No one has a good understanding of what ‘life’ is
iai News
The primary understanding of life is as a biological organism that takes part in evolution. But this is a mistake. Sara Walker here argues our idea of what life is doesn’t stand up, there are several counter-examples, and we can see life in a number of different and radical ways.
One of the most popular definitions for life circulating in scientific communities is that “life is a self-sustaining chemical system capable of Darwinian evolution.” This definition was first developed in an exobiology discipline working group organized by John Rummel, who at the time was manager of NASA’s Exobiology Program. Although the definition was developed under the auspices of a NASA working group, it is by no means the official NASA definition, as is sometimes claimed in popular news outlets. It’s not even necessarily a widely accepted definition.
Gerald Joyce, a highly respected RNA chemist, has been misaccredited as the sole author of this definition, which he himself will point out. This is because in 1994 he wrote about the working group’s definition in the foreword of a book titled Origins of Life: The Central Concepts. RNA, short for ribonucleic acid, is believed to have played an early role in the origin of life, at least by those scientists who adhere to the RNA World hypothesis. This model proposes that life started with RNA, as opposed to DNA (deoxyribonucleic acid), as the genetic material. During the last few decades, the RNA World has been considered the leading hypothesis for the origin of life on Earth. Gerry studies the in vitro evolution of RNA molecules to understand potential mechanisms of chemical evolution in the putative RNA World. He and his colleagues have demonstrated amazing capabilities in RNA, such as the ability for self-replication and evolution under controlled conditions. Because RNA chemistry isolated and evolved in a test tube can fulfil so many functions of living biochemistry, it is understandable one might arrive at a definition of life as a self-sustaining chemical system capable of Darwinian evolution.
A lot of people use this definition and like it. But at the same time, like all definitions for life, it fails to deliver on solving the hardest problems. It has not allowed us to prove a mechanism for the origin of life nor design new instruments to search for and measure the presence of alien life on another world.
