In 1838, Charles Darwin wrote some notes, to himself, about marriage

If Marry: 

Constant companion & friend in old age who will feel interested in one

Someone to take care of house

Charms of music & female chit-chat

Intolerable to think of spending one’s whole life like a neuter bee 

Object to be beloved & played with

A nice soft wife on a sofa with a good fire & books & music perhaps 

If Not Marry: 

No children - arguments for and against this

No one to care for one in old age

Free to go where one likes and enjoy conversation of clever men at clubs

Perhaps quarrelling

Less money for books etc

Cannot read in the evenings 

Marry Q.E.D.

One year later, in 1839, he married his cousin, Emma Wedgwood.