http://www.nature.com/news/2010/101128/full/news.2010.635.html
According to a new study on mice, aging (ageing for my Austalian and British friends) is reversible! If you want cancer that is. However, this is still a huge breakthrough in aging research, and may lead to a future race of immortal people...or mice.
On another note, the aging in the test mice was premature, not natural.