The narwhal is found predominantly in the Atlantic and Russian areas of the Arctic Ocean. Individuals are commonly recorded in the Canadian Arctic Archipelago ,  such as in the northern part of Hudson Bay , Hudson Strait , Baffin Bay ; off the east coast of Greenland ; and in a strip running east from the northern end of Greenland round to eastern Russia ( 170° East ). Land in this strip includes Svalbard , Franz Joseph Land , and Severnaya Zemlya .  The northernmost sightings of narwhal have occurred north of Franz Joseph Land, at about 85° North latitude.  Most of the world's narwhals are concentrated in the fjords and inlets of Northern Canada and western Greenland. They are able to survive in depths of up to 1,500 m (4,920 ft) below sea level. 
Depression may have started in our hunter-gatherer past (the way we have lived for at least 90% of our history). When an aging hunter (who would have been old by his early 30s) began to lose his speed and agility, his feelings of uselessness and alienation from his tribe may have been a prompt for the tribe to rally round and support him. Similar feelings may have haunted the aging female (again, in her 30s) in the face of her declining fertility prior to menopause. Investing in the survival of her grandchildren may have given her a sense of purpose (and an evolutionary edge).