Listening to podcasts the last couple of years I heard a couple of ways in which 10K is significant in human history.
Around 10,000 years ago civilisation began as the development of farming meant that large groups of people were able to stay in one place indefinitely without exhausting the food supply.
And in pre-industrial Britain 10K was about as far as an adult was prepared to walk to reach their daily employment.
Not quite as significant, but definitely more surreal is me running 10K this morning, after beginning C25K at the end of August, and being on the IC two weeks ago.
My slowest ever pace by some margin, but I don't care. My objective was 10K by Christmas, and amazingly - to me - I made it. A through the looking glass moment!