This indeed goes back to the point that there’s no firm line between subsorting and speciation, only a grey area, so any tree we draw will always be a crude approximation of a biological reality. The distinct branches of trees only ‘work’ up to a certain point, just like newtons laws pf gravity only work for certain scales.

Again, thanks for making me realize this!

The point that this doesn’t place us at the crown of evolution still stands of course, especially because language as we find it in humans doesn’t seem to be a logical or necessary outcome of evolution. But a wonderful ‘coincidence’, of course!

As Geoff Pullum, a very distinguished linguist, put it on Language Log:

At present Language Log has nothing to say, except to utter a long series of about 25 successive alert calls warning you that anything concretely tied to present dangers apparent in the immediate spatiotemporal environment cannot bear a very strong relation to natural use of a human language. The things we say are not just long sequences of “Watch out!”, “Fore!”, “Timber!”, “Stop thief!”, “Hey!”, “Ouch!”, and so on.

This is not to say that only humans can have language, but we can say quite authoritatively that all the research done to date in the field of animal communication has provided no evidence that animals have anything like it.

In terms of the ‘relative phenotypic changes’ arguement, it all depends on what you see as a more interested phenotypic change. Humans obviously look a lot more different from the blobs that they came from, but bacteria have adapted so many more varieties in genetic sequence, even though they look somewhat the same. And as you point out in your comment, bacteria are capible of much quicker genetic change; antibiotic resistance spreads through bacterial populations much quicker than bacteria/viral resistance spreads through human populations.

@Doug: There’s nothing wrong with playing devil’s advocate: it keeps one sharp ;).
It is clear that evolutionary rates may differ. After all, homologous proteins may be under different selection pressures in different species. This has oft been misinterpreted as ‘more or less evolved’. Two years ago, it was found that chimpanzees had more fast-evolving protein sequences than humans did. Media quickly picked this up as ‘Chimps are more evolved than humans, OMG!’ (apart from the headline, this piece from Discovery covered the research fairly well). If one would follow this kind of reasoning, bacteria and viruses would be the most evolved species on earth, since their sequences change the fastest in the living world!
Your last example is a great one! The whale clearly underwent more morphological changes than the shark underwent, since it adapted to extremely different environments in its evolutionary history. But I’m hesitant to say that the whale ‘evolved more’, precisely because it implies that whales are more advanced somehow. For the shark too, is a highly derived form from the common ancestor of sharks and whales..

I’d like to call the ‘something’, ‘complexity’. I can fully agree with the statement that mammals are more complex than bacteria. Being multicellular (to name one thing) requires division of tasks, detailed regulation of gene expression (when and where) etc. The regulatory networks are more complex than in bacteria, who primarily change gene expression when environmental conditions change.

I hope this somewhat addresses the valid points that you raised!