It’s always irked me the way Sims 4 genetics are determined. Skin, hair, eyes, etc are all a 50/50 chance between the parents. The only exception is occasional skin blending. I’ve even gone to the point of not having mixed racial couples because it annoys me so much! Yes, I know, I obsess over the strangest things in this game that most people couldn’t care less about. But, since I’ve played Sims 2 and 3 almost exclusively for several months I’ve become fascinated by genetics.
Credit for all of the following information goes to other simmers! Mostly Laura from Postcards from Sierra Nova… yet again. I used her Sims 4 birth roll as a basis for my own that she was so wonderful to have a download link to in her own genetics post. Another source was a Sims 2 forum post on The Sims Daily by Simmerville called Freckles or not? Glasses or not? Next is a Sims 2 Sullivan Sims article Expanded Genetics. There is an article Height Meets Genetics on the Sims 2 Millwood blog. If you look at my genetics roll there is a “just in case” roll for if one day I decide to be wild and crazy and add height sliders. There’s also a Millwood article Dealing with Death. Not a happy-happy topic but Laura at Sierra Nova also has a roll for it and though it will likely take forever for my simmies to age I thought I’d add it to my ever-increasing rolls. Another short Sims 2 note on genetics is Thread&Sandpaper’s Bonus Genetics rule. All of this is just the tip of the iceberg of the research I have done recently on different topics!
Okay so! Here we go! Are you excited? Are you thrilled that I have found a way to make the game even more complicated than the personality profiles? No? Just me? Oh well, it’ll be here in case one day someone asks what the heck I’m talking about! My birth roll starts with their personality profile. So I know who the child will inherit traits from or if they will just be random like so:
An average roll is an average of the parent’s numbers. I always round up to make it easier. I don’t want to go as far as to mess with decimal points! I do this roll for six of the seven scales. Flirty gets it’s own individual roll because I feel like that’s not a genetics type thing. Here’s my teen flirty roll:
*teen flirty scale
0 auto unflirty
1 no roll
2 no roll
3 no roll
4 no roll
5 no roll
6 auto romantic
7 auto romantic
8 auto romantic and alluring
9 auto romantic and alluring plus roll
10 auto romantic, alluring, shameless, beguiling, and great kisser
The numbers you see at the ends in brackets are the weight that each one has. So it is more likely a child will roll a 5 than a 0 or 10. This is a personal choice. I don’t want a large number of my sims to be unflirty or players. I’m thinking of removing the auto romantic from 6 and 7 now that I’ve got a mod in that seems to really take that flirty mood seriously. Moving on!
closer to mother 
average between 
closer to father 
Again, my own personal preference. I would like an average between the parent’s skin tones more often than not but realize this doesn’t even always happen in the real world.
mother: black 
father: black 
grandmother paternal: black 
grandfather paternal: black 
grandmother maternal: blonde 
grandfather maternal: black 
mother: brown 
father: black 
grandmother paternal: dark brown 
grandfather paternal: alien 
grandmother maternal: green 
grandfather maternal: dark brown 
Okay, these two I change on a case by case basis this is taken straight from Laura’s rolls from Postcards from Sierra Nova. She also listed this nifty chart for weighing each color:
#hair– black  brown  blonde  red 
#eyes– dark brown  hazel/light brown  gray/green  blue 
So, I would change the color and weight number each birth roll. My current one doesn’t have grandparents, that’s why this is straight from hers. I’m not into enough generations to go that far. Or any generations at all… most of this has all been done with test families that I age up right away. But exciting stuff when I do! Here’s my height roll just in case I decide to go all out and try to use one of those mods one day:
closer to mother 
average between 
closer to father 
Laura’s has actual feet and inches and, again, adds grandparents but at this time it’s just something I’m sticking at the bottom of their profiles for future reference. Okay, let’s see. My next part is different from hers. A brand-new out of CAS sim’s roll (what I call a genetic string) looks like this:
There are three different variations of hair: HH=a lot of hair, in a man this would mean long hair and body hair (CC!) and he wouldn’t go bald ever. Hh or hH would be average hair and they may lose some hair later in life. hh is short hair, no facial hair, very little body hair and fairly early balding. Out of CAS I’m just using it to determine hair length for women but later on when they have kids they can pass the dominant or recessive genes on so it has much more impact.
Glasses next! I almost never give my sims glasses. Did you know almost all of the population needs glasses to some extent sometime in their lives? Like 70% or something! Moving on… just like with hair GG means glasses desperately needed. Gg or gG would mean that at some point, probably later in life they will need glasses. And gg means no glasses at all! Now, how does this work? Have you noticed that in the Goth family Bella and Mortimer don’t have glasses but both Cassandra and Alexander do? Both of them must have carried a dominant gene Gg or gG and passed to both kids GG! Fascinating, I know.
A bit of fun with freckles and beauty marks. So many sims are rolling them I need to get more CC ones! FF is lots of freckles same with BB. Ff/fF and Bb/bB mean just a little. I’ve been giving the kids the same beauty mark as their parent that they inherited them from since there aren’t many options. Obviously, ff and bb mean none.
Note: Once again, I’m having to split one of these in half! I got to the end of this and it was over 2,000 words! So, I’m putting one little last part here and the rest of the explanations will be in a second part. Grr…
Okay, I got to this point and this was already 1700 words! (before cutting part out) Yikes! And I read over it and realized I hadn’t even told you how I determine kid’s genetics based on their parents! Sheesh. Here’s from one of the experimental families I created while figuring this out:
Darrel Wiggins: Hh-gg-ff-bB-fm
Della Snyder: hh-gg-ff-bb-fm
Suzanna Snyder: hh-gg-ff-Bb-fm
Alton Wiggins: Hh-gg-ff-bb-fm
If it is dominant and recessive like Darrel’s Hh I roll for it. I don’t know how it works in the real world but this is how I do it because whoever I learned this from did it that way and I like it. As you can see, Alton got that H. If they are the same like the two recessive’s in the glasses gg is passed just as is. The daughter got the father’s cheek beauty mark. And, like I said, I have no idea how I’m going to do the feminity/masculinity. I might just scrap that roll in the birth roll and just keep it for CAS sims to keep from doing the same thing I’ve always done.
(The whole femininity/masculinity explanation is in the removed part as well as how I do the random rolls. Sorry!)