It shouldn’t take 20 panels to tell a joke.
Seems like it’s not telling a joke, but instead making a statement about Humanity.
And to deliver this profound message of “people are inherently distrustful” they needed 20 panels.
They could have done this in one. Have each caveman holding out one hand to pass food and the other hand holding a club behind their backs.
Want to really illustrate the groundbreaking idea that people don’t trust each other? Make a second panel with knights replacing the cavemen and swords replacing clubs, then a third panel swapping in businessmen holding pistols.
If humor wasn’t the goal that’s… fine, but being long-winded in a format based on brevity undermines the message. Using 20 panels guarantees that half of the people who bother to look at the comic won’t finish it. Those that do will probably be bored or even resentful that their time was wasted, making them less receptive to the message.
Not everything needs to be rushed. Sometimes the build up makes the conclusion better. Slow the F down.
If your comic needs to be long form to build tension, that’s a graphic novel.
I find it interesting that your takeaway was “people are inherently distrustful.” While there is truth to that, my interpretation was that “progress can be slow, but it is progress nonetheless.” In this case the “slow” of the message was communicated through the panel count.