# Peter Ward: A theory of Earth's mass extinctions

Asteroid strikes get all the coverage, but Medea Hypothesis author Peter Ward argues that most of Earth's mass extinctions were caused by lowly bacteria. The culprit, a poison called hydrogen sulfide, may have an interesting application in medicine.

- Kind: Talk
- Year: 2009
- Runtime: 19 min
- By: TED.com
- Genres: Education, Science, Space, History
- Archive: [Internet Archive](https://archive.org/details/PeterWard_2008)
- Licence or status: [CC BY-NC-ND 3.0](http://creativecommons.org/licenses/by-nc-nd/3.0/) (as the archive states it)
- Who can watch: Tweens profiles and older (the archive gives no rating; placed by Invisible Network from its collection and subjects)

[Watch now](https://invisiblenetwork.ai/watch/archive/ia/PeterWard_2008?play=1)