"The strongest body-builder is not close to our ancestors, or to chimps, in strength."
While you have some good points the above is false. The strongest humans are stronger than the strongest chimps and stronger than our strongest ancestors on record. With a population of over 7 billion individuals to pick from and extreme training we have now produced some extraordinary physical specimens.
What chimps have is greater muscle density. If they were as large as our largest lifters and got the same training then they would probably be stronger. But they're not.