Ariew and Lewontin, "Fitness Confusions"

The following essay eventually was published in peer-reviewed journal, but the draft, imho, was better!

Here is the link

< a href=>Fitness Confusions

I cited another work by Lewontin in a reference chapter published by Springer-Nature AG Switzerland, but in retrospect, I wish I cited this paper.

Is there a topic here you wish to discuss? The thread seems to be just you saying you wished you once cited this instead of something else.

Thanks for commenting Rumraket. Nice to see you again.

Imho, this paper basically indicates many of the present evolutionary definitions of fitness based reproductive success is scientifically worthless.

Lewontin said the definition of fitness is one of the 4 major unsolved complications of the evolutionary process in Santa Fe 2003 winter bulletin. That’s the paper I cited, but this paper with Ariew is way more in depth regarding the actual problem.

If something as basic as fitness can’t even be defined (or at least measured in an environment-independent way) then lots of evolutionary claims are at best uncertain if not falsified.

This shows much of the theories of natural selection to date, in as much as they are dependent on confused definitions of fitness that, have no relevance to the problem Darwin tried to solve in Origin of Species Chapter 6, “organs of extreme perfection and complication”.

If anything evolutionary fitness is anti-correlated with complexity as shown in numerous experiments and observations.

This does not bode well for Dawkins Blindwatchmaker hypothesis.

Worthless. Of no worth. None.

I think that’s piling it on rather thick, don’t ya think?

The paper asserts no such thing of course. It discusses reasons why one might not be able to apply the same proxy of the concept in all situations, but that’s a far cry from saying it is of no worth.

Take something as nebulous as the concept of health. To be healthy. Is there such a thing as being healthy? Can we make sense of it? Can we talk meaningfully of being healthy or unhealthy?
I think we can, even though it’s always going to be very complicated and context specific, we can still make statements about some being more healthy than others, and have various proxies for the state of their health. An obese person can be more healthy than a slim/athletic one in all sorts of ways we can measure, which we take to be sensible aspects of health.

So even though there might not be just one fits-all definition of health that can fully capture everything we could have in mind about it, that doesn’t mean it is worthless.

Fitness is like that. Whatever we might mean by it, it has something to do with the capacity of an organism and it’s descendants to persist successfully against the challenges it faces in it’s environment.

That of course doesn’t follow at all, and fitness clearly is environment-dependent. Your mistake is in thinking evolution must involve some some unobstructed and ever increasing gain in some absolute measure of fitness, rather than it being some measure of the capacity to persist within some environmental niche.

Your confusion likely comes from having been influenced by creationist misrepresentations of evolutionary biology, where it is presented as if evolution must always amount to this idea of some absolute measure of improvement.

As I have been explaining to creationists on this forum now for years, this view is of creationists own making. It was never a product of Darwin’s theory that evolution says there is some absolute unconditional measure of fitness applying to any and all environments, that must and will only ever increase.

Fitness is specific to an environment and a niche, and is not equal to (or even necessarily correlated with) something like the total number of functions, the overall complexity, the amount of information, or anything like it. You must uncouple all these concepts from each other and realize they can change independently of each other.

I made this figure to illustrate how to think about it:

It can be anti-correlated, that doesn’t mean it always is anti-correlated. You must learn to dispense with dichotomous thinking.

It can be anything from anti to positively correlated of course, so you can’t say fitness can’t be part of an explanation for complexity. You can only say it isn’t necessarily the explanation for the evolution of increased complexity.

Of course, we know of other evolutionary reasons why complexity can increase without it involving positive selection.


How would you determine the fitness of camels and whales in environment independent ways? It is characteristics that suit them to their environment which result in reproductive success.


Thank you for your comment.

That’s not my problem that’s evolutionary biology’s problem because if they assert something evolved and don’t know the environment that made something more fit than another, then that’s a faith statement to say it evolved a complex system through a process that favored reproductive efficiency – whereas the weight of experimental evidence is reproductive efficiency favors simplicity.

Faith statements are ok, I’m a religious person, but faith isn’t to the level of an empirical verifiable theory.

From the paper:

no scalar reproductive fitness measure can be derived from
reproductive schedules that allows statements of the form, “Type A
is more fit than type B.”

That’s pretty bad. I can say something has more mass than something else, I can say something is longer than something else. That helps the scientific process.

If one can’t unequivocally say something is more fit than another, then the Blindwatchmaker claim is based on faith, not on actual measurement.

But they aren’t saying that necessarily happened, that “something became more fit than another”.

Nor are they saying that something necessarily became more complex because this increase in complexity resulted in increased fitness in that environment (not sure what you mean by “reproductive efficiency”). Just that that is one among multiple possible evolutionary accounts of how it could have happened.

Your confusion now stems from drawing a parallel to your religion, as if scientific statements about the past are offered with a sort of authoritarian declarative certainty.

Inferences about the past are made in science by comparing models intended to account for the data in a predictive way, with the patterns in the data.
We have models that very successfully account for X, which gives us confidence those models are approximating something about what happened in history, isn’t a faith statement.

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Not in a way where it must apply unconditionally under all circumstances.

There are of course many circumstances in which we can perfectly sensibly say that Type A is more fit than Type B in this environment. I’m going to say that, all else held equal, an allele conferring antibiotic resistance to a bacterium exposed to antibiotic, makes it more fit than a non-carrier of that allele.

I’m going to say that in the open ocean twenty miles from shore, a shark is more fit than I am.

So perfectly sensible and comprehensible.

But one can say that, it just won’t apply across any and all environments.

You can say a lot of stuff, but you can’t always measure it or make direct comparisons for all sorts of practical reasons. Weight is how we normally measure mass. A feather on the surface of a neutron star will weigh more than you will on the surface of Jupiter, yet you’d think you have more mass. So mass and it’s measurement is actually a relational property in practice. In relation to the Earth’s gravitational field, at a certain distance to it’s core. Go somewhere else, you will measure your mass differently using the same scale.

Ironically the definition and measurement of mass is a well-known problem in the philosophy physics.

Oh, I see. So when Sanford et al (which sometimes includes Cordova) talk about “fitness entropy” that is a worthless discussion? Hmmm …


fitness entropy
Oops of course it is genetic entropy. Whose effect they measure as decline of mean fitness.


And to think, Sanford wrote an entire book that is worthless. What a shame!

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This strikes me as grasping for a rhetorical point. Species are also notoriously hard to define, but the general concept of breeding populations is hardly falsified and certainly exists. We do not get to tell nature to confine itself to our neat definitions and demarcations. Biology does what it does, and we take note of it.

In any event, in a given population that is in some sort of equilibrium with the resources available, there are going to be more offspring than can be supported. Those who make it will do so at the expense of those who do not, thus certain traits will be favored by a particular environment. If there is another outcome possible, I do not know what it is.

It does not have to be a complex system, and where complexity is increased that is incidental to adaptation and not some goal.

Whales have lost their hind legs. While that would assist hydrodynamic efficiency, and is so connected with environmental drivers, that does not increase complexity. Fitness is not a problem for evolutionary biology, it is a problem for the whale.

As for being a faith statement, hydrodynamics as a selective environmental factor resulting in loss of hind limbs is an inference. An inference may lie anywhere from weak to essentially fact, but that is not based in faith. That nature loves you and has a wonderful plan for your life is not part of biology.


For starters, in science we try to falsify hypotheses, not claims.

I don’t see why. Perhaps you should explain in detail instead of making a blanket assertion.

That’s not a hypothesis, it’s a metaphor.

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I stand corrected. Thank you for the very helpful editorial suggestion.

Scales technically measure weight, not mass. Weight is dependent on the gravitational field, mass does not.


Genetic entropy is the claim genomes decay, fitness may or may not be the best measure of genetic entropy. Gene loss, regulatory loss, functional compromise of genetic systems are better metrics of genetic entropy.

I advocated for this view of genetic deterioration (that is deterioration not measured primarily by loss of reproductive efficiency) and I’m happy to report this view is reflected our 2021 reference chapter, and it is an improvement of some of the framing of the original 2004 book by Dr. Sanford.

Lenski essentially gave one the best titles for an evolutionary paper which said, “…genomes decay despite sustained fitness gains…” for one of his infamous LTEE bacterial lineages.

There are other titles like, “gene loss by natural selection” or “genome reduction as the dominant mode of evolution”.

Andreas Wagner cited Lewontin and said this:

Beyond the commonplace that fitness means the ability to survive and reproduce, fitness is difficult to define properly, and nearly impossible to measure rigorously…these difficulties mean that an unassailable measurement of any organism’s fitness does in practice not exist.


If weight can’t be measured in an environment-independent way, wouldn’t that mean lots of physics (and grocer’y) claims are at best uncertain if not falsified?

Or is some double-standard being used here?


How could functional compromise be measured without reference to some form of fitness?


Also, if fitness could be defined in an environment-independent manner, wouldn’t ‘survival of the fittest’ imply that we should be left with only one species on Earth?

The whole idea is completely ridiculous. :roll_eyes: