Those fed softer food had more crowded premolars, rotated or displaced teeth, and narrower dental arches.

吃较软食物的松鼠猴，前臼齿会比较拥挤，更多转向或移位的牙齿，牙弓更狭窄。

This frequent force exerted on the palate, as well as your resting tongue posture can affect the dental arch.

这种对上颚施加的持续不断的力以及你舌头休息时的姿势会对牙弓造成影响。

And if we go back to these pictures, we notice that these people have relatively broad faces with broad dental arches.

如果我们再回头看那些图片，我们会发现那些人的脸都相当宽并且牙弓也很宽。

Simply put, by pulling the tongue down and breathing through the mouth, the monkeys developed smaller dental arches and crooked teeth.

简单来说，通过垂下舌头，用嘴呼吸，猴子的牙弓变小，且牙齿变歪了。

If you compare a prehistoric skull to a modern day skull, you'll find that we used to have far broader dental arches.

如果把史前人类和现代人类的头颅相比照，你会发现过去的人类有着更宽的牙弓。

The paper reports that “the common finding was a narrowing of the mandibular dental arch and a decrease in maxillary arch length, causing an incisor cross-bite.”

“最普遍的情况是下颌牙弓变窄，上颌弓内缩，从而导致门牙反咬合。”

Another effect of having the tongue on the roof of the mouth is that, especially when young, it widens the dental arch, which helps to have straight teeth.

舌头抵在上颚对嘴部的另一个效果是这样可以扩展牙弓，帮助牙齿生长的更平直，尤其是在人年少的时候。

Spending most of your day chewing on things hard enough to wear the teeth down to that extent could exert enough direct and indirect force to morph the facial skeleton and dental arch.

为了使牙齿磨损到那种程度，将一天中的大部分时间花在咀嚼很硬的食物上会对颅骨带来足够多的直接和间接影响，使面部骨骼和牙弓发生改变。