[evilduck]

The dirt in your back yard hasn't been around for 4.4b years. Topsoil (decayed organic material and newly eroded rocks mostly) is usually pretty 'young' on geological timescales.

[lutorm]

Not in that form, but the vast majority of the matter certainly has been part of the Earth for that long.

By the same definition, I'm not 40 years old either, because practically no part of me is left since I was born.

[mathattack]

Right, but at least we can say you're a relatively old "living" creature where age is a more relevant number. (I'm getting up there in "relatively old" years too.)