Alter Self allows the caster to assume the form of a small or medium, humanoid-type creature. It explicitly states that it's even adding corresponding abilities:
If the form you assume has any of the following abilities, you gain the listed ability: darkvision 60 feet, low-light vision, scent, and swim 30 feet.
This makes me wonder whether, even though it's not exlicitly mentioned, it will also take abilities away that the casting creature already has - in other words, if the casting creature is a Dwarf (which by default has 60ft darkvision) and turns itself into a human, does it lose darkvision?
Is there any other kind of ability that is taken away by it without being explicitly mentioned by the spell? I'm thinking primarily of racial traits such as the Catfolk's Sprinter ability (10-foot racial bonus to their speed under certain conditions), which seem to make no more sense after altering oneself.