The games cabin said Far Cry Primal receives a day one update that’ll run you around 591.6 MB on the PS4 (possibly same on other platforms)
Here’s the patch notes:

Patch 1.01

Stability and Performance
A. Improved performance and stability.
B. Improved lighting and exposure Weapons and HUD
A. Fixed timing specific visual glitches on weapon HUD.

Wildlife and AI
A. Fixed low repro companion navigation issues.
B. Fixed various edge case animation issues.
C. Improved mammoth visual on object destruction.
D. Improved animal behaviour when triggering a fight.

Design and progression
A. Tweaked and balanced XP rewards.
B. Fixed damage ratio after using a recipe
C. Improved overall balancing for economy and buffs.

Gameplay
A. Fixed timing specific issues with lit weapons during animations.
B. Fixed issues with lit weapons during cinematics at night
C. Improved player navigation and small collision issues.
D. Improved camera transition and minor collision issues on cinematics.
E. Tweaked NPC spawn locations.
F. Improved companion behavior.