Darwin, Lamarck and the ants

The educational reality I can talk about here in this blog is the reality in which I grew up: my experiences as a student and after that my experiences at the other side of the process, as a teacher, from the early 90’s to last year — I don’t give classes anymore. Yes, this is a biased view, but I never meant to generalize it: I bear very clearly in mind that what I know and the pedagogical experiences I have refer to my country and my country only. I don’t know much about biology classes in other countries, and I hope, for their best, that they are not like what I experienced.

Let me explain the problems in my point of view, and I apologize if I sound a little harsh. First, the overwhelming amount of data: teachers try to deliver the maximum amount of data they can, and students try to memorize the maximum amount of data they can. Just data, without analysis, critical thinking, explanation or utility. But the problem is not simply that: the information itself has a lot of errors and mistakes. Not only there are inaccuracies, as they are virtually the same in different didactic materials, in almost every textbook. The high school biology books in my mother country are astonishingly similar: even the sequence of the chapters is the same! I remember in 94 somehow have come into my hands a French baccalaureát biology book, and I was fascinated: not because the book was fantastic, but also because the approach was so different, the sequence of the chapters and the general organization was so unusual to me! I must confess that I regret to this day having not purchased a copy.

In my mother country not only the textbooks are quite similar, but also the evaluation questions are almost identical. Who has not lost patience in solving, being a student or teacher, questions like “what is the correct sequence of the speciation process?” This is so repetitive that most students, without even properly understanding the disruption of gene flow or what this disruption means, think every geographical isolation process will lead inexorably to a reproductive isolation (and that is simply wrong).

Another category of questions about evolutionary biology in high school exams and in SAT-like exams, and that are the subject of this post, are those types of questions that ask us to choice whether a given sentence or utterance is according to Darwin or to Lamarck thoughts. This kind of question is, sadly, very common. And, in my view, they have a serious problem.

Here is an example, taken from the national exam for courses (which evaluates students in their last university year) of 2001:

Cepaea nemoralis is a terrestrial snail capable of producing a wide variety of coloration patterns in its shell, from light to dark. This snail is preyed upon by a bird, which locates the snail through vision. In an area inhabited by this snail species, there was an increase in vegetation cover and researches showed that the number of snails with dark shell has been increasing gradually. Explain why snails with dark shell increased in that area, in accordance with: a) lamarckists ideas; b) Darwinists ideas. “

This kind of questions holds a series of different flaws. Initially, there is the psychic and telepathic aspect of these exam questions: how can I know what happens at the mind of two Europeans who died in the 19th century? Even if I were their acquaintance I couldn’t presuppose what they’d say, and many of these exam questions ask “how Darwin and Lamarck would explain this phenomenon?”. What these poorly conceived exam questions are really trying to ask is if a given statement fits in a Darwinian paradigm or in a Lamarckian paradigm (some of these exam questions  avoid this blunder, as is the case of the example abovementioned). Secondly, asking whether a given utterance is a Darwinian one or a Lamarckian one is not an appropriate way to measure the learning of evolutionary biology in high school or in undergraduation.

But my biggest objection to this kind of exam question is that there is a philosophical and epistemological problem: the student is asked to describe how Lamarck would interpret a given phenomenon, and then he is asked to describe how Darwin would interpret the same phenomenon. It turns out that, in science, a theoretical structure (or even before that, a hypothesis) is discarded when it is no longer able to properly explain the phenomena it should explain, and the number of “holes” in the theory becomes so big and so obvious that the theory is no more capable to stand on, and must be discarded. The Lamarckian paradigm is obviously incorrect, and this is known since the late 19th century. Therefore, what happens is not only that a Lamarckian statement will differ from a Darwinian statement, or that a Lamarckian would explain a phenomenon in a way and a Darwinist otherwise: there are a lot of phenomena that Darwinists would explain in a way and that the Lamarckians would… not explain! At all!

That’s precisely why Lamarckism (or any other incorrect scientific hypothesis) was discarded a long ago: it cannot explain a lot of phenomena.

I like to illustrate this with the case of ants.

Female castes of 'Pogonomyrmex baldius' ant: queen (with wings), major worker and minor worker (photo by Adrian Smith).

Female castes of ‘Pogonomyrmex badius’ ant: queen (with wings), major worker and minor worker (photo by Adrian Smith).

I came across this case for the first time when I read the “origin of species”. It’s not too much regret that a lot of people dedicated to the most diverse branches of biology have never read the “origin”. I know it is scientifically outdated, but it is a work of a clarity, sobriety and style that is really impressive. That being said, let’s get back to the case. The excerpt about the ants is at the very end of Chapter VIII:

Thus, as I believe, the wonderful fact of two distinctly defined castes of sterile workers existing in the same nest, both widely different from each other and from their parents, has originated. We can see how useful their production may have been to a social community of insects, on the same principle that the division of labour is useful to civilised man. As ants work by inherited instincts and by inherited tools or weapons, and not by acquired knowledge and manufactured instruments, a perfect division of labour could be effected with them only by the workers being sterile; for had they been fertile, they would have intercrossed, and their instincts and structure would have become blended. And nature has, as I believe, effected this admirable division of labour in the communities of ants, by the means of natural selection. But I am bound to confess, that, with all my faith in this principle, I should never have anticipated that natural selection could have been efficient in so high a degree, had not the case of these neuter insects convinced me of the fact. I have, therefore, discussed this case, at some little but wholly insufficient length, in order to show the power of natural selection, and likewise because this is by far the most serious special difficulty, which my theory has encountered. The case, also, is very interesting, as it proves that with animals, as with plants, any amount of modification in structure can be effected by the accumulation of numerous, slight, and as we must call them accidental, variations, which are in any manner profitable, without exercise or habit having come into play. For no amount of exercise, or habit, or volition, in the utterly sterile members of a community could possibly have affected the structure or instincts of the fertile members, which alone leave descendants. I am surprised that no one has advanced this demonstrative case of neuter insects, against the well-known doctrine of Lamarck.

Try to ask yourself: what would be the Darwinian explanation for the evolution of the various species of ants (or any other social insect with sterile castes), and what would be the Lamarckian explanation. Do this as a mental exercise. I like to ask this now and then to colleagues in the area, and it is curious to see how some of them try, in every way, to imagine how a Lamarckian would explain this phenomenon, with the more outlandish explanations.

What matters here is not what would be the explanation: the Lamarckian paradigm simply can’t produce any explanation for the evolution of insects with sterile castes! These are the failures, along with a number of other historical and scientific processes, that end up demolishing an existing paradigm or theory. So, the student is not required pro provide an explanation of “how would Lamarck explain this phenomenon”. He can simply say “there is no explanation”, or “Lamarck would not be able to explain it”.

Darwin’s theoretical structure is much broader than Lamarck’s one. The two paradigms, Darwinian and Lamarckian, are so distinct, the latter in its essentialism and the former in its materialism, that they don’t seem to be from the same century. My opinion is, in a nutshell: enough with these exam questions that explore the Darwinian/Lamarckian dichotomy. There are so many other interesting issues, so many ingenious ways of evaluating evolutionary biology concepts and so many other important aspects of evolutionary biology to be asked about that it’s not difficult to a competent and creative teacher or professor to easily develop truly effective and appropriate questions.


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