The form and function of living things are the result of a spontaneous process of evolution. In the “absence” of a designer, there are many aspects of biological design that we are still unable to understand or imitate. It is amazing, for example, that a single fertilized egg develops into the system with complex forms and functions. The mechanisms that enable us to receive external stimuli through our senses and to move and think as humans do are still under study and difficult to imitate. It is both natural and naive that we had come to expect this to be due to the reactions within a cell which is unique to a living thing and undiscovered by mankind. Such claims, which have been made repeatedly since the time of the ancient Greeks, had been collectively called the “vitalism.”

However, the history of biology since the 20th century has been one of the challenge of explaining the design of organisms without the vitalism. When modern biologists are asked about the design of organisms, the conventional answer is that the unique functions of organisms are largely conducted by proteins and that the order of nucleotides in DNA determines which kind of proteins organisms possess. It is also thought that the DNA sequence is spontaneous and was optimized by the evolutionary process of mutation, inheritance, and selection. This idea is supported by biochemistry, which since the 19th century has shown that many chemical reactions occurring in living organisms can be reproduced outside the organism. There remains no evidence that the unknown chemical reactions predicted by the vitalism occur inside cells: proteins are made from DNA sequences, proteins can process information in an intelligent way to some extent, and the network of reactions (metabolic map) of multiple proteins and biomolecules can reproduce all life.

Now that we know all the essential mechanisms of biological design, is it enough to discover one molecule at a time that corresponds to the design of an organism? Many researchers believe that this is not enough and that there are many unsolved problems in science. A few examples follow.

The connection between micro- and macro-design: proteins are molecular machines with limited functions. How do intelligent functions emerge from the random assembly of unintelligent molecules? How individual organisms come together to maintain ecosystems is also not well understood. The connection between the micro and the macro has long been discussed in non-biological fields, and efforts to understand it continue, borrowing ideas from physics and using computer simulations. For example, how do birds form flocks (Vicsek et al. 1995)? How do microscopic chromatophores come together to form the body surface pattern of a fish (Kondo & Miura 2010)?

Designing with fluctuations: the state and number of biomolecules is not fixed and fluctuates like a machine. However, at the functional level of living organisms, fluctuations appear to be suppressed. For example, the mechanism by which we perceive red comprises fluctuating intracellular chemical reactions, but the perception of red itself appears to be stable each time. The differentiation of an undifferentiated cell into a tissue such as the heart or the lungs occurs without fluctuations. How are we to understand this (Tom 1980)? Fluctuations also exist at a macroscopic level. For example, the diversity of individual physiques and personalities, and the fluctuations in sexuality, which cannot necessarily be divided into two genders, may be due to intrinsic fluctuations in the phenomena of life. What is the significance of these fluctuations?

A special initial state of life: a large body of evidence suggests that life has a single origin. In other words, the chain of organisms giving rise to organisms has likely never been broken since it began long ago. No other chemical reaction is so enduring. Did the cell start out in a very special initial state, different from other substances, and does it still maintain that special state? If so, how can we describe this peculiarity (Ohno 2009)?

Science is the process of showing the design of nature by means of mathematical formulae and material words. The scope of ‘nature’ that science deals with expanded in the 20th century to include the design of living things. Since the beginning of the 21st century, there seem to be increasing opportunities for the design of art and engineering to intersect with the design of living things. For example, the field of soft robotics, which uses soft materials like living organisms to create artificial objects, is emerging. Optimization algorithms based on biological evolution exemplify how biological mechanisms can influence human design. The Bio-Food Lab, a facility for dealing with organisms and food, has been built on the Ohashi campus, and research into design using biomaterials is commonplace. The question of the design of living organisms is one not only for biologists but will be increasingly discussed in art and engineering.

(ITO Hiroshi)

関連する授業

Design Futures Course Simulation (Theory)

Design Futures Course Simulation (Practical)

Design Futures Course Chronobiology

参考文献

• Alberts, Bruce, Alexander D. Johnson, Julian Lewis, David Owen Morgan, Martin C. Raff, Keith Roberts, Peter Walter（2017）(『細胞の分子生物学 第6版』中村桂子・松原謙一監訳、ニュートンプレス)
• Hans, Driesch (1914) The History and Theory of Vitalism, London, Macmillan（ハンス・ドリーシュ（2007）『生気論の歴史と理論』米本昌平訳、書籍工房早山）
• Kondo, S. & Miura, T. (2010) “Reaction-Diffusion Model as a Framework for Understanding Biological Pattern Formation.” Science 329, 1616–1620.
• René, Thom (1972) Stabilité Structurelle et Morphogénèse, Essai d’une Théorie Générale des Modèles, Benjamin-Cummings（ルネ・トム（1980）『構造安定性と形態形成』彌永昌吉・宇敷重広訳、岩波書店）
• Vicsek, Tamás, András Czirók, Eshel Ben-Jacob, Inon Cohen, and Ofer Shochet (1995) “Novel Type of Phase Transition in a System of Self-Driven Particles,” Phys Rev Lett 75, 1226–1229.
• 大野克嗣（2009）『非線形な世界』東京大学出版会