 It has enjoyed self-government since the division of the Duchy of Normandy in 1204.The earliest evidence of human activity in Jersey dates to about 250,000 years ago (before Jersey became an island) when bands of nomadic hunters used the caves at La Cotte de St Brelade as a base for hunting mammoth and woolly rhinoceros.Rising sea levels resulted in it has been an island for approximately 6,000 years and at its current extremes it measures 10 miles east to west and six miles north to south.