Trust Darwin to take a particularly reductive view of the necessity of love and marriage.

A few months before he asked his cousin Emma to marry him, the naturalist jotted down a few of the pros and cons on the idea of taking a bride. Highlights: "If marry – means limited. Feel duty to work for money." "Object to be beloved and played with – better than a dog anyhow." "Charms of music and female chit-chat... but terrible loss of time."

If you're wondering, Emma said yes. They had 10 children together and remained happily married until Darwin died 44 years later. The full list makes for illuminating reading.