Jayne. The man they call Jayne. He robbed from the rich and he robbed from the poor. He stabbed people in the back and he gave 'em what for...
On the surface... Jayne is an orc. Brutality and sex and a limited comprehension of most things is all he seems to offer the verse. Oh, he's got some loyalty to his clan... he cherishes his mom's gift and he supports her through brigandry.
But we love him. We love an orc.
Brutality. "Pain is scary." "Tell us where the stuff's at, so I can shoot ya." He is a master. His collection of weapons is impressive. He ability to shoot and brawl are depended upon by Mal. He won't flinch from torture. But his brutality extends beyond mere violence. He is brutal to society. He likes intimidation and mean spirited comments backed up by the threat of intimidation. And he likes crime... He likes obtaining money through the use of his skill set... coercion and violence.
Sex. "I'll be in my bunk." "I could stand to hear some more." "I could get nekkid." "Can I start getting' sexed already?" Jayne's testosterone level is off the charts. He's good to go all the time. But it's highly interesting to note that he does not ever mix sex and brutality. So... he's not actually an orc.
Mental ability. "You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here!" "Well, don't say it!... Oh, well now I know that." "Well, I don't like the idea of someone hearin' what I'm thinkin'." Jayne's a classic thug. He's not dumb, just uneducated... and he's never developed his mind because his muscles could get everything he wanted... sex and money. And yet, his intelligence for crime, escape, fighting, avoiding fighting, betrayal.... i.e. self-survival is extremely high. In a dog, we'd call it instinct...
But Jayne is neither a dog nor an orc...
He's survived the 'verse so far by knowing when to run, fight, quit, join, and switch sides. At the final fight in Serenity, Zoe asked, "Do you really think any of us are going to get through this?" To which Jayne replied, "Well... I might." He'll do what he has to... because that's what he's done his whole life.
It was plain fairly on that it was not a question of if Jayne would turn on Mal, but when. And I was stunned when it was sooner than later. And that led to a chain of events that changed Jayne's outlook.
Jayne knew Mal should have killed him. Jayne finally got caught... and was given a second life.
He started sharing his wealth with the crew. For the rest of humanity, we know belonging to a community means sharing because we care. Jayne had to be surprised that the crew was nicer to him. He also liked the fact that he now had some respect from Simon even if it was based on a lie. I think this taste of community led him to join in the assault on Niska. Jayne started to care when he found out the benefits of sharing. After Simon figured the whole thing out, he healed Jayne before letting Jayne know that he would never turn on him. I know Jayne was part of the crew, but not the community.... while Simon was part of the community, but not really part of the crew. Simon's mercy showed Jayne he could join the community if he wanted.
Also, River's threat impressed Jayne thoroughly.
So, in addition to violence, libido, and ignorance, Jayne had something new to offer the 'verse... gratitude to his community and loyalty to his captain.
On a different note...
I do think that Whedon broke the story when Mal pardoned Jayne. Mal's mind was changed when Jayne said, "Don't tell 'em what I done." It did not seem enough for me... Was Jayne remorseful? Did Jayne mean the Tams or the entire crew? How could Mal know Jayne would not harbor a grudge, but be grateful? Jayne had earned death. He knew it. He'd always knew that someday he might get caught and die a violent death. But Whedon kept Jayne alive and I enjoyed the rest of the story... yet I always think Jayne should have died.
