1. Richard Dawkins’s thought experiment – imagining a super-long bookshelf containing a photograph of every individual in a single line of descent from a fish ancestor to yourself – is a brilliant and thought-provoking one. It’s slightly unfortunate, though, that this video about it is hosted on the YouTube channel of a supporter of “Intelligent Design”…

  2. What was left unstated is how long ago this fish ancestor lived. Obviously earlier generations were short compared to the human one of around 20 years, and the starting point of this example must be less than 600 million years.

  3. This is an excellent illustration of time collapsed so that it can be viewed presently. Most people can understand ten years, twenty, even fifty years, but they have trouble relating to millions of years. This is an excellent solution that makes it accessible for easy understanding. Imagine if this was actually created and displayed. What a vast and powerful presentation this would make. Good job Richard.

  4. Just today my nephew related how a friend of is used the “why  are there still monkeys around” argument against evolution.
    So I suggested to counter that with “why are there still trees around” as we are also descended from the same ancestor as trees.
    I think that that is correct.

  5.  Yes, that’s right. The tree of life has one single root and ultimately all life is related. Regarding why are there still monkeys around I think there are two other responses. First of all there is nothing in evolution that requires that if species Y evolves from species X that species X has to go away. Its possible that Y could evolve to fill a different niche than X, different diet, etc.  In the case of chimps though the actual truth is that humans evolved from a common ancestor of the chimp, not the chimp as it currently exists and that ancestor is indeed extinct.

  6. This thought experiment involves getting to grips with the scales of evolutionary time.

    (Runs for cover stage left),

  7. This is a very useful analogy. Also I like the parallel description of the maturation of an individual human, which should bring the concept right home to all but the dimmest individuals. There is still something else that might help correlate the progress of an almost infinitesimally slow process like the postcard stack with the inevitable changes between species. I can’t put it into words exactly. It’s sort of like there is a “species indicator” which begins to move towards the next category in line but as there is no sharp demarcation the indicator begins to stretch, tending towards the next category. At some point, the accumulated changes are sufficient to cause the indicator to “jump” to the next category. I guess that’s how I would try to explain the fact that although there are 185 million generations from my fish ancestor to me, there are not 185 million categories (or species) of creatures over that time span.

    Of course, it would be simpler if there were only 185 postcards as Richard says at around the 1:00 mark, 🙂


  8. I think the question “Why are there still trees around?” would only cause confusion. The question “Why are there still monkeys around?” is prompted by the idea that we are descended from monkeys. We *are* descended from monkeys, by any reasonable definition of the term “monkey”, but we are not descended from trees. In fact, from a cladistic point of view, we *are* monkeys.
    However, I think you’re onto a good strategy with your modification of the question, and turning it back on the asker. Answering a question with a question often helps clarify the assumptions behind the original question.

    To answer the question, pick a group from whom your nephew’s friend is descended, and ask why there are still members of that group around. For example, if the friend is of Irish descent, you can ask, “Well, if you are descended from Irish people, why are there still Irish people around?” It’s pretty much the same principle as with the monkeys, and is easier to understand, as it does not require an understanding of evolutionary timescales.

  9. Agrajag – I think Richard Dawkins’s point is that the change is, to a good degree of approximation, continuous. Every individual belongs to the same species as his or her parents, and also to the same species as his or her children. If every organism that had ever lived was still available for examination today – as is the premise for this thought experiment – the concept of a “species indicator” would be a non-starter.In reality, of course, the vast majority of organisms are not only dead, but also absent from the fossil record. The remaining record is just a sporadic smattering of dots where we like like to see a continuum.We humans, as observers of this smattering of dots, and as beings with a love of categorisation, can draw rings round particular smatterings, and say, “This is one species,” and, “This is another,” but it is important to understand that these rings are human constructions, and are fairly arbitrary. If such a complete set of records of our ancestors were available to us, as described in the thought experiment, we would all be able to see that.


    I think it would have probably lived some time during the Devonian period (aka the “Age of Fishes”) – say around 400 million years ago? Any later than that and our ancestors would have been land-based tetrapods of some kind or other.

  11. Doesn’t look like it. I think you have to sign on to Disqus to do that. The new system is discussed here

  12. Good video for Father’s Day 🙂

    The title reminds me of Neil Shubin’s ‘Your Inner Fish’.

  13. Neanderthal parents did not give birth to homo sapiens, but many comments on YouTube provide us with evidence that the converse may indeed be true.

  14. But, if we continue it means we will come to the molecule that was before life existed. It means a hydrogen atom was my mother! 

  15. By co-incidence I was thinking last night as I was falling asleep about how you might intuitively  represent the gradual nature of evolution and the astounding time scale.  Then here it is! It would be nice if this clip included some estimate of the length of the stack of photos, and showed a computer graphics of it, showing the relative position of various landmarks. I had a similar idea, follow man back with morphing, but instead of showing the whole story in 2 minutes, take a month or a year. You view it on your computer.  The important thing is psychologically NOTHING appears to be happening.  Creationists have a picture of it happening at breakneck pace.  However, the year oddometer that accompanies the snail-like morph whirs by at breakneck speed.

  16. I laughed (not a derisive laugh but an astonished one) when I saw my what my grandfather likely resembled 185 million generations ago. It was all the more surprising to me because reading it on the iPad, one swipes the cliff-hanging page and then there’s the fish on the next page.

    I don’t know if in the print edition it’s that way or if the picture is just on the opposite side of the book which I think, wouldn’t have had the same astonishing effect on me.


  17. If my math is correct, and these photographs were 0.010″ thick, and they were placed on a shelf, it would be about 29.2 miles long.  That’s an extensive Family Album, despite only going back to where they would have needed a waterproof camera….

  18. Thanks I think that nationality descent is probably a easier to understand ploy. I can imagine however both being used.

  19. The common ancestor of us and the chimpanzees is not extinct. Its descendants didn’t die out. They are still around today. We are its descendants. So are the chimpanzees.

  20. It’s a beautifully simple explanation: one I’ll use to unconfuse myself the next time this universe’s beauty overwhelms me. (Yes I know he’s referring to evolution, not cosmology, but the ‘family album’ seems appropriate for any BIG enquiry – though religions’ stack of pictures wouldn’t be too high, would it?).

  21. Has anyone been able to find a good computer animation video of something like this thought experiment?  I found a couple of videos on youtube, but nothing that great.

  22. There’s a Muslim guy I meet sometimes in the Sports Centre sauna, who told me that everything that is happening now in science was predicted in the Qur’an. I must say I haven’t come across a single mention of anything yet, but I’ll wade on.

    Anyway, I presume he doesn’t believe in evolution – well it certainly isn’t mentioned in his good book – so, the next time I see him I’ll tell him about this chapter in The Magic of Reality; I’ll wind him up just for fun!

    Incidentally, I recommend the book.

  23. I didn’t say we were descended from trees. But I think I know what you are getting at.

    How does one get started with quotes. I cannot even find the passage that I want to quote from. And how do you get one’s gravatar to appear?


    If there were 185 million photos, and we take a second to view each photo, it will take about 5 years and 10 months to finish viewing all the photos. 
    However, if we view them at 24 pictures per second (like a film projected at 24 frames per second), then it will only take about 3 months (89 days) to view the 185 million photos. 

    But 3 months is still a long time.

  25.  In reply to comment number somethingorother which said


    I thought this one was great, though probably not exactly what you are looking for. The relevant part is the guy walking in the other direction.

  26. TreenonPoet seems confused about the Homer video. Since this thought experiment is about the evolution of our ancestors from fishes to humans, the relevant part is the part that shows Homer changing from a fish to a human.
    The slobbish fellow going the other way is just a brief, throwaway joke about how it seems that some people are “de-evolving”. He is not relevant to anything (other than humour).

  27.  Oliver Pereira, I was not being that serious. The parallel between the guy unevolving and the gradual nature of the changes observed by looking back through the photographs was really just an excuse to link to the Homer video. (I had not seen a reference to the video for some time.) By the way, I thought that the ‘throwaway’ joke was simply about the unidirectionality of time.

  28. At top, if you select newest first they order in that direction. Likewise, most popular fucks it all up.

  29. My 185 millionth great grandfather’s nephew’s 185 millionth descendant still is a fish.

  30. Nobody explains evolution the way Dawkins does. His each statement is precious and full of profound wisdom. 

  31. after watching the debate Richard Dawkins vs.william lane Craig debate.one of the things that i   seen is,how separated we still are over religion as a human race.the debate was interesting but religion cant keep using the god word to emplane what every time it dose not have an answer. and it only seems to be religions thinking that is separating people for self protection.    

  32. It is no coincidence that amoebas contain the largest geomes. The databases were in place which contained a plan to reproductively distribute the generative processes of creation. We cannot debug or detect these plans, but the successive end products attest to this fact.

  33. I really don’t understand how people can’t understand evolutionary or geological time.

    How does a still frame relate to a full-length feature film? How do ones and zeroes relate to the World of Warcraft?

    It ought to be well understood by now that some scales are meant to fuck with your mind. The capacity for things to change far outstrips our imagination of possible changes. So, given enough time, expect to be stunned by change.

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