Which of these fits gap 22?

Directions: Complete this passage by selecting the most suitable option for the corresponding gap.

Islands are bodies or pieces of land that are completely ______(21)_____ by water, and are cut off from larger bodies of land that are attached to a continent and are called mainland. Islands have been homes to different cultures throughout our history. Separated from mainland, and relatively isolated, some islands of the oceans still carry the older cultures and _____(22)____ of humans. Islands also preserve animals and plants, in rather _______(23)______ conditions. In fact, it was through his visit to the Galapagos Islands, and through observing the animals there, that Charles Darwin came to _____(24)_____ the theory of evolution of man.