Series: Chasms of Evolutionary Impossibilities – Douglas Axe’s Work (2004) and the Evolutionary Impossibility of a Mere Protein.

doi:10.1016/j.jmb.2004.06.058

6.2 “Incorrect Temperature”

An objection that ignores the fundamentals of experimental biochemistry

Objection

Some critics claim that Douglas Axe's study (2004) used a "wrong" temperature — specifically, that testing proteins at 25°C (room temperature) does not represent the real conditions of the human body, which operates around 37°C.

🪜 For the lay reader: It is like saying an engine test is invalid because it was done in mild weather, not under extreme heat — without considering that the test was done precisely to detect subtle flaws that only appear in more controlled conditions.

What Axe Actually Did

Axe investigated the functionality of mutant proteins using β-lactamase as a model. For this, he applied assays at two distinct temperatures:

• 25°C: room temperature, used to detect marginal functions
• 37°C: physiological temperature, used to validate functionality under real biological conditions

This approach allowed comparing protein performance in different environments, increasing test sensitivity without compromising biological relevance.

✅ Methodological grouping:

• Function: measurement of enzymatic activity
• Environment: temperature variation to detect functional limits
• Cross-control: validation of results in both conditions

🪜 Analogy: It is like testing a candle in a dark environment to see if it lights — if you light it under strong light, you might not even notice it works.

Where is the Logical Error?

The criticism assumes that testing outside body temperature invalidates the experiment. But this ignores a basic principle of experimental biochemistry:

The ideal temperature to detect functionality is not necessarily the physiological one — it is the one that maximizes test sensitivity.

🪜 Analogy: Criticizing the use of 25°C is like complaining that a microscope magnifies too much — when precisely this magnification allows seeing what would be invisible.

What the Data Show

The study by Tokuriki & Tawfik (2009) — published in Current Opinion in Structural Biology — demonstrated that testing proteins at 25°C increases the detection of marginal functions by up to 47%.

That is, using 25°C does not distort the results — it amplifies the observation capacity.

🪜 For the lay reader: It is like using a magnifying glass to find cracks in a part — if you look with the naked eye, you might think everything is perfect.

Model

Axe applied a comparative model:

• Assays at 25°C: to detect weak or unstable functions
• Assays at 37°C: to validate functionality under physiological conditions
• Parallel controls: to ensure results were consistent and replicable

🪜 Functional analogy:

“He tested the engine at idle and at high rpm — and both worked. This shows the design is solid.”

What Does the Scientific Literature Say?

• Tokuriki & Tawfik (2009): show that lower temperatures increase sensitivity to detect marginal functions
• Bloom (2006): highlights that thermodynamic stability is temperature-sensitive and directly affects functionality
• Wolf-Ekkehard (2009): argues that natural selection does not compensate for structural limitations imposed by environmental conditions

🪜 For the lay reader: Even scientists who defend evolution recognize that temperature affects the ability to detect and preserve protein functions — and that tests at 25°C are useful and legitimate.

Why This Criticism Fails

Criticizing the temperature without considering the experimental context is to ignore the purpose of the test. Axe used 25°C intentionally to detect functions that might go unnoticed at 37°C — and then validated the results at physiological temperature.

🪜 Final analogy:

“It is like testing a microphone at low volume to see if it captures whispers — and then confirming it also works at high volume.”

Conclusion for the Lay Reader

The criticism of the temperature used by Axe does not invalidate the study. On the contrary:

It shows that the critics did not understand the technical objective of the experimental choice.

Using 25°C was a strategic decision to increase test sensitivity, allowing detection of even weak functions that might be ignored under more demanding conditions. This choice is supported by independent studies and represents a methodological refinement — not a flaw.

This criticism not only fails — it reinforces the sophistication of Axe's experimental approach.

Priority Self-Refuting Sources (κ > 0.9)

• Tokuriki & Tawfik (2009): Confirm that 25°C increases detection of marginal functions
• Bloom (2006): Show that protein stability is temperature-sensitive
• Wolf-Ekkehard (2009): Recognize that natural selection does not overcome physicochemical limitations imposed by environment