Not gonna lie, I rejoice in demonising Photoshop for its role in spreading visual lies and viral fakeage. But pinning the blame solely on Photoshop is misplaced: Manipulating photos didn't start with the digital era; the first faked photo dates back to the mid-1800s.
New Statesman chronicles the history of fake or tampered images, which started (as far as we can tell) with Hippolyte Bayard's "Self Portrait as a Drowned Man," in which the photographer manipulated a photo to portray his own suicide-by-drowning, because he felt shafted for not being recognised as one of the inventors of photography. (In a perhaps ironic justice, he may now go down in history as one of the inventors of faked photography.)
Gaze on it above, in all it's fake glory.
Before the invention of Photoshop (which, happy 25th birthday, you fake), image doctoring (or "retouching," to use the less pejorative term) was done by combining two or more negatives, or cutting and pasting multiple photos together, using ancient tools like scissors, glue, and paintbrushes.
As New Statesman writes, this was sometimes done for art's sake, or money's sake; other times, to spread horrible warped images of war. But it wasn't always nefarious — NASA used to hand-assemble composite images in order to, say, study the surface of the moon:
Some have gone down in history, their fakery unknown, as is the case with this famous photo of Teddy Roosevelt riding a moose:
In fact, manipulating photos was common enough throughout the 19th century that as early as 1946 an instructional book was sold detailing how to do it: Shortcuts to Photo Retouching For Commercial Use.
The internet is still, and will forever be, a vortex of misinformation. But it didn't start the trend.