Seventy’s Course in Theology [Salt Lake City: Deseret News, 1907-1912], 1:166 “…some may deny that the mongrelization of the Southern people would offend the race notion—would corrupt or degrade the Southern stock of humanity. If so, then such a one has yet to learn the largest-writ lessons of history and the most impressive doctrines of biological science.
That the negro is markedly inferior to the Caucasian is proved both craniologically and by six thousand years of planet-wide experimentation; and that the commingling of inferior with superior must lower the higher is just as certain as that the half-sum of two and six is only four.” — B. H. Roberts (more…)
Where Is Wisdom? p. 390; “…Intermarriage between members of these great racial divisions are possible, but the progeny are usually feeble, not long-lived, and of poor physical quality; and no permanent self-propagating, homogeneous races can be generated by such intermarriages. Hence these different classes of mankind amount in effect to a difference in species. … Then as regards language, there is a very important difference…The Negro languages are also simple and not adapted for conveying any but the simplest ideas and thoughts.” – 
