Common Trends in Evolution

Does evolution repeat itself? Could evolution repeat itself? Where do people stand in relation to the thoughts of  Gould and Conway Morris?

Gould has a point, everything is in a state of becoming. As Heraclitus would say, all is change. Replay the tape and nothing would be the same. But would or could there be any similar trends? Would life in general proceed in such a radically different way that Gould makes out?

From “Life’s Grandeur”, Gould states:

“…no persuasive or predictable thrust toward progress permeates the history of life…

“Wind the tape of life to the origin of multicellular animals in the Cambrian explosion, let the tape play again from this identical starting point, and the replay will populate the earth (and generate a right tail of life) with a radically different set of creatures. The chance that this alternative set will contain anything remotely like a human being must be effectively nil, while the probability of any kind of creature endowed with self-consciousness must also be extremely small.”

Conway Morris disagrees with Gould’s conclusion. He champions an inevitable path and cites convergent evolution as evidence which suggests this.

In “The Crucible of Creation” he states,

“What we are interested in is not the origin, destiny, or fate of a particular lineage, but the likelihood of the emergence of a particular property, say consciousness. Here the reality of convergence suggests that the tape of life, to use Gould’s metaphor, can run as many times as we like and in principle intelligence will surely emerge.”

I’m interested in what people have to say about this and its relation to topics such as the emergence of bilateral symmetry and differentiation from head to tail, extreme specialization, encephalization, endothermy, caring for young, transitions from aquatic to terrestrial living and other related topics. These processes have occurred multiple times in different lineages over time.

267 thoughts on “Common Trends in Evolution

  1. CharlieM: If you see an organism in front of you what do you see? You see a brief instance of the reality of that organism. To “see” it in reality, not the physical constituents which come and go, and not even the form in front of you which is just one aspect of its dynamic form, is to look upon the archetype.

    What we see is very much a matter of the workings of our perception. Our perceptual systems pick out characteristics which work well for recognition. That makes a perceived archetype an artifact of how our perception works.

  2. CharlieM: The evolution of life reveals a general trend towards increasing freedom from the constrains of the surrounding environment. There are many ways in which creatures evolve to become more free in this respect.

    I don’t think that’s correct.

    Birds have freedoms that we don’t have.

    When you look more closely, the “freedom from constraints” is very much a matter of the niche. You see this as a general trend, because you concentrate on on the niche that humans exploit.

  3. Neil Rickert: I don’t think that’s correct.

    I think it’s dead backward. Evolution generally rewards lineages for being even MORE suitable for their environment, and thus more dependent on it, not less.

  4. Neil Rickert:
    CharlieM: If you see an organism in front of you what do you see? You see a brief instance of the reality of that organism. To “see” it in reality, not the physical constituents which come and go, and not even the form in front of you which is just one aspect of its dynamic form, is to look upon the archetype.

    Neil Rickert: What we see is very much a matter of the workings of our perception. Our perceptual systems pick out characteristics which work well for recognition. That makes a perceived archetype an artefact of how our perception works.

    Senses alone tell us nothing about relationships. It is only when we combine them in thinking that we become aware of connections. We understand that there are many creatures that belong together in the group we call mammals. Is this grouping a reality or just an artefact of our perception works?

  5. Neil Rickert:
    CharlieM: The evolution of life reveals a general trend towards increasing freedom from the constrains of the surrounding environment. There are many ways in which creatures evolve to become more free in this respect.

    I don’t think that’s correct.

    Birds have freedoms that we don’t have.

    Indeed. And birds enjoy more freedom than their archosaur ancestors did. Endothermy gave them more freedom of movement and acquiring flight gave them even more freedom to move about the planet. And learning ability gave them greater freedom of behaviour.

    When you look more closely, the “freedom from constraints” is very much a matter of the niche. You see this as a general trend, because you concentrate on the niche that humans exploit.

    I did not restrict this trend to humans alone. Modern flying insects have more freedom than their earthbound ancestors. Dolphins have the freedom to play and more manoeuverability than their distant relatives the sharks. Birds, I’ve discussed above.

  6. Flint to Neil Rickert:
    Neil Rickert: I don’t think that’s correct.

    Flint: I think it’s dead backward. Evolution generally rewards lineages for being even MORE suitable for their environment, and thus more dependent on it, not less

    Just like evolution rewarded the dodo for being dependent on the peaceful environment of its island home? Just like it is rewarding the orangutan for being totally suited to the disappearing rain forests of SE Asia?

    If we want to use language such as “evolution rewards”, then evolution rewards those lineages that more adaptable to ever changing environments by giving them novel abilities.

  7. CharlieM: Just like evolution rewarded the dodo for being dependent on the peaceful environment of its island home? Just like it is rewarding the orangutan for being totally suited to the disappearing rain forests of SE Asia?

    If we want to use language such as “evolution rewards”, then evolution rewards those lineages that more adaptable to ever changing environments by giving them novel abilities.

    I think you have accidentally made an interesting point – whether evolution rewards the ability to adapt to totally new environments as well as suitability for the current environment. Evolution would not even happen if the ability to adapt didn’t exist, because environments have changed, usually slowly, since forever.

    However, the way evolution handles this is generally through a branching process. Studies of fossils in the American West have been instructive. Millions of years ago much of that land was warm, flat, low elevation. Over the ages, as the Rockies developed and the plate moved north, the environment became more and more different. And what paleontologists noticed is that lineages appropriate to the warm low-lying lands did not change to track the environment. Those lucky enough to survive (for a while) because they just happened to have appropriate characteristics lasted, those thoat lacked them died out – but new species, better adapted, took their place. And this process continued for many millions of years, with evolution tracking environment through the branching of new species. THAT is how evolution handles adaptation.

    Evolution does not, and cannot, accommodate sudden drastic environmental changes. Human activities are recognized as causing another great die-off of species, millions of them worldwide and accelerating. “Novel abilities” take thousands of generations at minimum, and even then these abilities aren’t all that novel. We’re talking millions of years here. Paleontologists estimate that the average species (before humans screwed everthing up) lasted on average about 15 million years, the first 2 or 3 million in the act of branching.

    So just to be clear, evolutionary change is so slow in human terms that all too many people deny it happens at all. So slowly that any new species that have arisen since homo sapiens has existed, are nearly identical to their immediate ancestors still. Modern humans haven’t been around long enough to be a good measuring baseline to track evolution. We need a few million more years for that.

  8. CharlieM: Senses alone tell us nothing about relationships.

    That probably depends on what you mean by “senses” and what you mean by “relationships”.

    We understand that there are many creatures that belong together in the group we call mammals. Is this grouping a reality or just an artefact of our perception works?

    You seem to be asking what’s the real meaning of “real”. And I don’t think there’s a real answer to that. The word “real” means what we want it to mean, and it pretty much has to be that way. Words get their meaning from the way they are used.

  9. CharlieM: Senses alone tell us nothing about relationships. It is only when we combine them in thinking that we become aware of connections.

    That’s not quite right. There are lots of relations in perceptual consciousness — spatial, temporal, and other kinds of perceptual discriminations such as “x is larger than y”, “z is earlier than q”, “g is louder than w”, “t is darker than s”. These perceptual relations are mostly independent of more abstract kinds of relations, such as logical relations (“x entails y”) or functional relations that abstract from perceptual characteristics (e.g. recognizing that a can opener and a wine bottle opener belong to the same generic kind).

    We understand that there are many creatures that belong together in the group we call mammals. Is this grouping a reality or just an artefact of our perception works?

    Is this a question about whether higher-order taxa are natural kinds?

  10. Kantian Naturalist: That’s not quite right.

    Is anyone ever right? Asimov’s point about being less wrong resonates.

    There are lots of relations in perceptual consciousness — spatial, temporal, and other kinds of perceptual discriminations such as “x is larger than y”, “z is earlier than q”, “g is louder than w”, “t is darker than s”.

    The general point is comparison. Given a yardstick to compare, one can decide whether one is getting more or less accurate. Is there, beyond everything, an objective reality where all observations and measurements agree? I dunno.

  11. Flint:

    CharlieM: Just like evolution rewarded the dodo for being dependent on the peaceful environment of its island home? Just like it is rewarding the orangutan for being totally suited to the disappearing rain forests of SE Asia?

    If we want to use language such as “evolution rewards”, then evolution rewards those lineages that more adaptable to ever changing environments by giving them novel abilities.

    Flint: I think you have accidentally made an interesting point – whether evolution rewards the ability to adapt to totally new environments as well as suitability for the current environment. Evolution would not even happen if the ability to adapt didn’t exist, because environments have changed, usually slowly, since forever.

    However, the way evolution handles this is generally through a branching process. Studies of fossils in the American West have been instructive. Millions of years ago much of that land was warm, flat, low elevation. Over the ages, as the Rockies developed and the plate moved north, the environment became more and more different. And what paleontologists noticed is that lineages appropriate to the warm low-lying lands did not change to track the environment. Those lucky enough to survive (for a while) because they just happened to have appropriate characteristics lasted, those thoat lacked them died out – but new species, better adapted, took their place. And this process continued for many millions of years, with evolution tracking environment through the branching of new species. THAT is how evolution handles adaptation.

    Evolution does not, and cannot, accommodate sudden drastic environmental changes. Human activities are recognized as causing another great die-off of species, millions of them worldwide and accelerating. “Novel abilities” take thousands of generations at minimum, and even then these abilities aren’t all that novel. We’re talking millions of years here. Paleontologists estimate that the average species (before humans screwed everthing up) lasted on average about 15 million years, the first 2 or 3 million in the act of branching.

    So just to be clear, evolutionary change is so slow in human terms that all too many people deny it happens at all. So slowly that any new species that have arisen since homo sapiens has existed, are nearly identical to their immediate ancestors still. Modern humans haven’t been around long enough to be a good measuring baseline to track evolution. We need a few million more years for that.

    Let’s take a specific example from the millions of years of evolution. The arrival of endothermy.

    The article, The Evolution of Endothermy–From Patterns to Mechanisms begins:

    What makes endothermy one of the most fascinating traits in evolution? Metabolic heat production required a complex degree of coordination from the organism to the molecule to achieve a high, stable body temperature (Tb), or homeothermic endothermy, which has convergently evolved as key trait of birds and mammals (Crompton et al., 1978). The resulting expansion of endotherms into thermal niches that were not accessible to ectotherms, whose Tb is dictated by ambient temperature (Ta), proved to be the crucial evolutionary advantage. Yet, the evolutionary framework and events leading to endothermy are still unclear.

    Multicellular life thrived for millions of years without the need for animals to be endothermic. Animals were somewhat restricted by the fluctuating temperature of their surroundings. Along came the coordinated changes which accompanied an animal’s ability to self-regulate its temperature despite fluctuating external conditions.

    People can talk about more niches becoming available, but the fact is that it gave these animals a greater freedom from external conditions than their ectothermic cousins. The niche widens.

    And it’s not as if this development meant the demise of these ectothermic animals. They still thrive today and in a way that is more energy efficient than the endotherms. The endotherms gain their freedom through reduced efficiency.

  12. Neil Rickert:
    CharlieM: Senses alone tell us nothing about relationships.

    Neil Rickert: That probably depends on what you mean by “senses” and what you mean by “relationships”.

    By senses I mean our perceived world without the element of thinking. By relationships I mean the causal connections between the separate elements given by the senses.

    CharlieM: We understand that there are many creatures that belong together in the group we call mammals. Is this grouping a reality or just an artefact of our perception works?

    Neil Rickert: You seem to be asking what’s the real meaning of “real”. And I don’t think there’s a real answer to that. The word “real” means what we want it to mean, and it pretty much has to be that way. Words get their meaning from the way they are used.

    Think about it. Can we say that a finger exists independent of the whole body? It is the whole which gives meaning to the part. Likewise, can we say that a horse exists independently of the group we have given the name “mammal”?

    If you can distinguish your wide awake consciousness from your dream consciousness then you have some idea of what is meant by reality. I’m talking about levels of reality, not absolute reality.

    When we are looking for a measure of reality we can speak about mammals without having the concept “horse”, but not vice versa.

  13. Kantian Naturalist:
    CharlieM: Senses alone tell us nothing about relationships. It is only when we combine them in thinking that we become aware of connections.

    Kantian Naturalist: That’s not quite right. There are lots of relations in perceptual consciousness — spatial, temporal, and other kinds of perceptual discriminations such as “x is larger than y”, “z is earlier than q”, “g is louder than w”, “t is darker than s”. These perceptual relations are mostly independent of more abstract kinds of relations, such as logical relations (“x entails y”) or functional relations that abstract from perceptual characteristics (e.g. recognizing that a can opener and a wine bottle opener belong to the same generic kind).

    Your description of perceptual consciousness is not what I meant by “senses”. I am talking about senses in the same way that a Bourdon gauge senses pressure. It is what impinges on us before the associated thinking becomes active. From sense impressions alone the moon is larger than any star in the night sky.

    CharlieM: We understand that there are many creatures that belong together in the group we call mammals. Is this grouping a reality or just an artefact of our perception works?

    Kantian Naturalist: Is this a question about whether higher-order taxa are natural kinds?

    It’s a simple question about wholes and parts.

  14. Alan Fox: The general point is comparison. Given a yardstick to compare, one can decide whether one is getting more or less accurate. Is there, beyond everything, an objective reality where all observations and measurements agree? I dunno.

    Everything in time and space is relative. There are no absolutes in the physical world.

  15. CharlieM: Along came the coordinated changes which accompanied an animal’s ability to self-regulate its temperature despite fluctuating external conditions.

    How long did that take, do you think? That “along came the changes”? What sort of time period would that be?

  16. OMagain:
    CharlieM: Along came the coordinated changes which accompanied an animal’s ability to self-regulate its temperature despite fluctuating external conditions.

    OMagain: How long did that take, do you think? That “along came the changes”? What sort of time period would that be?

    I don’t know but I think it happened in a relatively short period of time in evolutionary terms. Fossil dinosaurs display a range in the development towards endothermy. And we know that archaeopteryx had well developed flight feathers in the Jurassic period so I would imagine coverings acting as insulators would no doubt also have been present.

    Placodes are local thickenings of the epidermis develop in the production of integumental structures such as hair or feathers. It has been found that placodes also develop in reptiles:

    Scientists have long debated whether these skin appendages evolved independently or had a single origin. To find out, Nicolas Di-Poï and Michel Milinkovitch at the University of Geneva in Switzerland studied skin development in embryos of Nile crocodiles (Crocodylus niloticus; pictured right), corn snakes (Pantherophis guttatus) and bearded dragons (Pogona vitticeps). They found that reptilian scales, like feathers and mammalian hair (mouse embryo pictured left), develop from a group of cells called the anatomical placode (pictured as dark blue spots). These appear only briefly during development in snakes and lizards, and were previously not detected and so thought to be missing in these animals.

    It would seem that early reptiles had the potential to acquire integuments which would have helped in temperature control but they stopped short in their development and so they have remained more reliant on obtaining heat directly from the environment.

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