Milestones at the Origin of Life

TL;DR

This paper reviews key evolutionary milestones in the origin of life, proposing a sequence of events from homochirality to cellular life, emphasizing the importance of biochemical and environmental factors in this process.

Contribution

It offers a proposed chronological order of critical milestones in prebiotic evolution, highlighting the role of homochirality, metabolism, genetics, and cell formation.

Findings

Homochirality emerged as the first major milestone.

Metabolism and genetics established via homochiral enzymes 4 billion years ago.

Cells with division formed in hot spring environments.

Abstract

Living organisms have some common structures, chemical reactions and molecular structures. The organisms consist of cells with cell division, they have homochirality of protein and carbohydrate units, and metabolism, and genetics, and they are mortal. The molecular structures and chemical reactions underlying these features are common from the simplest bacteria to human beings. The origin of life is evolutionary with the emergence of a network of spontaneous biochemical reactions, and the evolution has taken place over a very long time. The evolution contains, however some "landmarks" and bottlenecks, which in a revolutionary manner directed the evolution, and the article tries to establish the order of these events. The article advocates that a possible order in the emergence of life is that the first milestone in prebiotic evolution is at the emergence of homochirality in proteins. The homochirality of peptides is, however, with instability and racemization which causes aging of the peptides and mortality. The metabolism and genetics are established through homochiral enzymes in the Earth's crust for $\approx$ 4 Gyr ago. Finally, the cells with cell division are established in the Hot Springs environment at the interface between the crust and the Hadean Ocean.