Ernest Shackleton was born on 15 February 1874 in Kilkea near Athy, County Kildare, Ireland, about 46 miles (74 km) from Dublin. Ernest's father was Henry Shackleton, and his mother was Henrietta Letitia Sophia Gavan. His father's family was Anglo-Irish, originally from Yorkshire, England. His mother's family was Irish, from counties Cork and Kerry. Ernest was the second of their ten children and the first of two sons; the second, Frank, achieved notoriety as a suspect, later exonerated, in the 1907 theft of the Irish Crown Jewels.
In 1880, when Ernest was six, Henry Shackleton gave up his life as a landowner to study medicine at Trinity College, Dublin, moving his family into the city. Four years later, the family moved again, from Ireland to Sydenham in suburban London. Partly this was in search of better professional prospects for the newly qualified doctor, but another factor may have been unease about their Anglo-Irish ancestry, following the assassination by Irish nationalists of Lord Frederick Cavendish, the British Secretary for Ireland, in 1882.
From early childhood, Shackleton was a voracious reader, a pursuit which sparked a passion for adventure. He was schooled by a governess until the age of eleven, when he began at Fir Lodge Preparatory School in West Hill, Dulwich, in southeast London. At the age of thirteen, he entered Dulwich College. The young Shackleton did not particularly distinguish himself as a scholar, and was said to be "bored" by his studies. He was quoted later as saying: "I never learned much geography at school ... Literature, too, consisted in the dissection, the parsing, the analysing of certain passages from our great poets and prose-writers ... teachers should be very careful not to spoil [their pupils'] taste for poetry for all time by making it a task and an imposition." In his final term at the school he was still able to achieve fifth place in his class of thirty-one.
Shackleton in 1901, aged 27
Shackleton's restlessness at school was such that he was allowed to leave at 16 and go to sea. The options available were a Royal Naval cadetship at HMS Britannia, which Dr Shackleton could not afford; the mercantile marine cadet ships Worcester and Conway; or an apprenticeship "before the mast" on a sailing vessel. The third option was chosen. His father was able to secure him a berth with the North Western Shipping Company, aboard the square-rigged sailing ship Hoghton Tower.
During the following four years at sea, Shackleton learned his trade, visiting the far corners of the earth and forming acquaintances with a variety of people from many walks of life, learning to be at home with all kinds of men. In August 1894, he passed his examination for Second Mate and accepted a post as third officer on a tramp steamer of the Welsh Shire Line. Two years later, he had obtained his First Mate's ticket, and in 1898, he was certified as a Master Mariner, qualifying him to command a British ship anywhere in the world.
In 1898, Shackleton joined Union-Castle Line, the regular mail and passenger carrier between Southampton and Cape Town. He was, as a shipmate recorded, "a departure from our usual type of young officer", content with his own company though not aloof, "spouting lines from Keats [and] Browning", a mixture of sensitivity and aggression but, withal, sympathetic. Following the outbreak of the Boer War in 1899, Shackleton transferred to the troopship Tintagel Castle where, in March 1900, he met an army lieutenant, Cedric Longstaff, whose father Llewellyn W. Longstaff was the main financial backer of the National Antarctic Expedition then being organised in London. Shackleton used his acquaintance with the son to obtain an interview with Longstaff senior, with a view to obtaining a place on the expedition. Longstaff, impressed by Shackleton's keenness, recommended him to Sir Clements Markham, the expedition's overlord, making it clear that he wanted Shackleton accepted. On 17 February 1901, his appointment as third officer to the expedition's ship Discovery was confirmed; on 4 June he was commissioned into the Royal Navy, with the rank of sub-lieutenant in the Reserves. Although officially on leave from Union-Castle, this was in fact the end of Shackleton's Merchant Navy service.