Why do some species flourish and others falter? Sometimes it just comes down to luck.

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FYI: We try to leave jargon out of our videos, but if you want to learn more about this topic, here are some handy keywords to get your googling started:

- Bering land bridge: an ancient land bridge that connected Asia and North America at various times during the Quaternary glaciation, allowing Homo sapiens and other species migrations.

- The Holocene extinction: (also referred to as the Sixth extinction or Anthropocene extinction) is the ongoing extinction event of species during the present Holocene epoch (since around 10,000 BCE) mainly due to human activity. The Holocene extinction includes the disappearance of large land animals known as megafauna, starting between 9,000 and 13,000 years ago, the end of the last Ice Age.

- Atlatl (spear-thrower): is a tool that uses leverage to achieve greater velocity in dart-throwing.

- Bile bears: sometimes called battery bears, are bears kept in captivity to harvest their bile, a digestive fluid produced by the liver and stored in the gallbladder, which is used by some traditional Chinese medicine practitioners, though there is no evidence that bear bile has any medicinal effect, and no plausible mechanism by which it might work.

Species featured in this video:
- American black bear (Ursus americanus)
- Asian black bear (Ursus thibetanus)
- Black-footed Ferret or American polecat (Mustela nigripes)
- Steppe polecat (Mustela eversmanii)
- Humans (Homo Sapiens)
- Prairie dogs (genus Cynomys)


Credits (and Twitter handles):
Script Writer: David Goldenberg (@dgoldenberg)
Script Editor: Emily Elert (@eelert)
Video Illustrator: Ever Salazar (@eversalazar)
Video Director: Emily Elert (@eelert)
Video Narrator: Henry Reich (@MinutePhysics)
With Contributions From: Alex Reich, Kate Yoshida, Peter Reich and Rachel Becker
Music by: Nathaniel Schroeder: http://www.soundcloud.com/drschroeder

Image Credits:

Mustela nigripes - USFWS Mountain Prairie

Mustela eversmanii - Andrei Kotkin (used with permission)

Ursus americanus - Ryan E. Poplin

Ursus thibetanus - Guérin Nicolas

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Schieck, B., McCown, W. (2014). Geographic distribution of American black bears in North America. Ursus, 25-1(24-33). Retrieved from http://www.bearbiology.com/fileadmin/tpl/Downloads/URSUS/Vol_25_1_/Scheick_and_McCown_2014_Ursus.pdf

Pappas, S. (2014).Humans Blamed for Extinction of Mammoths, Mastodons & Giant Sloths. LiveScience. Retrieved from: http://www.livescience.com/46081-humans-megafauna-extinction.html

Feng, Y., Siu, K., Wang, N., Ng, K., Tsao, S., Nagamatsu, T., Tong, Y. (2009). Bear bile: dilemma of traditional medicinal use and animal protection. Journal of Ethnobiology and Ethnomedicine, 5:2. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2630947/

Biggins, D., Hanebury, L., Miller, B., Powell, R. (2011). Black-footed ferrets and Siberian polecats as ecological surrogates and ecological equivalents. Journal of Mammalogy, 92(4): 710-720. Retrieved from https://www.fort.usgs.gov/sites/default/files/products/publications/22786a/22786a.pdf

Direct download: ME_86_-_Which_Bear_Is_Best.mp4
Category:general -- posted at: 12:00pm EDT