European Brown Bear Study: Aggression has Human Hunting Selection Component

In an article published in Molecular Biology and Evolution, Italian researchers mapped the genetics of European Marsican Brown bears (ursus arctos). They found evidence indicating the bears had been selected by human hunting pressure to be less aggressive. From yale.edu:

 To investigate, Italian researchers mapped the genes of Marsican bears and compared them with the genes of brown bears in Slovakia and the U.S. Their study, published in Molecular Biology and Evolution, found clear evidence that the Marsican bears had been selected for lower aggression.

The study has confirmed what naturalists, ranchers, hunters and wildlife managers  assumed to be true. Grizzly bears (ursus arctos) in the lower 48 states of the United States were known as especially aggressive since they became widely known in the Anglosphere after the Lewis and Clark expedition. Lewis and Clark first reported on ursus arctos as described to them by Indians on the Missouri river. From the Lewis and Clark Journals, Lewis, April 13, 1805:

 the Indians give a very formidable account of the strengh and ferocity of this anamal, which they never dare to attack but in parties of six eight or ten persons; and are even then frequently defeated with the loss of one or more of their party.

Lewis at first thought the “white” (ursus arctos) bears were actually wary and shy:

  tho’ we continue to see many tracks of the bear we have seen but very few of them, and those are at a great distance generally runing from us; I thefore presume that they are extreemly ware and shy; the Indian account of them dose not corrispond with our experience so far.

Their experience and opinion of grizzly bears (ursus arctos) soon changed to concur with what they had heard from the Indians. From Lewis, May 11, 1805:

I must confess that I do not like the gentlemen and had reather fight two Indians than one bear; there is no other chance to conquer them by a single shot but by shooting them through the brains, and this becomes difficult in consequence of two large muscles which cover the sides of the forehead and the sharp projection of the center of the frontal bone, which is also of a pretty good thickness.  

In 100 years of settlement and intense hunting, ursos arctos in the Americas had been selected so only those who fled from humans survived. The last 50 of those years included the development and wide spread use of cartridge firearms. One of the last redoubts of the grizzly population in the lower 48 states was in the mountains of the New Mexico/Arizona border. Montague Stevens spent years actively hunting grizzly bears in the area, from 1889 to 1901. In his book, Meet Mr. Grizzly, he says, on page 251:

 He will seldom attack a man unless the latter first molests him. As a matter of fact, he would rather run away than fight.

Stephen Herrero believed selection by hunting was the reason black bears seldom attack people. The same logic applies to grizzly bears. From his paper:

©2025 by Dean Weingarten: Permission to share is granted when this notice and link are included.

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