Bighorn horns not so big
First posted on homepage: 12 December 2011 (GMT+10)
Re-posted on homepage: 9 December 2020 (GMT+10)
Trophy hunters making the pilgrimage to Canada’s Ram Mountain, Alberta, home to the world’s biggest bighorn sheep, are being increasingly disappointed. Ram Mountain has long been a magnet for sport shooters of North America’s mountain sheep,1 but rams with the large horns so highly prized by hunters are now hard to find.
A world-class trophy ram is regarded as an extremely valuable commodity, with hunting permits being auctioned for very large sums. How large? One sport shooter paid over a million Canadian dollars in 1998 and 1999 for permits to hunt trophy rams in Alberta.
But such is the decline in horn size of Ram Mountain’s rams, that in recent years hunters have gone home empty-handed, not having found any sheep with horns larger than the minimum regulation size.
Researchers who documented the decline in horn size over the past three decades say it is “an evolutionary response to sport hunting of bighorn trophy rams” (emphasis added).2,3 They noted that ram body weight has also declined, essentially confirming earlier suspicions that selective removal of large-horned rams was reducing the overall genetic fitness of the bighorn sheep population.4,5 By killing the largest rams “of high genetic quality” before they reach their breeding peak, the hunters have depleted the genes for big horns and fast growth. These “undesirable evolutionary consequences” of trophy hunting “will be extremely difficult to reverse”, say the researchers (emphasis added).2
It’s not evolution!
To the extent that the researchers have observed that selective culling of large-horned rams at Ram Mountain has diminished the size of rams and their horns, with concomitant reduction in variety in the gene pool and a deterioration in the population’s “genetic fitness”, the researchers are correct. But these changes are not an “evolutionary response” or “evolutionary consequence” as they have nothing to do with evolution. Evolution—the supposedly information-gaining process by which, over millions of years, some primeval soupy ‘seep’ became sheep—is nowhere in evidence here.
Instead, Ram Mountain’s bighorn sheep population has lost genetic information, not gained it. Note the researchers’ own admission that “such changes will be extremely difficult to reverse”. Indeed, despite the recent drop-off in hunting (because hunters could not find rams with horns larger than the minimum legal size), “horn size has not recovered”.3 This strongly parallels the “crash” of the cod fishery off the Canadian coast, where cod have failed to return to their former size despite the Canadian government’s closure of the fishery in 1992 in order to let it recover.6 It seems that once the genes for large size are lost, they’re gone forever.7
Hunting seems to have had similar impacts upon moose, too, which now have smaller antlers than was the case just a few decades ago. And selective ivory poaching is thought to be the cause of a dramatically increased frequency of tuskless elephants in many African populations.
Note that in all these instances the selection pressure is essentially an artificially-imposed version of ‘natural selection’. Neither such ‘artificial’ nor ‘natural’ selection is in any way ‘evolution’ as it can only favour certain genes over others, it cannot generate any new genetic information. Rather, selection (whether artificial or natural) can only operate on (i.e. cull out) genetic information that already exists.8 And that’s exactly what’s been happening on Ram Mountain.
References and notes
- The mountain sheep at Ram Mountain are classified as Ovis canadensis. Some mountain sheep elsewhere in North America are classified as Ovis delli. Return to text.
- Coltman, D., O’Donoghue, P., Jorgenson, J., Hogg, J., Strobeck, C., and Festa-Blanchet, M., Undesirable evolutionary consequences of trophy hunting, Nature 426(6967):655–658, 2003. Return to text.
- Whitfield, J., Sheep horns downsized by hunters’ taste for trophies, Nature 426(6967): 595, 2003. Return to text.
- Dey, P., Bighorn sheep suffering decline of the fittest, University of Alberta Express News, www.archives.expressnews.ualberta.ca, 10 December 2003. Return to text.
- FitzSimmons, N., Buskirk, S. and Smith, M., Population history, genetic variability and horn growth in bighorn sheep, Conservation Biology 9(2):314–323, 1995. Return to text.
- Catchpoole, D., Smaller fish to fry, Creation 30(2):48–49, 2008; Return to text.
- Similar selection pressures from harvesting of wild game species post-Flood (i.e. in the last 4,500 years) could also explain their often smaller size today compared to fossil counterparts. Return to text.
- See also: Wieland, C., Muddy waters: clarifying the confusion about natural selection, Creation 23(3):26–29, 2001. Return to text.