# Could we breed for intelligence simply by breeding for brain/body ratio? (animals) **URL:** \ **Category:** Factual Questions\ **Created:** [August 25, 2014, 7:34am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445 "2014-08-25T07:34:03Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Critical1](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Critical1](https://boards.straightdope.com/u/Critical1)\ **Post date:** [August 25, 2014, 7:34am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/1 "2014-08-25T07:34:03Z")
The title says most of it, I was thinking if we started with an already clever species and could find a way to pick out and breed the ones with the highest brain to body ratio we might be able to get smarter pets. Dogs, Ravens/Crows were my main ideas but any critter would do for the purposes of experiment. The logic behind this is simply that the Brain/Body ratio seems to be one of the bigger correlations to intelligence. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [August 25, 2014, 8:09am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/2 "2014-08-25T08:09:09Z")
> [@Critical1](#): > > The logic behind this is simply that the Brain/Body ratio seems to be one of the bigger correlations to intelligence. Not really. Even in cross species comparisons the correlation, if it exists at all, is far from direct, and I doubt whether there is any within-species correlation. Come to that, measuring the intelligence of animals in anything more than a very rough, qualitative way, is pretty much impossible. (It ain’t really that easy to measure it meaningfully in humans either.) ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [August 25, 2014, 8:53am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/3 "2014-08-25T08:53:49Z")
You would certainly do better to determine different aspects of human-like intelligence, come up with tests for those which could be passed by an animal, and then cull/breed based on the results of the tests. Likely, that would result in larger brain mass over time, but in a more useful fashion. Say, for example, that you wanted to find the strongest man in the world, so you decided to measure the thickness of each man’s bicep. The result would be that you get someone with some hormonal disease that causes misshaped limbs, a massively obese man, or some crazy bodybuilder that’s been injecting silicone into his arms. You almost certainly wouldn’t end up finding the strongest man in the world. Or say that you want to breed the fastest horse in the world, so you start breeding really tall horses, figuring that a bigger horse is going to go faster than a smaller horse. Just as likely, all that’s going to net you is the independent discovery of the square-cube rule and how it applies to the materials and structure of bones. Generally, if you want to get the best results, it’s better to measure the thing you actually want to measure, not some secondary thing that’s possibly correlated. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [August 25, 2014, 9:29am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/4 "2014-08-25T09:29:19Z")
What **Sage Rat** said. If you breed for a bigger cranium, you may get organisms with a bigger gap between brain tissue and the skull, the same number of cells just less densely-packed, or an increase in the size of more “primitive” organelles instead of the cortex. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [August 25, 2014, 11:16am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/5 "2014-08-25T11:16:42Z")
> [@Critical1](#): > > The logic behind this is simply that the Brain/Body ratio seems to be one of the bigger correlations to intelligence. “Correlation” is the key word here. To overuse a tired cliche, correlation is not causation. ---
**Author:** ![filmstar-en](https://avatars.discourse-cdn.com/v4/letter/f/50afbb/32.png) [@filmstar-en](https://boards.straightdope.com/u/filmstar-en)\ **Post date:** [August 25, 2014, 12:20pm UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/6 "2014-08-25T12:20:14Z")
If you try to breed certain characteristics you often degrade others. It is a zero-sum game. Human beings can communicate by speech, but to make a voice box the jaw shape is altered and this leads to about 20% of people having trouble with compacted back teeth. So we get to talk, but some may die from from these problems. We have large brains, but the needs a large skull which leads to a percentage of women are going to die in childbirth. Big brains consume large amounts of energy, so the digestive system has to be adapted to deal with higher energy foods and the brain has to ensure the body gets enough to eat. If you look at dogs, which are peculiar, in that huge variations body shape can bred in just a couple of generations. Many breeds suffer from all kinds of ailments. Deafness, blindness, lots of arthritic and eye problems. Simply breeding for brain/body ratio will mean that something else is going to be underdeveloped and it may not result in an intelligent animal, just one the dies young. Design, in many areas, is a whole series of tradeoffs. Nature has a way of evening things out. I guess one day we might get to the stage where we can genetically engineer animals to have subtle qualities like ‘intelligence’ and for them not to be disadvantaged in some other serious function. Intelligence is something which is not straightforward to define. How do you measure it in animals is not easy. It is very debatable how to define it in humans. I had a friend who had a sheep dog. You would think that they are clever the way they round up sheep and it is impressive to watch. However, I was informed that that they were less impressive when you realise that is ALL they can do well. They are pretty dumb at most other things. They are one-trick ponies. We have a tendency to project human qualities onto animals that are often not really true. What is that…Anthropomorphism. Which is…not very clever.:dubious: ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [August 25, 2014, 4:41pm UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/7 "2014-08-25T16:41:20Z")
Restating what others have said. The OP’s assumption is that a high brain/body ratio equals intelligence. That isn’t necessarily so. There’s a correlation in nature because intelligence requires a high brain/body ratio but we don’t know it’s a two-way relationship. If we artificially breed animals for a high brain/body ratio, we’d undoubtedly achieve our goal. But we could easily end up with animals that have a high brain/body ratio but are no more intelligent than the control group. Here’s an analogy. You’re a government official that wants to encourage people to have more children. You discover that families with a higher than average number of children tend to live in larger than average houses. So you revise your tax policy to encourage the building of larger houses. The result is you’ll probably see an increase in the size of houses - but you might not see an increase in the size of families. ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [August 25, 2014, 4:54pm UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/8 "2014-08-25T16:54:35Z")
There are a whole range of fairly common developmental disorders generally known as [megalencephaly](http://en.wikipedia.org/wiki/Megalencephaly) that produce an abnormally large brain. Many (if not most) of these disorders are also associated with cognitive disorders. If you select for large brain alone, this is what you’re going to get, and the resulting animals certainly won’t be more intelligent. ---
**Author:** ![Ulfreida](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ulfreida/32/8014_2.png) [@Ulfreida](https://boards.straightdope.com/u/Ulfreida)\ **Post date:** [August 25, 2014, 8:48pm UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/9 "2014-08-25T20:48:25Z")
Just popped in to point out that I cannot think of an example of humans selecting for smarter in their domestic animals. Quite the reverse, for good reason. Carry on. ---
**Author:** ![Critical1](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Critical1](https://boards.straightdope.com/u/Critical1)\ **Post date:** [August 26, 2014, 2:37am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/10 "2014-08-26T02:37:15Z")
> [@filmstar-en](#): > > If you try to breed certain characteristics you often degrade others. > > It is a zero-sum game. Evolution is hardly zero sum. If it were we would have stopped at the single cell. > [@Ulfreida](#): > > Just popped in to point out that I cannot think of an example of humans selecting for smarter in their domestic animals. Quite the reverse, for good reason. > > Carry on. Border Collies? Bred for Intelligence specifically. Looking at the rest of the replies it would still be interesting to breed for raw intelligence if you could hammer out how to do that with different species over longer terms, could you keep breeding the smartest border collies for even greater intelligence? ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [August 26, 2014, 2:53am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/11 "2014-08-26T02:53:09Z")
> [@filmstar-en](#): > > If you try to breed certain characteristics you often degrade others. > > **It is a zero-sum game.** > > \ > Design, in many areas, is a whole series of tradeoffs. > > **Nature has a way of evening things out.** Just want to say that neither of those two sentences (emphasis added) are factual. They sound nice, in a folk-science sort of way, but simply aren’t true. ---
**Author:** ![Ulfreida](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ulfreida/32/8014_2.png) [@Ulfreida](https://boards.straightdope.com/u/Ulfreida)\ **Post date:** [August 26, 2014, 3:00am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/12 "2014-08-26T03:00:44Z")
> [@Critical1](#): > > Evolution is hardly zero sum. If it were we would have stopped at the single cell. > > Border Collies? Bred for Intelligence specifically. > > Looking at the rest of the replies it would still be interesting to breed for raw intelligence if you could hammer out how to do that with different species over longer terms, could you keep breeding the smartest border collies for even greater intelligence? Border Collies are not, in fact, bred for intelligence. Their intelligence is a byproduct of the work they are bred to do. The smartest Border Collie is not as bright as an average coyote or wolf. However, this is something of a tangent to the thread. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [August 26, 2014, 4:14am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/13 "2014-08-26T04:14:45Z")
While we’re on the subject, is it true that koalas have the lowest brain/body ratio of any species? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [August 26, 2014, 4:26am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/14 "2014-08-26T04:26:13Z")
> [@Little\_Nemo](#): > > While we’re on the subject, is it true that koalas have the lowest brain/body ratio of any species? I assume you must mean mammals, since reptiles, amphibians, etc have much lower ratios than any mammal. I’ve never heard that about koalas, and I believe that shrews and moles may have lower ratios than most marsupials. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [August 26, 2014, 4:50am UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/15 "2014-08-26T04:50:05Z")
> [@Colibri](#): > > I assume you must mean mammals, since reptiles, amphibians, etc have much lower ratios than any mammal. > > I’ve never heard that about koalas, and I believe that shrews and moles may have lower ratios than most marsupials. These animals may have have small brains but they have small bodies to match. So the ratios can be surprisingly high. A human and a mouse, for example, have about the same brain/body ratio. And a tree shrew has a ratio that’s four times higher than a human’s. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [August 26, 2014, 3:06pm UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/16 "2014-08-26T15:06:19Z")
> [@Little\_Nemo](#): > > These animals may have have small brains but they have small bodies to match. So the ratios can be surprisingly high. A human and a mouse, for example, have about the same brain/body ratio. And a tree shrew has a ratio that’s four times higher than a human’s. What do you mean by “these animals”? I was referring to shrews and moles (Leptotyphla). Tree shrews, despite the name, are more closely related to primates than they are to shrews. Mice of course are not closely related to shrews at all. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [August 26, 2014, 3:31pm UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/17 "2014-08-26T15:31:34Z")
> [@Little\_Nemo](#): > > A human and a mouse, for example, have about the same brain/body ratio. This explains how the mice were able to design and build Deep Thought. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [August 26, 2014, 5:04pm UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/18 "2014-08-26T17:04:29Z")
This is only partly a pile-on, when I hiccuped at “zero-sum” game. Evolution is not a zero-sum game. By definition, I would think, but I’m no game theorist. But putting evolution in that context is clever and the topic can always use one-line comparisons. So **filmstar-en** ’s post is zero-sum, by my rules. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [August 26, 2014, 5:06pm UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/19 "2014-08-26T17:06:31Z")
If we bred foxes for floppy ears, would we get gentle and domesticate-able foxes? ---
**Author:** ![Critical1](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Critical1](https://boards.straightdope.com/u/Critical1)\ **Post date:** [August 26, 2014, 5:44pm UTC](https://boards.straightdope.com/t/could-we-breed-for-intelligence-simply-by-breeding-for-brain-body-ratio-animals/696445/20 "2014-08-26T17:44:28Z")
> [@Leo\_Bloom](#): > > If we bred foxes for floppy ears, would we get gentle and domesticate-able foxes? interesting question…[This Video](http://vimeo.com/26671405) has a good bit about the russian fox domestication experiment. While they weren’t going for floppy ears they did get them. (Not sure where it starts but its a great watch if you like dogs at all)