- Registration time
- Last login
- Online time
- 0 Hour
- Reading permission
This post was edited by Singularity at 2012-7-5 14:01|
In a related study, Dr. Suzanne Shultz and her colleagues at the University of Oxford have found that in Britain, where the habitat for birds has been reduced in recent decades as a result of increasingly intensive farming, the numbers of birds has declined. The decline has been greatest among birds with smaller brains, apparently because they have been less successful in adapting to the changed environment. Larger brained birds have been able to migrate into towns and cities and thrive there.
The same relationship holds true for domesticated as opposed to wild species of mammals. Dogs have a lower encephalization index than wolves, and the same is true for domesticated pigs, horses, llamas, ferrets, etc. compared to wild variants. This is clearly a genetic trait because wild animals kept in captivity for several generations do not decrease in brain size, nor do domestic animals that go feral increase in brain size in just a few generations. Experiments have shown that wild animals are considerably smarter than their domestic kin; they have to be, since they do not depend on humans and have to fend for themselves. Many also have complex group behavior in the wild that is lost or diminished in captivity.
| A lot smarter than his barnyard cousins. |
The amount of brain loss that results from domestication varies by species, but those that originally had high encephalization indices lose the most. Tame laboratory mice do not suffer any brain loss at all compared to their wild cousins. Tame guinea pigs have 5 to 7 percent less brain mass than wild guinea pigs, and lab rats have lost only about 9 percent through domestication.
The more intelligent wild animals give up more brain mass when they are domesticated: Llamas and alpacas — 19 percent; cats — 23 percent; dogs — 29 to 34 percent, depending on the breed; sheep — 30 percent; pigs — 34 percent. The decline in intelligence for a species is roughly in proportion to the percentage of brain mass that has been lost.
The message of all these studies is clear: A larger brain helps a species solve new problems. It can make the difference between survival and extinction when environments change. Brain size counts — even for birds.
Roth, G. and Dicke, U. Evolution of the brain and intelligence. TRENDS in Cognitive Sciences 9 (5): 250.
Beals, K. L., Smith, C. L. and Dodd, S. M. Brain size, cranial morphology, climate and time machines. Current Anthropology, 1984. 25, 301–330.
Henneberg, M. Comment on Beals Dodd and Smith. Current Anthropology, 1984. 25, 321–322.
Lynn, R. Race Differences in Intelligence: An Evolutionary Analysis. Augusta, GA: Washington Summit Publishers, 2006.
Maklakov, A. A., Immler, S. Gonzalez-Voyer, A. Rönn, J. & Kolm, N. Brains Sex and the city: big-brained passerine birds succeed in urban environments. Biology Letters, 2011, published online 27 April
Shultz, S., Bradbury, R. B., Evans, K. L., Gregory, R.D. & Blackburn, T. M. Brain size and resource specialization predict long-term population trends in British birds. Proceedings of the Royal Society, B, 2005, 272, 2305–2311.
Vernon, P.A., Wickett, J.C., Bazana, P.G. and Stelmack, R.M. The neuropsychology and neurophysiology of human intelligence. In R. J. Sternberg (Ed) Handbook of Intelligence. Cambridge, UK: Cambridge University Press, 2000.