We calculated pre–supernova evolution models of single rotating massive stars .
These models reproduce observations during the early stages of the evolution very well , in particular Wolf–Rayet ( WR ) populations and ratio between type II and type Ib , c supernovae at different metallicities ( Z ) .
Using these models we found the following results concerning long and soft gamma–ray burst ( GRB ) progenitors :

• GRBs coming from WO–type ( SNIc ) WR stars are only produced at low Z ( Z _ { LMC } or lower ) .

• The upper metallicity limit for GRBs is reduced to Z \sim 0.004 ( SMC ) when the effects of magnetic fields are included .

• GRBs are predicted from the second ( and probably the first ) stellar generation onwards .