However, there are certainly common elements in the world's moral systems - common in ways that are not explicable by cultural common descent.
They could be explicable by common evolutionary descent: for instance, our ethics probably evolved because it was useful to animals living in large groups or packs with social hierarchies.
If there is one such optimum, and many systems eventually find it, moral realism would have a pretty good foundation.
No, not at all. That optimum may have evolved to be useful under the conditions we live in, but that doesn't mean it's objectively right.
You don't seem to be entering into the spirit of this. The idea of there being one optimum which is found from many different starting conditions is not subject to the criticism that it's location is a function of accidents in our history.
Rather obviously - since human morality is currently in a state of progressive development - it hasn't reached any globally optimum value yet.
In this video, Julian Savulescu from the Uehiro centre for Practical Ethics argues that human beings are "Unfit for the future" - that radical technological advance, liberal democracy and human nature will combine to make the 21st century the century of global catastropes, perpetrated by terrorists and psychopaths, with tools such as engineered viruses. He goes on to argue that enhanced intelligence and a reduced urge to violence and defection in large commons problems could be achieved using science, and may be a way out for humanity.
Skip to 1:30 to avoid the tedious introduction
Genetically enhance humanity or face extinction - PART 1 from Ethics of the New Biosciences on Vimeo.
Genetically enhance humanity or face extinction - PART 2 from Ethics of the New Biosciences on Vimeo.
Well, I have already said something rather like this. Perhaps this really is a good idea, more important, even, than coding a friendly AI? AI timelines where super-smart AI doesn't get invented until 2060+ would leave enough room for human intelligence enhancement to happen and have an effect. When I collected some SIAI volunteers' opinions on this, most thought that there was a very significant chance that super-smart AI will arrive sooner than that, though.
A large portion of the video consists of pointing out the very strong scientific case that our behavior is a result of the way our brains are structured, and that this means that changes in our behavior are the result of changes in the way our brains are wired.