Every trait of an individual is in some way adaptive.
Pretty Well Wrong: evolution is messy - it depends on genetic variations in the population which for all intents and purposes can be treated as random. A lot of stuff gets "left in" organisms because while it doesn't do any good, it doesn't do any harm either, at least in terms of the evolutionary game, which is to live long enough to reproduce. This is why we have wisdom teeth, those veins around the anus that turn into haemorrhoids in later life and (sometimes) heritable genetic diseases. They don't make a difference in evolutionary terms because they're not usually enough to kill you before you have kids.

Evolution is driven by competition between individuals to be the fittest.
Half wrong: looking at the social behaviour of humans and other animals we can see patterns of competition and co-operation between individuals. For example, within the wolf pack, wolves compete for the positions of alpha male and alpha female because these members of the pack have the mating privileges. On the other hand, wolves co-operate when they hunt. In the human pack, we compete for status in various ways but we have well developed forms of social co-operation as well. Evolutionary fitness is rarely as simple as light moths get eaten, dark moths don't or aggressive tigers live, cowardly tigers die.

So there's the eminently fiskable Gummo Trotsky take on evolution. I hope it goes some way towards explaining my beef with explanations of social phenomena, such as income and class differences, in terms of biology: even if it's via the indirect route of correlations between income and IQ. To complete the picture we need to take a look at IQ testing and statistical correlation. I'm saving that for later.