# On the Sudden Appearance of Groups of Allied Species in the Lowest Known Fossiliferous Strata explained — The Origin of Species

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

## What happens

Darwin addresses the formidable objection that many groups of allied species appear suddenly in the lowest fossiliferous strata, without clear precursors. He argues that vast periods must have elapsed before the Cambrian, during which life existed but left few traces due to metamorphism, denudation, and the imperfection of the geological record. He cites evidence from Barrande, Hicks, Logan, and Dawson, and uses Lyell's metaphor of an imperfectly kept history to explain the apparent abruptness.

## Themes in this chapter

### Imperfection of the Geological Record

Darwin argues that the sudden appearance of groups in lowest strata is due to the incomplete and metamorphosed nature of the fossil record.

### Extinction and the Succession of Forms

The sudden appearance of allied species and the absence of transitional forms are discussed as serious difficulties.

### Common Descent and the Tree of Life

Darwin asserts that all Cambrian and Silurian trilobites are descended from a single crustacean, applying the theory of common descent to ancient forms.

## Character check-ins

### Charles Darwin

Author; argues for vast pre-Cambrian periods and the imperfection of the geological record.

### Sir Charles Lyell

Cited as a geologist who disputed the view that the lowest Silurian represents the first dawn of life; his metaphor of an imperfect history is used.

### M. Barrande

Added a lower stage beneath the Silurian system, abounding with new species.

### Sir R. Murchison

Believed the lowest Silurian stratum showed the first dawn of life.

### Edward Forbes

Disputed the conclusion that the lowest Silurian represents the first life.

### Agassiz

Maintained the immutability of species; also maintained the view that large islands existed near continents.

### Mr. Croll

Estimated about sixty million years since the Cambrian period.

### Pictet

Mentioned among eminent palaeontologists who maintained the immutability of species.

## Key lines

> I look at the geological record as a history of the world imperfectly kept and written in a changing dialect.

Darwin views the fossil record as an incomplete and evolving narrative.

_Uses Lyell's metaphor to explain the apparent abrupt appearance of species._

> The case at present must remain inexplicable; and may be truly urged as a valid argument against the views here entertained.

Darwin admits that the absence of pre-Cambrian fossils is a serious objection to his theory.

_Acknowledges the difficulty honestly._

> Thus the words, which I wrote in 1859, about the existence of living beings long before the Cambrian period, and which are almost the same with those since used by Sir W. Logan, have proved true.

Darwin's earlier prediction of pre-Cambrian life has been confirmed by Logan's discovery of Eozoon.

_Shows vindication of his hypothesis._

## Links

- HTML: https://www.betterreads.online/discover/the_origin_of_species_se/chapters/on-the-sudden-appearance-of-groups-of-allied-species-in-the-lowest-known-fossiliferous-strata
- Book: https://www.betterreads.online/discover/the_origin_of_species_se
- All chapters: https://www.betterreads.online/discover/the_origin_of_species_se/chapters