Introduction

Georges CHAPOUTHIER1 and Marie-Christine MAUREL2

1 ICM-CNRS, Paris, France

2 ISYEB-CNRS-MNHN, Sorbonne University, Paris, France

One of the essential characteristics of living beings, perhaps the most important, is an explosion of their forms, linked to the extreme diversity of environments to which they have been able to adapt. It is precisely the multiplicity of these astonishing morphologies, in all its facets, that this book aims to explore.

Of course, this diversity is rooted in the very origin of life itself, as Marie-Christine Maurel relates. The diversity of physical and chemical conditions on Earth during the Hadean period, as well as the diversity of planets and the multiple bodies of the solar system, may have led to the formation of molecules, organizations and protocells with a wide variety of shapes and metabolisms. The different chemical elements of the primitive ocean and fossil traces from the first stromatolites could provide evidence of this. Thus, biodiversity is original and current research is discovering multiple ways of "existing", far from a standardized vision of life.

These considerations lead, of course, to the great founding question: what is life? This is what Andreas Losch tries to answer. If it is clear that, in the final analysis, living matter can be summed up as creations of physics and chemistry, and if it is true that there is no such thing as a mysterious "vital principle", would life not then find its specificity precisely in the very explosion of its forms? But then a question of language arises. What we call "life" in everyday language, what we have an existential experience of, is not necessarily what life is at the scientific level, where material bases matter more than forms. As with other complex concepts, "life" is in fact an ill-defined combination of properties that mineral substances do not possess, where form plays a key role, and "words to describe it" are still missing. Indeed, how will "robots" and other machines describe it in a few decades?

In living beings that are already constituted, form becomes, as Jean-Pierre Gasc shows, a means of knowledge. From Aristotle to Cuvier, function is interpreted in relation to morphology. Nowadays, more emphasis is placed on the weight of the physical framework, which suggests that form is an adaptation to environmental constraints, as evidenced for example by the symmetry of bilaterians, the appearance of even appendages (allowing "'appendicular' movement on land") or the "cephalization" of mobile animals. In the second chapter, Jean-Pierre Gasc recalls the central role of the theses of the Scottish zoologist D'Arcy Wenworth Thompson, in his famous book On Growth and Form, which holds "an almost legendary place in scientific literature" and which makes him, in a way, the prophet of the link between form and functional adaptation.

We know today that, while genes define the major parameters of the form of living beings, the essential part, the definitive shape, is constituted by the almighty processes of epigenesis. Jonathan B. Weitzman leads us along these astonishing embryological paths which, going beyond the genetic basis, lead, in successive stages, to the generation of form in the developing embryo. Today, much is known about the epigenetic mechanisms by which environmental signals and genetic characteristics are integrated and contribute to the formation of beautiful forms, underlying the epigenetic landscape so dear to Waddington's heart.

The very original world of protists and bacteria is presented to us by Guillermo Paz-y-Miño-C and Avelina Espinosa. The numerous strategies by which these beings detect and communicate with each other to survive and develop offer striking examples of the explosion of forms at the microscopic level. These processes also provide a better understanding of the evolutionary strategies involved in the transformation of forms, such as inclusive selective value, whose adaptive success is due to direct descendants but also to kin selection.

Florian Jabbour and Guilhem Mansion tackle the fascinating field of plant forms. "The myriad of plant forms has always been - and still is - a source of astonishment, contemplation and even inspiration to which man cannot remain oblivious". However, the authors show that this diversity, which could be described as 'anthropocentric', is not the same one perceived by other representatives of the animal kingdom, such as pollinating insects, "often sensitive to signals that can only be observed in ultraviolet light". The authors analyze how plant forms emerge, both in terms of individual development (ontogenesis) and lineage evolution (phylogenesis), and how these evolutions allow plants to adapt to the surrounding environment and the constraints it imposes, as well as the possible constraints of internal operation. Lastly, the authors devote a large part of their chapter to all the ways in which human societies have used these plant forms for their own benefit.

Forms are not only manifested in the architecture of living beings, but also, particularly in animals, in their performances and achievements. Robert Jaffard addresses one of the most central performances of the psyche: memory. He analyzes the different forms of memory that allow an individual to adapt its behavior to the constraints and changes in its environment. Ranging from the simple phenomenon of habituation present in invertebrates to the highly sophisticated ability to form memories, these different forms of memory are juxtaposed as the nervous system becomes more complex.

Another area that contributes, in an essential way, to the performance of animals is that of sensory universes, of which Dalila Bovet offers us a detailed overview. Chemical sensitivities such as taste or smell, mechanical sensitivities such as touch or hearing, electromagnetic sensitivities such as vision, but also electrical, magnetic or thermal sensitivities; here are some of the innumerable sensory forms that have enabled animals to develop such particularly complex behaviors.

Beyond living beings, robots are built by human beings on basics inspired by living forms. In particular, they possess very interesting social and emotional forms, which Laurence Devillers explains. She shows that, although these forms are simulated, we "anthropomorphize" the behavior of machines. We imagine living things in artificial forms. She therefore explains the need to talk about ethics and transparency in the design of these machines that non-experts are far from understanding, and who could easily manipulate us.

On the technological level, mimicking the living, its forms, in order to develop and design medical technologies - orthoses, prostheses and other systems of electrophysiological or cognitive functional substitution, intra or extracorporeal - is a necessity in order to reconstruct anatomy and restore physiology. After placing this question in a historical and epistemological perspective, Didier Fass extends critical reflection to forms of thought or treatment by medical and symbiotic machines. He explains the associated concepts and the theoretical principles necessary to understand the organization of living organisms, which are essential for designing and modeling medical artifacts in integrative bioengineering. Thus, he describes the basic needs for biocompatibility and bio-integration as well as the fundamental requirements, including those of form(s), of "human-artificial" engineering for medicine and for "augmented humans". In conclusion, the author proposes a perspective of integrative bioengineering with the bioprinting of medical devices and tissue engineering.

On a more general and philosophical level, Georges Chapouthier wonders whether, despite their extreme diversity, biological forms (both anatomical and mental), and consequently man-made technological forms, which have a common origin, might not also have common principles of construction. According to him, all forms of life or systems that mimic life would indeed result from the repeated application of two main principles: juxtaposition of similar units; and then integration of these units to form more complex structures, of which the original units then become parts. Just as in a mosaic, the new complex structures (the "whole") then leave a degree of autonomy to the parts that make them up.

The book ends with a philosophical reflection by Jean-Michel Besnier on the very role of "form" in our 21st Century society. The current trend seems to be to forget form and replace it with a fluid potentiality where "nothing remains, everything evolves and offers itself to mutations and transformations". From this perspective, almighty "information" does not just aim to complement form. It aims, according to some authors, to totally replace it with "power", "a process that has gotten rid of formal conditions". Besnier analyzes and underlines the dangers of this process, a triumph of blind technology, supported by transhumanist, often catastrophist currents, where "power finally escapes the mind, that is to say, human control". Through this "deformation", "the absence of form is equivalent to violence and death".

This superb conclusion gives all its relevance and all its legitimacy to our work, which is, as we have seen, a plea, with multiple voices, for...