Just for a few moments, I promise! Let me explain why I feel the need to put all this into writing first. If this bores you, feel free to skip to the next post (above) where I discuss the next age transitions and birth.

Thinking that the community at large might be interested in this experiment, I posted a message on the Official BBS to help others to find this blog and the information they may be seeking regarding complications in their genetic patterns. I was, admittedly, a bit taken aback when I got a response “explaining” sim genetics to me. As somebody who has, in changing schools, sat through three complex biology classes that discussed human genetics, I think my handle on how genetics works is pretty good. Additionally I’ve read the strategy guide cover to cover a couple of times as a result of not having been able to play until I purchased a new computer.

I try not to be offended when something like this happens, but it’s particularly difficult when the person posting the response seems to be weary of responding to similar questions or suggestions. To those who think that sim genetics work correctly 100% of the time, you need to be reading this blog. You need to be in contact with people who play the Legacy Challenge, because it’s through the generations that the problems become most pronounced.

Anyway… For those who don’t understand how sim genetics are SUPPOSED to work, here is an explanation. Some parts come from the Prima Guide and others are paraphrased.

Let’s start with a quote from the Guide, page 138 (of the University Guide).

“One bit of extremely simplified genetics first. For every trait, humans get one gene from one parent and one from the other. These pairs of genes are called “alleles.”

Simplied my foot! For those who have never learned genetics, this might not be so easy. So here’s my explanation.

For the sake of argument I have brown hair and blue eyes (my hair is actually auburn but I can’t argue genetics given that both my parents had brown hair).

My father had brown hair and blue eyes and my mother had brown hair and blue eyes. Therefore I received the following alleles:

Hair: B/B
Eyes: b/b

Those are the alleles. Hopefully you’re still with me here.

I’m going to skip a few paragraphs of the guide and then come back to them… Let’s continue.

The guide tells us that “there are four Maxis hair colors, and each is either dominant or recessive.” This works the same as human genetics, by the way.

The four hair colors are :
Brown (dominant)
Black (dominant)
blonde (recessive)
red (recessive)

And there are five Maxis eye colors:
Brown (dominant)
Dark Blue (dominant)
blue (recessive)
green (recessive)
gray (recessive)

For those who don’t understand dominant and recessive genes, it should work this way:

Pairing a CAS parent with a dominant hair color with a CAS parent with recessive hair color will result in the offspring displaying (expressing) the dominant hair color. For example:

A CAS parent with Brown hair paired with a CAS parent with blonde hair will (should) result in offspring with Brown hair. It works the same way for eye color.

But what happens if you pair two CAS parents who both have recessive hair color? For example, a blonde haired male with a red haired female? The resulting offspring will have an equal chance of expressing either blonde or red hair (in theory). This might mean time for another experiment on my part!

That covers, in brief, how hair and eye color genetics work (or are supposed to work) in The Sims 2.

The next part of genetics (as listed in the Prima Guide) is skin tone. This should be a bit simpler.

According to the Prima Guide page 139 (of the University Guide):

“Just as with hair and eyes, Sims carry one skin tone gene from each parent (for Create-A-Sim Sims, it’ll be the same on both sides). Unlike with hair and eyes, however, there is no dominance in skin tone: the choice of which tone to pass on is random.

“The resuling child, therefore, ends up with two skin tone genes, one from each parent. If those genes are the same, the child will have that skin tone (e.g., if she gets S2 and S2, she’ll be S2).

“If, however, the tones are different, the child can randomly express any skin tone in between the two. For example, if a Sim receives S2 and S4 from his parents, he can be S2, S3 or S4. When he reproduces, however, he passes on either S2 or S4 to his child.”

That’s pretty simple and self-explanatory. As an example, therefore, a child born to a pale parent (S1) and a black parent (s4) can be pale, white, tan/brown or black. A child born to a pale parent (S1) and a white parent (S2) will be either pale or white.

Again, pretty simple and self-explanatory.

The final part of sim genetics is personality. This is where apparently I forgot to double-check the guide before launching this experiment, because the way personality genetics work is very interesting.

From the Prima guide, page 140 (University Guide):

“A Sim’s Personality is also inherited. For each Personality trait, the child receives the trait’s point assignment from his father, his mother, or at random.”

The important part here is “or at random.” Those sims I’ve been coming up with who have a niceness of 10 when both their parents have less than five reflect the fact that personality is random. However, if I understand correctly through my own game play, the children will not posess any personality traits their parents don’t posess. Therefore, if both parents are lazy 0, the child will also be lazy 0.

I don’t understand the genetics of facial features enough to discuss them at this point in time… I’m going to have to study up on that and report back later.

Anyway…

Now we all understand second-generation genetics. Hopefully it’s pretty simple. But third-generation genetics get more complicated, and should result in greater variances in the appearance of the offspring (though personality still works exactly the same).

Let’s talk about hair since hair and eye color work identically to one another.

As an example you start with two CAS Sims. Let’s use Jonathan and Alyssa Corbett.

Jonathan has Black hair and Alyssa has red hair. Therefore the children (should) have Black hair. Those are the genes they express.

Their alleles, however, are now a bit different (although the Guide doesn’t talk about it in this way. I’ll use a table similar to those I was taught with.

B r
B r

As you can see, the offspring now have two sets of genes. In this case they have two dominant genes and two recessive genes. Their parents each had two genes which were identical. These offspring have two genes which are different. So which expresses? The dominant gene of course! But we’ve already discussed all that. So what happens when they reproduce?

Let’s say Armond (B//r) meets Betsy (b/b). Armond has black hair inherited from his father and carries the recessive gene for red hair. Betsy has received blonde haired genes from both of her parents. They have children together. Their children’s tables look like this:

B r
b b

And things become a bit more mixed-up and potentially confusing! Clearly we have a dominant gene. But we have three recessive genes. In this case, the resulting offspring have a 75% chance of having blonde hair and a 25% chance of having black hair. Red hair will not express.

And so the generation game continues on in that way.

But what about those playing the legacy challenge who are only ‘breeding’ with NPCs? Well, NPCs have pure genes. That means that Remington the maid (Brown hair) has the hair allele B/B. If he marries Armond and Betsy’s Black haired child, that child will receive Bl/B and will express either black or brown hair (50/50 chance).

I hope this has made sense to some of you who are trying to understand the complexities of sim genetics!