Biocurious is a weblog about biology, quantified.

Biology is harder than physics?

by PhilipJ on 3 January 2008

Just before the new year, Rosie Redfield (at RRTeaching) blogged about biology being more difficult than physics. Why?

Biological processes of course are consequences of physics and chemistry, which is why we require our biology students to study the physical sciences. But organisms are also historical entities, and that’s where the complexities arise. The facts of physics and chemistry are constant across time and space. Any one carbon atom is the same as any other, and today’s carbon atoms are the same as those of a billion years ago. But each organism is different. That’s not just a statement that fruit flies are different from house flies. Rather, each fruit fly is different from every other fruit fly alive today, and from every other fruit fly that ever lived, and it’s the differences that make biology both thrilling and hard.

No disagreements from me here. The laws which govern physics and chemistry are contant across the universe (though there is some debate as to their constancy in time). Without the strict adherence to the laws we observe, physics and chemistry would be near impossible to understand. It is lucky for biology that this is how the world works, because, as Rosie notes, biology depends on it!

Skipping ahead, here’s where I get confused:

Even genetically identical cells are not functionally identical. When a cell divides its molecules are randomly distributed between the two daughters; because ‘randomly’ does not mean ‘evenly’, these daughters will have inherited different sets of the proteins and RNAs that carry out their functions. And even if the two cells had identical contents, these contents would still have different interactions – repressors bump into cofactors at different times, DNA polymerase slips or doesn’t slip at different points in its progress along a chromosome. Understanding the how and why of biological phenomena thus requires us to consider historical and ecological factors that are many orders of magnitude more complex than those of physical systems.

When trying to understand biological systems (nay, any kind of system, be it a crystal or a batch of cells), much ultimately depends on the type of measurement. Every measurement does not need to take into account the histories and ecological factors that make up every individual cell – it is impossible to know them to the required resolution that such data would be useful. When and where a DNA polymerase may stall on the chromosome in a particular cell of a mL culture containing billions upon billions of cells is effectively irrelevant for a huge number of interesting experiments I might want to do with those cells — say, the study of expression of a particular gene with a gene chip.


The critical word is probably ‘population’. Biologists rarely try to define it, but they use the term everywhere to refer to similar but not identical organisms or cells (or even molecules) that interact in some way. ‘Population thinking’, the realization that species are populations, not pure types, is said to have been key to Darwin’s insight that members of a species undergo natural selection. And population thinking is probably what makes biology so much more complex than the physical sciences.

Here’s where I think my ultimate displeasure with the post lies. That biology is more complex than physics (though what exactly is limited to the realm of physics is now very much in question) is a reasonable statement: the most common biological molecules are much too complicated to apply something like the Schroedinger Equation and expect to understand anything about them, but “complex” and “difficult” are not the same thing. That physics has traditionally been confined to the well-defined and “simple” systems like infinite lattices of identical carbon atoms, doesn’t make it “easier” to study than biology. I don’t even know what it could mean for one field of science to be “easier” than another, given that everyone studying a science is different, like, as Rosie mentions above, how each fruit fly is different from every other fruit fly. Some people find the mathematics required to understand physical systems extremely difficult, while others don’t have the required attention to detail to perform a successful experiment in a biology lab. To do any kind of science, however, it is the same: you require critical thinking and quantitative analysis of experiments to make any sense of your results. This is true from particle physics all the way up to ecology.

Rosie’s opening paragraph ends with the following:

[I]n reality biology is much more complex than the physical sciences, and understanding it requires more, not less, brain work.

I hope someone in the social sciences gets wind of this and belittles biologists. Sociology is obviously more complex than biology, so it cleary requires more brainpower to be a social scientist than a biologist, right? Rutherford’s famous statement that all science save physics is mere stamp collecting wasn’t a useful thing to say, and this isn’t much better.

  1. bill    3341 days ago    #

    Rutherford’s famous statement that all science save physics is mere stamp collecting wasn’t a useful thing to say, and this isn’t much better.

    It isn’t any better, IMO. Who needs another pointless pissing match?

  2. alec    3341 days ago    #

    I agree with you. Complexity is definitely not identical to difficulty.

  3. Fred Ross    3341 days ago    #

    Being complex is also not the same as being complicated. Biology is complicated, definitely, but I have yet to see any real evidence that it is complex, that is, that it requires a certain minimal amount of computational power to say something about it.

    I think the real problem at hand is that biologists haven’t actually assimilated the mindsets of thermodynamics, probability, and statistical mechanics which are absolutely necessary to biology.

    Well, that and most biologists are completely blinded by bits of DNA and proteins and can’t see anything else in an organism.

  4. ponderingfool    3341 days ago    #

    When and where a DNA polymerase may stall on the chromosome in a particular cell of a mL culture containing billions upon billions of cells is effectively irrelevant for a huge number of interesting experiments I might want to do with those cells — say, the study of expression of a particular gene with a gene chip. ***************************************
    Given you most likely start with a starter culture it may actually be important, especially where you take your aliquot from the starter culture. Those cells on the sides of the culture are under different conditions than those growing at the interface between the air and the media which are both different than those growing within the center of the culture.

    Also think about protein over-expression in E. coli. Differences can be seen between colonies which in theory have the same genetic background. It would be foolish not to take that into account when designing your experiments and when trying to understand your results.

  5. Larry Moran    3340 days ago    #

    Sociology is a small subset of biology. It can’t possibly be more complex than biology unless a part can be more complex than the whole.

    Is that what you learn in physics? :-)

    See my comment on

  6. Andre    3340 days ago    #

    I agree with Bill. The historical, contingent nature of biology is an important difference between it and a lot of physics (but certainly not all of physics!) and is worth discussing but the idea that one is harder than the other is just trolling.

  7. Doug    3339 days ago    #

    Modern physics apparently does not recall that the Greek root of physics means ‘Nature’, hence the name of one of the most prestigious journals.

    I do agree with Andre that “… the idea that one is harder than the other is just trolling.”

    Biology has had contributions from many physicists, engineers, chemists and other scientists, including a variety of individuals devoted to the healthcare field.

    There seems to be a lack of recognition that contributions of both theory and / or application from diverse vocations has a wealth of knowledge greater than the specialist of a single profession.

  8. Rosie Redfield    3339 days ago    #

    Hi Philip,

    I just came here from Larry Moran’s blog. Thanks for carefully reading my post before commenting on it.

    My post is on my teaching blog because it’s aimed mainly at biology students. Its primary goal is to counter their foolish expectation that they success in biology depends mainly on memorization.


  9. Kurt L. Hanson    3331 days ago    #, always thought stimulating.

    I believe the better student, or innovator, possesses a seed, a kernal or core idea or concept they will then use to rally their curiousity and motivation for learning around. Since tenth grade biology, the concept of homeostasis in biological systems I found to be fascinating, and with this in the back of my mind the intense bombardment of facts from class was anything but difficult or complex to organize and understand. The flurry of discordant bits of knowledge are pieces to this mysterious puzzle. The pieces are dissected to then find some aspects are relevant and more interesting, other apects are irrelevant to homeostasis and …? not forgotten, perhaps ignored is the better word.

    Difficult and complex seem to apply only when I find I have to apply what I know to another’s premise, and then to reply in some sensible way. Someone attempts to apply theological points to the subject of homeostasis, and I find any response to be difficult and complex, this being so only because of their seeming irrelevancy.

    I would tend to think the critical word is relevancy. I am in the process of learning the facts and the cause and effects of some particular matter, and for what? What is the goal? Hopefully, you know, someone is not attempting to learn how to move a bulldozer to sharpen a pencil. That would be difficult, and extremely complex. Ditto’s religious dogma and the homeostasis of biological systems.

    Finding time to read all the blogs, and then further investigating what may or may not be relevant from what I’ve just read, all the while hoping to someday win a Nobel, this is the difficult part for me, I suppose. {:-}

    Rose, Fred’s last paragraph sort of hinted at if biology is to be learned for an understanding of “the reality of the situation,” if the student of biology is to grapple with the idea for a meaning and purpose to life, ie. the principles of biology, and using this as an impetus for learning and understanding the course material, perhaps rally your students around the notion of how the archaen earth environment wrought the first unicellular organism into existence. You may want to focus on an explaination for the Cambrian explosion too, though this may divert their attention away from biology.

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