Nestled within the tarmac lasso around London formed by the M25 motorway but feeling very far in time and space from the city, Charles Darwin’s home, Down House, has a spooky quality: it feels like he just popped out. His office is strewn with correspondence and open books, specimens of insects and fossils; his chair, fitted with castors so he could roll around like a Dalek collecting things, still seems to retain the impression of his body. A wooden slide is propped against a wall: Darwin had made it to fit over the staircase, so the children could slide down on cushions. Article continues after advertisement In fact the presence of his children lingers: a mulberry tree growing up the side of the house, gnarled and propped up on stilts, is the same tree the Darwin children would climb down from their bedroom window. There’s a display about poor Annie Darwin, her father’s favorite child, who died aged ten, whose death stripped her father of his last intellectual respect for a Christian god.…