A Look at Genetics in The Sims 3

Case Study 2: Different Levels of Melanin

The Yamazaki Family
(Sidenote: Kiba uses a non-default skin and because of the lightness of it, it may affect any chances for incomplete dominance or this couple just doesn't have a high percentage chance for incomplete dominance for skin color in their genes like Nathaniel and Trinity.)
(Sidenote 2: Kiba and Simone are founders and created in CAS while Yoshi and Naomi were created as teens using the Play with Genetics feature from Kiba and Simone. The other four children were born in-game.)

Kiba and Simone are married with 6 children. They have 4 sons and 2 daughters. One of their daughters, Megumi has a lighter shade of black (60, 60, 60), close to jet black, than her father’s pure black hair (0, 0, 0).


Megumi’s Approximate Hair Color Compared to Her Father’s


These instances of the same hair color but varying in lightness or darkness may be associated with imitating different melanin levels of eumelanin and pheomelanin.

Eumelanin is responsible for creating black or brown color. If there is little of this melanin present in an individual then their hair color will be light and can consist of many color variations of blonde. If there is a lot of this melanin present then the hair color will be dark and consist of many color variations of brown or black.

Pheomelanin is responsible for creating red or orange color. Those with orange or red hair can have varying amounts of eumelanin which results in different hair colors such as auburn or strawberry blonde.

As mentioned before, like skin color, hair color is a polygenic trait.

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This is an old CAS Play with Genetics Test.

Mother ‘s Hair Color
R: 48, 38, 28
B: 97, 56, 23
H: 120, 74, 43
T: 74, 48, 30


Father’s Hair Color
R: 40, 40, 40
B: 65, 65, 65
H: 36, 36, 36
T: 62, 62, 62


Child 11’s Hair Color
R + H + T: 150, 110, 75
B: 150, 95, 50


Because his hair is orange and his mother's is brown and his father's is black then this must be a recessive hair color of one of them.

Child 3 has a different variation of black than her father's
R + H + T: 40, 40, 40
B: 70, 70, 70


Child 10 seems to have a darker color of a recessive blonde based on the root color from her siblings with blonde hair. So melanin levels can also affect recessive hair colors too in TS3. Fascinating. Also, because child 10 has a lighter black root hair color than her father's but a darker blonde recessive base hair color then technically that's an example of codominance besides differing melanin levels in recessive hair colors. So one parent has blonde and the other has orange recessive hair colors.
R: 60, 60, 60
B: 70, 60, 40
H + T: 50, 40, 20

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Another Play with Genetics Test

Father
R: 123, 67, 19
B: 171, 93, 35
H: 190, 116, 58
T: 194, 119, 56


Mother
R: 48, 38, 28
B: 97, 56, 23
H: 120, 74, 43
T: 74, 48, 30


Son


Daughter


The children’s hair color is:
R + H + T: 150, 110, 75
B: 150, 95, 50


One of the parents has black as a recessive trait and I think purple eyes is a mutation? Though I read that purple eyes do exist but rare based on lack of melanin in the iris and how light is reflecting from the blood vessels in the eyes which gives off a purple hue. If I even remember that correctly. I guess it may be associated with albinism but don't really know. I am starting to wonder if a mutation chance is higher or lower in some Sims. Perhaps there is a lot of information that gets randomized once a Sim is created. How much hidden Sim Data could one Sim have?


During other test and examples of families living in the Sim world, some Sims do not create children with varying lighter or darker colors, as in, strictly either the mother’s or father’s hair or skin color exactly. However, other Sims it seems, have genes showcasing a chance for incomplete dominance and a chance for lighter or darker versions of the parent's hair color or recessive hair color(s).

Are there hidden hair color presets that are rare to see or are these actually being calculated in some way from a hidden gameplay mechanic? Maybe a bit of both? Either way, it seems to happen under certain conditions in order to see these types of unique hair colors. I suspect there may be more of those.

Does hair color blending exist in TS3 but just rare depending on the coupling and genes? It definitely seems that way. Like a box of chocolates, you never know what you are going to get but at the same time makes sense and follows something based on reality. I am going to take an educated guess the genetic system is based on more than just the principles of inheritance by Gregor Mendel.

“Our modern understanding of how traits may be inherited through generations comes from the principles proposed by Gregor Mendel in 1865. However, Mendel didn't discover these foundational principles of inheritance by studying human beings, but rather by studying Pisum sativum, or the common pea plant.”

“Today, whether you are talking about pea plants or human beings, genetic traits that follow the rules of inheritance that Mendel proposed are called Mendelian.”

(https://www.nature.com/scitable/topicpage/gregor-mendel-and-the-principles-of-inheritance-593/)