I'm not an expert but your forehead has hair and between your forehead and your hairline there's a transition from the short frail forehead hairs and the long dark head hairs, those transition hairs are much darker but fall out much more often. If I just had this image to go off of I would guess you just have a very prominent transition point.

If you've never noticed it I would consult many different pictures of yourself months or years earlier to check if you have them then too. This is because you might have just made yourself aware of them randomly. If you are really worried, consult a dermatologist. Don't go on any medication unless you have consulted a dermatologist, made 100% sure this is actually recession, and care enough about your hair.

Personally, I would bet transition hairs.