Around 1880, an increasingly famous Darwin had suffered years of illness.
Descent of Man, sexual selection, and botany
More detailed articles cover Darwin’s life from Orchids to Variation,
from Descent of Man to Emotions and
from Insectivorous plants to Worms
Despite repeated bouts of illness during the last twenty-two years of his life, Darwin pressed on with his work.
He had published On the Origin of Species as an abstract of his theory, but more controversial aspects of his
“big book” were still incomplete, including his views on humankind’s descent from earlier animals, and possible causes underlying the development of society and of human mental abilities. He had yet to explain features with decorative beauty but no obvious utility. His experiments, research and writing continued.
When Darwin’s daughter fell ill, he set aside his experiments with seedlings and domestic animals to accompany her to a seaside resort where he became interested in wild orchids. This developed into an innovative study of how their beautiful flowers served to control insect pollination and ensure cross fertilisation. As with the barnacles, homologous parts served different functions in different species.
Back at home, he lay on his sickbed in a room filled with experiments on climbing plants. Visitors included Ernst Haeckel who had spread a version of Darwinismus in Germany. Wallace remained supportive, though he increasingly turned to Spiritualism.
The first part of Darwin's planned “big book”, Variation of Plants and Animals Under Domestication, grew to two huge volumes, forcing him to leave out human evolution and sexual selection. It sold briskly in 1868 despite its size, but interest tailed off. He wrote most of a second section on natural selection, but it remained unpublished in his lifetime.