The Expression of the Emotions in Man and Animals public by arguing that humans had "animal traits", and instead charmed them by telling stories of "human traits in animals", thus avoiding too much explicit talk of natural selection at work. Darwin preferred to leave the evolutionary implications hanging. Korn points out that the book has never been out of print since 1872, calling into question Ekman's talk of "Darwin's lost masterpiece". The "Editor's notes" at the "Mead Project source page" on the book comment that Darwin concluded work on the book with a sense of relief. The proofs, tackled by his daughter Henrietta ("Ettie") and son Leo, required a
Animals' Rights: Considered in Relation to Social Progress Salt is undoubtedly ahead of his age by many years." A new edition of the book was published in 1980 with a preface by the Australian philosopher Peter Singer, who is well known for his work on the ethics of treatment towards animals (specifically in the book "Animal Liberation"). The 1980 reissue prompted a review from Stephen Clark who praised Salt's book with some provisos. He states that Salt's attempt to blame the treatment of non-human animals on the theological doctrine of man having "dominion" over the natural world was mistaken. Animals' Rights: Considered in Relation to Social Progress Animals'