Everybody has it to some extent, some have it more than others. I think it has something to do with development of the brain. On the other hand there are also those who scam other people into believing they have it, Ms. Cleo comes to mind.
We, humans sometimes feel like we have. Others claim to have. Ever walked into a room and you feel like you've been there before. Someone speaks and you can finish the sentence, even though you didn't know the answer?
To some extent, but it's not something concrete, like some people can sense when something bad is going to happen, but can't tell what it is, some people are mediums, can talk to the dead, but most mediums can't tell who they are talking to or if they can they can't actually talk to them, stuff lie that
Technically we all have more than 5 senses. The 5 senses we know today were catagorized by Aristotle and we stuck with them ever since. Actually we have more than 5, a sense of gravity, sense of temperature, sense of direction. So yes, humans do have a sixth sense.