It never ceases to amaze me how many different dog breeds were created from the domestication of the wolf. The same amazement occurs when I look at how many races of humans there are and how different we too, can appear from one another.

1) Relatively speking, are the differences between dog breeds the same as the differences between human races? (genetic mutations, etc.)

2) Some dog breeds are noted as being 'more intelligent' thus having better problem solving skills and being faster learners such as collies, retrievers and poodles. So if this type of difference can occur amongst dog breeds that are all the same species, why can it not occur amongst human races that are all the same species?

3) I know the race and intelligence theories are rather controversial but if there can be physical differences between human races, owing to the environmental demands, why can't there be also cognitive differences?

4) And why isn't it valid to state that some races are more/less intelligent than others?

I'm hoping for an answer that touches on the genetic and evolutionary aspects. Thanks.

I think a really important point to grasp is that "race" in a human context is not a biologically well defined concept. It may/may not be better defined in sociology but I am not sure. The wiki page has quite a good overview
http://en.wikipedia.org/wiki/Human_genetic_variation (see section on categorisation of the world population section).

Humans harbour plenty of genetic variation and this is - to some extent -  structured both spatially and by self-identified ethnic group. So you can, for instance show there are genetic differences between sub-saharan African populations, and European ones. However, you could also show genetic differences between Norwegians and Germans - does that make them different races?  Furthermore 1) the structuring is imperfect, 2) it does not correspond to people's simple preconceptions (of e.g. black people, white people), 3) genetic variation among groups (however defined) is low relative to variation within groups; and, 4) to the extent that "races" exist in humans, matings have always occurred between groups (promoting genetic homogeneity).

Contrast this with dog breeds for which we have selectively bred traits under artifical selection while actively preventing inter-breed matings (or rather cross-bred offspring are not considered breeds). Could we do this in humans? As a thought experiment (i.e. leaving aside the ethics) - yes, and I am sure that we could select for more intelligent and less intelligent human breeds (or ones with floppy ears etc ). However, this has not been done in humans while it has in dogs. Hence the concepts of dog breeds and human races are not really comparable.

To answer 3 and 4, given that there are some genetic differences among e.g. geographically defined human groups despite extensive admixture, there is no reason in principle why these could not be present at genes influencing cognitive performance (provided selection for "intelligence" is not too strong). However, in the absence of any scientific evidence (and recognising that defining and measuring intelligence in a way that is not culturally biased is itself problematic), assertions that some races are more/less intelligent than others, should (in my view) be seen as plain old ugly pedjudice.