Long thought never to have been inhabited and to be in a pristine ecological state, Henderson Island (southeast Pacific) is now known to have been colonized and then abandoned by Polynesians. Bones from an archaeological site on the island associated with 14C dates of ≈800 and ≈500 years B.P. include specimens of 12 species of birds, of which 3, a storm-petrel and two pigeons (Nesofregetta fuliginosa, Ducula cf. aurorae or D. pacifica, and Ducula cf. galeata), no longer occur on Henderson, and two others (Puffinus nativitatis and Sula sula) still visit but are not known to breed. The vanished species were presumably exterminated by Polynesians and the biota of Henderson Island can thus no longer be regarded as being in an unaltered state. The prehistoric abandonment of various small, unarable islands by Polynesians may have been due to the depletion of seabirds and pigeons, the only readily available food source. The species of pigeons identified from Henderson are known historically only from distant archipelagos and have never before been found sympatrically. Distributional patterns resulting from man-caused extinctions may give rise to erroneous interpretations of the relationships and evolutionary history of insular organisms. Certain endangered species, such as Ducula galeata, might effectively be preserved by reintroduction to abandoned islands that they occupied before human intervention.