Nature writing has come a long way since the day in 1845 when Henry David Thoreau packed his bags and wandered out to his cabin in Concord, Massachusetts. ‘We need the tonic of the wilderness – to wade sometimes in marshes when the bittern and the meadow-hen lurk,’ he intoned in Walden, the account of his two-year stay. ‘We can never have enough of Nature.’ Most eco-theorists nowadays would raise an eyebrow at this. If, as Thoreau implies, we can choose to step in and out of nature at any moment, then we are necessarily distinct from it.

We might see the Scottish writer Martin MacInnes’s three novels as a linked body of work designed to rebut this sentiment, to collapse the boundaries between the human and the non-human. MacInnes has been banging this particular drum since the publication of his 2016 debut, Infinite Ground, a postmodern murder mystery in which fungi colonise the human brain and bodies are subsumed into the landscape. His latest book is by far his most ambitious attempt yet to novelise his thesis. A 500-page science-fiction epic that takes us from the sea’s hadal zone to the furthest reaches of the solar system, In Ascension is conceived, as MacInnes writes in an author’s note, ‘as an attack against the assumption that humans are somehow “outside the (earth) system”’.

The mouthpiece for this idea is Leigh, a Dutch scientist whose postgraduate research on algae and their links to early lifeforms leads her, early on in the book, to a placement on an Atlantic submarine, Endeavour, tasked with exploring a newly discovered sea-floor vent several times deeper than