Nothing in biology makes sense...

Academic articles rarely have catchy titles. One that has - and that is also frequently cited - is Nothing in Biology Makes Sense Except in the Light of Evolution.

Its full citation is:

Dobzhansky, Th. (1973). Nothing in Biology Makes Sense Except in the Light of Evolution. The American Biology Teacher. 35 (3): 125–129.

A transcript of the article is on biologie-lernprogramme.de. An article about it is on Wikipedia.

The article was written by the eminent Ukrainian-born evolutionary biologist Theodosius Dobzhansky (1900-1975) when living and working in the USA. Significantly, it is an essay that argues that Christianity and evolutionary biology are compatible. Furthermore, it argues in support of theistic evolution. Irrespective of their personal religious beliefs, few biologists would advocate theistic evolution professionally. Most keep their scientific work and their religious views separate. That being the case, it is open to question how widely this essay has been read by those citing it.

The citations the article continues to receive could be more for its title than its content. What the essay title encapsulates is a statement of how evolution pervades and relates to every aspect of biology. The phrase states vividly and concisely something all informed biologists recognise - that evolution is at the very heart of all of the life sciences. It is in this sense that the article is sure to continue to be cited.

What is easy to overlook is what the essay title implies. The implication is that without evolution, biology, in fact, makes no sense.

In their book Evolution and Healing (published in the US as Why We Get Sick), Randy Nesse and George Williams modified the essay title to make specific reference to medicine. They proposed that nothing in medicine makes sense except in the light of evolution. Upon this notion, evolutionary (Darwinian) medicine rests.

Fun fact

I once set a multiple-choice exam question for a biology paper that read...

According to Theodosius Dobzhansky (1973), ‘Nothing in biology makes sense...’

(A) ...at all

(B) ...except in the light of evolution

(C) ...

(D) ... I have forgotten the other incorrect choices I offered.

How many students got it right, I do not remember (although it was the majority - if not all of them). I remember very clearly how relieved I was when I found that nobody had chosen (A), implying that nothing in biology makes sense... at all.

[Full citation for the above:

Nesse, R. and Williams, G. (1995). Evolution and Healing. London, Weidenfeld and Nicolson.]

First Steps in Anatomy and Physiology

When studying the human body, the first steps taken by most students have a lot in common. It does not matter if one is aiming for a professional qualification or whether one is studying the human body out of mere interest. When anatomy and physiology are combined, this is particularly so. Anatomy and physiology are two separate sciences with very different histories. However, for teaching students not studying medicine, they are often combined into a single unit of study. That there are textbooks combining the two sciences illustrates this. There is a lucrative market for such books. Courses in life and health sciences are very numerous. Thus, publishers vie for market share. As a result, the textbooks available have settled on a similar layout and style. Any textbook that bucks the trend will not appeal to a mass market and will not be as commercially successful. As a result, textbooks have converged on a similar approach.

The three overhead projector transparencies (OHTs) mentioned in previous posts represent three common themes in these textbooks. All these textbooks open with an introductory chapter with a title such as Orientation. It is unnecessary to describe in detail here the content of that chapter. Instead, it is important to note how the conceptual framework for the rest of the book gets laid down in this chapter. The Orientation chapter introduces the ideas behind each of the OHTs I mentioned elsewhere.

OHT-1

OHT-1 depicts how the body is divisible into different levels of organisation. The image in the earlier post is interpretable in two ways.

(i) Organisms consist of organs. Organs consist of tissues. Tissues consist of cells. Cells consist of chemical molecules.

Alternatively, one can go in the opposite direction.

(ii) Chemical molecules form cells. Cells form tissues. Tissues form organs. Organs form organisms.

Usually - as in my OHT-1 - a directional arrow is given. However, one may go in either direction. Although a viable option, thinking simultaneously in both directions is not suggested.

The above provides the conceptual framework within which the reader begins to think. Different textbooks offer different versions of what I refer to as OHT-1. In due course, I will post some I have collected over the years.

OHT-1 is a very simplified and incomplete portrayal of what the body is really like. That should be obvious. However, that incompleteness goes uncommented upon and unexplored.

OHT-2

OHT-2 depicts the different physiological systems into which the body is divisible. It would be more accurate to say that it represents how the author or editor of the textbook chooses to divide the body. There are often subtle differences in the naming and sequencing of different body systems. For example, the muscles and bones may be presented as two distinct systems or as a single musculoskeletal system. Again, this provides the conceptual framework within which the reader begins to think.

In the rest of the textbook, each system gets a separate chapter. Details of each system's structures and processes follow. These begin at the organ level and proceed into finer and finer detail.

There is never a chapter at the end of these textbooks that puts everything back together again. (That, in effect, is the Humpty Dumpty Problem.) The physiological systems remain as separate systems. There is never a conceptualising of what the structures and processes mean to the life of the person studying the subject. After all, what they are studying is what they are.

I used to ask students to have in mind this question at all times:

What does this structure or process confirm on me?

Focusing that question on the individual student (the 'me' in the question) was meant to make the subject more pertinent and less abstract.

OHT-3

OHT-3 represents the concept of homeostasis. Homeostasis colours the intellectual framework for understanding much of physiology. As stated in another post, I avoided talking about homeostasis except to say why I was avoiding it. While it is a concept very much ingrained in biological thought, it is not without its critics. That should be acknowledged. However, that is rarely the case. Neither should it be accepted uncritically. That is often the case. The typical description of homeostasis is an uncritical statement of orthodoxy - a statement of a belief held by biologists. Furthermore, it is a belief frequently misunderstood and misrepresented.

Sara Tells My Stories

Following a lecture I had just given, an undergraduate student approached me and asked if I had taught a girl called Sara some years before. I replied that I had. I remembered her very well. "I thought so," the student said. "She tells the same stories that you do."

Before coming to university, this student had attended a preparatory course elsewhere; Sara had been one of her lecturers. The anecdotes she was now using to illustrate her teaching were ones I had used for mine. I did not mind that my stories were being (re-)told by somebody else. Instead, I was delighted. Something about my teaching was proving useful!

There are plenty of textbooks to consult for the facts and figures one needs to teach a course. However, they do not contain anecdotes. Those I had told had stuck in Sara's mind. Anecdotes provide embellishments not found elsewhere. They serve as aides-memoirs. They never appear in isolation. They are always used to illustrate course content. They are hooks upon which the much drier facts and figures hang and come to life. They serve to make what is dull more vivid.

(I think, that makes this anecdote an anecdote about anecdotes.)

The ‘Non-OHT3’

I briefly mentioned an overhead transparency I nicknamed OHT1 in an earlier post. I also mentioned how, although there was no official OHT2, there was an image I would have used. Both of these I shall be dwelling on in greater detail in future. Here, I point out a third transparency that was deliberately absent. Thus, I call it the ‘Non-OHT3’. There is, of course, no accompanying image. This absent transparency represents how the idea of homeostasis (sometimes spelt homoeostasis) was deliberately missing from my teaching.

That may seem strange. High school pupils studying biology learn about homeostasis. As described there, it is something essential for life. It is a vital characteristic possessed by organisms such as ourselves. Definitions of homeostasis describe the body maintaining a stable internal state despite external changes. The word ‘balance’ is often applied - I suggest somewhat indiscriminately. It remains a popular notion even in higher education. I know of physiology books written based on the principle of homeostasis. I contend that that is because it is a notion expounded uncritically. It makes sense until analysed carefully.

I deliberately avoided discussing homeostasis except to urge caution when reading about it. It gives the impression of a somewhat passive body. Instead, the body is highly active. Those who have looked at homeostasis carefully have raised doubts about its voracity. Accordingly, they have proposed alternative dynamic alternatives.

I shall return to these in due course.

A Strange Place for Taste Buds?

One of the first anecdotes I heard as an undergraduate was about taste buds being present around the anus. Since it was mentioned briefly in a lecture, there was no opportunity to discuss it further. Who made the discovery was not mentioned. I subsequently tried to find out more. As a postgraduate student, I mentioned it to a couple of colleagues. One said that he had also heard this but knew nothing more. Another wondered whether it might be salivary glands rather than taste buds. The salivary gland idea makes sense. Salivary glands would lubricate the anus, easing the passage of the faeces.

We are used to the idea of tasting food as it goes in. Apart from enjoying certain flavours, disliking others is particularly important. What tastes unpleasant is often also harmful. Such food is best spat out. Tasting spent food on the way out seems odd - if not pointless.

I recently discovered an article in New Scientist (Jan 27th 2024. No 3475) called Why are there taste receptors on our testicles? (What we used to call taste buds were referred to as taste receptors.) The article pointed out that taste receptors are present in the guts of rats. That is a finding made in the 1990s. Subsequent work found them in our guts also. Finding this spread of taste receptors - between mouth and anus - is not necessarily strange. All the parts mentioned so far belong to the gastrointestinal tract. Perhaps genes responsible for their formation are expressed randomly throughout. However, taste receptors are now known to be present in other organs and tissues not part of the gastrointestinal tract. They are present in the heart, brain, bladder, lungs, body fat and, as the article’s title implied, the testicles.

Our choice of words may be causing problems. I still use the old taste bud terminology. Using the term taste receptor may be no better. We associate taste with our mouths. It is a mental construct. It is something in our consciousness - a product of the mind/brain. They are neither taste buds nor taste receptors as such. They are, more generically, sensors. These sensors detect things about the body. They provide information that forms a basis for a physiological response. The nutritional and energy states of the body are perhaps what is detected. Instead of finding taste receptors throughout the body, sensors found more widely have a specialised role in the mouth. They give us information our minds experience as taste.

What began as an anecdote heard as an undergraduate student in the late 1970s now forms the basis for new ideas about the human body. It is an organism permeated with sensors monitoring itself in ways far more extensive than previously imagined.

'OHT2'

While I had an overhead transparency I nicknamed OHT1, there was never a specific ‘OHT2’ - hence the inverted commas. Had there been, it would have been the one shown here. The ideas conveyed by this image typically came soon after OHT1. This illustration also showed the textbook approach taken to the subject. It also provided a basis from which to start asking questions.

As with my OHT1 post, I am posting it here without further commentary. I will return to it at a later stage. For now, it is something for the visitor to look at and ponder over.

(From:
The Coloring Review Guide to Human Anatomy
By McMurtrie, WH, Krall Rikel, J & Rikel, JE.
Wm. C. Brown Co Publishers 1989)

OHT1

Before the advent of computer applications like PowerPoint or Keynote, lecture illustrations were often drawn or printed on transparent acetate sheets. These were then placed on an overhead projector and shown on a screen. When I taught anatomy and physiology in those days, there was one image I always used. That illustration showed the textbook approach taken to the subject of anatomy and physiology.

The illustration got the nickname ‘OHT1’. That meant ‘OverHead Transparency #1’. It was not necessarily the first transparency shown. (The first gave my name and contact details.) However, that transparency was of foremost importance. I used it to start asking questions.

I am posting it here without further commentary. I will return to it at a later stage. For now, it is something for the visitor to look at and ponder over.

(From:

The Coloring Review Guide to Human Anatomy

By McMurtrie, WH, Krall Rikel, J & Rikel, JE.

Wm. C. Brown Co Publishers 1989)