# On the Absence or Rarity of Transitional Varieties explained — The Origin of Species

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

## What happens

Darwin addresses the challenge of why transitional varieties are not commonly found in nature or the fossil record. He argues that natural selection, acting alongside extinction, tends to eliminate parent forms and intermediate links. The imperfection of the geological record, the historical fragmentation of continents, and the competitive advantage of more numerous forms over rarer intermediate varieties all contribute to the rarity of transitional forms. He concludes that species appear as well-defined entities because intermediate varieties are typically short-lived and supplanted.

## Themes in this chapter

### Natural Selection and the Struggle for Existence

Central to the chapter: natural selection drives extinction of parent and intermediate forms, shaping species boundaries.

### Imperfection of the Geological Record

Key explanation for the absence of transitional fossils; the record is less complete than commonly assumed.

## Character check-ins

### Charles Darwin

Author and primary narrator, presenting his theory and addressing difficulties.

### De Candolle

Cited for observations on the abrupt disappearance of alpine species.

### Edward Forbes

Referenced for similar observations in marine dredging.

### Mr. H. C. Watson

Provided information on the rarity of intermediate varieties.

### Asa Gray

Provided information on the rarity of intermediate varieties.

## Key lines

> Thus extinction and natural selection go hand in hand.

Extinction and natural selection are closely linked processes.

_Highlights the core mechanism that eliminates transitional forms._

> The crust of the earth is a vast museum; but the natural collections have been imperfectly made, and only at long intervals of time.

The Earth's crust is like a museum, but its fossil collections are incomplete and collected only at rare intervals.

_Metaphor for the imperfection of the geological record._

> This difficulty for a long time quite confounded me.

This problem puzzled me for a long time.

_Darwin admits the challenge of missing intermediate varieties in continuous areas._

## Links

- HTML: https://www.betterreads.online/discover/the_origin_of_species_se/chapters/on-the-absence-or-rarity-of-transitional-varieties
- Book: https://www.betterreads.online/discover/the_origin_of_species_se
- All chapters: https://www.betterreads.online/discover/the_origin_of_species_se/chapters