Several revised versions were produced during Wells' lifetime. He kept notes on factual corrections he received from educators around the world. The last revision in his lifetime was published in 1939. In 1949, an expanded version was produced by author & scholar Raymond Postgate, whose additional material initially expanded the timeline thru WWII, with subsequent additions thru 1969. Postgate respected that readers wished "to hear the views of Wells, not Postgate" & endeavored to preserve the original authorial voice in his revisions. In the later editions, G.P. Wells, the author's son, updated the early chapters about prehistory to reflect current theories; previous editions, for instance, reflected the credence given to the Piltdown Man hoax. The final edition appeared in 1971, but earlier editions are still in print.