Introduction

• Evolutionary biology and developmental biology have traditionally been separate disciplines.
• The paper suggests that these two fields can be integrated into a single discipline, using a unified conceptual framework.
• Evolutionary biology focuses on adaptation, selection, and survival, while developmental biology focuses on the life histories of individual organisms.
• The authors propose that we view life as a continuous cell lineage, from the last universal common ancestor (LUCA) to all living organisms today.
• This approach challenges the traditional view of what constitutes an “individual organism.”

The Concept of Biological Individuality

• The traditional idea of a biological “individual” is being reconsidered due to the discovery of symbioses and microbiomes within organisms.
• New concepts such as “holobionts” show that organisms consist of multiple cooperating and competing biological systems, rather than being singular entities.
• For example, termites and their fungal partners coevolve as “extended organisms,” blurring the lines between the organism and its environment.
• Similarly, symbiotic relationships between plants, pollinators, and microbes also challenge traditional notions of individual organisms.

How Evolutionary and Developmental Biology Can Be Integrated

• To fully understand evolution and development, the authors suggest a “scale-free” approach.
• This involves applying the same theoretical tools to both evolutionary and developmental processes, regardless of scale.
• The “free-energy principle” (FEP) is presented as a unifying concept that explains how systems minimize differences between expected and observed conditions.
• The FEP is used to describe biological systems as information-processing systems, where all processes are interconnected across different scales.
• This scale-free framework allows us to study biological systems from the molecular level to the ecosystem level using the same fundamental principles.

Randomness vs. Outcome-directed Processes

• Evolution is traditionally seen as a process driven by random variation, where outcomes are shaped by natural selection acting on random mutations.
• However, developmental processes are outcome-directed and involve highly orchestrated mechanisms to produce consistent, predictable outcomes (e.g., cell differentiation).
• The paper suggests that both randomness and directed outcomes can coexist in biological processes, depending on the scale and context.
• For example, genetic mutations might be random, but the development of an embryo follows a directed, predictable pattern.
• The authors argue that evolutionary and developmental processes should be seen as interconnected and capable of influencing each other.

Gene-Centric vs. Non-Gene-Centric Inheritance

• The modern synthesis of evolutionary biology has focused heavily on the gene as the unit of inheritance and selection.
• However, the paper challenges this gene-centric view by recognizing the importance of non-genetic factors, such as bioelectric signals and environmental influences, in shaping development and inheritance.
• For example, bioelectric signals in planaria can determine head-tail morphology and are inherited across generations, even without changes in the genetic code.
• This suggests that information can be stored and transmitted through processes beyond DNA, such as epigenetic modifications and bioelectric signals.

Multilevel Evolutionary Theory

• Evolution happens at multiple levels, from genetic and cellular to cultural and ecological scales.
• The paper introduces the concept of “extended organisms,” where the boundaries of the organism are not limited to the genetic material but include symbiotic and environmental factors.
• This extended view of evolution emphasizes the dynamic interplay between various biological and environmental systems.
• The holobiont, which includes both the host organism and its microbiome, is a prime example of how evolutionary processes operate across multiple scales.

Cooperation vs. Competition

• Traditionally, evolution is seen as a competition for survival among individuals and species.
• However, cooperation is also a crucial part of evolution, as seen in symbiotic relationships and multilevel selection processes.
• In development, cooperation is key to producing functional, coordinated structures within an organism (e.g., the cooperation between different cell types to form tissues).
• The paper highlights the complexity of evolutionary and developmental processes, where both cooperation and competition play roles at different scales.

Causal Interaction vs. Informative Communication

• Evolutionary biology tends to use causal language, focusing on how organisms shape their environment through actions like predation or competition.
• Developmental biology, on the other hand, focuses on how cells communicate with each other to coordinate processes like differentiation and morphogenesis.
• The paper suggests that both evolutionary and developmental processes involve communication and information flow, rather than just causal interactions.
• For example, cells use signaling pathways to communicate and guide each other’s behavior, much like how neurons transmit information to control body movements.

Homogeneous Systems vs. Heterogeneous Systems

• Evolutionary biology often studies interactions between different species (heterogeneous systems), while developmental biology typically focuses on homogeneous systems (e.g., within a single organism).
• The concept of the holobiont challenges this distinction by recognizing that organisms are composed of multiple interacting systems (e.g., the human body and its microbiome).
• These interactions can be cooperative or competitive, and understanding them requires considering multiple levels of biological organization.

Conclusion

• The authors propose a new, integrated view of evolutionary and developmental biology that considers life as a single, continuous system.
• This scale-free approach emphasizes the interconnections between various biological processes and challenges the traditional boundaries between evolution and development.
• By adopting this new perspective, we can develop a deeper understanding of biological systems and create new experimental methods and tools.
• The authors believe that this approach will lead to new insights in areas such as medicine, bioengineering, and synthetic biology.

观察与结论

• 进化生物学和发育生物学长期以来被视为独立的学科。
• 这篇论文建议通过统一的概念框架将这两个领域结合为一个学科。
• 进化生物学侧重于适应、选择和生存，而发育生物学侧重于个体有机体的生命周期。
• 作者提出，我们应该把生命视为一个连续的细胞谱系，从最后的共同祖先(LUCA)到今天的所有生物。
• 这种方法挑战了传统的“个体有机体”概念。

生物个体性的概念

• 由于共生体和微生物群落的发现，传统的“个体有机体”概念正在被重新考虑。
• 例如，“全生物体”这一新概念表明，有机体由多个相互合作和竞争的生物系统组成，而不是单一实体。
• 例如，白蚁和真菌的共生关系表明，基因、形态、行为和环境的多个方面在演化过程中共同进化。
• 同样，植物与授粉者和微生物之间的共生关系也挑战了传统的个体概念。

如何将进化生物学和发育生物学结合

• 为了全面理解进化与发育，作者建议采用“无尺度”的方法。
• 这意味着将相同的理论工具应用于进化和发育过程，而不考虑尺度。
• 文章提出的“自由能原理”(FEP)是一个统一的概念，解释了系统如何最小化预期与观察条件之间的差异。
• FEP将生物系统描述为信息处理系统，从分子级到生态系统级，所有过程都在不同尺度之间相互连接。
• 这种无尺度框架使我们能够使用相同的基本原则研究生物系统。

随机性与目标导向过程

• 传统上，进化被视为由随机变异驱动的过程，最终结果是通过自然选择作用于随机突变形成的。
• 然而，发育过程是目标导向的，涉及精心编排的机制，产生一致的、可预测的结果（例如，细胞分化）。
• 论文认为，在不同的尺度和背景下，随机性和目标导向的结果可以共存。
• 例如，基因突变可能是随机的，但胚胎的发育遵循一个有序的、可预测的模式。
• 作者认为，进化和发育过程应视为相互关联、彼此影响的。

基因中心遗传与非基因中心遗传

• 现代综合理论着重于基因作为遗传和选择的单位。
• 然而，论文挑战了这一基因中心的观点，认识到非遗传因素（如生物电信号和环境因素）对发育和遗传的重要作用。
• 例如，平面虫的生物电信号可以决定头尾的形态，并在世代间遗传，尽管基因组没有改变。
• 这表明，信息不仅可以通过DNA存储和传递，还可以通过表观遗传修饰和生物电信号传递。

多层次进化理论

• 进化发生在多个层次，从基因到细胞，再到文化和生态系统的尺度。
• 论文介绍了“扩展有机体”的概念，其中有机体的边界不仅限于基因材料，还包括共生体和环境因素。
• 这种扩展的进化观念强调了各种生物学和环境系统之间的动态相互作用。
• 全生物体是进化过程中在多个层次上起作用的主要例子。

合作与竞争

• 传统上，进化被视为个体和物种之间的竞争过程。
• 然而，合作也是进化中的关键部分，表现在共生关系和多层次选择过程中。
• 在发育过程中，合作是产生功能协调的结构（例如，不同细胞类型之间的合作）所必需的。
• 论文强调了进化和发育过程的复杂性，其中合作和竞争在不同的尺度上发挥作用。

因果互动与信息交流

• 进化生物学通常使用因果语言，侧重于有机体如何通过捕食、竞争等行为塑造环境。
• 发育生物学则侧重于细胞如何通过信号传递相互协调以控制分化和形态发生。
• 论文认为，进化和发育过程不仅仅是因果互动，还涉及信息的流动和交流。
• 例如，细胞通过信号通路进行沟通，引导彼此的行为，类似于神经元如何传递信息来控制身体运动。

均质系统与异质系统

• 进化生物学通常研究不同物种之间的互动（异质系统），而发育生物学则通常关注均质系统（例如单个有机体内的互动）。
• 全生物体的概念挑战了这一区分，认识到有机体由多个相互作用的系统组成（例如人类及其微生物群落）。
• 这些互动可以是合作的，也可以是竞争的，理解它们需要考虑生物学组织的多层次结构。

结论

• 作者提出了一种新的综合进化和发育生物学的观点，将生命视为一个连续的生物个体。
• 这种无尺度的方法强调了各种生物过程之间的相互联系，挑战了传统的进化和发育之间的界限。
• 通过采用这种新观点，我们可以开发出更深入的生物学理解，并创建新的实验方法和工具。
• 作者认为，这种方法将带来医学、生物工程和合成生物学等领域的新见解。