a layout designed to circumvent jamming typewriter keys

BTW, the supposed origin of the QWERTY layout is uncertain, and the story about it being based around avoiding adjacent bigrams has been called into question often enough (PDF, see pg. 169ff). You can see there plenty images of typewriters that had O next to U still (I was left of U), which if you think about bigrams makes no sense as especially back then it was one of by far the most common ones.
The supposed slowdown is also false as explained in the PDF, as early typewriters were used to receive morse-code, and could type at 60-80 words per minute while the best morse senders capped at ~30, meaning that no slowdown would have been perceivable anyways.

One proposed origin could be that the early still-not-quite-there developments were based on most people using 4-8 fingers to type not all 10, and alwys the inner fingers and discarding the outer ones.