great britain was probably first inhabited by those who crossed on the land bridge from the european mainland. human footprints have been found from over 800,000 years ago in norfolk and traces of early humans have been found (at boxgrove quarry, sussex) from some 500,000 years ago and modern humans from about 30,000 years ago. until about 14,000 years ago, it was connected to ireland, and as recently as 8,000 years ago it retained a land connection to the continent, with an area of mostly low marshland joining it to what are now denmark and the netherlands.