What happened was that Aveling's mistress was Marx's daughter, and when both Darwin and Marx were dead, Marx's papers became muddled up with Aveling's papers, and a letter from Darwin saying, "My dear sir, thank you very much but I don't want you to dedicate your book to me," was mistakenly supposed to be addressed to Marx, and that gave rise to this whole myth, which you've probably heard.
Lo que pasó fue que la amante de Aveling era la hija de Marx. Y cuando ambos, Darwin y Marx, murieron, los documentos de Darwin y Aveling se traspapelaron y una carta de Darwin decía: ” Mi estimado señor: Muchas gracias, pero no quiero que me dedique su libro ”, fue erróneamente interpretada como dirigida a Marx originando todo este mito del cual probablemente han escuchado antes.