# Analogical Resemblances explained — The Origin of Species

> Chapter companion for The Origin of Species by Charles Darwin.

## What happens

Darwin explores the distinction between true affinities based on common descent and analogical or adaptive resemblances that arise from convergent evolution. He discusses mimicry in butterflies as described by Mr. Bates, where unprotected species evolve to resemble protected ones for survival, illustrating natural selection. He also examines other analogical resemblances across different classes, such as the fin-like limbs of whales and fishes, and the jaws of dogs and Tasmanian wolves, emphasizing that such similarities do not indicate close evolutionary relationship.

## Themes in this chapter

### Natural Selection and the Struggle for Existence

Central to explaining mimicry: rare, persecuted species that resemble protected ones gain survival advantage, illustrating natural selection in action.

### Adaptation and the Utilitarian Doctrine

Analogical resemblances are adaptive, serving functions like protection or locomotion, but are not indicative of common descent.

### Common Descent and the Tree of Life

Darwin emphasizes that true affinities are based on descent, while analogical similarities can mislead classification.

## Character check-ins

### Charles Darwin

Author and narrator, presenting the argument on analogical resemblances and natural selection.

### Mr. Bates

Naturalist who first described butterfly mimicry in South America, providing key evidence for natural selection.

### Mr. Mivart

Mentioned in context of the resemblance between a mouse and a marsupial, which Darwin explains as adaptive convergence.

### Lamarck

Acknowledged as first to call attention to the distinction between real affinities and analogical resemblances.

### Mr. Wallace

Cited for describing cases of imitation in Lepidoptera of the Malay Archipelago and Africa.

### Professor Flower

Mentioned as an authority who agrees with Darwin's conclusion on analogical resemblances in teeth.

## Key lines

> The resemblance in the shape of the body and in the fin-like anterior limbs between dugongs and whales, and between these two orders of mammals and fishes, are analogical.

Similarities in body shape and limb structure between dugongs, whales, and fishes are due to convergent adaptation, not shared ancestry.

_Darwin distinguishes analogical from homologous traits._

> Mr. Bates may almost be said to have actually witnessed the process by which the mimickers have come so closely to resemble the mimicked; for he found that some of the forms of Leptalis which mimic so many other butterflies, varied in an extreme degree.

Bates observed that Leptalis butterflies varied greatly, and those varieties that happened to resemble common, protected butterflies were more likely to survive and reproduce.

_This illustrates natural selection through mimicry._

## Links

- HTML: https://www.betterreads.online/discover/the_origin_of_species_se/chapters/analogical-resemblances
- Book: https://www.betterreads.online/discover/the_origin_of_species_se
- All chapters: https://www.betterreads.online/discover/the_origin_of_species_se/chapters