Conifers use resin to protect themselves. This resin contains diterpenes, which act as a natural defense against insect pests. Some of these substances existed before conifers evolved, while others developed independently in different tree species later on — presumably to protect against bark beetles. A key factor in this process is the evolutionary mechanism known as "epistasis": previous genetic changes pave the way for new defenses. These findings help us better understand the natural power of plant defenses and may lead to more sustainable plant protection methods.