Are there biological facts that the theory of evolution does not explain and does not need to explain?

The theory of evolution is the overarching unifying theory in biology. Are there biological facts that the theory of evolution does not need to explain? Or does the theory of evolution have to explain every fact about life? According to the theory of evolution every species and every individual of a species is the result of evolution. That would imply that every feature of an organism must somehow be explained by the theory of evolution. 

Aerodynamic forces on a bird (Videler, 2012)

Even at the time when I was a student and attended evolutionary biology courses and did lab experiments on evolution, I had the vague idea that the theory of evolution was incomplete, although at the time I couldn't say why, or what exactly was missing (here). There is so much to explain, and "A change in gene frequencies over time" and "Differential reproduction of heritable variation" seem far too simple for the task. Yes, there was a Second and Third Evolutionary Synthesis, but still a lot was missing. Obviously, the planetary, geological and cosmological context of evolution is often missing in the textbooks. Last year I blogged about the fact that evolution textbooks are suffocating: very low levels of Oxygen!  My list of top 20 evolution books (blog) reflects my preoccupation with the question of what is missing. Furthermore, physicist Rolie Barth pointed out physical factors and constraints in evolution (blog) [1]. At the other end of the spectrum: is evolution supposed to explain human behaviour, intelligence, consciousness, psychology, language, culture, civilization, war? What is the scope of the theory? Where does it end?

A few days ago I had an interesting discussion with google-AI about the question: Are there biological facts that the theory of evolution does not need to explain?  The initial answers seemed incorrect and incomplete. So, I demanded better answers and google-AI came with surprisingly insightful answers:

1. What evolution does NOT need to explain: The physics of how cells physically move, stick together, or split. For example, when a sheet of cells bends into a tube, it follows basic laws of fluid mechanics and surface tension.
2. What evolution DOES need to explain: Why the cells bend into a tube at that exact moment, in that specific location, to form a spinal cord. The timing, the instructions, and the genetic switches that trigger those physical movements are entirely shaped by natural selection.
3. What evolution does NOT explain: The electromagnetic forces that allow a hydrogen bond to form between Adenine and Thymine. That is pure physics and chemistry.
4. What evolution DOES explain: Why a specific three-letter sequence (like UUU) maps to a specific amino acid (like Phenylalanine), and why this map is nearly universal across all life.
5. Evolution does NOT explain: Why a hydrogen bond forms at all, why the universe is made of matter instead of antimatter, or the laws of thermodynamics that govern energy conversion.
6. Evolution DOES explain: How life hijacked those inescapable physical realities and organized them into the intricate, Mendelian, metabolic, developmental masterpiece we call biology.

Additionally:

• Lipid Bilayers: Amphiphilic lipid molecules automatically assemble into complex, spherical, semi-permeable cell membranes when exposed to water, driven entirely by hydrophobic physical forces.
• Membraneless Organelles: Inside the cell, proteins and RNA's undergo liquid-liquid phase separation—similar to droplets of oil separating in water. This thermodynamic behaviour spontaneously forms highly organized, functional compartments (such as the nucleolus) without needing an explicit genetic blueprint directing every coordinate.

These examples can be expanded with:

Microtubules: the self-assembly of microtubules. The proteins themselves are inherited, but they self-assemble into microtubules. 

Biochemistry: See also the primacy of biochemistry as opposed to genetic determinism [2].

Bio-electricity: "Without bioelectricity, your cells couldn't communicate, your muscles couldn't move, and your heart wouldn't beat." [3]:

• The Cellular Battery: Membrane Potential
• Nervous System Communication
• Muscle Contractions (Powering Movement and the Heart)
• Wound Healing and Tissue Regeneration
• Specialized Biological Superpowers (Electroreception, Electrogenesis)

Quantum effects: photosynthesis. 

Mechanical forces: Venus flytrap [4].

Van der Waals forces that hold molecules together (Gecko).

Hydrogen bonds (DNA bases).

Aerodynamics (birds, bats, insects), hydrodynamics (fishes, dolphins, blood flow).

Gravity: Effect on body size (scaling laws).

etc. 

 

It seems very reasonable that evolutionary theory doesn't need to explain physical and chemical phenomena, because it is a biological theory. Physics and chemistry do explain physical and chemical phenomena. A biological theory can take them for granted, isn't it?

However, there is a problem. For a full scientific explanation of the evolution of life on earth, one cannot do without additional non-biological explanations. But organisms are undivided wholes. They can't be subdivided into biological, chemical and physical parts. So, must we conclude that the theory of evolution, as a biological theory, by definition is incomplete? [5]. Could it be that the theory only has to explain how biological things have evolved, and not all the details of how they work precisely? Would it be enough to demonstrate which genes and which mutations are involved in creating a specific trait and how it contributes to fitness? Does the theory need to include aerodynamics to explain the origin and evolution of flight? Finally, if new scientific discoveries are made on a daily basis, how can the theory of evolution ever be complete? I am afraid that the question of the scope and completeness of the theory of evolution is a rather complex and elusive question. Maybe, several quite different questions. Anyway, the question is too wide-ranging and too tricky to settle in one blog post. 

Notes

1. See also this blog where Rolie Barth explains that "Protein evolution can draw from a reservoir of a limited number of physically possible structures".
2. Nick Lane say about the primacy of biochemistry contra genetic determinism: Genes evolved simply to stabilize and optimize these already functioning biochemical pathways, rather than starting from scratch to build the cell. Also: The electrical origins of life!  
3. According to https://gemini.google.com 
4. Fast cell wall softening causes Venus flytrap closure, Science, 11 Jun 2026
5. Note: Could that be the cause of my gut feelings about the incompleteness of the theory of evolution half a century ago? 

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Autonome wereld en theodicee bij Taede Smedes (3)

"Het blog over Autonome Wereld bij Taede Smedes (2) is een van mijn meest bekeken blogs. En er kwamen soms vreemde reacties. Iemand die je een Taede Smedes-kenner zou kunnen noemen, schreef dat Taede Smedes nooit over het probleem van het kwaad had geschreven. Dat vond ik een vreemde bewering.
In een vorig blog (1) schreef ik over het probleem van het kwaad zoals beschreven in het boek God en Darwin van theoloog-godsdienstfilosoof Taede Smedes. Het probleem werd in dat boek maar heel kort aangestipt omdat het boek over een ander onderwerp ging. Toch werden er in dat boek zeer belangrijke en revolutionaire uitspraken gedaan. Sommigen (2) beweerden dat Taede Smedes nooit iets over het probleem van het kwaad had geschreven, en daaruit volgde op de een of andere manier dat ik het helemaal mis had. Of zo iets. Onzin! Onwetendheid! Smedes heeft wel degelijk over het probleem van het kwaad geschreven in zijn boek God en de Menselijke Maat (2006). Met name in Hoofdstuk 11 (toelichting, literatuurlijstje) (bewijst ook dat hij zich met de literatuur heeft beziggehouden)." 

Tot zover een draft blog dat ik nooit heb afgemaakt. Ik publiceer het nu ongewijzigd zoals het sinds 2011 als draft is blijven staan. De aanleiding is een blog van Taede Smedes: Lieke Marsman – Een oproep tot leven, 4 juni 2026. Dat blog opent met de woorden:

"Ik heb het feit dat kanker bestaat altijd gezien als een van de belangrijkste argumenten tegen het bestaan van een bovennatuurlijke God. ... Dat kanker bestaat, toont voor mij aan dat een bovennatuurlijke Schepper-God – zoals voorgesteld in het christendom – niet kan bestaan. Zo’n God is voor mij dan ook een illusie."

Je kunt in ieder geval vaststellen dat Smedes in de loop der jaren consistent is gebleven in dat opzicht [3].

Noten

1. Autonome wereld en theodicee bij Taede Smedes (2) Het probleem van het kwaad, 28 november 2011. 
2. Uitgerekend filosoof Jan Riemersma heeft vele malen gezegd dat je vooral Taede Smedes moest lezen. Overigens is het helemaal niet relevant of Smedes 'nooit over het probleem van het kwaad' geschreven heeft. Het gaat er om wat hij wel geschreven heeft. Daar doe ik het mee.
3. Dit blog van Smedes over hetzelfde onderwerp had ik nog niet eerder gezien: Sluit zinloos lijden het bestaan van God uit? 17 mei 2010.

A likely breeding case of the Common Hoopoe in the Netherlands

Common Hoopoe / Hop / Upupa epops ©GertKorthof

The Hoopoe is a rare and unique bird in The Netherlands. It has an unusual combination of a movable crest like that of a cockatoo, and a long beak curved slightly downwards like that of an Eurasian Curlew (wulp). The plumage is a combination of an inconspicuous brown and a striking black-and-white pattern. The food-seeking behavior is mostly on grasslands and clearings in the forest, but it breeds in tree cavities like a woodpecker.

©GertKorthof

Recently, I was fortunate enough to watch this beautiful bird in the wild in The Netherlands. It landed on a bare spot in the forest about 20 meters (65 Feet) away from where I was walking. From my position, I could observe, photograph, and film it perfectly. After a few minutes, it flew away. I was able to make a short video:

A short video clearly shows the hurried way of foraging.

Evidence for a breeding case

The bird is very busy gathering food for short moments during most of the day on different locations and returning again and again. It has been observed that the birds repeatedly fly with food in their beaks in the same direction. They are usually very relaxed, but this bird was very busy. I have seen pictures made by another birder that clearly show a Hoopoe flying away with an insect in its beak. That is the best, albeit indirect, proof of a nest with young. This is not the same as fledging, the stage that the young leave the nest. Only then can it be called a success.

I have submitted my observation to waarneming.nl. The image recognition system (ObsIdentify) resulted in a 100% certain identification. Not really a surprise for an easily recognizable bird. This observation appeared to be under embargo and is only visible to myself and authorized persons. So, I can't see how many observations have been submitted. My observation was automatically approved. This shows that manually approved observations of the bird on the same location must have existed already at that moment. Despite its rareness, there are a lot of Hoopoe observations visible in waarneming.nl at many locations in The Netherlands, but these aren't breeding cases.

How rare is the Hoopoe in the Netherlands?

Hop Upupa epops. breeding 2021-2023 SOVON

Hop Upupa epops. Non-breeding 1989-2014 SOVON

See for more data:  SOVON [3]

 

Fun facts

Peterson, Mountfort, Hollom, Kist 1964 [2]

My first serious bird guide, at the time it was referred to as 'De Kist', now 62 years old, has a Hoopoe on the cover! How charming! They placed a very rare breeding bird on the cover! Field characteristics of the Hoopoe:

"Searches for food mainly on open ground. Nests in tree cavities and the like. Very rare breeding bird of open woodland. Reappeared for the first time since 1943, after 30 years. Rare migrant from mid-August to late October and in spring in April and May." (page 195)

The map in this bird guide shows that the Netherlands lie above the northern border of the breeding area. Birds showing up in The Netherlands could be called pioneers venturing into unknown territory. This could explain why the number of birds fluctuates from year to year. I imagine that after a good breeding season in southern countries, young birds migrate north. Their usual food grasshoppers and lizards are relatively rare in our country, so the pioneer birds must adapt to other prey [1]. They must be flexible.

A bird encyclopedia published between 1770 and 1829 DE NEDERLANDSCHE VOGELEN: [4]

De Nederlandsche Vogelen. (Grutto op omslag)
Compare with a modern bird guide.

 

3 pages about the 'UPUPA' or HOPPE. [4]

 

The illustration is of high quality and is absolutely sufficient to identify the bird. The author describes the bird as a rare breeding bird. It was difficult to locate the nest of the bird. Between 1747 and 1778 it has not been seen. This shows how irregular the presence of the bird was at the time. However, the most striking fact in modern eyes is the fact that the author received a (dead!) breeding pair of Hoopoes complete with eggs and part of the 'nest' that had been captured (?) shot(?) from the wild! Fun fact: the author mentions that the famous philosopher Aristotle already knew the bird [5].

 

Title plate of book III clearly showing a Hoopoe..

Finally, the Hoopoe is present in the holy book of Christians, The Bible: " It is mentioned in the Old Testament as one of the birds that the Israelites were forbidden to eat under the dietary laws of the Mosaic Law." [6],[7].

 

Notes

1. R.M. Teixeira (1979) Atlas van Nederlandse broedvogels. page 212-213. 
2. Dutch translation of: Peterson, Mountfort, Hollom 1964) A Field Guide to the Birds of Britain and Europe. Translated and adapted by Mr. J. Kist.
3. SOVON, (Stichting Ornithologisch Veldonderzoek Nederland, Sovon Dutch Centre for Field Ornithology) is the most reliable source of the numbers of bird species in The Netherlands. The most recent report is Broedvogels in Nederland 2024. The Hoopoe is described on this page with an estimated number of 5-7 breeding cases. (information from Klaas van Dijk 2 Jun 2026).
4. DE NEDERLANDSCHE VOGELEN free online edition. 'Hoppe' is the old name of the Hop.
5. I checked it, and indeed: THE HISTORY OF ANIMALS by Ari" target="_blank">on this pagele, tr with an estimated number of 5-7 breeding cases. nslated by D'Arcy Wentworth Thompson, Book VI.
6. It is mentioned in the Old Testament as one of the birds that the Israelites were forbidden to eat under the dietary laws of the Mosaic Law. Leviticus 11:19, Deuteronomy 14:18. Unclean for consumption: the Hoopoe is grouped with other "unclean" and detestable birds (like vultures and bats). It is indeed repeatedly mentioned in the literature that droppings accumulate in the nest and are not cleaned up. Understandable that it is an 'unclean bird'. However, it is possible that this fact has been endlessly copied without first-hand observations! Most birds keep their nests clean due to the risk of infection. [added: 2 Jun 2026]
7. Vogels in de Bijbel geeft 21 vogels, waaronder de Hop, maar ook de Struisvogel! Dat kan natuurlijk niet, want de Struisvogel komt alleen in Afrika voor. [4 juni 2026]

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