When Jane Goodall first witnessed Gombe chimpanzee David Greybeard fishing for termites by manipulating blades of grass in 1960, the line between humans and other animals suddenly became blurry. Tool use was no longer uniquely human, leading Dr. Louis Leakey, Jane’s mentor, to famously say, “Now we must redefine tool, redefine man, or accept chimpanzees as human.”
I remember that the discovery of chimpanzees making and using crude tools was considered revolutionary back in the 1960s.
I note that if enough biologists and others remembered what they read in various sources they would not have been so shocked.
Charles Darwin wrote in Descent of Man in 1871:
The tamed elephants in India are well known to break off branches of trees and use them to drive away the flies; and this same act has been observed in an elephant in a state of nature.
Darwin provided a reference to a publication from 1871.
A few years ago I read online a 19th century book for "young future scientists" - kids - which I think was about elephants. And it mentioned that elephants were observed to take twigs in their trunks and use them to clean gunk out of glands in the sides of their heads.
J.R.R. Tolkien, in The Two Towers, Book Three, Chapter III, "The Black Gate is Closed" has a discussion of oliphaunts, the prehistoric elephants of Harad. Sam says:
...But I've heard talk of the big folk down away in the Sunlands. Swertings we call 'em in our tales; and they ride on oliphaunts, 'tis said, when they fight. They put towers and houses on the oliphaunts backs and all; and the oliphaunts throw rocks and trees at one another...
And I don't know if Tolkien read somewhere about elephants throwing things, but elephants have been observed throwing stuff.
And elephants have been observed performing those and many other types of tool use in the decades following Goodall's discovery: Weapons, Ear Cleaners, and Fly Swatters: Elephant Tool Use
So elephants are one example, out of many, of how unobservant biologists would have been to be as shocked by the discovery of chimpanzee tool use as I seem to remember them being.