1 Introduction

The teaching and learning of evolutionary ideas represent an ongoing challenge and present a range of problems in different educational systems and at different levels. We are particularly interested in the stage leading up to the choice of university career, a stage after which many young people will no longer have the opportunity to study questions related to evolutionary biology. What they learn of biological evolution afterwards may then have little or no bearing on their understanding of nature, particularly of the origin of life and the way life changes. These questions include, for example, the biology of the human body, its adaptations, its diseases and immune system, antibiotic resistance, genetically modified foods, the physiological changes of adolescence and throughout life, the use of biotechnology, research into human gene editing, genetically modified and transgenic organisms, and other knowledge that is crucial for modern life (Poiani, 2012).

The importance of evolutionary thought as a part of basic civic education is beyond doubt. So, what would it mean to say that a high school graduate has learned about evolutionary thought to a satisfactory degree? At minimum, we think it is important to agree on the following: (a) that the phenomenon of life can be explained in terms of natural causes, (b) that organic life is continually transforming, (c) that organisms and the environment form dynamic systems that change continuously, (d) that any given species descends from another, (e) that, at some point, there existed a common ancestor of all contemporary species, (f) that the human being has resulted from these transformations, and (g) that our cognitive capacities can be partially explained in evolutionary terms.

Traditional programmes insist on teaching high school students to construct their evolutionary ideas on exclusively Darwinian foundations. In contrast, we suggest a complementary proposal, based on historical practice and which employs the original ideas that Jean-Baptiste Lamarck (1747–1829) developed in his Philosophie Zoologique (1809a, b).Footnote 1 We argue that, via an understanding of what Lamarck was responding to when presenting his theory, these ideas can have a positive effect on the teaching and learning of evolutionary ideas. They make up a set of ideas that additionally responded to others of Lamarck’s interests and constituted an overview of nature, life in general and the social world in which Lamarck lived: his ideas responded to the biological, philosophical, and political debates that he participated in (Corsi, 2011, 9).

Historiographically, the most important Lamarckian contributions to evolutionary theory as objects of study have been thought to be his ideas on the influence of the environment and the inheritance of acquired characters. However, as Corsi (2006) points out, even a contribution such as the very idea of ‘biology’ is usually reduced to the familiar mention and his brief definition of the term in Hydrogéologie (1802), when there is a posthumous manuscript, published by the zoologist Pierre-Paul Grassé in 1944, where Lamarck puts forward a proposal for a new and broader understanding of nature.

There is also, as noted above, the example of the origin of the species Camelo-pardalis, which derives historically from Georges Cuvier and Charles Lyell, whose interpretation of Lamarck is based on a conscious desire for self-transformationFootnote 2 although Lamarck presented the giraffe as a case of the inheritance of acquired characters, modulated by an environmental force (Lamarck, 1809a, b, T. I, p. 256). [He originally presented the case in Recherches sur les causes des principaux faits physiques in 1802, p. 208.]

In Lamarck’s example, it is clear that he is thinking about the role of the environment. It is also quite clear that there is a fundamental difference between contemplating a transformation process modulated by ‘desire’ — which is not the case in Lamarck’s explanation — and a transformation process ‘partially modulated by the environment’. Nor, in the sense in which it has been traditionally interpreted, does this modulation have a goal; that is to say, Lamarck was not saying there is an ontological commitment to the idea of the tendency to complexity, aiming at a final objective. He wrote, ‘It is above all in living bodies, and mainly in animals, that we believe we perceive a goal in nature’s operations. This goal however, is as elsewhere, only a simple appearance and not a reality.’ (Lamarck, 1815, T. I, 324).Footnote 3

The role of the environment has been interpreted in at least two ways in explanations of evolution: active and passive. In its active role, the environment is considered to modulate evolutionary processes and act directly on hereditary transformations (traditionally related to Lamarckism). In its passive role, it is considered by certain authors to function as a filter for random hereditary variations (these being traditionally related to Darwinism).

Underlying Lamarck’s explanation of transformation is the idea that there is a process by which organic forms adaptFootnote 4 to continual changes in circumstances (without purpose — at least, no conscious purpose). Lamarck takes the process currently known as adaptation to occur in the following order: (1) there are environmental changes, (2) changes in habit arise, (3) those changes generate adaptations to the new, changing circumstances in the individuals that constitute a group of organisms, and (4) these changes are transmitted to the offspring. In this process, one may note an adaptive teleology with the environment modulating the adaptive route, but at the same time, as can be seen in Lamarck’s work, there is an adaptive diversification, such as in the different ways in which mammals have adapted to ‘different circumstances’ (Lamarck, 1809a, b T. I, pp. 253–259).

Even though Lamarck explains the role of the environment in the transformation process, at the time of writing his Philosophie Zoologique, his central objective was far more radical and profound. Beyond arguing what the processes of change in species were, his purpose was to argue for the continuous transformation of life, generated by natural causes, taking the natural originFootnote 5 of living creatures as a starting point. His goal, as he pointed out, was to challenge the idea that species were created and thereafter remain unchanged. Consequently, we argue that his ideas on the transformation of species merit inclusion in a programme that teaches a broader conceptualisation of evolutionary thought. In our proposal, we show the depth of Lamarck’s ideas, and simultaneously the way that evolutionary thought was constructed, beginning with Lamarck and his relevant questions about nature.

Lamarck and other naturalists observed the visible effects of environmental conditions on organisms and assumed that these effects had a direct correlation with the nature of heredity. We now know that the visible effects of the environment (known in the past as acclimatisation) are due to epigenetic phenomena, relevant for the life history of organisms. Lamarck thought such processes were important in the processes of transformation of the species. What is important here is that Lamarck clearly saw that nature was submerged in a process of continuous transformation and that some species descended from others. For example, we may note Lamarck’s discussion regarding Ranunculus, a genus in which some species have two types of leaves, one type for under-water conditions and the other for floating on the surface. The differences led one to believe, Lamarck noted, that one single species was actually two different species, but crucially, that the change of some important factor leads to alteration in the parts of these living bodies. (Lamarck, 1809a, b, T. I, p. 230).

In the last few years, texts on epigenetic phenomena, such as those by Eva Jablonka and Marion Lamb (2014), have provided accounts of the importance of the effects of environmental conditions on processes of embryonic development and on physical development in general, as well as the way that these influences shape specific epigenetic patterns in each individual’s history. Without going into what effects they might have on the evolutionary history of species, some of these conditions are so important that they have a direct impact on organisms’ health, growth, or development. We therefore suggest that it is important to point out how the environment contributes to individuals’ life histories. This is particularly important in the case of human beings: because of the care required for the individual’s physical and mental health, it is essential to recognise and appropriately emphasise different moments in one’s life.

As GregoryRadick has written, the history of science can provide examples that, when not doctrinaire,Footnote 6 can be used to show that specific historical conditions can inform and possibly even improve the practice of science and make current discussions more meaningful (Radick, 2016, p. 293). Using historical examples has been shown to be an effective way of involving students more intensely in their own scientific work, particularly during basic and secondary education (Fouad et al., 2015). Given that science is also a product of historical, social, and cultural influences, it will be helpful to use historical examples to teach and support key elements of science (McComas, 2008). We suggest that the study of Lamarck will demonstrate the importance of the basic concepts of evolutionary thought, provide some nuance to the standard depiction of Lamarckian thinking as simply flawed (including the various processes that led to its construction), and can be strengthened by resources from the history and philosophy of science.

Using history and the philosophy of science (HPS) in the teaching of science is not new: incorporating history and philosophy as pedagogical resources reflects an effort going back several decades. The importance of this has been pointed out by various authors, including Michael R. Matthews (1989), who has highlighted the importance of philosophy and history in the teaching of science because they provide a better picture of the nature of science, including the presentation of some of the conclusions made by science, framed by the way in which they arise and become approved, are debated, are rejected, or remain in the field of explanations (Matthews, 1989, 7). The discovery of these facets of the construction of knowledge can be stimulating for students’ conceptual development.

‘The benefits of a historical approach to the teaching of school science have been well canvassed […] Research on … student performance… has established other positive results including increased understanding of science, increased interest in the subject, enhanced critical thinking…’ (Matthews, 1989, 7). However, despite these benefits, Kostas Kampourakis and Ross Nehm (2014) have ‘demonstrate[d] that while HPS is of central importance to a deep understanding of evolution education, too often its contributions are poorly realized’.

In the practice of teaching biology, historical resources have also been used to teach evolutionary thinking (Jensen and Finley, 1995; Jiménez-Aleixandre, 1994, 1996). Among these efforts to include philosophy and the history of science in biology teaching, the Biological Sciences Curriculum Study (BSCS) has had an important role. It was introduced in the early 1960s and has been adopted in many countries, including Israel, Australia, and Brazil. In addition to achieving effective methods of learning science, the BSCS programme’s principal objective has been to establish a close, congruent relationship between biology teaching and the methodological and conceptual development of contemporary biology (Ausubel, 1966).

Within this programme, the most frequently used historiographic resource is Lamarck’s theory, presented in contrast with Darwin’s. In particular, this series was the first to present ‘the example of the elongation of giraffes’ necks’ to illustrate differences between the two theories. While the example does serve to distinguish the two theories, although representative of Lamarck’s ideas, it does not represent them appropriately and it has, since then, been adopted by the majority of other biology textbooks.

It has, since then, been adopted by the majority of other biology textbooks.Footnote 7 In many cases, the Lamarckian example is given as an alternative, albeit incorrect theory, contrasted with natural selection (Jensen & Finley, 1996). The main concepts that are contrasted are natural selection versus the inheritance of acquired characters. Not only are the theories differently presented in reviewed textbooks but the authors too: Darwin as a model scientist and Lamarck as ‘a speculative theoretician’, his theoretical propositions being ‘remarkably deformed and changed from their original formulations’ (Almeida & Falcão, 2010). In these examples of the use of these comparative historical resources, one of the goals is to get students to abandon their alternative, Lamarckian conceptions and understand the process of natural selection (Settlage, 1994).

The pedagogical use of this contrast between Lamarck and Darwin has generated a debate about whether students should really be considered to have Lamarckian ideas (Kampourakis, & Zogza, 2007) or if the models are suitable for teaching evolutionary thought (Enderle et al., 2009), since various studies have shown that, for various reasons, students find great difficulties in learning evolutionary ideas. The causes of this include ‘the intrinsic complexity of this area of knowledge; the lack of conceptual precision in some texts; the lack of a historical-philosophical vision, coupled with the fragmentation of knowledge prevailing in the teaching and learning of science; the absence of a contextual framework for teaching evolution that is designed for and available to teachers; students’ alternative notions; conceptual reconstruction of evolutionary learning associated issues; tensions and conflicts in the world views of students and teachers; and epistemological obstacles.’ (Álvarez Pérez and Ruiz Gutiérrez, 2016).

Taking these antecedents into account, as well as the difficulties found in teaching evolutionary thought, and considering that Lamarck’s contributions went beyond the notion of inheritance of acquired characters — that in fact this idea was actually a marginal account in his explanations, we believe it to be important for school classrooms to use other historical fragments that can stimulate debate and critical reflection on the origin, development, and nature of evolutionary thought.

2 Basic Elements of the Lamarck Proposal

We will now present the evolutionary ideas that Lamarck developed and indicate their potential for teaching, studying, and discussing evolutionary thought in the classroom. These ideas are as follows: (1) the species as an arbitrary concept, (2) the ancestor–descendant relationship, (3) organic diversification from a common plan of organisation to a branching series, (4) the continuing, gradual transformation of species, and (5) natural causality to explain the origin of species, including the human race (with our moral capacity), as a result of natural processes of transformation.

As will be seen, the above are vitally important points within the contemporary vision of evolutionary theory, and hence we argue that it should be a priority to include them within teaching, above all as a way of reinforcing historical explanations as part of scientific education.

These fundamental principles (or general principles as Lamarck called them) are part of the theoretical underpinnings of Lamarck’s argument. Taken together, or in some cases in part, with their modifications, they remain the foundations upon which current evolutionary explanations are built and we consider that, for the teaching of evolutionary thought, they are ideas that continue to generate compelling reasons for contemplating the phenomena of life in general.

Lamarck was convinced that a set of rules and philosophical principles were necessary for the study of zoology and other divisions of natural science. Following these led to the unavoidable conclusion that nature had successively formed all bodies endowed with life (Lamarck, 1809a, b, T. I, p. ii–iii). These ideas represent an intellectual legacy that has, for various reasons, been underappreciated.

In our view, Lamarck’s philosophy or fundamental principles were what guided his study of the nature and origin of animals: he looked at their general and special characters, their organisation, the causes of their development and diversity, and the faculties which they developed (Lamarck, 1809a, b, T. I, p. xviii),Footnote 8 in addition to the efforts he made to understand the physical causes of life and its transformation. In other words, the above are the propositions that encompass the philosophical idea that guided Lamarck’s attempted explanation of natural phenomena, the search for natural causes.

After the publication of his 1779 work on botany, Flore françoise, Lamarck focused on a philosophical programme, grounded on materialism in two senses: firstly, methodological, taking everything to originate from nature itself: ‘From the extent and the dimensions of matter, its form necessarily results, of which the admirable varieties produced by the infinite modifications of this matter constitute the beauty of the universe and, in some way, the fruitfulness of nature.’ (Our translation, Lamarck, 1794, p. 20). And secondly, a philosophical materialism, holding that nature could be the cause of itself: ‘Matter can neither increase nor decrease in quantity, for only the power which could create it, can destroy it, and is likewise necessary to return it to nothingness.’ (Our translation, Lamarck, 1794, p. 21). This view will later be used ambiguously in three of his works: Philosophie zoologique (1809a, 1809b, p. 361), Histoire naturelle des animaux sans vertèbres (1815), and in Système analytique des connaissances positives de l’homme of 1820, where he conserves methodological materialism.

Lamarck’s writings are ‘thoroughly characteristic of the late Enlightenment’ as Jonathan Hodge (1971) points out, closer in spirit to the eighteenth century than the nineteenth or twentieth. Nevertheless, his work was deeply rooted in the framework of the French materialism which underwent significant development during the eighteenth century, going in a profoundly radical direction. Lamarck was aware of this, though his work presents a far more moderate face, one shared with contemporary authors. Lamarck discovered the ideas of radical materialism in the works of Baron d’Holbach and at his salon, which he attended along with George Cabanis, Jean-Jacques Rousseau, Condorcet, and other figures of the Enlightenment to discuss social, political, philosophical, and scientific ideas. Among the ideas that were discussed were those of the founder of modern materialism, Jean Meslier (Onfray, 2007), who competes historiographically with Baruch Spinoza, the Spanish philosopher, for the title of ‘father of materialist thought’ (Blom, 2011, 128–130). With respect to this question, we must remember that, unlike Spinoza, Meslier was not seeking to substantiate the existence of God theologically nor did he equate nature with God (as per Spinozist pantheism), he simply went directly to a statement that filled some of the most eminent figures of the Enlightenment ‘with terror’ (Letter from Voltaire to d’Alembert, February,1762, quoted in d’Holbach, 1910, 33). In his Testament, Meslier was to say that God was an invention of our brains, a product of matter (Meslier, 1864). This was a work that in Voltaire’s words had to be purged of atheism, because it took ‘the sweet yoke’ away from men and left ‘the nature of good and evil without foundation’. In his book Histoire naturelle des animaux sans vertèbres (1815), Lamarck did not miss the opportunity to criticise Voltaire’s position regarding his theological explanation about the origin and nature of good and evil (Lamarck, 1815, 329–330).

Meslier’s radical materialism can be detected in d’Holbach’s Système de la Nature. D’Holbach attempts to explain the ‘origin of the physical and the moral in man’ in materialistic terms (in terms of natural causes), an idea that will be taken up, firstly by Georges Cabanis in Rapports du physique et du moral de l’homme (1802), and later by Lamarck in his Philosophie zoologique (1809a, b), where he too aims to explain the ‘origin of the physical and the moral in man’. Although, as pointed out by Hodge (1971), one of his central concerns was the diversity of nature, secondarily, he came to the problem of the transformation, origin, and nature of the human being, and, after 1800, this also became one of his central concerns. To understand the matter, he thought it necessary to first discuss and clarify ideas and concepts developed within the tradition of natural history and the study of animals. We shall reflect on certain of these ideas and suggest that they make teaching Lamarck and his ideas on the transformation of species important.

3 The Species as an Arbitrary Concept

A crucial element in Lamarck’s ideas of transformation is his use of the concept of species as it is a useful tool for organising knowledge about organic life. Taking the concept of the species to be an arbitrary entity, Lamarck argued that the species, as such, does not exist, that there are only individuals (Lamarck, 1809a, b, T. I, p. 21).Footnote 9 Indeed, one may conjecture that there was a direct connection between his ideas and nominalism for, in Lamarck’s Philosophie zoologique, we find evidence of the nominalist position with respect to the problem of the real existence of the species. He found the term ‘species’ convenient, though he did not believe that the species as such actually existed.

What one may be perfectly certain about is that his rejection of the idea that the ‘species’ had an actual, real existence was a deeply held belief. This is an idea which he almost certainly acquired from his mentor, Georges-Louis Leclerc, Comte de Buffon, (see, for example, Volume I of Buffon’s Histoire Naturelle, where he states that only individuals exist in nature and that genera, orders, and classes exist only in our imagination, Buffon, 1749, p. 38). Buffon had previously approached the concept of species by considering it to be a continuous succession of individuals (Sloan, 1987, p. 123). To Lamarck, this was an idea that signified an infinite transformation and an aspect of the essential qualities of matter (Lamarck, 1794, p. 19).

On the topic of infinite variation, Lamarck wrote, ‘Throughout nature, wherever man strives to acquire knowledge he finds himself under the necessity of using special methods, 1st, to bring order among the infinitely numerous and varied objects which he has before him…’ (Lamarck, 1809a, b, T. I, p. 17).

But these groupings, he goes on:

… of which several have been so happily drawn up by naturalists, are altogether artificial, as also are the divisions and sub-divisions which they represent. Let me repeat that nothing of the kind is to be found in nature, … We may, therefore, rest assured that among her productions, nature has not really formed either classes, orders, families, genera or constant species, but only individuals who succeed one another and resemble those from which they have sprung (Lamarck, 1809a, b, T. I, p. 21).

We suggest that in the exposition of Lamarck’s Philosophie zoologique, there is an emphasis on thinking about how our need to understand nature forces us to construct concepts that will allow us to understand it. Up to a point, this allows us to postulate the relative existence of the species as a temporary state of elements shared by a group of individuals that we group together as a species.

Lamarck’s redefinition of species, variety, and race is based on his rejection of the essentialist nature of these concepts. In addition to his position on immutability, his position with respect to the non-existence of species is also consistent with his denial of the extinction of species because he considered that earlier generations had given rise to new modified generations. For Lamarck, an individual variation did not necessarily result from the processes of transformation, but from other natural regularities and irregularities in the intrinsic processes of reproduction and generation (two concepts that, at the time he was working, had different meanings to those found in contemporary biology). Nevertheless, then as now, reproduction and generation are among the processes that make the connection from one generation to another possible. In Lamarck’s interpretation, the descendant will be different from its immediate ancestor. For all that the essentialist concepts seemed obvious and correct, they reflected a belief that he sought to refute because through reproduction and generation, the constancy of species is apparently shown in perpetuity (Lamarck, 1809a, b, T. I., pp. 54–57).

Despite the fact that Lamarck doubted the extinction of the species, he came to consider that it was one of the more important problems of natural history; he thought that knowledge of shellfish ‘could enlighten us on the nature of the successive changes that have affected the various parts of their surfaces’. This problem, according to Richard W. Burkhardt, was one of the most important sources of inspiration leading to his intellectual transformation (Burkhardt, 1972, 421). Lamarck recognised that there were shells that had analogous living species, but others did not have such counterparts (Burkhardt, 1972, 424). Did he ever wonder why this asymmetry came about? Did he ever think that some species become extinct while others were transformed? Did it cross his mind that while some succeeding generations are interrupted, others continue to transform and diversify? The answer to this question is yes, he did indeed come to think that there were those two possibilities.

Glick and Kohn affirm that: ‘Darwin considered that most of the plant and animal species that had lived in the course of geological time were already extinct. For Lamarck, however, there was no extinction, and hence no branching tree.’ (Glick & Kohn, 1996, 83). Even if Lamarck had not accepted extinction, which as we will see later was not the case, this does not imply the non-existence of transformation with diversification.

‘His theory’, Glick and Kohn point out, ‘which was not a quite a theory of evolution in the strictest sense of descent with modification from ancestors, was that plants and animals progressed upward along the great chain of being. He did not accept the notion of extinction: when a species disappeared from the fossil record, he reckoned it was because it had changed into something else. A corollary to this view was that he denied the reality of species; for him, the chain of being was continuous.’ (Glick & Kohn, 1996, 82). However, Glick and Kohn do not mention that Lamarck states that ‘many people are mistaken in believing that there is a graduated chain linking the different bodies that have been produced.’ (Lamarck, 1815, 52). ‘Imagination alone has been able to give rise to such an idea, which is ancient, and which has been renewed in various modern works. But I shall prove that there is no real chain that generally links the productions of nature, and that it can only be found in certain branches of the series they form’ (Lamarck, 1815, 53). As shown in the Philosophie zoologique, there is ‘a link between all animal forms from a spontaneous generation of the first beings in the series’. In the Histoire Naturelle, he contemplates the idea that there could be at least two spontaneous generations, without being very clear about which of these two branched series of invertebrates the vertebrates descend from.

Burkhardt, and other authors (for example, Glick & Kohn, 1996; Hodge, 1971), are of the opinion that the Philosophie zoologique cannot be considered a precursor of The Origin of Species, but that Lamarck’s evolutionary thinking must instead be understood in its historical context. We agree that the conception of evolution within contemporary biology differs substantially from Lamarck’s (and even differs from Darwin’s). Nevertheless, the questions that motivate our search for explanations of the origin of species, their transformation, the relationships between them, and their relationship with the environment are based on certain principles that, to a degree, could be taken as similar to those that seek to explain transformation in terms of causes and natural autonomy, and seek to explain such problematic concepts as that of the ‘species’. Our understanding is based on the idea that each author has an explanatory framework from which he seeks to explain evolution.

Lamarck’s radical proposal, which would eventually lead to the collapse of essentialist conceptions, had its origins in philosophical principles inherited from the materialist discussions of the eighteenth century. In Lamarck’s work, unlike that of his predecessors, it can be seen that infinite variation is not an idealistic notion, is not disorganised, nor does it progress in all directions. Rather, it is controlled by nature and is, firstly, subject to the intrinsic processes of generation and reproduction, and, secondly, to environmental circumstances that, according to Lamarck’s interpretation, may or may not produce action that leads to progress or its opposite.

4 From the Common Plan of Organisation to a Branching Series

Lamarck thought that there was a regularity in the generation of individuals, given the similarity between them. In simple terms, this placed the idea of the species within the ancestor–descendant relationship. In his words, ‘any collection of like individuals which were produced by others like themselves is called a species’ (Lamarck, 1809a, b, T. I, p. 21). For Lamarck, nature with features such as irritability had generated life and sentience,Footnote 10 and had been producing an infinite variation of organic forms for generation after generation.

This idea of infinite variability of life is also associated with that of the infinite variation of circumstances. When Lamarck referred to the idea of the infinite variations of circumstances, he was referring to the multiple possibilities that could occur and generate new forms.

Given these two ideas: the non-existence of species and infinite variation, we may take it that Lamarck had discarded both the idea of the fixity or immutability of species and the idea that a species is a natural [real] entity created by a superior being — by denying the existence of the ‘species’, he denied that such a thing as the ‘species’ had been created. This made it possible for him to assume that organic life was immersed in a process of continuous transformation. Hence, he wrote that nature had formed ‘… only individuals who succeed one another and resemble those from which they sprung’ (Lamarck, 1809a, b, T. I, p. 21). Evidence for this idea is clearly visible in the ‘common plan of organization [of vertebrates] … that has undergone numerous modifications, some of them very large, through the influence of the environment of the animals and of the habits which each race has been forced to contract by the conditions in which it is placed.’ (Lamarck, 1809a, b, T. I, p. 159–160).

Lyell objected to this idea on the grounds that extending it into the past meant accepting defective evidence and fallacies in the argument, and led to the conclusion that there was a common origin of all animals, of man himself and irrational beings (Lyell, 1832, p. 21).

Hodge (1971) states that Lyell’s interpretation of Lamarck ‘is mistaken in three fundamental respects. He takes Lamarck to be proposing primarily a theory of the origin of species, he presents it as a theory of common ancestry and as an attempt to explain the fossil record. This allowed Lyell to separate the question of common ancestry from Lamarck’s discussions of spontaneous generation and the alleged invariable progress from more simple organisms to those above them in the scale of perfection.’ (Hodge, 1971, 333).

We have already pointed out that Lamarck does not have an ontological commitment to the scale of perfection, there is even a rejection of the Great Chain of Being, and there are his statements that the notion of having an objective is only an impression in the brain, rather than one of nature’s realities. Giving Hodge the benefit of the doubt, we can entertain the idea that Lyell’s interpretation of Lamarck was incorrect. Nevertheless, ‘This radical misrepresentation of Lamarck’s position (which was followed by Whewell too) was of the greatest importance for the development of Darwin’s and Wallace’s thinking on the origin of species. Lyell’s version of Lamarck influenced them as Lamarck’s own writings could never have done.’ (Hodge, 1971, 333–334). Couldn’t this ‘radical misrepresentation’ that stimulated the thinking of the young Darwin and Wallace also stimulate the thinking of our young students in school classrooms?

In his discussion, Lyell discusses precisely the concept of species, aiming to refute Lamarck’s ideas and all their implications, including the possibility of the origin of new species and their continuous transformation. Lamarck, says Hodge, ‘plays his ace’ in this discussion on ‘the origin of new species’ which again, according to Hodge (1971), is not about the origin of new species. We agree that Lamarck has an eighteenth-century conception of nature, from the moderate, late enlightenment, rather than the radical one, but a materialist one that seeks to account for the natural origin of species and their continuous transformation. Yet the ‘ace’ that Hodge (1971) mentions is, in our opinion, the discussion that broke with the old traditions of the divine origin and immutability of species. It is a relevant ace, well worth discussing in the classroom. The argument transformed Lyell’s ideas, and through him, Darwin and Wallace’s ideas, even if we grant that Lyell had misinterpreted Lamarck.

The dynamics of transformation were therefore rooted in the dynamics of the constant (and variational or differential) reproduction of organisms. Such individuals as existed reproduced with similar individuals and left offspring that were always different, particularly when conditions were different.

It has traditionally been argued that Lamarck’s evolutionary ideas reflect a history of mutually unlinked parallel lines and do not represent a theory of descent with modification (e.g. Panchen, 1992, p. 60; Glick & Kohn, 1996, p. 82). However, although Lamarck did not explore the idea in greater depth, he never denied that life diversified. On the contrary, he realised that different organic forms shared a relationship of origination with other organic forms and, in a sense, Lamarck’s outline may be considered a phylogenetic tree, showing relationships between organisms according to their origin. In other words, Lamarck postulated a relationship of kinship and community of descent between different taxa (Tassy, 2011, p. 90). This is despite the fact that at first, he had proposed a linear ladder like Bonnet’s and so may have been influenced by the philosophy of the Great Chain of Being (Kutschera, 2011, p. 5), an idea that presents a clumsy image of what would later become the idea of a common ancestor.

Lamarck suggested that the simplest species arose continuously on the surface of the Earth by spontaneous generation, and that a gradual transformation began with these primitive, unspecialised forms, guided by both the trend toward complexity and environmental influences, until the most complex forms were attained, suggesting a series of ramifications (Lamarck, 1809a, b, T. I, p. 457–465). In principle, he accepted that all animal forms descended from at least one or two spontaneously generated events,Footnote 11 as illustrated by the only image included in the Philosophie zoologique (Lamarck, T. I, 1809a, b, T. II, p. 463).

In contrast with the criticism of mutually unlinked parallel lines, Lamarck stated that the dynamics of transformation was branching: ‘I do not mean that existing animals form a very simple series, regularly graded throughout; but I do mean that they form a branching series, irregularly graded […] It follows that the species terminating each branch of the general series are connected on one side at least with other neighbouring species which merge into them’ (Lamarck, 1809a, b, T. I, p. 59).

Hodge (1971) suggests that Lamarck’s use of the word ‘branche’, and his famous branching diagram illustrating these speculations in Philosophie zoologique, ‘have invariably led commentators quite mistakenly to take this scheme as a genealogical reconstruction of the common ancestries joining the divergent limbs of a tree of descent’. However, Hodge continues — ‘a look […]at Lamarck’s final and much more systematic and explicit treatment of the scheme, given six years later, in a ‘Supplément’ to the first volume of the Histoire Naturelle, shows at once how entirely remote were his presuppositions from those of any theory of common ancestry.’ (Hodge, 1971, 344).

Of course, there is no theory of common ancestry in either Philosophie zoologique of 1809 nor in the Histoire naturelle des animaux sans vertèbres of 1815, but neither is there an ordering of the great chain of being that tends to a purpose. It was an attempt to organise ‘the products of nature in a natural way’ with all the gaps in knowledge on relationships of origin of which Lamarck was unaware, although he did assume that links between the various groups exist. Lamarck added:

‘Now, how are these animals linked with vertebrates via a real transition? Of course, this transition is not yet known […]. These problems will undoubtedly remain unsolved for a long time; but we may already surmise that, in its production of different animals, nature did not execute a single and simple series.’ (Lamarck, 1815, 460).

In the Philosophie zoologique, Lamarck took all animals to have their origin in a single act of spontaneous generation. In the Histoire naturelle (1815), the discovery of new species and the visible differentiation of the nervous systems made Lamarck contemplate the possibility that there were two series with different origins. In the scheme of the Philosophie zoologique, vertebrates have a clearer relationship with invertebrates, in his second scheme Lamarck entertained more doubts about which group could really be linked with which at its origin.

Considering these difficulties, Lamarck thought that we were facing two dimensions of organisation in nature: ‘One that offers the simple series that we must use in our books and in our courses, to characterize, distinguish and present the observed animals; a series that will generally place us on the progression that occurs in the composition of the different organizations of animals […]. The other that presents the particular series, with its simple branches, that nature seems to have formed by producing the different animals that currently exist.’ (Lamarck, 1815, 461).

The second type of organisation is linked to the origin and relationships between organisms which are produced ‘by a general power that encompasses in its domain all objects that we can perceive, as well as those that are beyond the scope of our observations, and that immediately gave existence to plants, animals, as well as other bodies. It is truly a limited and somehow blind power; a power that has no intention, purpose, will; a power that, however great it may be, can do nothing other than what it does […] – that power,’ Lamarck says, ‘we call nature’ (Lamarck, 1815, 311–312).

5 Gradualism and Deep Time

Historiographically, Lamarck’s explanation of transformation has been considered a doctrine having the Darwin brand, ‘a doctrine of development and progression’. Taking this into account and given that Darwin’s explanation is not considered to be a doctrine of development and progression, Lamarck cannot then be either an ancestor, a precursor nor a founder of evolutionary thought. This is because, according to several authors, Hodge among the most important, his explanation of evolution lacks the notion of ‘common ancestry’ or at minimum the key question of the evolutionary programme, an interest in explaining the origin of new species or a notion of species in line with the contemporary ideas (Hodge, 1971, Glick & Kohn, 1996), or even the gradualism that would indicate the influence of Lyell on Darwin rather than Lamarck (Hull, 2014, 802). With historiographic reservations and without venturing statements about influences or antecedents, we consider that, regardless of whether there exists a conceptual influence from Lamarck to later authors, we should like to highlight the aspect of gradualness and deep time in the explanation of the origin of new species in Lamarck’s thought.

Gillispie has remarked (Gillispie, 1958, p. 389) that, ‘It [was] to be doubted, however, whether the uniformitarian philosophy of Charles Lyell was as essential to Darwin’s success as is usually said, … For Lamarck had been his own Lyell’.

In order to argue in favour of this point, we return to the third point of our exposition as this will help us to understand the issue of gradualism within an evolutionary framework, particularly when Lamarck explicitly states his conclusion that ‘nature has produced all the species of animals in succession, beginning with the most imperfect or simplest, and ending her work with the most perfect, so as to create a gradually increasing complexity in their organization […]’. (Lamarck, 1809a, b, T. I, p. 266).

For the possibility of change to be accepted, however, it must be accepted that these processes occur over a considerable period of time. That, however, did not pose a problem for Lamarck as he believed that, given enough time to form new species, an infinite variation in the circumstances of nature had gradually formed the animals as we know them (Lamarck, 1809a, b, T. I, p. 266) and further believed that the considerable period of time had existed, amounting to hundreds or thousands of centuries.

Lamarck mentioned the gradual transformation process repeatedly in various parts of his work and in his books, originally in his Hydrogéologie (Gillispie, 1958, p. 389). The impossibility of witnessing the transformation of species first-hand led first Cuvier and then Lyell to try to refute Lamarck’s statement: ‘That all the organized bodies of our earth are true productions of nature, wrought successively throughout long periods of time’ (Lamarck, 1809a, b, T. I, p. 65).

With the process being so gradual, long periods of time are required. To illustrate what happens in nature on timescales inaccessible to human experience, Lamarck employed the model of the transformation of domestic species (Lamarck, 1809a, b, T. I, pp. 226–227, 267). In his view, the fundamental question was that domestic species did not exist in nature, attributing the cause of the forms of species — as we know — to a gradual transformist response, modified by circumstances.

All domestic species, both plants and animals, were, in Lamarck’s words, the product of domestication: horses, donkeys, pigeons, wheat, corn, etc. Lamarck assumed that domestic species had their ancestors in wild species. He suggested, for example, that all breeds of dogs descended from a wild species, he surmised that this ancestor could be a wolf or something similar (Lamarck, 1809a, b, T. I, 229), intuitions that we can mention when teaching that domestic species are also products of the transformation generated by the practice of domestication.

On wheat, he wrote, ‘Is it not the case that cultivated wheat (Triticum sativum) is a plant which man has brought to the state in which we now see it? I should like to know in what country such a plant lives in nature, otherwise than as the result of cultivation. Where in nature do we find our cabbages, lettuces, etc., in the same state as in our kitchen gardens?’ (Lamarck, 1809a, b, T. I, p. 227.)

Lamarck deduced that domestic species were transformations from wild species — a fact known from horticultural and agricultural practices — having been cultivated over a period of centuries, and that something similar occurred in nature, where the ages available might be sufficient to transform species. Nonetheless, Lamarck noted, ‘There is one strong reason that prevents us from recognising the successive changes by which known animals have been diversified and been brought to the condition in which we observe them; it is this, that we can never witness these changes’ (Lamarck, 1809a, b, Volume II, p. 464), to which he adds:

If the duration of human life only extended to one second, and if one of our ordinary clocks were wound up and set going, any individual of our species who looked at the hour hand of this clock would detect in it no movement in the course of his life, although the hand is not really stationary. The observations of thirty generations would furnish no clear evidence of a displacement of the hand, for it would only have moved through the distance traversed in half a minute and this would be too small to be clearly perceived; and if still older observations showed that the hand had really changed its position, those who heard this proposition enunciated would not believe it, but would imagine some mistake, since they had always seen the hand at the same point of the dial. I leave my readers to apply this analogy to the subject in hand. (Lamarck, 1809a, b, Volume II, p. 465).

The clock metaphor reveals how important it was for Lamarck to explain the depth of time in the history of life. It contrasts the immensity of time that nature needed to carry out changes in the transformations of species with the brevity of human existence, an existence so fleeting that any awareness of the events of transformation occurring in nature might seem impossible.

A feature of the grandeur of the human mind, he noted, was that it had become aware of these changes and had realised that the human being was the result of these very transformations (Lamarck, 1820).

6 Natural Causality and the Origin of Species, Including the Human Being

In contrast to the historical narratives that have described Lamarck’s system as being idealist and metaphysical, Lamarck’s ideas are an example of an early theorisation that sought an explanation for the transformation of organisms in naturalistic terms. For example, at the end of the first volume of Philosophie zoologique (1809a, b), Lamarck disagrees with the conclusion accepted at his time: ‘Conclusion adopted hitherto: Nature (or her Author) in creating animals, foresaw all the possible kinds of environment in which they would have to live, and endowed each species with a fixed organization and with a definite and invariable shape […]’ (Lamarck, 1809a, b, T. I, p. 265). His own, naturalistic vision being:

My individual conclusion: Nature has produced all the species of animals in succession, beginning with the most imperfect or simplest, […] so as to create a gradually increasing complexity in their organization; these animals have spread at large throughout all the habitable regions of the globe, and every species has derived from its environment the habits that we find in it and the structural modifications which observation shows us (Lamarck, 1809a, b, T. I, p. 266).

Lamarck’s search for natural explanations of things, for example, the origin of life, clearly indicates his materialistic beliefs. The same approach can be seen in his explanation of transformation. Lamarck was additionally interested in being able to draw lines, if they existed, that separated the physical and moral aspects of the human being and the physical and moral aspects of the animal world. Lamarck took moral aspects to encompass the entire set of cognitive phenomena, or those of the mind, their nature, and their historical origin. These moral phenomena included memory, the ability to make judgments, language, rationality, imagination, emotions, sensitivity, and, of course, consciousness. These are questions he went into in depth, dedicating to them practically the entire third of his Philosophie zoologique.

Prior to the Philosophie zoologique (1809a, b), Lamarck offered ‘nature’ as the single cause of organic transformations and the origin of life in the works that he wrote in the years after the French Revolution. Lamarck did not conceal his allegiance to materialism — in the philosophical sense — supporting ideas such as nature being the cause of itself and nature being eternal. It was his belief that: ‘The amount of matter cannot increase or decrease, for only that power which could create could destroy it, and it is not even necessary to return it to nothing’ (Lamarck, 1794, p. 21).

In the Philosophie zoologique of 1809, he stated he thought that the idea of nature being eternal, and hence as having existed for all time, was ‘for me an abstract opinion’ and that he could have ‘no positive knowledge on this subject’ (Lamarck, 1809a, b, T. I, p. 361). In consequence, he therefore preferred to think that there was a First Cause or … a Supreme Power (Lamarck, 1809a, b, T. I, p. 361).

Nevertheless, he assumed that nature acted independently. In later works, such as the Système analytique des connaissances positives de l’homme (1820), Lamarck did use the word ‘DIEU’ (Lamarck, 1820, p. 15, 40, 44, 74, 810–12), possibly ambiguously in a literal sense, contrasting with the much more materialistic stance of his early works and certain paragraphs in the Système analytique itself. It seems to us entirely possible that the explanation for this is not that Lamarck had abandoned his materialist methodological and philosophical positions for deist or pantheist ones, but was rather adapting to circumstances due to the control of publications instituted after the restoration of the monarchy (see Corsi, 1987, 2012) and particularly the censorship that the Bourbon monarchy exerted.Footnote 12

The Philosophie zoologique as an evolutionary explanation leads explicitly to a rejection of God’s direct intervention in the creation of mankind and of all species in general. As another element in the march of nature, Lamarck, like Buffon, included the human being as the product of a gradual and continuous process of transformation: ‘to believe that man possesses an immortal soul […] all that we can ever say on this subject is baseless and purely imaginary’ (Lamarck, 1809a, b, T. II, p. 187).

Intelligence, the fundamental characteristic of our species, was not the product of a rational soul, Lamarck believed, but rather the product of natural processes and could be studied, he suggested, as a particular property of life arising from inert matter. The brain and all its cognitive, rational, sentient, and moral powers were nothing more than the result of the physiological functions of the nervous system and the fluids (Lamarck, 1809a, b, T. I, p. 364).Footnote 13

7 Implications of the Lamarck Proposal

It is our hope that this proposal will help provide the elements necessary to show how science teaching can be enriched by taking the history of science as a starting point. It is worth clarifying that the historical evidence given here is not based on a thorough reconstruction of the history of evolutionary theories, nor is it a profound explanation of Lamarck’s social and political context. Rather, it is our aim to highlight fundamental ideas that Lamarck developed in great detail, thus referring to a rather typical historiography, a history of ideas, which in practical terms allows us to focus exclusively on the concepts.

One of our objectives in reviewing Lamarck’s ideas is to show students that the history of science is far richer and more diverse than the ‘official’ or ‘traditional history’ would have it. The issue is not to downplay the contributions of others, but to point out the number of examples available. This should be considered a strength rather than a weakness as it shows that key concepts for the understanding of evolutionary thought are present in the work of various authors. For example, Contemporary Debates in Philosophy of Biology, the collection edited by Francisco Ayala and Robert Arp (2010), provides us with an example of the ‘disagreements’ in biology, and how, from the standpoint of philosophy, different explanations on the same topic may be suggested. Similarly, Kostas Kampourakis, in his work on the importance of the philosophy of biology for education, reminds us how different the understanding of science can be when it is approached from a philosophical perspective (Kampourakis, 2013, p. 2). It is our suggestion that this is similarly true for a historical perspective.

The question is now, ‘What are the implications of each of Lamarck’s concepts for teaching evolutionary thinking?’ Our starting point is that teaching science should demonstrate, and above all, help to consolidate, the key aspects of what scientific practice actually is. For example, scientific knowledge derives from peer-to-peer discussions where theoretical diversity means that unanimous consensus will not necessarily arise. In short, what should be emphasised is the dialogue of ideas.

Lamarck’s discussion of the existence or non-existence of species is a good example. Firstly, to speak of ‘species’ today is to return to an arbitrary concept. This not only sounds provocative but also inappropriate, given that evolutionary thought is based on the idea of species, being one of the basic concepts needed for understanding and explaining evolution. If we follow Lamarck’s reasoning, discussing individuals helps to demonstrate the existence of ‘infinite variation’; it emphasises the enormous importance of diversity, as opposed to the — sometimes forced — search for identical characters within groups of individuals (an unfortunate practice, for example, when aiming to construct a ‘natural notion’ of human races).

Although it may not successfully resolve the dilemma of the concept of species, a way of overcoming the contradiction between the idea of the actual existence of species and the radical denial of their existence has been postulated in contemporary biology. This is to grant the ‘species’ (as well as varieties and breeds) a relative existence in general terms, circumscribed by specified limits in space and time. This notion may be found in statements by Ernst Mayr (2002), Massimo Pigliucci and Jonathan Kaplan (2003), Robin O. Andreasen (2007), and John S. Wilkins (2009), among others, and it comes very close to the recognition of the species as an arbitrary grouping of biological communities that are capable of reproduction and leaving offspring with variations which, sooner or later, will be able to give rise to new species (or new entities whose existence is limited in space and time).

Lamarck began by considering the non-existence of species and infinite variability when assuming the possibility of organic transformation. Exactly the same reasoning can be used with students. Lyell pointed out, in his arguments against Lamarck, that if Lamarck’s conjectures were correct then we would finish by accepting that all life descends from a single ancestor. As Lyell understood this, and Lamarck explained it, individuals reproduce and their offspring is always different. That is, parents were different, grandparents different, and each earlier generation was different. The crucial point in Lamarck is that those earlier generations began their diversification from ‘the same plan of organization’ in one or two initial forms for all animals currently existing, whether vertebrate or invertebrate. For Lamarck, all present-day animals are modifications of the same plan of organisation. According to this line of reasoning, as there exist only individuals that reproduce leaving similar offspring, and as continuous diversification responds exclusively to changing circumstances, there is no, nor will there ever be a final end point. For Lamarck, the fact was that individuals were the entities that actually existed in nature. It is to these real entities that we refer in their temporary groupings as species. These are the individuals that reproduce, leaving similar offspring. Then, many generations later, the differences will be so great that, when trying to understand nature, they will be grouped into new species, which will also have only a relative existence.

Today, the role of diversity in understanding natural processes is fundamental. The severity of problems such as climate change and the consequent loss of biodiversity might diminish if students were to become more keenly aware of the idea of diversity. Furthermore, by taking Lamarck’s work as a reference point, it can be shown how, based on historical evidence, fundamental concepts for evolutionary thought, such as diversity, may be found in different authors.

Lamarck’s thinking is not only important as a historical precursor of the discussions of organic life’s transformation processes, and the inclusion of the human being, but also because of the questions he raises about the origin and nature of ‘moral phenomena’, many being questions for which evolutionary biology is still seeking the best explanation. This can be seen in the work of Simona Ginsburg and Eva Jablonka (2019), where respect is given to Lamarck as a thinker who raised important questions about the boundaries of the mental life of animals and of human beings. There is nothing unusual about including Lamarck in a twenty-first-century work for one of his goals in the Philosophie zoologique was to explain the origin and nature of the human being’s physical and moral facets — the moral, as mentioned, referring to everything related to the phenomena of the mind, including consciousness.

The important questions for Lamarck and for evolutionary biology are to discover how the transition from the non-living to the living occurred, and how the moral, rational, conscious, and sensitive soul of the human being arose from animal life (Ginsberg and Jablonka, 2019). Lamarck’s work was an evolutionary attempt to explain unresolved problems within biology: the origin, transformation and nature of consciousness, and the phenomenon of morality. Lamarck recognised that his three-part Philosophie zoologique was largely dedicated to the phenomena of morality, the first part being dedicated to ‘general principles on the phenomenon of life’, which he considered necessary for understanding questions about the origin of the physical and the moral in the human being in naturalistic terms. He then addressed the issue in the whole of the third section, having assumed that the human being is a species that had branched out from others.

8 Conclusions

Lamarck not only created an evolutionary framework but he also developed and elaborated on a set of general principles for understanding the origin, nature, and relationships of the living, a profound zoological philosophy in which the human being was included as yet another animal species, a ‘bipedal twig’ running laterally to the branches of sister species (quadrupedal humans), a species that had achieved a position where it was capable of understanding its own origin, and the relationship it had with other species and life in general.

As we know, Lyell did his best to refute Lamarck’s evolutionary theory, but we also know that he was eventually persuaded by its theoretical principles, and confirmed that, since the first edition of his Principles of Geology, he had changed his mind about ‘transmutation’ (Browne, 2011, p. 219). This change of heart can be seen in the letter that Lyell sent to Darwin in March 1863, where he accepted that, after reading Lamarck’s work again ‘and remembering when it was written, I felt I had done him injustice.’ (Lyell to Darwin, 1863).

Nonetheless, previously, in 1832, Lyell had rejected Lamarck’s proposal for transformation, and his work had popularised an unfortunate image of Lamarck’s ideas, summarised in the statement dealing with the lengthening of the giraffe’s neck, a process that Lyell interpreted as being generated by the animal’s ‘desire’ to reach the highest branches, becoming the image we dogmatically teach in our school classrooms. We argue that the time has come to correct this misunderstanding and teach instead the general principles of Lamarck’s evolutionary thought. The structure of his ideas contains far greater intellectual merit and, as a complementary element in the teaching sequence discussed above, can provide students with invaluable knowledge of evolutionary thinking.

Lamarck’s basic ideas have been incorporated into the work of the various authors who have explored evolution. In a way that is analogous to heredity, his theoretical principles have been continued with modifications in the various accounts of evolution. These theoretical principles are hardly ever associated with Lamarck, but it is his intellectual legacy, with that of others, such as Buffon, Cuvier, and Lyell, that lies beneath the conceptual framework of all (or almost all) evolutionary accounts.

If the objective of teaching evolution is to lay the necessary foundations for understanding the subject, emphasising the causal nature of the processes, understanding these processes in completely natural terms, and highlighting the enormous importance of diversity in evolution, Lamarck’s ideas are chronologically at the beginning: his ideas are the starting point from which evolutionary thought sets out on its long path.

Finally, while Lamarck studied ‘the diversity of animal organization, in each family, in each order and, above all, in each class’, he discovered the mutability of species. It was not, naturally, his research programme and he did not have the questions we have today, moreover, in many ways, as Hodge points out, ‘the mutability of species in changing conditions occupied a logically quite secondary place in the explanation of organic diversity.’ (Hodge, 1971, 329). But in this attempt to study and understand the diversity of nature, he discovered one of the great secrets of nature: the transformation of species, an area of investigation which continues to generate questions that stimulate scientific research.

Recognising the way in which Lamarck discussed concepts such as ‘species’ or ‘environment’ is useful for illustrating the importance of the discussion in scientific practice. Discussing the existence of species as real entities aims to assess their importance in areas such as systematics, while at the same time recognising the limitations involved in the use of such concepts, both when conceptualising the question, ‘What is a species?’, and the methodological difficulties implied in the delimitation of a species. Similarly, returning to the discussion on the role of the environment in the transformation of organisms is go down a road such as the one proposed by Gregory Radick, i.e. to teach students modern biology, at least in the sense that nowadays the importance of the environment in evolutionary processes is increasingly accepted.

In the words of Kostas Kampourakis and Ronald Numbers: ‘Students, educators, and general readers need to acquire a knowledge of scientific content and also to understand what is called ‘the nature of science’: how science is done, what kinds of questions scientists ask, and what kinds of knowledge they produce’ (Numbers & Kampourakis, 2015, p. 3). Accordingly, the proposal to teach evolution by starting from historical sources will put an end to myths that penetrate to the heart of evolutionary theory and will allow us to teach a history of biology that is more precisely in line with the events of the past.