What Causes Indentations On The Top Of The Scalp?

I'm a 30yr old woman & recently noticed 2 indentations on the top of my scalp running anterior to posterior...approximately 8cm behind the hairline, 8cm long, and approx .6 cm deep. One is directly on the top/center with the other to the right. I am 5'7", approx 180lbs, & vegan with no health issues. What the heck? :(

My husband says I'm turning into a Klingon. lol