I recently attempted a challenge that leverages the Sims 3 "roll the dice" feature of genetic inheritance. In this challenge you start by creating a Sim with a custom hair color and custom eye color. Ideally something fun and unusual. (I chose turquoise hair and salmon-y orange eyes). Then you keep having kids with another Sim until you get a kid with the same hair and eye color, and that is your heir.

 

All well and good, right? But my Sims had TWENTY KIDS and NOT ONE OF THEM had the right combination of hair and eye color. Maddening!

 

Earlier Sims games had more complex genetics. For Sims 3 the development team simplified things. For one thing, only a Sim's appearance and hidden traits are inherited. Gone are the days of The Sims, when a baby inherited some of their personality from their parents. (That was a weird thing, anyway.)

 

The inheritance points are all of the facial features that you can control in Create-A-Sim. In other words, wardrobe, makeup, and hair style are not inherited. Most players probably notice the hair and eye color most often. But the nose, eye shape, jawline - all of these features are inherited from one parent or the other, as well.

 

As far as hair color goes, the color that gets passed on is the color that your Sim has when they conceive. This means that if a Sim was born with blonde hair, but you change it to bright green, it's the bright green that they have a chance to pass on to their child.

 

Eye color cannot be changed in-game "legally." However, there is a mod that will let you change the eye color of an existing Sim.

 

Occasionally a trait may "skip a generation," meaning that the game reaches back to the grandparents for one trait or another. I saw this a few times, when a baby was born with dark blue hair. (Their grandmother was an Imaginary Friend doll that I made real, who eventually married the Sim she was assigned to at birth. Kinda creepy, right? I agree.)

 

And finally, we have a pretty whopping 10% "random" factor. This means that each kid has a 1 in 10 chance of getting a totally random trait. In the case of eye and hair color, it's always a "normal" color that the game provides by default. So far as I know, kids won't randomly be born with neon orange hair. (Too bad!)