Yeah you can! I'm currently doing A Level history, and although I did it at GCSE, I have friends that didn't, and they're doing fine. The content for history is honestly not that difficult - especially if you enjoy the topic - it's literally a case of memorization. BUT answering exam questions will be difficult without GCSE knowledge, especially the source questions. With exam technique, I feel like you pretty much build upon what you already know from GCSE, e.g. you can get away with using the same stock phrases in GCSE source questions, and still get a decent mark (which is what I did) but that's certainly not the case at A Level - your answers have to be much more sophisticated. Ultimately, if you think you'd enjoy history then take it, but you will have to work on exam questions. Don't pick it cause you think it'll look good, because you'll end up hating it!