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My impression is that physicists who say this usually don't know much about the theory and evidence for evolution. (I am trained in physics, I now do biophysics

by ealloc 10y ago

My impression is that physicists who say this usually don't know much about the theory and evidence for evolution. (I am trained in physics, I now do biophysics). What about the beautiful and often very precise linear relationship between radioactive dating of the fossil record, and genetic dating using the molecular clock? What about the beatiful correspondence often found between the principle components of genetic variation and geographical position (isolation by distance)? What about all the biochemical discoveries related to DNA function (including the existence of DNA itself), how mutations occur, about heritability? What about everything we've discovered about genome composition and how it changes over time? (duplicate genes, pseudogenes, transposons, hotspots of various kinds). Is a DNA sequence less precise than a spectral line?

xaa 10y ago
(Bioinformatics) I wonder if he means not that evolution is false/unfalsifiable/irreproducible, but that it is not really a very predictive theory. I agree there is a lot of evidence that it happened and continues to happen, but predicting how it will happen, i.e., how an organism will evolve, what genes will mutate etc, in a certain environment, is very difficult and really basically impossible. > What about the beatiful correspondence often found between the principle components of genetic variation and geographical position (isolation by distance)? Funny you mention this. There is a student I work with trying to observe this with metagenomics data with much less success than you might imagine.
- magicalist 10y ago
  > but predicting how it will happen, i.e., how an organism will evolve, what genes will mutate etc, in a certain environment, is very difficult and really basically impossible. By that measure physics isn't predictive either. Any moderately complex system and the best we can do is statistical models, often with little to no predictive power.
  - xaa 10y ago
    I agree that the problem is complex systems, not biology per se. But physics is able to be quite predictive because it is able to isolate one basic phenomenon at a time and model it with great precision (gravity, electromagnetism, particle physics, etc). Then, if we want to build devices based on these phenomena from the ground up, we can also do that and predict their behavior with great accuracy (e.g., behavior of a electrical circuit). This is not currently possible at all in biology because even the most minimal functional, self-reproducing biological system is very complex. Indeed even a single protein is quite complex. I suppose by "complex" in this context I mean: lots of acting entities, and many physical laws operating at once rather than just a few. Physics does have predictive problems when it is applied to weather, climate, etc, because those are complex systems. But that kind of the thing is a minority of the subject matter in physics.
    - magicalist 10y ago
      > Physics does have predictive problems when it is applied to weather, climate, etc, because those are complex systems. But that kind of the thing is a minority of the subject matter in physics. There is a far greater number of humans working in applied physics than in characterizing isolated aspects of theoretical systems so I'd question how you judged "minority" there :) Perhaps our disagreement is just in choice of words. The idea that "physics", and all that encompasses, is somehow more predictive than a subset of biology was what triggered my response. If instead you said we have excellent models for simple questions in particle physics, we may have agreed :) As I mentioned on a sibling comment, a simple question like "how an organism will evolve" is of course enormously complex, and if we're going to evaluate the "squishiness" of our answers to it, it's better compared to our ability to predict specific storms a year in advance or how a protoplanetary disk will evolve into a specific configuration of planets. We don't cite those as squishy because we recognize the complexity of the systems involved (and the relative primitiveness of our models).
      - xaa 10y ago
        Well, "physics" really encompasses just about everything, including biology, so I am implicitly limiting it to things which would not fall into another, more specific field, such as engineering or meteorology. Right, word choice. Using any definition for "physics" close to this, while the percentage of biological questions that involve complex systems is close to 100%, it is much lower in physics. The subsets of physics problems that do involve complex systems will suffer the same predictive problems. In fact, this conversation has got me wondering whether "complex system" really means anything more than "a system whose behavior is hard to predict". I know that complex systems have other common attributes, but really the unpredictability seems to be the defining feature. This is a long way of saying "I agree that we don't really disagree" :)

by ealloc 10y ago

xaa 10y ago

(Bioinformatics) I wonder if he means not that evolution is false/unfalsifiable/irreproducible, but that it is not really a very predictive theory. I agree there is a lot of evidence that it happened and continues to happen, but predicting how it will happen, i.e., how an organism will evolve, what genes will mutate etc, in a certain environment, is very difficult and really basically impossible. > What about the beatiful correspondence often found between the principle components of genetic variation and geographical position (isolation by distance)? Funny you mention this. There is a student I work with trying to observe this with metagenomics data with much less success than you might imagine.

magicalist 10y ago
> but predicting how it will happen, i.e., how an organism will evolve, what genes will mutate etc, in a certain environment, is very difficult and really basically impossible. By that measure physics isn't predictive either. Any moderately complex system and the best we can do is statistical models, often with little to no predictive power.
- xaa 10y ago
  I agree that the problem is complex systems, not biology per se. But physics is able to be quite predictive because it is able to isolate one basic phenomenon at a time and model it with great precision (gravity, electromagnetism, particle physics, etc). Then, if we want to build devices based on these phenomena from the ground up, we can also do that and predict their behavior with great accuracy (e.g., behavior of a electrical circuit). This is not currently possible at all in biology because even the most minimal functional, self-reproducing biological system is very complex. Indeed even a single protein is quite complex. I suppose by "complex" in this context I mean: lots of acting entities, and many physical laws operating at once rather than just a few. Physics does have predictive problems when it is applied to weather, climate, etc, because those are complex systems. But that kind of the thing is a minority of the subject matter in physics.
  - magicalist 10y ago
    > Physics does have predictive problems when it is applied to weather, climate, etc, because those are complex systems. But that kind of the thing is a minority of the subject matter in physics. There is a far greater number of humans working in applied physics than in characterizing isolated aspects of theoretical systems so I'd question how you judged "minority" there :) Perhaps our disagreement is just in choice of words. The idea that "physics", and all that encompasses, is somehow more predictive than a subset of biology was what triggered my response. If instead you said we have excellent models for simple questions in particle physics, we may have agreed :) As I mentioned on a sibling comment, a simple question like "how an organism will evolve" is of course enormously complex, and if we're going to evaluate the "squishiness" of our answers to it, it's better compared to our ability to predict specific storms a year in advance or how a protoplanetary disk will evolve into a specific configuration of planets. We don't cite those as squishy because we recognize the complexity of the systems involved (and the relative primitiveness of our models).
    - xaa 10y ago
      Well, "physics" really encompasses just about everything, including biology, so I am implicitly limiting it to things which would not fall into another, more specific field, such as engineering or meteorology. Right, word choice. Using any definition for "physics" close to this, while the percentage of biological questions that involve complex systems is close to 100%, it is much lower in physics. The subsets of physics problems that do involve complex systems will suffer the same predictive problems. In fact, this conversation has got me wondering whether "complex system" really means anything more than "a system whose behavior is hard to predict". I know that complex systems have other common attributes, but really the unpredictability seems to be the defining feature. This is a long way of saying "I agree that we don't really disagree" :)