---
title: "1 Extinctions Quotes By Stephen J. O'Brien"
description: "1 Extinctions quotes by Stephen J. O'Brien. Plus more from Stephen J. O'Brien and more Extinctions sayings from other authors."
image: "https://sms4smile.com/quotes/i/2ea/stephen-j-o-brien-43665_extinction_the-cause-of-these-great-extinctions-the_3202046.jpg"
---

> [“The cause of these great extinctions, the most extensive in the seventy-million-year record for mammals, is a mystery. The two prevailing guesses, climatic environmental pressure or the destruction caused by human immigration in these regions, are at a stalemate. Nearly…](https://sms4smile.com/quotes/stephen-j-o-brien/the-cause-of-these-great-extinctions-the-most-extensive-in-the/)

[Stephen J. O'Brien](https://sms4smile.com/quotes/author/stephen-j-o-brien/)

[Image](https://sms4smile.com/quotes/i/2ea/stephen-j-o-brien-43665_extinction_the-cause-of-these-great-extinctions-the_3202046.jpg)

## Other authors on Extinctions

## More by Stephen J. O'Brien

> [“Left alone, the Florida panther would be remembered as a textbook exercise on how to go extinct while your abundant and vociferous advocates argue…](https://sms4smile.com/quotes/stephen-j-o-brien/left-alone-the-florida-panther-would-be-remembered-as-a-textbook/)

[Stephen J. O'Brien](https://sms4smile.com/quotes/author/stephen-j-o-brien/)

> [“The evidence of cheetah genetic monotony would only grow. Bob Wayne, a talented postdoctoral fellow in our lab, examined cranial measurements and the bilateral…](https://sms4smile.com/quotes/stephen-j-o-brien/the-evidence-of-cheetah-genetic-monotony-would-only-grow-bob-wayne-a/)

[Stephen J. O'Brien](https://sms4smile.com/quotes/author/stephen-j-o-brien/)

> [“Field biologists studying large and charismatic animals wanted to know if their own species had genetic problems. I listened carefully to stories of koalas…](https://sms4smile.com/quotes/stephen-j-o-brien/field-biologists-studying-large-and-charismatic-animals-wanted-to/)

[Stephen J. O'Brien](https://sms4smile.com/quotes/author/stephen-j-o-brien/)

> [“Within a few months Mitch Bush, head veterinarian at the National Zoo, and David Wildt, a young reproductive physiologist working as a postdoctoral fellow…](https://sms4smile.com/quotes/stephen-j-o-brien/within-a-few-months-mitch-bush-head-veterinarian-at-the-national-zoo/)

[Stephen J. O'Brien](https://sms4smile.com/quotes/author/stephen-j-o-brien/)

> [“Over the past sixty years a rather impressive assembly of respectable taxonomists and evolutionary biologists have tried to unseat the biological species concept for…](https://sms4smile.com/quotes/stephen-j-o-brien/over-the-past-sixty-years-a-rather-impressive-assembly-of-respectable/)

[Stephen J. O'Brien](https://sms4smile.com/quotes/author/stephen-j-o-brien/)

> [“Taxonomy, also called systematics, is the science-based hierarchical classification of the world's species. The area had traditionally been an obscure academic discipline dominated by…](https://sms4smile.com/quotes/stephen-j-o-brien/taxonomy-also-called-systematics-is-the-science-based-hierarchical/)

[Stephen J. O'Brien](https://sms4smile.com/quotes/author/stephen-j-o-brien/)

> [“It seems a shame that less than 1 percent of all the species that ever lived survive today and that only about 5 percent…](https://sms4smile.com/quotes/stephen-j-o-brien/it-seems-a-shame-that-less-than-1-percent-of-all-the-species-that/)

[Stephen J. O'Brien](https://sms4smile.com/quotes/author/stephen-j-o-brien/)

> [ “\[Giant northern elephant seals\] were presumed extinct as late as 1912 when a group of eight seals was spotted on Guadalupe Island in the… ](https://sms4smile.com/quotes/stephen-j-o-brien/giant-northern-elephant-seals-were-presumed-extinct-as-late-as-1912/)

[Stephen J. O'Brien](https://sms4smile.com/quotes/author/stephen-j-o-brien/)

> [“The cause of these great extinctions, the most extensive in the seventy-million-year record for mammals, is a mystery. The two prevailing guesses, climatic environmental…](https://sms4smile.com/quotes/stephen-j-o-brien/the-cause-of-these-great-extinctions-the-most-extensive-in-the/)

[Stephen J. O'Brien](https://sms4smile.com/quotes/author/stephen-j-o-brien/)

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