I recall a recently translated anko that explained the requeriments for having a yukkuri that would go Astron, it was a really complex process to be done artificially but the factory has dominated it, and in Nature it was extremely rare for it to happen.
In that story the whole point was that making "Astron Capable" yukkuris was a good source of steel, since, while rare in the wild, the process was dominated and used to mass produce them to some degree, basically "it's so easy to breed yukkuris that it becomes cost effective." making the long and complex process bearable.
That's rather interesting too. What type of metal would it turn into? Steel? Iron? Most stories just say "metal" but there's so many different kinds.
Now if you can manipulate the composition of the metal, it's possible to even create one that's made out of rare metals that the earth is so sorely lacking. In fact, you can even say that with the correct "guidance", yukkuris can usher mankind into a new era where resources such as rare metals will no longer be fought over because they are so plentiful.
poweryoga said: Yukkuris, is there anything you can't do.
Being actually Easy instead of that being a "informed attribute"? Because let's be honest Yukkuris stopped being easy after that Dick Wizard modifying them or something...