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.
Successe che la signora di Aveling era la figlia di Marx, e dopo la morte sia di Darwin che di Marx, gli scritti di Marx e Aveling si mischiarono, e una lettera di Darwin che dice: ”Mio caro signore, la ringrazio molto ma non voglio che dedichi il suo libro a me” si pensò, per errore, che fosse indirizzata a Marx. E questo diede origine alla leggenda metropolitana,