Higgs Paul G
Origins Institute and Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada.
J Mol Evol. 2017 Jun;84(5-6):225-235. doi: 10.1007/s00239-017-9799-3. Epub 2017 Jun 29.
Darwinian evolution requires a mechanism for generation of diversity in a population, and selective differences between individuals that influence reproduction. In biology, diversity is generated by mutations and selective differences arise because of the encoded functions of the sequences (e.g., ribozymes or proteins). Here, I draw attention to a process that I will call chemical evolution, in which the diversity is generated by random chemical synthesis instead of (or in addition to) mutation, and selection acts on physicochemical properties, such as hydrolysis, photolysis, solubility, or surface binding. Chemical evolution applies to short oligonucleotides that can be generated by random polymerization, as well as by template-directed replication, and which may be too short to encode a specific function. Chemical evolution is an important stage on the pathway to life, between the stage of "just chemistry" and the stage of full biological evolution. A mathematical model is presented here that illustrates the differences between these three stages. Chemical evolution leads to much larger differences in molecular concentrations than can be achieved by selection without replication. However, chemical evolution is not open-ended, unlike biological evolution. The ability to undergo Darwinian evolution is often considered to be a defining feature of life. Here, I argue that chemical evolution, although Darwinian, does not quite constitute life, and that a good place to put the conceptual boundary between non-life and life is between chemical and biological evolution.
达尔文进化论需要一种机制来产生种群中的多样性，以及个体之间影响繁殖的选择性差异。在生物学中，多样性由突变产生，选择性差异则源于序列的编码功能（如核酶或蛋白质）。在此，我提请注意一个我称之为化学进化的过程，其中多样性是通过随机化学合成而非（或除了）突变产生的，并且选择作用于物理化学性质，如水解、光解、溶解度或表面结合。化学进化适用于可通过随机聚合以及模板导向复制产生的短寡核苷酸，这些寡核苷酸可能太短而无法编码特定功能。化学进化是通向生命之路的一个重要阶段，介于“仅仅是化学”阶段和完全生物进化阶段之间。本文提出了一个数学模型，阐明了这三个阶段之间的差异。化学进化导致的分子浓度差异比无复制选择所能达到的要大得多。然而，与生物进化不同，化学进化并非无限制的。能够进行达尔文式进化通常被认为是生命的一个决定性特征。在此，我认为化学进化虽然属于达尔文式进化，但并不完全构成生命，并且划分非生命与生命概念界限的一个恰当位置是在化学进化与生物进化之间。
