Does Biology Have Laws?

Science is our way of trying to understand the universe, to make sense of the patterns of objects and behaviours around us and explain the regularity of the world we experience. We use several different words to characterize the ideas and explanations we come up with. A hypothesis is an informed conjecture, a speculation about world which needs to be tested, while a theory is a well-supported, coherent framework which explains some aspect of the universe. Scientific “laws” seem to fall somewhere in between; while they’re very well-supported, they tend to assert things about the world rather than offer an explanation. For example, Newton’s law of gravity enables us to predict the gravitational attraction between two objects but doesn’t explain why objects are attracted to each other.

Most of the laws that people are familiar with probably come from physics or chemistry. What about biology? Does biology have laws? I'm not sure if there are, but it seems to me that evolution (or perhaps ecology) are the most likely fields to furnish biological laws -- that is, predictive biological statements that are sufficiently general to escape the particular context of life on Earth. One candidate might be “every species will either speciate or go extinct”. It may seem uninspiring or simplistic, but it’s not that different from Newton’s first law of motion: “objects in motion tend to stay in motion and objects at rest tend to stay at rest unless disturbed by an outside force”. It may not really explain what’s happening, but it does capture a reliable pattern we observe and, at least to me, suggests that something deeper underlies it.

Maybe we should look for an example with more weight, something which is more insightful and not just descriptive. How about “populations of living creatures evolve via natural & sexual selection and/or genetic drift.” That has a bit more depth than the first suggestion; it’s even part of an elaborate theoretical framework involving lots of equations (for those who suffer from math envy). Sure, there’s room for argument — especially about what “living creatures” means — but let’s assume we could agree about the wording: could it be a law of biology? Why or why not?

When I broached this topic elsewhere, someoe suggested "Living organisms harvest energy and use it to distance themselves from chemical equilibrium", which also sounds to me like a good candiate for a biological law. Does that seem to you like a potential law of biology or just a description/definition? What's the difference betwee the two?

So, what do you think? Is it possible for there to be “laws of biology”? It’s a pretty big topic, so maybe these prompts will help get you thinking:

What do you think “law” means (in the context of science)?
Are any of the suggestions here a good candidate for a “law of biology”? Which is the best?
Can you suggest any other potential laws of biology?
Why is it so much easier to talk about laws of physics?
What about chemistry? Economics? Anthropology?

8 Comments

August 14, 2014 | 07:30 PM

Posted By: Gert Korthof

You ask 'Why it's so hard to formulate laws of biology?' and 'Why is it so much easier to talk about laws of physics?'
An important factor must be that physical objects are dead, far less complex, all atoms of an isotope are identical, while biological 'objects' are literally unique individuals with a history. Considering these differences it makes no sense to demand universal, exceptionless laws in biology.

I fully agree with your "I think there are general principles that we simply haven't properly explored or articulated yet".
Indeed, fist we need to investigate the available 'laws', 'rules', 'principles', such as:
Rubner's Law; Bergmann's rule; Kleiber's law; Allometric scaling laws; Hutchinson's ratio, Rensch's rule; Constructal law and more...
and find out why they are not universal.
It seems to me that most promising are those 'laws' related to energy, metabolic rate, body size, temperature, food chains, ... in other words: physical properties.

August 13, 2014 | 04:24 PM

Posted By: Sedeer el-Showk

Hi Gert,

Yes, that's exactly what I meant about McShea & Brandon's law.

It seems very difficult to come up with good laws in the realm of biology, or at least much more difficult that in other fields. The best examples we've come up with all seem overly simplistic or somehow irrelevant (eg, Hardy-Weinberg). To me, the biggest problem is that none of the suggestions I've come up with (or heard) feel particularly insightful or enlightening; I don't feel like they reflect or increase our understanding of the underlying mechanisms.

I think there's value in considering the question of _why_ it's so hard to formulate laws of biology. I suspect it has to do with how biological phenomena emerge from chemical and physical processes, and the apparent freedom that results (or perhaps 'non-contingency' - there's a better, technical term that escapes me at the moment). Having said that, I think there are general principles that we simply haven't properly explored or articulated yet; for example, the 'equations of the brain' that Adam shared seem like good candidates for general principles of neurobiology. So I'm torn between 'biology is too contingent for laws' and 'our understanding of biology is too parochial'....

August 11, 2014 | 09:04 AM

Posted By: Gert Korthof

Hi Sedeer el-Showk,

I agree. McShea & Brandon's Law has the inherent danger that it boils down to something uninteresting like: complexity increases unless it decreases.

According to (some or most?) philosophers of biology there are no exceptionless laws in biology. Elliott Sober (1993) Philosophy of biology.

The Hardy-Weinberg law seems to be an exceptionless natural law, but if I understand Sober correctly, these laws are exceptionless because they are essentially mathematical, not empirical laws.
All empirical biological laws seem to have exceptions, so are not real laws. There are regularities.

An evolutionary law related to McShea & Brandon is:
Dollo's law of irreversibility states that "An organism is unable to return, even partially, to a previous stage already realized in the ranks of its ancestors". (wikipedia)

I think, Dollo's law could be interpreted as the underpinning of McShea & Brandon's law.
However, Dollo's law is not an exceptionless law, becasue exceptions are proposed.

Maybe, Crick's Central Dogma (genetic information flows from DNA to RNA to protein) is a biological law. But reverse transcription appears to be an exception. The central dogma could be reformulated as: information never flows from proteins via RNA to DNA.
As far as I know there are no exceptions to that law.

August 08, 2014 | 01:19 PM

Posted By: Sedeer el-Showk

Gert: I think it's an excellent proposal, though one that may be open to debate. At this point, I think my biggest criticism would be that the caveat ("tendency...may be opposed by") is enough to make the proposition able to account for a very wide (too wide?) range of observations. So it's an intriguing idea, but I guess I feel like it perhaps needs to be a bit more firm. One might say, for example, "Evolving systems generate an increase in complexity and diversity except when opposed by X." That seems to have more predictive power and to be more testable. If we see an evolving system that isn't becoming more complex, we should look for X. Part of the trouble, of course, is that I don't know what would fill in for X in my version. Are biological systems too complex and variable to be reduced to such straightforward statements or is our understanding of them just too poor?

I wasn't familiar with McShea & Brandon's book, so I'm glad you brought it to my attention. I'll have to read it when I get the chance.

Adam: That looks like an interesting paper. Thanks for sharing it!

August 07, 2014 | 05:24 PM

Posted By: Adam Calhoun

Yeah, I incidentally recently published a review article on this topic (that information could be a kind of 'unifying principle' across any organism

http://papers.cnl-t.salk.edu/PDFs/Information%20Theory%20of%20Adaption%20in%20Neurons%2C%20Behavior%2C%20and%20Mood%202014-4187.pdf

I think a lot of it will be identifying the 'boundary constraints' before we can figure out what the unifying principles are; that will be the (or, a) hard part

August 06, 2014 | 07:06 AM

Posted By: Gert Korthof

Hi Sedeer el-Showk,

What do you think about this law:

"In any evolutionary system in which there is variation and heredity, there is a tendency for diversity and complexity to increase, one that is always present but may be opposed or augmented by natural selection, other forces, or constraints acting on diversity and complexity."

It looks like an elaboration of your second law, but actually it is from:
Daniel W. McShea, Robert Brandon (2010) "Biology's First Law: The Tendency for Diversity and Complexity to Increase in Evolutionary Systems", University Of Chicago Press.

Gert Korthof

August 05, 2014 | 06:43 PM

Posted By: Sedeer el-Showk

Thanks, Adam! I don't know much about neuroscience, so I'm not familiar with the equations/laws in your post. From what I gathered, they strike me as consequences of evolution shaping the nervous system, and so they seem like pretty good candidates for laws. That is, they may well be universal in the sense that any evolved intelligence will be bound by the same physical constraints and so will come up with similar solutions. What do you think?

August 05, 2014 | 05:36 PM

Posted By: Adam Calhoun

Not laws, as such, but I listed some equations which either describe the nervous system or describe what the nervous system is 'doing':

http://neuroecology.wordpress.com/2014/08/04/monday-open-thread-are-these-the-equations-of-the-brain/

For instance, we can describe neural firing almost exactly using the Hodgkin-Huxley equations. We can also describe how sensory neurons respond to the world by determining how they would maximize their information about the world.