aAlison Muotri, a medical research lab in California, has used chemistry to turn skin cells into neurons, which multiply to form “organoids” — globes of interconnected brain cells. Organoids can proliferate to hundreds of thousands of cells, live for years, and even produce detectable patterns of brain waves, like those of premature babies. “The most incredible thing is that they build themselves,” says Muotri. He also wonders if they might one day become conscious.
Such turbulent scientific work, unknown until 10 years ago, challenges our ideas about life, inquiry For bioethicists and philosophers. as American science writer Carl Room writes: “Brain organoids are troubling because we feel in our bones that life should be easy to understand. These clusters of neurons prove that’s not the case.”
In this subtle and intense meditation on the science of life filled with memorable insights into biology’s past and future, Zimmer draws on the extraordinary complexity and diversity of life, as well as the ingenious efforts of scientists to investigate how it originated and how it happened. Cast light on. could be disclosed. developed in another world.
Descartes thought that life was explained by matter in motion: animals were just complex clockwork mechanisms. Others disagreed, arguing that life was distinguished by a “vital force”. Charles Darwin’s grandfather, Erasmus Darwin, anticipated evolution by suggesting that this force was transferred from one generation to the next, changing over time to produce different forms. It helped inspire one of the most famous and disturbing fantasies about the nature of life – Mary Shelley frankenstein (1818). In the novel the scientist Victor Frankenstein, who revives a stitched corpse, is plagued by the question: “I often asked myself, does the theory of life proceed?”
Our brains are very good at recognizing signs of life, recognizing complex activities, and trying to read intentions in them. There are also widely accepted “identities” of life. They include metabolism (living alchemy by which food is turned into energy), information gathering, homeostasis (how an organism preserves the conditions of life within itself), reproduction, and development.
But what about those things that live on the “edge of life” and test the limits of our definitions? Moss can survive drought. One that had dried up and turned into a glacier was revived after 600 years. Other organisms can, too: “If you pour water on someone who has just died of dehydration, they will not sit. – becomes an animal that walks, feeds, breeds.” Known as “cryptobiosis”, this is the third stage between life and death.
There are more viruses in one liter of seawater than in humans. But are they alive? They certainly evolve like other forms of life, as we see from the new forms of COVID-19 that are constantly emerging. But many scientists say that, strictly speaking, they are not alive, because they need the cells of another creature to multiply. According to Zimmer, they “cross the edge of life”.
Carol Cleland, a philosopher working with NASA’s Astrobiology Institute, told Zimmer that the search for a definition of life is in vain. Definitions serve to organize concepts. But life is not something that can only be defined by a combination of concepts: “We don’t want to know what the word Life Means to us,” she says. “We want to know what life is like.” Is“
Instead, he argues, scientists should work toward a theory that explains life; Non-scientists might be surprised that one doesn’t already exist.
A new theory explains life as a special way of putting things together. This is called the “assembly principle”, and essentially it counts the number of steps it takes to build something. A simple molecule may require only one step to be formed from atoms, but a living organism needs much more than that: materials made by living things require more than 15 steps – they are excellent. make form. are complex. This may reveal the difference between random chemistry and living things: “Life is a state of matter that can form things spontaneously, with multiple assembly steps.”
One of the originators of this theory of life is chemist Lee Cronin, who developed a simple Experiment To demonstrate assembly theory at the University of Glasgow. He has built a robot that can perform thousands of experiments by mixing different chemicals in a Petri dish: the raw material for creating life, he hopes.
He calls it Dropfactory. The robot is “programmed with curiosity” and learns from experiments, creating droplets in petri dishes: “These living droplets, these fickle droplets of active matter, are not life. But they may be a dry race to make it.” are.” Huh.
The idea is that a few droplets will trigger complex reactions, creating new compounds that can store information – a state of life. Cronin’s drops may even be declared alive one day. “I’m pretty sure we’ll have solved the problem of the origin of life in the next few years,” he says. “But then everyone would go: ‘Oh, that was easy.'”
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Life’s Edge: The Search for What It Means to Be Alive by Carl Zimmer is published by Picador (£20). Order your copy here to support Guardian and Supervisor GuardianBookshop.com. Delivery charges may apply.