[ WP ] A race of slaves who really are genetically inferior

I believe `` genetically inferior'' needs to be defined better here, or perhaps left to the imagination of the author? 
 
 Now, the question is, do you mean **race** or **species**? What we came to call race in sci-fi and fantasy settings are actually usually different species ( except for those which can interbreed and successfully produce non-sterile offspring; half-elves, half-Vulcan, etc., which still begs the question on their origins, where the elven-human thing is actually scientifically not plausible, but oh well, fiction. ) 
 
 I think we REALLY have to make a good bit of brainstorming here before we can create such a fictional race, because there is a point where obviously prominent genetic inferiority may cross the border to differentiate the populous as a completely separate **species**. 
 
 Let's see here; there *must* be different levels of genetic inferiority: 
 
 1. One may be missing a certain chain that has no observable effects ( or may, but is very hard -yet not impossible- to prove scientifically ). **Counter argument**: This would literally make every individual a different race in itself due to genetic variance, including identical twins the minute their genes start to receive individual mutations. Does n't really make sense. 
 
 2. One may be missing a certain protein, causing elevated intolerance to certain substances for that particular race ( ie. higher chance of lactose intolerance in East Asians, elevated risk of sickle-cell anemia in Mediterraneans, increased risk of diabetes and asthma in Africans, elevated psoriasis/eczema in Caucasians/White ). **Counter argument**: Note that all these examples are an `` elevated risk'' and is not genetic inferiority *per se*. So in a fictional sense, this fictional race *must have* a 100 % distribution of this particular genetic mutation which would make them truly genetically inferior and give them a significant disadvantage, which brings me to the third level, explained below. 
 
 3. A race can have an attribute that is highly observable and pronounced, with very close to 100 % distribution within the race, that actually provides an observable ( dis ) advantage over the others. Fairly common examples are physical attributes that measurably give an advantage to that particular race in sports. **Counter argument**: Is there really physical advantages that cause sports success among certain races, or is it the result of a cultural thing? Do fast/slow twitching muscle fibers really affect sprinting and swimming abilities, or can the unequal distribution at swimming medalists be due to the lack of training facilities? Why are East Asians more prone towards things that require brain power? Is it because they have a more analytical brain due to being subjected to learn very difficult alphabets such as Chinese/Kanji? Why are Indians generally considered to be good software engineers? Can it be just a statistical advantage due to their large population, or an economic factor where intangible production that is only dependent on manpower is a much better option for a country that has a very low GDP per capita? If whites are so much more adapted to the cold climates, how come Africans can live in the Northern countries? Is it really true that blacks ca n't get sunburn? ( they can, by the way ). We can never know how much the genetic differences have a role in this without taking these other factors into account. 
 
 4. The genetic difference is so vast that cognitive abilities are severely different ( mental capacity is at most at the level of a 9 year old compared to a normal human ) or physical attributes give a significant advantage ( can run like 95km/h rather than the 44.72km/h, that of Ussain Bolt, or has a maximum lifespan of 15 years, can breathe in freshwater, can photosynthesize, etc ). **Counter argument**: Well, this may imply that the other race is actually inhuman, does n't it? 
 
 So yes, this brings me back to my question: do you mean **race** or **species**?
