Complex sentence: He came from a humble seafaring background, began his naval career as a boy seaman in 1891, and ten years later joined Captain Scott's Discovery Expedition, 1901--04, as an Able Seaman.
Split into simpler sentences: He came from a humble seafaring background and began his naval career as a boy seaman in 1891. Ten years later he joined Captain Scott's Discovery Expedition, 1901--04, as an Able Seaman.