FWIW, I was raised in a Christian family, hung around a lot with fairly Christian people, and was a Christian myself for several years -- and discussions on this BBS were the first time I ever heard of Christians who believed that death was caused by sin.

Edit: Though when I went and looked, Romans ch5 does say so. Though it's not of course even reported as being the words of Christ. Those Christians who aren't young-earthers (Catholics and most Anglicans, for instance) are pretty much obliged to concede that, even just on this planet, death existed long, long before any humans did, and thus before any sin.

Peter