Anderson was the Shooto 167 pound champion when he was 27 years old so anything is possible. A lot of people don't realize that UFC originally signed Anderson back in 2001 to fight for the 170 pound welterweight belt then held by Canada`s own Carlos Newton at UFC 34, Silva was replaced for the title mach by Matt Hughes who went on a long run as UFC 170 champ after defeating Newton in controversial fashion. The Silva vs Newton fight eventually happened at PRIDE 25 in Japan.
And yes, Anderson was a stringbean early in his career, he deliberately packed on weight in 03-04 when his mma career was stalled and he was planning to switch to kickboxing so he would be heavy enough to compete in K-1.
I have followed Anderson`s career since 2000; he`s always been the best, even though he hasn`t always been widely recognized as such.
Anderson fighting at 170:
http://youtu.be/0gZWKUsvdd0
http://youtu.be/x0NgwbloGks
http://youtu.be/x7sXks7Ocmo
Anderson vs Hayato Sakarai for the Shooto 167 pound belt in 2001:
http://youtu.be/aH7pjZqo7Og