Like any business rivals, comic book publishers have routinely "borrowed" popular characters and concepts from their competitors. However, there were a handful of times when publishers created characters that were so similar, yet appeared so close together, that one publisher copying the concept from the other was a virtually impossibility.
We've seen this "superhero synchronicity" with Marvel's X-Men and DC's Doom Patrol. We saw it again with the Red Tornado and the Vision. Now, as we trade the world of bright colored costumes for the murky mysteries of the swamp, let's consider the question:
Of course, before we look too closely at these two goop-encrusted gentlemen, the concept of the supernatural swamp man predates both of them by about thirty years!
As the "template" for all shambling muck monsters to come, Theodore Sturgeon's 1940 short story "It" featured a man who died in the swamp, but rose again as a vengeful half-man, half-rotting vegetation creature. Obviously inspired by Sturgeon's swamp man, Hillman Periodicals created the first comic book swamp man named The Heap in 1942. Starting out as a minor villain, the Heap soon became a recurring character in Airboy Comics until the title was canceled in 1953.
Another notable swamp-bred creature of the Golden Age was Solomon Grundy, whose name was taken from a 19th century nursury rhyme. Making his debut in All-American Comics #61 (1944), Grundy became a recurring villain of the Justice Society of America...and continues to plague them today!
Now that we've established that the shambling swamp monster has a rather long pedigree, let's flash forward to the late 1960's and early 1970's, as American comic books reflect a new horror craze sweeping the popular culture. Readers were buying supernaturally-themed comics as fast as DC and Marvel Comics could crank them out, which spawned a coincidence as mysterious as the swamp itself.
Cover dated May of 1971, a Marvel anthology named Savage Tales #1 hit the stands (click the cover images for a larger view). One of the black and white magazine's short stories featured the tale of biochemist Ted Sallis, who desperately injected the "miracle drug" he developed into his own system to protect it from sinister forces. Pursued into a swamp, Sallis ends up drowning...but was later revived by a combination of his formula (and supernatural forces) into a creature known as the Man-Thing!
Cover dated July of 1971, DC's House of Secrets #92 featured the story of Alex Olson, an early 20th century scientist who was caught in a lab explosion (triggered by a treacherous lab partner) and dumped into the swamp. Revived by a combination of chemicals and supernatural forces, Alec transformed into the monstrous Swamp Thing!
At this point, you might be thinking "Hey, Man-Thing beat Swamp Thing by a full two months!" Ah, but remember, in the comic book biz it typically takes three to four months to create and print a comic book from start to finish...so the two month gap between Savage Tales #1 and House of Secrets #92 tells us that DC wouldn't have had a prayer creating a Man-Thing knock-off in such a short period of time.
Nearly a year later, Man-Thing made the jump to color comics and battled Ka-Zar in Astonishing Tales #12 (June) and #13 (Aug), followed by a starring role in the Adventure Into Fear title beginning with issue #10 (October of '72).
October of 1972 also marked the first issue of the Swamp Thing series. Encouraged by the sales of his debut appearance, DC commissioned the same creative team (Len Wein and Bernie Wrightson) to update the character's origin to the present day. Obviously, DC was now fully aware of Marvel's Man-Thing, since the updated Swamp Thing origin made Alec Holland (previously "Alex Olson") a "a scientist working on a secret bio-restorative formula", who was murdered by a gang of bad guys and later restored to life by his secret formula.
Further muddying the already muddy swamp water was the fact that, in between Swamp Thing's first and second appearances, his co-creator Len Wein wrote the story for Man-Thing's second appearance, originally slated for Savage Tales #2 (but ultimately published in the aforementioned Astonishing Tales #12).
Confused yet? Good...because now it's time to introduce yet another element of confusion to the swamp man mystery! Hitting the stands in March of 1971 (two months before Man-Thing's debut in Savage Tales #1) was Skywald Publications' Psycho #2 featuring a revival of....THE HEAP! (Remember him?)
It looks like supernatural swamp men were on plenty of people's minds during the winter and early spring of 1971!