Among his other books were On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insects (1862), Expressions of the Emotions in Man and Animals (1872), which sold almost 5,300 copies on its first day, The Effects of Cross and Self Fertilization in the Vegetable Kingdom (1876) — a subject that came improbably close to Mendel's own work, without attaining anything like the same insights — and his last book, The Power of Movement in Plants. Finally, but not least, he devoted much effort to studying the consequences of inbreeding — a matter of private interest to him. Having married his own cousin, Darwin glumly suspected that certain physical and mental frailties among his children arose from a lack of diversity in his family tree.

Darwin was often honored in his lifetime, but never for On the Origin of Species or Descent of Man. When the Royal Society bestowed on him the prestigious Copley Medal it was for his geology, zoology, and botany, not evolutionary theories, and the Linnaean Society was similarly pleased to honor Darwin without embracing his radical notions.