Harry Thompson in The London Times:
This Thing of Darkness — three years in the writing — came out last week and is a true story concerning the voyage of the Beagle and the friendship between Charles Darwin and Captain Robert FitzRoy, whose journey together round the world, whose discoveries and whose increasingly acrimonious debates laid the groundwork for Darwin’s theory of natural selection. In those days people routinely took the most enormous risks with their lives. FitzRoy and Darwin quite happily clambered aboard a Royal Navy “coffin brig” for many years (a little barrel-shaped production-line surveying packet so nicknamed because a quarter of their number never came back). Their arguments took place in a tiny storm-tossed cabin no more than 5ft square, the single oil lamp creaking in its gimbal, their shadows by turns retreating and advancing as they boxed each other across the walls.
FitzRoy, a brilliant sailor and one of the great unsung heroes of British history (he also invented weather forecasting along the way), was a rising star, a devout Christian who had come to believe that God’s ordered universe is just that: a sort of huge machine where everything is done to a purpose, where all natural phenomena might theoretically be predicted, in which all men have the right to live side by side in absolute equality, regardless of colour.
Darwin, his “gentleman companion”, was by contrast a relative nobody, a parson-in-waiting who had tagged along to help FitzRoy find geological evidence for the Old Testament. Increasingly his discoveries drew him towards a vision of an alternative universe, a merciless world of random cruelty in which the strongest won out by right (the strongest, of course, being middle-class white men from middle England).