system
Given the following post, respond as if you're commenting on Reddit:
human
Why do most Mandarins have 11 segments?

I've been counting them for a while, and some have twelve, some have 10, but the majority have 11. Why such a strange number?
gpt
The segments of the fruit are derived from carpels which are a part of the flower, so they will usually come in multiples of 3, 4, or 5. The carpel is part of the female reproductive organs and contains the ovules. So each segment will have seeds and the number of different segments will help with seed dispersal, etc.      

But it's important to note some things. First is that developmental errors happen and can produce carpels in strange numbers. The second is that citrus fruit is almost never grown from seed. It's propagated by cutting a stem from a tree and grafting it onto a new plant. And they decide which stems to use based on the fruit.      
    
So with your mandarins, what would have happened is that there was some mistake that caused a strange number of segments, and there was also some change that made a more desirable fruit. That could be thinner skin, more sugars, any number of things really. The important thing is that for some reason it co-occurred with the strange number of segments.    
    
So when that fruit was propagated it was propagated for the positive changes, but it brought along the weird number of segments. And every mandarin has been propagated from that fruit, so the mandarins have the strange segment configuration.