The olive tree is a marvel of longevity. How does a tree who’s seed sprouted during the Bronze Age in 2000BC still bear fruit and oil today in 2000CE? How does a tree survive drought, flood, frost and fire, biotic and abiotic attacks century after century and still bloom every spring? We asked these questions and we found that, apart from the incredible over all design of it’s natural ecology, the phytoalexins or plant defence chemicals, play in important role in its longevity. These phytoalexins are produced by the tree to defend from microbial attacks, they prevent disease and control infection. They are very stable compounds due to their molecular structure and are non-biodegradable; they are like the tree’s immune system. These phytoalexins are at peak potecy just before the onset of ripening or colour change and have great significance for human health due to biological activity in the human body.