Big beast extinction blamed on prehistoric fire starters

[bertine]

I know this is an odd question but why does it have to be people starting the fires? Couldn't it have been a wild fire out of control? I don't know, this sounds very much like "people started burning all the grass on purpose" opposed to "people started a fire that spread all over". Why would they start fires like that? To clear the land? Isn't that a little before agriculture?

http://www.newscientist.com/news/news.jsp?id=ns99994028