Short answer, yes.
When the animals came to the zone, the animals and the mutants learned from each other both when it comes to roles and talents.
But this is totally up to the GM. In my new MYZ campaign, I am using the starter book scenarios to start up. In that, the animals and mutants don't start off as friends. So I let the two "classes" have their own roles now at the beginning. If the players can make the two arks be friends, I will let all the roles and talents be open to "the other class". This will of course affect characters that takes the Jack-Of-All-Trades talent and newly created characters. But this is just me in my new campaign. I my old campaign, I simply described for the players how the animals came to the zone and how they become friends, pregame. So in that campaign, all roles and talents was open from start.
“I’d say thistles, but nobody listens to me, anyway.” - Eeyore