Goodness sakes, real history is difficult enough to piece back together without the added confusion of intentional fakery. But humans being what we are, fakes exist.
This particular fake, supposedly a mummified mermaid, is mid-19th century in origin. But of course faux relics, etc., were being painstakingly (Shroud of Turin) or not-so-painstakingly (pig bones substituted for saints’ bones) by at least the 12th century.
It’s easy to guffaw, I suppose, about the gullibility of our forebears, who might have thought this proved mermaids existed. But of course this is the same time period in which dinosaur fossils are coming to light for the first time in significant numbers. If those beasties were real, why not this one? She sure looks real.
I find myself simultaneously appalled at the fakery and utterly impressed with the skill and ingenuity that went into creating it.