The Descent of Man/Chapter I
Darwin first states that the similarity between the human skeleton and the skeletons of other animals was "notorious". Scientists had even seen a similarity between the human brain and that of an orangutan. He mentions the diseases humans can catch from other animals and human illnesses which monkeys also suffer from including "apoplexy, inflammation of the bowels, and cataract in the eye." He also mentions that monkeys can develop a liking for "tea, coffee, and spiritous liquors" and that he has seen monkeys "smoke tobacco with pleasure." Other similarities between man and monkeys include:
- Manner of reproduction, including prenatal development.
- Helplessness of infants.
- Difference in size and strength between male and female.
- Tissue structure.
- Male nipples.
Other animal features which man has to a lesser extent include:
- Muscles that move the scalp and ears.
- The connection of the sense of smell with memory.
- Body hair, including eyebrows.
- "Lanugo," or wool-like hair on fetuses.
- Wisdom teeth.
- Vermiform appendix.
- A fissure in the upper arm bone.
- A tail bone or coccyx.
He even includes illustrations and photographs from other sources.
In the final paragraph, Darwin emphasizes the "community of descent' among all vertebrates and that only prejudice and arrogance keep people from seeing this.