Don’t know your past, don’t know your future

December 18, 2017 • 10:00 am

by Greg Mayer

My friend and colleague Jon Losos has recently published a book, Improbable Destinies: Fate, Chance, and the Future of Evolution (Riverhead Books, New York) that will be of considerable interest to WEIT readers. The main question addressed by the book is this: To what extent is the course of evolution predictable? And, in particular, what do the phenomena of convergence tell us about the answer(s) to this question.

Improbable Destinies by Jonathan B. LososJon is best known for his work on the adaptive radiation of West Indian Anolis lizards, and anoles are famous for displaying convergent community structure on the islands of the Greater Antilles: the same ecologies, morphologies, and behaviors have evolved multiple times among the islands of the archipelago. On each of the Greater Antilles, a suite of sympatric lizards have evolved independently, and each island’s suite contains species of analogous morphology and behavior, each analogue associated with particular stations in the vegetation.

Anole ecomorphs, showing characteristic size, station, and morphology; each of these has evolved tow or more times independently in the Greater Antilles. From Losos, 2009, based on E.E. Williams
Anole ecomorphs, showing characteristic size, station, and morphology; each of these has evolved two or more times independently in the Greater Antilles. From Losos, 2009, based on work of E.E. Williams.

The similarities in ecological structure and function across phylogenetically independent lineages of anoles is quite striking, and has been hailed as an example of how natural selection can mold recurring adaptations. When I told my thesis advisor, Dick Lewontin, that I could predict the ecology and morphology of the next species of anole to evolve on Jamaica, Dick, who was not a fan of the supposed ubiquity of adaptation, was a combination of dismayed and mildly dubious.

So, in this book, someone who is arguably ‘Mr. Community Convergence’ takes a broader look at evolutionary convergence for a general audience. The book is written in a colloquial, conversational style, the text sprinkled with puns, alliteration, cultural allusions (e.g. the Horta), words like “bamboozled”, “glom” and “Aussie”, at least one neologism (“arboles”, for big trees, partly a borrowing from Spanish, but also undoubtedly influenced by the English word ‘anoles’, itself a borrowing from Carib through French), and, shockingly for an academic, correct use of the word “rubric”. Reading it, in fact, provides an experience very much like talking with the author. While conversational tastes may differ, I regard this as a plus for the book, and a plus for its non-scientist readers. The approach also advances one of Jon’s other goals in the book, which, as we’ll see, is to put a human face on the practice of science.

He begins by surveying the phenomena of natural history for evidence of predictability and evolutionary convergence. The phenomena are manifold: from convergent traits (long nectar sipping bills), to whole organisms (ichthyosaurs and dolphins), to whole communities (Greater Antillean anoles); and a long set of rules about how animals respond to particular environmental conditions. Rodents, for example, get big on islands, while elephants get smaller, and warm blooded animals in the arctic have short legs, and in deserts they are pale. The list goes on.

Jon recounts many such cases. In discussing the case of anoles, he includes a lot of his own experiences in growing up to be a herpetologist, and this is where we see clearly the second main theme of the book, which is to show how it is scientist’s do their work, and how they come to study the things they study. But after recounting these cases, he also devotes a chapter to evolutionary idiosyncrasy, the “one-offs” of evolution, like aye-ayes, the grub-digging primates of Madagascar, and, much though Simon Conway Morris might wish it weren’t so, that other really unique primate, Man.

Jon knows, though, as Stephen Jay Gould liked to say, that all questions in natural history are ones of relative frequency. Almost anything you can think of in natural history occurs– but does it occur very often? Jon concludes that Conway Morris has shown convergence to be more common than some have thought, but not ubiquitous.

Switching from comparative evidence to experimental evidence, the book then switches to closely observed cases of evolutionary change in the field and in the lab. Jon now becomes a journalist, visiting research sites and the scientists who work at them, going in to the details of a number of studies. He devotes a chapter each to the guppies of Trinidad, his own experimental work on Bahamian anoles, Rothamsted Experimental Station in England, sticklebacks, fruitflies, and Richard Lenski’s monumental Longterm Evolution Experiment on E. coli (which gets two chapters). A feature of each of these chapters are interviews with the scientists involved, who recount their motivations for the work, how they conducted it, and, in many cases, how their own interpretations have evolved over time.

In these chapters we see the scientists’ and the author’s views changing (evolving?), but eventually we want to know what the author, having reviewed the phenomena of convergence in extenso, finally concludes. And the last part of the book provides this for the reader. It is not the conclusion that Simon Conway Morris would prefer—we (i.e. humans) are not an inevitable consequence of evolution. As Jon succinctly puts it:

The fact is, we humans are an evolutionary singleton—nothing else like us has ever evolved on Earth anywhere, any time. The ubiquity of convergent evolution in general would seem to provide scant support for our evolutionary inevitability.

And what about life in general? Convergence does reveal that there are often similar ways of dealing with similar environments. But this doesn’t mean the ‘same’ organisms will recur. As Jon writes:

… here on Earth, species frequently do evolve similar features in response to similar environmental conditions. So, even if a humanoid or a platypusoid (or a chameleonoid or kiwioid) is unlikely to have evolved elsewhere, that’s not to say that extraterrestrials would look completely unfamiliar. An extraterrestrial might even be a mashup, platypus-style, of many different parts borrowed from different Earth inhabitants.

His conclusions are thus contra Conway Morris. There are certain principles (e.g., in hydrodynamics, a stiff surface parallel to the direction of motion can prevent roll) that are instantiated again and again, but how they play out depends on the starting point. If you are a toothed tetrapod, being a predator involves having sharp teeth, but not if you’re a cephalopod (which involves beaks, and not teeth at all). A number of mammalian lineages have become large herbivores living on prairies or savannas, but that does not require, as in horses and antelope,  hooves for running across the prairies– hopping works quite nicely as well, as kangaroos have shown us. Jon’s conclusion reminded me of W.K. Gregory’s notion of “habitus and heritage”. (Jon should like this comparison, since, as an undergraduate student of E.E. Williams, who was a student of Gregory, Jon is Gregory’s academic grandson.) According to Gregory, an organism’s habitus are those features of the organism which adapt it to its immediate conditions of existence, while it’s heritage are those features that it has inherited from its ancestors– the accumulated ‘adaptive wisdom’ of its progenitors. The habitus features must be derived from the existing heritage features, not ab initio from some engineer’s optimal solution. Thus the same conditions of existence may be adapted to very differently by different organisms with different heritages. Birds have evolved into large herbivores– geese on Hawaii, for example; and into large predators– eagles in general, and Haast’s eagle as a particularly striking example. But they don’t wind up looking like cattle or big cats. Where you go depends on where you are.

As Ziggy says, if you don’t know your past, you don’t know your future.

(Full disclosure: I am the unnamed graduate student on p. 58, and I am thanked in the acknowledgements. But my role in the book is minuscule, and I was thanked for providing a few minor facts,)

53 thoughts on “Don’t know your past, don’t know your future

    1. So what does “sub” mean in this context? I’ve seen it used online before but never was sure what it meant. Kind of surprising since I’m a computer professional but, hey, one learns something new every day. Searching online for an answer leads to several possibilities.

      1. It is, I believe, peculiar to this site. In order to subscribe and get emailed updates, you need to say something. If you have nothing particular to say…

        Shorter than “I have nothing to add but I do want to check this box and get email updates.”

  1. ” warm blooded animals in the arctic have short legs, and in deserts they are pale. ‘

    And then there are polar bears…

    1. There are reasons for pale color in the desert. Besides camouflage against light sand, the color reflects sunlight to slow down the suns’ heating effect.
      White fur in polar bears is camo, and the transparent hairs act like fiber optic cables to conduct sunlight right to their black skin.

        1. I’d want see the data on leg length–
          if they are relatively long, swimming might be the reason. But polar bears otherwise fit the ecomorphological rules pretty well. Arctic forms need lower surface area to volume ratio, and you get that by being big, roundish, with small extremities. Polar bears are the first two, and their ears, at least, are relatively quite small.


        2. Polar bears swim only with their forelimbs, but they need their very powerful rear limbs for their modes of hunting [even the odd reindeer it seems] from their favoured ice substrate & it’s a fair old waddle from the winter den to their snacks! I think an easy way for them to conserve even more heat would be for the rear limbs to remain the current length, but for the bag of skin/fat to attach nearer the knees.

        3. Would’t call them a marine mammal really, but definitely the most marine of all bears. Note that the short and stocky shape is more important when small (surface/volume ratio). Polar bears are the largest extant bears, have by far the most blubber and apparently have a ‘solar tube’ kind of hair.

            1. Yes, I know, but I still would not call them that.
              They spend most of their time on land (or ice), they hibernate on land (or ice, please add that to every time I say land), give birth on land and spend their first weeks on land, they mostly hunt on or from land, pull their prey from the sea to eat on land. They can survive inland, without sea. They are good swimmers, but even better runners (on land), they do not catch prey while swimming (AFAIK).
              In other words, despite them being called Marine Mammals, they are nothing like real marine mammals, like pinnipeds, sirenians or cetaceans.

  2. The past is almost always the road to the future so as unpredictable as evolution seems to be, it is not impossible to project into the future.

  3. You thoroughly convinced me, I’m definitely going to get this book. Was always fascinated by convergence and non-convergence to begin with. Will have to get it myself: I know since the age of 8-9 that Santa doesn’t exist.

  4. I’m commenting before reading this post–will read as soon as I get the chance, sorry if I repeat stuff in the OP.

    I saw Jonathan Losos last Thursday. He was speaking at the North Carolina Museum of Natural Sciences weekly Science Cafe.

    His talk started by giving waaaay too much credence to Conway Morris’ ideas that humans were destined to evolve. He also used terms like “evolution favors big brains”. He really seemed to support the idea that humanoid intelligent life was inevitable on other planets too. He stopped for questions/comments after that and I brought up CM’s designer biases. Losos said he finds no apparent bias in CM’s writings. I asked if he meant published papers or popular writings. He said neither.
    I also mentioned body plans and asked how anyone would realistically expect similar body plan construction if the evolutionary tape were begun again from the beginning.

    It really sounded as if he was making an apologetics talk for intelligent design. And I had been feeling tricked for attending his talk.

    Anyway, Losos did begin the next segment of his talk sort of disputing CM by pointing out how often convergence DOES NOT occur (but he used some real outlier species as examples–koala, platypus, kiwi, etc). He put more of an emphasis on random chance than he started. I felt he redeemed himself, but could have planted many misconceptions in listeners’ minds.

    Here’s the video of the talk.
    My comments are about 1/2 hour in. I’d love to hear if others think I was too hard on Losos at that point.

    I did get his book and will read it, but I wonder if I got the gist of his book in this talk. He said he’d just recently talked to Jerry about problems with Templeton Found funding.

    1. I don’t know enough about CM arguments to judge them, but evolution did produce big and intelligent brains independently several times. The trick is to have ’em in a body with prehensile hands or the equivalent. Flippers or a trunk won’t get you very far.

      1. I agree with the convergence of big brains, but his talk (and what I’ve seen of CM’s writings) really seemed to be heavy on teleological side. A bit too much for my own taste.

      2. Worth noting that big /= intelligent. Not necessarily anyway.

        Some birds are indisputably intelligent, on par with the smartest mammals. Being flying animals, their brains were selected to be small. Then there are cephalopods, of somewhat more modest smarts but still very bright animals, and their brains are very little like ours – very weird, in fact, being distributed in different parts of their bodies.

        In the end, I think intelligence is just another trait. If it is useful it will arise in any system that undergoes Natural Selection. In that sense I see it as “inevitable”.

        1. “If it is useful it will arise in any system that undergoes Natural Selection.”

          WILL? Wouldn’t “may” be more correct. Not everything that is useful HAS to show up in any system.

          1. I stand by “will”. Human style intelligence gets a BIG “may”, but intelligence of some kind? Absolutely will evolve in any system beyond a prokaryotic one. It is a powerful trait. Our kind of intelligence maybe not so much; we’ll see how long it lasts.

            1. I think “beyond a prokaryotic” really will not be the line in the sand for intelligence. Give bacteria & protists the vote!

      3. I wonder if Neanderthal could be considered convergent with Homo Sapiens? They separated from small brained Homo erectus about 300,000 years ago and as of 30,000 years ago they shared pretty much the same large brained niche when they met up in the Middle East and Europe.

        1. The species names get a bit arbitrary in this area, and not everyone agrees on which species is which. But I would say we both inherited our large brains from our common ancestor, and that brains got as big as they were going to get before we split.
          One line of designation that is pretty common is where fossils that are designated H. erectus were quite variable, with late-stage fossils over-lapping the lower range of H. sapiens & Neanderthal brain size. Later fossils in N. Africa and nearby parts of Europe are labelled as Homo heidelbergiensis, and from this we see the Neanderthals split off, living primarily in Europe, and H. sapiens staying in Africa. Brains sizes were our size, and sometimes even a bit larger. We can attribute the extra big brains to having bigger bodies. These archaic types were big people.

          1. So, I guess the answer is no, it’s not a good example of convergence. Although now we know we were rolling in the hay with Neanderthals which means we converged in another way. 😎

    2. Greg, I just had time to finish your post and it seems as if Losos’ talk style recapitulates his text style.

      He was a great speaker and the bits I’ve read in the book so far, illustrate his conversational style. Trouble is, if he writes like he talks, readers could be left with the feeling that he’s agreeing with CM’s ideas that it’s all about convergence (especially if readers don’t read the entire book).

    3. Hi Lynn – I haven’t seen you commenting on here for absolutely yonks. Welcome back!

      I agree with you regarding SCM. In fact I would go further & say he believes in the hidden, guiding hand of a purposeful Christian god & I suspect he may think Earth is extra-special as in it’s the crown of creation where god spread more magic than anywhere else.

      Here is my evidence:
      [1] SCM is an Anglican Christian
      [2] His favourite author is G.K.Chesterson
      [3] His book is called “Life’s Solution. Inevitable Humans In A Lonely Universe” [note the “lonely universe” bit]
      [4] Chapter 11 is titled, “Towards A Theology Of Religion”
      [5] The last paragraph of that chapter reads as follows:

      T]ne complexity and beauty of ‘Life’s Solution’ can never cease to astound. None of it presupposes, let alone proves, the existence of God, but all is congruent. For some it will remain as the pointless activity of the Blind Watchmaker, but others may prefer to remove their dark glasses. The choice, of course, is yours.

      [6] The final chapter is a parable where the author/reader meets aliens. They turn out to be just like us. Which is very ‘convergent’, but if one is a Christian then one believes we are in the image of god

      He qualifies as a creationist by any definition

      1. Thanks Michael, I lurk often here but sadly don’t have much time for the comments. Since Drumpf happened, I’ve been more worried about supporting science-based reason and being an SJW on other fronts.
        The former is why I really became concerned about Losos’ talk.

        I haven’t read CM’s books, but based on what I’ve heard of him, what Losos said about him, and the titles of his books Losos showed in the first half of his talk, I got the same impression you did (I was, of course, searching WEIT for CM info during that talk too).

    4. I think SCM got a lot of interesting ideas, his ‘library’ of convergence is impressive and brilliant.
      That being said, he got some things very wrong. It was SCM who put, despite describing it meticulously, Hallucigenia upside down, the wrong way round. I think his teleological (not to mention theological) inferences belong in the latter category: the wrong way round.

    1. Yeah, he used a picture of the Horta in his talk, when he was discussing that convergence DOES NOT always happen.

      1. btw, he redeemed himself a bit in my eyes with that picture. When he showed the “convergence” of hominid forms among TV and movie aliens, he didn’t show a single Star Trek alien!

  5. I was also curious about Losos’ use of the aye-aye as an illustration non-convergence with woodpeckers.
    Does convergence always have to be physical? Couldn’t we consider a behaviour convergent too? Both woodpeckers and Aye-ayes use sound to locate their prey, they just use different tools to extricate it.

    1. Well, he calls it kind of convergent, but very different. Yes, it is a good example how even what could be called convergent can be not really (or vice versa).

  6. While Dr PCC(E) is away eating his way through the Indian subcontinent, maybe we left behind could discuss (or look on in bewilderment) at a wrinkle in evolution. I think it on topic anyway.

    Humans killed off the Passenger Pigeon (Ectopistes migrators) a little over 100 years ago. If you’ll remember, the bird was once one of the most populous land vertebrates on earth with an estimated population at well over 5 billion before the slaughter began in the mid 19th century. At the turn of the 20th century the vast flocks had been destroyed and the species gone extinct. Lots of reasons were put forth for their susceptibility to the carnage with many suggesting they were already in decline and that humans accelerated a process that was already ion-going.

    This turns out to be false and the vast populations appear to have been stable for tens of thousands of years. So, if these animals were once the most populous in the world, how did human predation cause them to collapse and disappear so rapidly?

    It turns out it may be because of Evolution. (or should I say Evilution ;-)). A recent paper (cite and abstract below) suggests that one benefit of a large population – fast adaptive responses- can result in a surprising vulnerability; a near complete loss of neutral genetic diversity. Those are genetic variants (mutations) that are not under selection and therefore are “free” to change. Alleles (copies of genes) which are not under selection can, the theory goes, obtain mutations that, while having no benefits or deleterious effects, act as a wellspring of variability that can be helpful for the survival of a species that encounters new selective pressures. A kind of genetic tool kit – a resource to fall back on when selection gets rough.

    Passenger pigeons evolved to live in truly monstrously sized flocks, a strategy that makes predation avoidance and locating food resources less important for the individual. Such a loss of neutral mutations meant that when humans depleted the gigantic flocks the survivors, who were not adapted to living in small flocks, didn’t have the genetic variants that could be called into use.

    A similar phenomenon may be at play in some of the world fish stocks – the loss of the California Anchovy fishery in the early 20th century and the NorthEastern Cod fishery in the late 20th century.

    What is not clear to me is how (by what mechanism) are neutral mutations lost in this kind of phenomenon. The authors note this;

    “Theory predicts that larger populations will experience a greater impact of natural selection, both because they generate more mutations per generation and because selection is more effective in overcoming random drift when Ne is large”

    . This suggests (if I’m reading them rightly) that it is their very population size -a supposed bulwark against the slings and arrows of outrageous selection- that drove out many neutral mutations, thus leaving “large-population” adapted birds at a disadvantage when they suddenly found themselves in radically smaller flocks.

    Anyway, I thought this might be worth some comment and discussion while our host is off galavanting around India, bothering the locals for their hospitality and great eats and giving us all a virtual tour.

    Natural selection shaped the rise and fall of passenger pigeon genomic diversity. Science 17 Nov 2017:
    Vol. 358, Issue 6365, pp. 951-954

    “The extinct passenger pigeon was once the most abundant bird in North America, and possibly the world. Although theory predicts that large populations will be more genetically diverse, passenger pigeon genetic diversity was surprisingly low. To investigate this disconnect, we analyzed 41 mitochondrial and 4 nuclear genomes from passenger pigeons and 2 genomes from band-tailed pigeons, which are passenger pigeons’ closest living relatives. Passenger pigeons’ large population size appears to have allowed for faster adaptive evolution and removal of harmful mutations, driving a huge loss in their neutral genetic diversity. These results demonstrate the effect that selection can have on a vertebrate genome and contradict results that suggested that population instability contributed to this species’s surprisingly rapid extinction.”

    1. Thanks, that was really interesting.
      A third cause I heard -I’m not reallysure about the details- was that they (PP’s) were not just slaughtered, but that their breeding areas were destroyed too. (Of course that is not in contradiction of the loss of ‘neutral variation’ as a cause, but rather reinforces it)

  7. JAC: I have a long section on “whether humanoid intelligence was inevitable” in Faith versus Fact. The conclusion is that if mutations are truly indeterministic phenomena, then no, the course of evolution was not repeatable starting at the same point. If they’re not, and no quantum phenomenon intervene, then rewinding the tape to the EXACT starting point would give identical results. If you begin at a slightly different starting point, then all bets are off and you can’t say humans would inevitably have evolved. Gould conflates these two conceptions of “starting point.”

    Further, in a deterministic world, things like an asteroid strike on Earth is NOT a contingency or “luck”–they would have always happened from the same starting point. Read FvF for a further explication. I agree with Losos that humans probably weren’t inevitable, but he doesn’t take into account physical determinism in his analysis, as far as I know from having talked to him. Gould doesn’t deal with it either. “Contingencies” are not what Gould thinks they are in a physically determined universe.

    1. I definitely need to review that chapter. Thanks for the reminder!

      Fyi, I’ve got a coffee meeting planned with a local pastor (moderate, liberal, Lutheran) who incorrectly represented Darwin and evolution in some recent lectures on Genesis. I’ll be bringing your books to that meeting; I’ll focus on WEIT, but will definitely recommend FvF.

    2. I think sometimes people make type-token errors when they discuss determinism. So for example, there are many microstates that are consistent with a gas at a given T,P,V,n. I therefore offer that isn’t our *ignorance* that makes the statistical mechanics that result probabilistic exactly, but the fact that one is dealing with a *type*. The biological generalization I leave to biologists. 😉

Leave a Reply