It's the year 0200AD. Origins revisted -

Stan Hugill (1906-1992)

“Early shantying was, from what we know, little more than primitive chanting and wild aboriginal cries to encourage the seamen to keep time and work harder, and the fierce elemental yells on a rope known as 'sing-outs' were to be heard even in modern times aboard sailing vessels and occasionally aboard steamers while some sailing ship shellbacks still remain to sing them.
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Many research workers have delved into the past endeavouring to find ancient references to seamen singing at their work, but their efforts have produced little. Undoubtedly early seamen did sing at their work, but I rather fancy that in Greek and Roman galleys, triremes, and whatnot any singing that was done would be at the oars—rowing songs rather than heaving and hauling chants. Miss Lucy E. Broadwood, in the Journal of the Folk Song Society, writes in similar vein. Sir Maurice Bowra, who has kindly waded through many exisitng Greek texts on my behalf, has produced two sailor songs only, both from the Oxyrhynchus Papyri, and of these he writes: 'It is not certain that either of these pieces is a sea-shanty in the strict sense of the word, but the first looks as if it were sung by a group of sailors competing and the second is clearly a sailor's song.'”
[Hugill]

Safe to say Hugill & Longus disagree about the artistic mileage of the oar song.