Photo taken in the sun

[jasinfla]

I took this picture today & am just wondering where you see that split (part) in the back, right directly to the right of it where it looks like a half oval, is that hair in there thinning or have loss density there or is just the way it's brushed and is natural? Again, as you can tell, this was taken in the sun. Just for the record, my wife thinks I'm insane but I'm just not sure.

Also is something rogaine or niz or fin could help with?
Thanks in advance!