Fixes unfair birth quality penalties for modded races with non-human lifespans.
With this mod, long-lived races (e.g., Miho, Milira, Dragonian) will now keep the +50% birth quality bonus for centuries, while short-lived races will start gaining bonuses much earlier to match their rapid maturity.
As shown in the graph, with this fix, the peak birth quality bonus (+50%) for long-lived races can last for centuries.
Note: Example races shown share the same adult maturity age as humans (18 years). Races maturing earlier will have earlier peak birth quality years.
The Issue
In Biotech DLC, the birth quality bonus from the mother's age uses a fixed curve designed for humans:
Source: Reproduction - RimWorld Wiki[rimworldwiki.com]
This creates an issue for non-human modded races with different lifespans. For example:
- A race with a 1000-year lifespan only hits the birth quality bonus peak at age 20-30; meaning any world pawn spawned past this age receives an unintended penalty, even if they're still biologically young relative to their life expectancy.
- A race with a 40-year lifespan has its peak at the same 20-30 range, meaning they only get the full bonus during later age.
The Solution
This mod dynamically scales the mother's age curve based on each race's:
- Adult maturity age (when they become adults)
- Life expectancy (total expected lifespan)
The prime birth quality window is now proportionally adjusted so every race experiences the same relative bonus curve.
Detailed calculation logic can be found in the github README: https://github.com/SaltGin/BirthQualityLifespanFix/blob/main/README.md
Mod Settings
This mod currently includes these optional settings you can toggle:
- Lifespan Factor Affects Peak (on by default) - If a pawn's lifespan is affected by lifespan factor[rimworldwiki.com] stat (e.g., from cell instability genes), the peak birth quality window will adjust accordingly.
- Prevent Short Lifespan Penalty (off by default) - Guarantees a minimum 10-year peak birth quality window for races with lifespans shorter than humans. Enable this if your short-lived race has an unusably narrow window.
- Ageless At Peak Birth Quality (off by default) - Pawns with the Ageless gene will always be treated as within peak birth quality age.
Compatibility
Automatically works with any modded race. Safe to add/remove mid-save.
No known incompatible mods so far.
This mod uses the least invasive approach I could think of to handle this mechanic. Mods that adjust curve values or add quality bonuses should remain compatible. However, mods that completely replace or heavily modify the birth quality calculation logic may conflict.
If you encounter any issues, please let me know in the comments/posts.
Source: https://github.com/SaltGin/BirthQualityLifespanFix
