Life’s Edge by Carl Zimmer review – what does it mean to be alive?

This profound meditation on the science of life explores where it has come from and how it evolves

At a medical research laboratory in California, Alysson Muotri has used chemistry to change skin cells into neurons, which have multiplied to form organoids" - globes of interconnected brain cells. The organoids can expand 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 even wonders whether they could one day become conscious.

Such unsettling scientific creations, unknown even 10 years ago, challenge our ideas about life, raising questions for bioethicists and philosophers. As the American science writer Carl Zimmer writes: Brain organoids are troubling because we feel in our bones that making sense of life should be easy. These clusters of neurons prove that it's not."