All starters evolve at later levels, this is for balance. They've been beefed up a little.
Evolution Levels:
Bulbasaur lv26, Ivysaur lv42, Charmander lv26, Charmeleon lv46, Squirtle lv26, Wartortle lv46, Chikorita lv26, Bayleef lv42, Cyndaquil lv24, Quilava lv46, Totodile lv28, Croconaw lv40...