Modern experts such as Ernst Mayr, Jerry Coyne & Allen Orr, agree that Wagner first identified geographical speciation. However, his "migration theory" was based on a rather simple, Lamarckian idea of evolution. Wagner argued in letters to Darwin that he had missed a vital geographic component in understanding the evolution of new species. Darwin at first responded in a friendly way to these letters, and agreed that geographic isolation was important (although not the only mode of speciation). Later, he found Wagner's increasingly hysterical tone and one-sided argument upsetting, and wrote across his copy of Wagner's 1875 paper "most wretched rubbish," partly because Wagner ignored the importance of natural selection, and lifted parts of Darwin's theory that he liked without attribution, all the while claiming that Darwin's views were incorrect.