Listen, I love legacy and or generational play—please ignore the fact that I have not made it past Gen 1 in the very many saves I have played over 8 years—and I absolutely adore the main thing that comes with that time of play; watching the genetics play out. I wanna gush about discuss that with the community today. Granted, I am only truly experienced with the pet side of the Sims 3 genetics equation currently, but they're still genetics and they still fascinate me a lot, so I personally will be focusing on them specifically and will let others more experienced with the genetics of the Sims talk about the genetics of the Sims.

Acknowledging that there are people who think that the Sims 3 genetics for pets are awful, I actually have to disagree? To me, and going of my own experience with the Sims 3 and The Red Plumbob's Comparison Videos for the Sims 2 and 4, I think they're the best in the series. I think that the reason people believe the genetics in the Sims 3 pertaining to the pets are severely lacking is that in a vanilla game with no modifications to the code when you breed your dogs or cats and they have more than one baby, one of the babies will be a fucked up clone of the other one. Which means if you bred two dogs of the same fur and body shape i.e breed and they had more than one kid one of those kids was gonna look nothing like their parents, body and fur shape wise. Everyone thought this was a bug within the game for the longest time, and I did too until earlier this year, but it turns out it's not a bug but a feature. Ah, well, this is EA, of course it is.

But after fixing that, I have to say that just sitting and playing with genetics, whether that be in CAP or in-game, has become one of my greatest joys and how I've been having fun with the game while I wait for the day where I can complete my desktop comes. But to touch on the other games it would seem as though in Sims 2 and 4 that when it comes to the pet's genetics there's a lot of Either/Or going on. Does the baby pet inherit mom or dad's exact body shape? Does the baby pet inherit mom or dad's exact coat? Does the baby pet inherit mom or dad's exact eye color? etc, etc, which in my opinion makes their genetics kind of...uninteresting? But hey, if the Sims 2 and 4 genetics for the pet side of the equation is way more in depth than I'm thinking and making it seem please scream and shout at me about how I'm incredibly wrong, I wanna have a conversation about this. Moving on to the Sims 3 and how they handle pet genetics, I love how if you breed "twin" pets, i.e same dog or cat but unrelated to each other, or purebreed pets, i.e same breed of dog or cat, you won't get an exact clone of the parents. They'll be the same breed of course, with the same body and fur shape, but the resulting offspring will have a very slightly different coat, and that absolutely delights me because of the realism of it all. Of course, I understand that that would piss some people off because of the line of thought that if you breed clones you should get an exact clone, but honestly I'm too delighted by the realism to care. Oh and crossbreeding, don't even get me started on how much I love crossbreeding the animals in Sims 3, I think it is done so, so well. I can smash together a German Shepherd and Rhodesian Ridgeback and can look at their offspring and tell if they inherited their mom's skull shape. How fucking cool is that? And I could truly go on and on about crossbreeding, how I think the game handles the inheritance of physical features and how the game does the mixing of coats and creation of new markings, so let me cut this post off here and just say that smacking together two animals with coats that you would swear up and down would clash horrifyingly only to get a surprisingly drop dead gorgeous result is one of the best feelings I ever get while simming.

So in conclusion, I think the pet genetics in the Sims 3 are handled very, very well, minus the whole "bug that is a feature" thing, and can and will write a whole ass essay on it if appropriate. But for this first post I chose to focus on the pet side of the genetics in the Sims 3 because that's what I have experience with, but I wanna hear about the Sim side of things as well, which I'm sure the rest of the community here can share their insight on. I've seen quite a few mods that remove some things, like mutations and the weird inheritable puke green hair, and mods that do a new take on the genetics for the Sim side of things, and even Nraas has an advanced genetics section. So I can only guess that the genetics for the Sims in the Sims 3 aren't done really well, or at least not to the satisfaction of the community. But hey, I've never taken a deep dive into the genetics for the Sims so I can be absolutely dead wrong, feel free to say so if I am! As a last note, I have heard that the genetics for the Sims in Sims 2 are done a lot better, so I'd like to hear about that as well.

Let the conversation commence?

I think many people tend to write of TS3 genetics as bad do to it lacking the Dominant/Resesive system that was in 2. Personally while I appreciate EA attempting such a realistic method I felt that in practice it was far to simplified and far to easy to breed my sim familys into a corner so too speak. Having generation after generation of brown haired, brown eyed children gets boring rather quickly. Also not many people seem to know that not only are eye and heir either Dom or Res, so are facial features. So for instance if you breed a sim who has dominant eyes, nose, and mouth to a sim who's are resesive most if not all of their children will have the same eyes, nose, and mouth. I found this out the hard way once when I had a couple who's facial genes were nearly the complete opposite of each other. Ended up wondering why they kept having nearly identical children.
I like that in sims 3 each child has an equal chance of possessing either parents features as it means any couple can produce a far variety of looking children. Plus the fact that children have a small chance of getting features from grandparents or other random features help creat the "illusion" of resesive genes.
As for the random mutations that can happen, I understand why some may not like them, particularly when it's an ugly collar. I personally enjoy it when it happens since it can be realistic in a way. RL genetics are very complex and diffrent combinations of genes can have unexpected results. A brown eyed and blue eyed couple having a green eyed child for example. And if a child gets a hair or eye collar I don't like I can always take them into CAS and give them a new collar of my choosing. I typically will give them a collar similar but not exact to one or both parents. I find that can be fun as over time, besides just breeding in new genetics, I can also watch as certein genes gradualy "shift". Like watching blue eyes get lighter or darker or have brown hair get slightly redder over time.

I noticed the nephew of a Sim looked a lot like his uncle. Also I have some stunning cousins in game that all have blue eyes and blond hair. Their mothers are sisters.

Some tips on how to improve the genetics system in the Sims 3.

1. Disable "mutations" in a _XML file (Instance: 0x71BBAFC2BB6085C7). Change whichever value you find there to 0. You'll not see any sims with randomly assigned pink eyes and/or brownish/shitty-like hair color.
<kMutateHairColorChance value="0">
<kMutateEyeColorChance value="0">
2. In twallan's Story Progression+Extra module turn on Advanced Genetics and Genetic Skin Blending. It makes sure the skintone of a newly born sim is not inherited either from a mother or a father but it's a blend. For example, a child born to a white father and a black mother may be a different shade of brown.
3. Download Consort's Hair Color mod. Same as the genetic skin blending but applies to hair color.
4. Download NeuroBlazer's Random Genetics to make sure a newly born sim's face is no longer identical to a mother or a father but each slider is a blend between the two.
Example is my family. It's hard to tell if he is similar to his father or mother.

Oh, I wanted to bring this thread back to talk about something:

I think the reason the Sims 3 doesn't have the presence of Dominant/Recessive genes as seen in the Sims 2 is because I think that would be very difficult to implement with the introduction of the skin tone sliders, custom colors, and color gradients. That, coupled with the open world and story progression? I don't think it would've been easy with the technology of 2009, is what I'm saying.

(I'll also make note to download all those genetic mods at a later date. They sound excellent.)

I'm actually a fan of the TS3 genetics. They definitely aren't TS2 tier, but so far I'm a fan. Granted, I'm only on the 2nd generation of a legacy play, so we'll see how things play out.

One thing I've found quite useful is to have NRAAS immigration use existing world sims as references when generating new sims- if you have a good number of handcrafted sims in the world, it helps you avoid encountering same-face syndrome that usually arises out of the game having to use defaults templates, and I usually find that the results are more realistic as well.

I feel you, when my second generation children become adults I always stop playing, I don't know why.

I love how the genetics work in the sims 3, I know it's not realistic bit it gives variation and I love that. I was playing a game (an ISBI challenge) several months ago that I stopped playing but I wanted to share with you all the genetic variations I got in that generation. I have Nraas StoryProgression so I think it helped with the genetics too.

As you can see there is everything: clones, mixes and a mutation. My favorite is the 5th daughter, Astrid.

@LittleCheshire

You said you "fixed that" ("if you bred two dogs of the same fur and body shape i.e breed and they had more than one kid one of those kids was gonna look nothing like their parents") with a mod (I suppose?).
Would you kindly share what mod is this, if there indeed is such a mod? My Sim has an orange Siberian male and a fluffy birman female she hopes will mate soon... A mod is urgently needed!

@Simsica

Sure thing luv! You can find my mod here: No More Skinny Pet Clones!

Enjoy the kittens! (And if you're up for it, share pictures here too! I adore baby animals in the Sims 3!)

Thanks!

I'll see what I can do about the pictures, though. I plan to leave it to autonomy (using NRAAS Woohoo). Want to be surprised. Might take a day or two (IRL).

It's funny because one of the main reasons why I was so intrigued with TS2 is generations, yet I don't recall ever getting pass the 2nd or the 3rd generation. I mostly played with just the 1st generation with aging off and rarely had a family born in-game. So don't know much about genetics from the predecessor.

https://www.youtube.com/watch?v=t9u1zMCos8w

However, TS3 I actually do play with generations. Though because of my now custom life span, it is extremely long and mirrors the real world but the Sims version of it.

I find myself intrigued wondering who will the child look like. Sometimes they look like their mom or their dad or a combination of both or their grandparents. Not only do I take notice of facial features and physique but also hair, eye, skin colors. In some cases, the colors resemble one of the parents or grandparents. In other cases, the child comes out with a recessive hair or eye color when no known recessive trait is available for me to see in terms of it didn't come from the founder's (grandparents) or parents dominant traits.

Such as the Deangelo founders (grandparents) are now elders and have two children. They all have brown eyes. One of their children, their son, married a woman with brown eyes and they have two children. One is a toddler, who has blue eyes, and the other child is currently still an infant.

Another example are my Okotie-Eboh founders which I created some of their children in CAS when I created them. They all have brown eyes but the youngest child generated with blue eyes, which I decided to keep than re-roll. Oh and I almost forgot, I actually did change one of the kids DNA to resemble albinism.

And one more example are my Rumbaa founders who have 14 born in-game children and one of them came out with blonde hair. The father has brown hair and the mother has black hair. Also, I noted both eye colors are recessive but dominant for them. So I only seen blue or green eyes in all their children but since green is more dominant than blue, most of the children have green eyes which I thought very interesting in terms of biology/genetics. 11 out of 14 children have green eyes. 5 out of 14 children have black hair which implies subject to variation just like in real life.

[spoiler]

[\spoiler]

The dominant traits are the ones you see in that Sim, but the recessive traits are what you don't see but they are carriers of it to possibly pass down to future generations. A grandchild inheriting a grandparents hair color or eye color, etc is a recessive trait because it's something the parents do not possess for themselves but are carriers for it. In the case of founders, because there aren't any features to pick recessive traits, the game will automatically generate it though hidden from the player until it comes out in one or more of the descendants.

When it comes to mutated hair and eye colors, I change those because I honestly don't understand what they were trying to do with that. I would have preferred heterochromia, albinism, vitiligo, etc.

Another interest I have in TS3 genetics I notice is that facial features and physique also has higher or lower chances of being inherited depending on if it's on the dominant or recessive side of the pool. Though again TS3 does also display genetic variation which helps to further diversify the gene pool. Such as one of my Sims physique is the more to love type but both her parents and grandparents are fit.

I've been using RandomGenetics for a coupl of generation in my game and the results are really satisfying IMHO. I'm currently playing in Oasis Landing and my family and other residents are descendants of the original population i.e The Planesons, Orey etc. I moved in all the NPCs, the Homeless and the deceased whom I had resurrected in order to have more people in town. They have been mixing with each other for generations and now the resulting population is more homogeneous then at the very beginning but it's not a problem for me. Homogeneous population is not a bad thing after all.

I aged down my current adult sims to YA and aged up their 4 children to YA as well in order to compare their faces. Their sons look like their father, whereas daughters are similar to their mom. I do notice subtle differences in the facial features, though.