me on climate and Endangered Species(which realtes closly to understanding evolution)
    He and I are hoping the plante searches give us some clues to overcome our dead ends! The other simply said God did move on to something practical!

    PBS religion show mentioned this on a Darwin story and one evolutionary biologist said abiogensis is a big problem(along with issues of temp -mode and complexity) BUT he doesnt bring the issues up because of the fundies

    This is Terrible because without dicussing what we dont know science can not progress and the creations win-Sorry about my rant But have been very upset by the sieg on science -another reason for the economic collapse!

  • brian h February 9, 2009, 1:18

    Many comments here regarding the significant gap between development of life and development of intelligent life. While I think commenters are right to point out the difficulties in early advancement– developing mitochondria, becoming multicellular, etc– I think there’s some reason to believe that the latter stages are equally difficult.

    Going from complex life to “intelligent” life– where intelligent, I assume, is defined as technological– is no easy task. We’ve done it with the grace of many contingent factors that can easily go overlooked. It’s not just big brains that give rise to technology– we need both an biological means of manipulating the environment (arms, fingers, forward facing eyes), and the external resources to easily manipulate directly (without first use of other tools).

    Just as a narrow example: if trees had never evolved on Earth– and certainly their existence isn’t an evolutionary necessity– then would we or any other technological species have? There may be some other environment that could prompt finely tuned digital motor skills. But the confluence of environmental pressures that came from life in trees just so happened to be those seemingly necessary (but not sufficient, obviously) for technology. Not to mention the question of what we would have used as tools without wood? Early fuel? Our mastery of the planet today makes it easy to forget just how tenuous, contingent, and highly dependent on other species our initial situation was.

    As a perhaps less fantastic example, could technological species arise on a planet with complex life, but the surface of which was entirely covered in water (or some other liquid?). Is an early ability to make fire (requiring some flammable atmospheric gas) necessary for technological civilization? I assume at some point, an energetic heat source would be required for melting down and fabricating metals (unless there’s some other materials in which to rocket oneself into space). Maybe underwater volcanic vents could be enough?

  • Ron S February 9, 2009, 2:05

    Oh, I don’t know. Some say we only have to extrapolate back 6,000 years or so…

    As to the Drake equation, I have to say I put little stock in it. I think it is as much as andy implies: a way to pose a question. But that’s it. No mathematical formula, no matter how simple, pretty, complex or use of squiggly symbols, can generate one gram of data. Too often it is used to inordinately influence the direction of belief or inquiry, which very easily exceeds its domain of utility. Data comes from observation, not equations, and especially not from single equations with multiple unknowns. These unknowns truly are unknowns. Worse (to paraphrase a certain politician), there are the unknown unknowns.

  • Stargazer February 9, 2009, 7:20

    Everyone knows that we don’t know all the factors in the equation. That doesn’t mean the equation is pointless, but it does offer a tool for us to make increasingly more accurate estimations on the number of civilisations with resources and technology for interstellar communication.

  • Tibor February 9, 2009, 9:37


    we definitely will know more and more in expanding the Drake equation, but I do not see right now how we will be able to assert any accuracy to the numbers we get from it. What is the estimated error in the result? How to calculate it if we do not even have a starting point for some of the factors?


  • Ronald February 9, 2009, 10:56

    @brian h: your last point is quite interesting:
    I actually think that on a water planet a technological civilization could hardly or not arise. It must be extremely hard to conduct any chemistry, electromagnetics or metallurgy, let alone nuclear physics in a watery environment.
    This is why Cetaceans, such as dolphins or humpbacks, would most probably never develop a techno civ, despite their high and very promising intelligence.

    So, I agree, for a techno civ. you need more than just intelligence: a land-dwelling species, a sufficiently stable environment (yet not too comfortable in order to present sufficient challenges), sufficient of the right resources, particularly energy and construction materials.

    It took us a couple of hundred thousand years to discover (the use of) electricity and electromagnetism, nuclear physics, etc.

    But one thing we also know: once the age of discovery gets started, things can move really fast. Last century saw more scientific and technological discovery than all previous centuries combined and this century will most likely surpass all of them easily.

  • ljk February 9, 2009, 11:48

    David said:

    “BTW On separate Issue the Senate took out 6.5 Billion extra for NASA but that could easily be added back in the budget this summer so Marc and those in the deep space and proplusion efforts Fight for some of that!”

    A mere three decades after the peak of the Great Depression (1933),
    we had humans in space and probes on their way to the Moon and
    Venus. Six years after that, men walked on the Moon.

    Human economics and politics are transitory. The Universe is
    virtually infinite as far as we are concerned. Our problems will
    disappear in the blink of a cosmic eye.

  • george scaglione February 9, 2009, 13:11

    tibor,yes sir,when figuring as in the use of things like the drake – the main problem is most certainly that we can never be sure of what we are saying.very respectfully your friend george

  • John Hunt February 10, 2009, 1:11

    Is there anything specific about an underwater world that prevents a species from developing a language and intelligence in which they begin intelligently observing, communicating, recording, sharing their findings, and theorizing. They may have difficulty developing technology using only mouths and flippers but could they, over a longer period of time, none-the-less begin to understand the principles of physics, the existence and nature of planets and begin to understand what would be needed to leave travel in space. Is intelligence the key and so technologic development will eventually follow?

  • ljk February 10, 2009, 10:24

    We live at the bottom of a global ocean of air – is that so different
    from the aquatic kind?

  • kurt9 February 10, 2009, 12:40

    It possible that a waterworld (a planetary ocean) is likely to develop complex life. The Earth’s oceans are very salty because of the run off from the land. It is all of the dissolved elements (“salt”) in the ocean that allow the chemistry that makes complex life possible. We know this to be the case because most of the ocean’s biomass is along and just off of the continental shelves. The mid-ocean region is the ocean equivalent to a “desert”.

    A planetary ocean will be much less salty because their is no land for their to be run off from. The only source of dissolved ions will be from the occasional volcanic eruption on the sea-floor. If the ocean is deep (say, 30 kilometers or more), the material from such a volcanic eruption will dissolve and diffuse very slowly throughout the planetary ocean.

    A waterworld’s ocean will be much less “salty” than our oceans. Consequently, there will be much less biomass in that ocean than in ours. Since evolution is statistically driven, that biomass is likely to be much less evolved than ours.

    I think complex life is unlikely on a waterworld.

  • Christopher L. Bennett February 10, 2009, 14:08

    As I understand it, the Drake Equation was never intended to be something that could actually answer the question of how many civilizations are out there; it was developed as a teaching tool, a way of defining the problem and discussing the factors involved in our contemplations about life elsewhere. As Mr. Millis said in the quoted statement, it’s purpose is to help us think about the problem.

  • Ronald February 10, 2009, 16:12

    I agree with what you say about the low nutrient content and hence low biomass of a waterworld.
    However, I am not so sure that low biomass would logically also imply less evolution and less complexity. I think that evolution can take place almost equally well (fast) in a nutrient poor environment.

  • James M. Essig February 10, 2009, 21:27

    Hi ljk;

    I can see your analogy. Just as we humans developed off ground transport, perhaps intellegent sea creature could develop land travel within the atmospheric environmemt. Just as we human went from air travel to space travel, the sea based ETI might go onto air travel and then to space travel.

    I mean no insult in pointing out the obvious, but the analogies here are quite profound in scope although elementary.

    I saw on TV a few months ago a special that included a discussion of some type of concrete that can set underwater that was developed or invented I think by either the Ancient Romans, the Ancient Greeks, or the Ancient Egyptians, I not sure which. Perhaps combining different chemicals in an aquatic environment could produce exothermic reactions hot enough for metalurgy, infrastructure building and the like. If the aquatic ETI could then build water suits, they might then venture out onto land where they could eventually learn to assemble aircraft and eventually space craft.

    One crude analogy I give involves the great span in human technology of using mere oil lanterns or candles to see at night to; the use of precise photonics in speed of light fiber optic cable based communications, ground penetrating radar, and 3-D imaging of the human brain in MRI scans and the list of technologies that could really not be foreseen by our ancesters hundreds of years ago goes on and on.



  • Adam February 11, 2009, 2:35

    Hi Ron & kurt9

    There’s lots of assumptions in our discussions of rate of evolution and a lot of unknowns. I take the view that complex life was limited by geochemistry for aeons and the terminal oxygen pulse kickstarted the metazoans. With oxygen being produced by other means life might jump to that level in less than the aeons it took here. But that’s my assumption. Look at what you assume and it might be enlightening.

  • kurt9 February 11, 2009, 12:43

    I believe that more biomass means faster evolution because evolution is essentially statistical. The more biomass you have the more chance there is for changes to occur. Hence, more evolution.

  • Adam February 13, 2009, 2:43

    Hi kurt9

    As most of Earth’s biomass is in bacteria I’m not that sure I agree there’s more evolution that’s somehow different to what has gone on before. An awesome amount of gene-swapping and gene-creation occurs in the Archea and Prokarya, with the occasional passing on to the Eukarya, but metazoans and plants seem like sleepy backwaters away from the main action in some respects. Most of the cells in our bodies are actually bacterial – about 5 trillion somatic cells, 30 trillion blood cells, and 40 trillion bacteria. I know we have a certain attachment to our genetic identities but we’re a blip when it comes to evolution as a whole. Something else pushed metazoan evolution forward other than stochastic processes – symbiosis maybe provided the impetus towards better intercellular signalling that led to both plants and animals.

  • Ronald February 13, 2009, 5:39

    @kurt9: you may be partly (or rather indirecty) right about more biomass meaning more evolution.
    However, I would rather say: the more individuals and the faster reproduction, the more (or faster) evolution, all other things equal (the other factors being, in particular. environmental selective pressure, of course). If the individuals are very small (microorganisms), there can still be a lot with little biomass.
    And vice versa: even a large biomass ecosystem can be relatively monotonous and/or stable.
    But you are probably right about waterworlds and low evolutionary rates, for another reason as well: an oceanic world is probably relatively very stable, with very little change and hence very little selective pressure and need for adaptation.
    The open oceans on our planet are quite species (and biomass) poor and many species there are probably quite old or at least little changed over long periods of time.