Well, okay, let's take those one at time.
Super strength would mean a high degree of muscle mass, which in turn would mean bulk. There are quite a few ways that could be a disadvantage in some situations. For example, there are drugs and toxins that bind preferentially to and accumulate in muscle tissue. (The only one that springs to mind off the top of my head is digitalis, but I distinctly recall my profs in pharmacy school droning about others. I'm too lazy to go dig out my old texts though.) In an envoirnment that had low level contamination of such toxins, maybe in the water supply or food chain, people who were highly muscle bound would be much more likely to build up lethal levels. And if we had engineered our whole population to be that way, we would be in big trouble.
Second, bulk can be a *big* disadvantage in cramped or enclosed spaces. A big guy wouldn't be able to move freely, while a smaller faster opponent could rip him to bits. And again, if we had engineered our population so that everyone looked like Arnold Schwartznegger, we would have big problems coping with situations where speed and agility would be more important than strength.
Third, a person with lots of muscles has a higher metabolic energy burn than a small person, and has much less ability to store energy reserves than a person who is fat. Lean muscle burns energy very efficiently, but it doesn't store it. They would have a much harder time getting through times where the food supply was intermitant or non-existent than other types of people would. And agin, if our population consisted entirely of people like that, we would have problems.
Now, am I saying that being strong and having lots of muscles is a bad thing? Of course not. It's very usefull to have that in our genetic pool, but it is not usefull to tailor our gentic pool to simply that. That's especially true for the situation in WC4, where Tolwyn was proposing to prepare the human race for an interstellar war against unknown enemies and across many planets. To simply assume that all the envoirnments we'll end up in and all the enemies we'll face for the rest of our history will only challenge us in a way that suits the profile of the "ideal human" we've picked out in advance is a little optimistic to say the least.
Okay, let's look at intelligence. I agree that it's pretty hard to think of a drawback for superior intelligence, but I don't agree that you can achieve superior intelligence by genetic manipulation. I've heard people blithely say that genes make a person more intelligent, but I would be very interested to see where they're getting this from. Last I heard, there were no genetic, physical or bio-chemical markers that identify people as being more intelligent than the norm.
The simple fact is that scientists, dispite numerous attempts involving twin studies and so on, have failed to prove a causal link between genetics and intelligence that holds up to serious scrutiny. There are a couple of reasons for that.
First of course, just how do you determine superior intelligence? It's not something like height or weight that can be easily measured. A simple IQ test is invalid for a couple of reasons. First of course is the cultural bias, as people of the same cultural group as the predominant group that designs and adminsters any given test almost invariably outscore those from other cultures. Asian-Americans, for example, generally score several points on average below Caucasians, but tend to do better acedemically. Second, IQ tests only measure general knowledge and problem solving ability in a very limited context. It doesn't measure such things as goal setting, longer term planning, the ability to delay gratification, judgement, common sense and so on that we would associate with intelligence. And of those, it's almost impossible to seperate out what's innate and what's learnt. Because of all those factors that go into determining intelligence, it's just about impossible to make of clear definition of just what constitutes superior intelligence. Any judgment is pretty much arbitrary, and shaped by the judge's own viewpoints.
Then there's the effect of envoirnment, the old nature and nurture question. A massive proportion of our success in life is determined by where we start out and the help we get along the way. Just about anyone who is lucky enough to start out in a first world country will achieve more and be more successfull than a person born in a AIDS infested slum in Southern Africa. That's not any evidence of genetic superiority, just the luck of the draw. And since so much of human behaviour is learnt by imitation and repeation (from such basic things as speech and toilet training to what is socially and culturally acceptable to very unnatural skills like driving a car and flying a plane), how do we determine just what the cause of higher intelligence is? Are we more likely to be intelligent because we're born that way, or is intelligence learnt from the people around us?
To finish off a very long post, it's far from obvious or self explanatory that there are set superior genes. In the end, it comes down to a rather arbitrary judgement of what is superior and inferior. To go back to that AIDS post I made earlier, a gene that codes for a weak CD4 would have been considered inferior if we had found out about before we knew about AIDS, because it creates a weaker immune system than normal. Should we, in all our finite wisdom and lack of knowledge of what the future may bring, be trying to decide what the human race should be like genetically? Once the choice is made, there is no going back, and all the genes that we eliminated will be gone forever.
Best, Raptor