杏吧原创

Alive
Melanie Challenger, (UK); Penguin Random House (US)

When you think about it, being alive is a really strange state of being. The vast majority of the matter in the universe is lifeless hydrogen and helium, rocks and dust. Yet, somehow, here we all are: millions of species of microbes and plants and animals, all respiring and eating and trying to reproduce, some of us squawking, and some sleeping, all of us eventually dying. When we consider the sheer implausibility of life in the cosmos, wrote biochemist Jacques Monod in Chance and Necessity, 鈥渨e should feel strange and a little unreal鈥�.

Actually defining what life is has proved extremely tricky, so we tend to fall back on metaphors. One of the most prominent of the past century or so is that living organisms are machines. They have components, moving parts, complicated chemical signalling pathways to make things happen. In this view, even the brain is a kind of computer, one that responds to stimuli and performs calculations. Moreover, the machines have a purpose, shaped by evolution. In The Selfish Gene, Richard Dawkins argued that organisms are machines that exist to pass on their genes, that living things are just complicated by-products of genes copying themselves.

In Alive: The hidden intelligence of the living world, writer and broadcaster sets out to completely demolish this line of thinking. Living beings aren鈥檛 machines, she argues, nor do they exist purely to pass on genes. Instead, what defines living beings is agency and purpose. 鈥淟ife-forms pursue goals because they are alive, and life is, by its nature, purposeful,鈥� she writes.

The idea that organisms have goals and purposes is 鈥渢he most obvious鈥� answer to what life is, and also 鈥渢he most curiously neglected鈥�, argues Challenger.

From Ren茅 Descartes onwards, the idea that non-human animals have goals, feelings and even thoughts of their own has been treated with scepticism by zoologists and psychologists. Animal behaviourist C. Lloyd Morgan famously argued that we should never interpret an animal鈥檚 behaviour as evidence of a higher psychological process if it could also be explained using a simpler process. 鈥淢organ鈥檚 Canon鈥� went on to guide a century of research 鈥� even though it isn鈥檛 obvious what is meant by higher and lower psychological processes.

Challenger鈥檚 suggestion is that we can鈥檛 escape the idea of a self, something with agency, to explain the behaviours of living organisms. It鈥檚 just that we have removed it from the organisms themselves: either in the form of some separable soul or essence, or a set of genes that determine how organisms behave for their own ends. 鈥淏oth soul and gene are described as self-like agents, the true initiators of the acts of a life-form,鈥� she writes. In these views of the world, 鈥渓ife-forms themselves are marginalised鈥�.

Instead, we should see living beings as 鈥渟elf-determining鈥�, she argues: 鈥淟ife-forms use energy to remain locally discontinuous with the environment鈥� and what is phenomenal about this act is that it is self-generated.鈥� Challenger develops this idea over six chapters, exploring homeostasis (the mechanisms by which organisms maintain their internal environment), sensory perception, consciousness and intelligence. These can all be explained mechanistically using cells, molecules and physical forces, but they only make sense in the light of the whole organism.

Challenger is trying to reclaim the active nature of life. Even organisms like plants that don鈥檛 have brains, and therefore may have little or no conscious experience, are still responsive to their environments and act with purpose for their own ends. There is nothing automaton-like about animals or plants: that鈥檚 why the automata of sci-fi are so deeply, gut-level disturbing in contrast.

Cards on the table: I think Challenger is mostly right. The gene鈥檚-eye view of evolution misleads us because it gives too much agency and power to the genes. In reality, genes aren鈥檛 master controllers of cells, nor do they contain blueprints for entire organisms: they are part of a web of interacting systems that underpin life. Genes are important in cells, but are no more in control than any other component.

I can imagine two readerships for Alive, with drastically different responses. One valid reaction is that this is blindingly obvious. It鈥檚 transparently clear that animals act with purpose, out of sheer vitality and hunger, and joy and will to live. The thing is, the idea of life-as-automata has acquired a lot of power. Challenger argues that it developed alongside the rise of industrialised farming, which exploits and mistreats animals on a staggering scale: if you don鈥檛 quite believe animals are sentient, it鈥檚 easier to accept this globalised abuse. Today, synthetic biologists often treat life as, literally, programmable matter: they are the second readership, who will probably find Challenger鈥檚 position difficult to accept.

I do think Challenger has one major difficulty: her argument focuses on individual organisms. Whether it鈥檚 a bacterium or a shark, each acts for its own purposes. She is right to stress that individuals have great agency, but finds herself having to neglect or downplay the fact that individuality is fuzzy, and that individuals can only survive in ecosystems.

Consider your body. Yes, you are you and you act for yourself. But you are also home to trillions of microbes, which influence you, and some of which you couldn鈥檛 survive without. Challenger insists on treating the microbes as distinct from you; each follows its own goals and it just so happens they mostly coincide with yours. But this is, I think, to oversimplify.

She has a similar problem with eusocial insects, in which a single individual reproduces and the rest of the nest is sterile. Eusociality is one of those phenomena that does need explaining at the level of genes, at least to some extent. Challenger doesn鈥檛 like labelling eusocial ant colonies as 鈥渟uperorganisms鈥�, but her justification is weak. She argues that worker ants are still capable of rebelling against the system, so they aren鈥檛 fully integrated, but the same could be said of some of our cells 鈥� that鈥檚 why we get cancer.

My one other caveat is that her high-flown metaphors and philosophy-speak won鈥檛 be for everyone. Here鈥檚 an example: 鈥淭he activities of organisms are the literal embodiment of what we take the features of our world to mean, radically determined by the organisms themselves.鈥� If you have a low tolerance for this, you may find the book tricky, but the effort is worth it: Alive will help you see the living world afresh.

Michael Marshall is a science writer based in Devon, UK

Three more great reads on the meaning of life

by Carl Zimmer

Despite hundreds of attempts, we still don鈥檛 have an agreed definition of life. Science writer Carl Zimmer explores the many tricky edge cases, like viruses, which blur the line between life and non-life.

by Rowan Hooper

An ideal companion piece to Alive, Rowan Hooper (New 杏吧原创鈥榮 podcast editor) shows us the importance of understanding life as a community. Individual organisms are only part of the story.

by Kevin Mitchell

Neuroscientist Kevin Mitchell argues that living beings are 鈥渁gents acting with purpose鈥�, not mere machines responding to stimuli. His ideas were among the inspirations for Melanie Challenger.

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