"On the Phenomenon of Hybridity" was published the same year as Darwin's presentation of the theory of evolution in the "On the Origin of Species". At that time, Broca thought of each racial group as independently created by nature. He was against slavery and disturbed by extinction of native populations caused by colonization. Broca thought that monogenism was often used to justify such actions, when it was argued that, if all races were of a single origin then the lower status of non-Caucasians was caused by how their race acted following creation. He wrote: The difference of origin by no means implicates the subordination of races. It, on the contrary, implicates the idea that each race of men has originated in a determined region, as it were, as the crown of the fauna of that region; and if it were permitted to guess at the intention of nature, we might be led to suppose that she has assigned a distinct inheritance to each race, because, despite of all that has been said of the cosmopolitism of man, the inviolability of the domain of certain races is determined by their climate.