[Advaita-l] Varnashrama dharma begins in treta yuga?

[Santosh Rao]

Namskara,

in bhagavata purana 11:17:10 Krishna tells uddhava that in satya yuga, only
one social class was present. He says further that it wasn't until treta
yuga that the 4 varnas emanated from the purusha. Is it then correct to say
that varnashrama dharma begins only from treta yuga onwards? How exactly is
this to be understood?

Thanks