The idea that competitiveness, greed and aggression are innate in boys, and that the expression of these traits is normal, has been with us for centuries.
For the most part human civilisation has existed in communities where the males made the rules. It is no surprise that those making the rules made them to suit themselves.
The first reference I can find to ‘boys will be boys’ is in a series of letters between a British couple, Richard Griffith and Elizabeth Griffith, prior to their marriage in 1751, published in 1770:
Heaven bless them both! – though Jack is under a Cloud with me at present – but Boys will be Boys – and I endeavour to make my philosophy like yours – severe only to itself.
That citation doesn’t explicitly explain the meaning of the phrase as we now use it. The earliest example in print which does that is from the Vermont newspaper the Federal Galaxy, February 1799::
When the building is burnt, the carelessness of boys is a ready standing excuse for the matters – and it is in vain to expect that any corrections or admonitions given to the schollar will preserve the buildings.
Boys will be boys – and we have all been boys and recollect the thoughtlessness of our youth.
There was an equivalent ‘girls will be girls’ expression in Victorian England. This followed the reasoning of the nonsensical ‘boys are snips and snails and puppy dogs tails’ and ‘girls are sugar and spice and all things nice’.
The English writer Thomas Lister used ‘girls will be girls’ in that context in his novel Granby, 1826:
“She really used him rather ill.”
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How so?”
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Why, girls will be girls. They like admiration.”