The causes of the significant decline in intelligence in the past 150 or so years include
1. Differential reproduction such that the less intelligent have higher reproductive success than the more intelligent.
2. Relaxation of natural selection on those of lowest intelligence, due to the massive decline in child mortality rates - leading to an accumulation of deleterious mutations
http://iqpersonalitygenius.blogspot.co.uk/2013/02/what-are-genetic-causes-of-dysgenic.html
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Can the estimated intelligence of dogs tell us anything about the plausibility of the second of these mechanisms?
I made a blind hypothesis that (English) bulldogs would be among the least intelligent of dogs, due to my knowledge of the fact that most bulldogs have been, for several generations, born by Caesarian section, and that this would be consistent with a relaxation of natural selection
http://en.wikipedia.org/wiki/Bulldog#Health
I also hypothesized that dogs selected for the functional abilities (working dogs) - thus subjected to natural selection for ability; would be of higher intelligence than dogs selected for their appearance (show dogs - which would include bulldogs) - since these dogs would selectively be kept alive and bred from, even when subject to what would, in natural conditions, be fitness-impairing problems.
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On consulting the Wikipedia page on The Intelligence of Dogs
https://en.wikipedia.org/wiki/The_Intelligence_of_Dogs
I found my hypotheses both to be broadly consistent with the data:
Brightest Dogs
- Understanding of New Commands: Fewer than 5 repetitions.
- Obey First Command: 95% of the time or better.
- Border Collie
- Poodle
- German Shepherd
- Golden Retriever
- Doberman Pinscher
- Shetland Sheepdog
- Labrador Retriever
- Papillon
- Rottweiler
- Australian Cattle Dog
Lowest Degree of Working/Obedience Intelligence
- Shih Tzu
- Basset Hound
- Mastiff
Beagle - Pekingese
- Bloodhound
- Borzoi
- Chow Chow
- Bulldog
- Basenji
- Afghan Hound
There are apparent inconsistencies - such that Poodles and Papillons seem like show dogs, despite their intelligence; while Beagles used to be hunting dogs and bloodhounds used to be tracker dogs which would suggest they ought to have higher intelligence.
However, perhaps some of these data (Papillons?) are wrong; or the big Poodles are still used as working (gun) dogs; and perhaps pedigree Beagles and Bloodhounds have not been working dogs for many generations, and are now show dogs?
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Anyway - I present the data for what its worth.
As I say, it seems broadly consistent with my hypotheses based on the idea that relaxation of natural selection could rapidly lead to a decline in intelligence, due to accumulated deleterious mutations.
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