> What about architecture? There are plenty of buildings which have lasted over 100 years.

Agreed. That's what I was thinking of to when I wrote, "unless treated by humans".

Ah, I was thinking of pressure-treated wood [0][1] as opposed to "raw" wood.

[0] http://www.homedepot.com/c/discover_benefit_pressure_treated...

[1] http://www.strongtie.com/productuse/ptwoodfaqs.html