The emergence of natural selection, requiring that reproducing entities present variations that may be inherited and passed on, was arguably the most important breakthrough in the self-organization of life. In this Perspective, the assumptions governing biological reproduction are confronted with physico-chemical principles that control the evolution of material systems. In biology, the reproduction of living organisms is never considered to be reversible, whereas microscopic reversibility is an essential principle in the physical description of matter. Here, we show that this discrepancy places constraints on the possibility of finding kinetic processes in the chemical world that are equivalent to natural selection in the biological one. Chemical replicators can behave in a similar fashion to living entities, provided that the reproduction cycle proceeds in a unidirectional way. For this to be the case, kinetic barriers must hinder the reverse process. The system must, thus, be held far from equilibrium and fed with a non-degraded (low-entropy) form of energy. The ensuing constraints must be factored in when proposing scenarios that account for the origin of life at the molecular level.

自然选择的出现，要求繁殖实体呈现出可以遗传和传递的变异，可以说是生命自我组织中最重要的突破。在这一观点中，控制生物繁殖的假设面临着控制物质系统进化的物理化学原理。在生物学中，生物体的繁殖从未被认为是可逆的，而微观可逆性是物质物理描述的基本原则。在这里，我们表明这种差异限制了在化学世界中找到等同于生物世界自然选择的动力学过程的可能性。化学复制器的行为方式与生物实体类似，前提是繁殖周期以单向方式进行。为此，动力学障碍必须阻碍逆向过程。因此，系统必须保持远离平衡状态，并以未退化（低熵）形式的能量供给。在提出在分子水平上解释生命起源的情景时，必须考虑随之而来的限制因素。