Ever get the feeling that calling people the highest life-form on Earth isn't really saying that much? That a life span of 100 years is really quite short? That there's more to life than digital watches and spiffy towels?
Well, you'll have to deal with that last question on your own. The first two enquiries, on the other hand, have already been given a lot of thought. It seems reasonable that, being the fairly intelligent simian creatures that we are, we can replace the poorly designed bodies and minds nature has so arrogantly foisted upon us with something better. Not to mention doing something about the societies and environments we live in.
This viewpoint is called transhumanism and many people would claim that it's a pretty good idea. After all, who really wants to only live for a century when we'd like to get in a couple billion years at the least?
Now, proponents of transhumanism have several good points to make, and only a few are presented here, but they should still make a convincing argument.
As a species, human beings need improvements. One must simply look at the human body from an engineering standpoint to see the problem. It's damaged easily, can only survive in a narrow range of pressures and temperatures, is susceptible to a wide range of biological and chemical pathogens, and derives energy from a highly inefficient combustion process. Pretty much the only thing going for it is its self-repair capabilities, and even those are limited. On a chemical level, people aren't really all that different from jelly - just protein and water.
On the mental front, people fare little better. The human brain isn't a half-bad piece of equipment, judging by the fact that, almost without thinking, we can do things which our most powerful computers and best programming skills still have difficulty with. However, anyone can see it also needs improvements. Speed, memory, and processing power can all be enhanced, and it really ought to work outside of an aqueous environment. Carrying around a skull full of water can be inconvenient at times.
We're not always going to exist 'out here'. Eventually we may be able to download our minds directly into computers, which is a really nifty idea. Being largely freed from real-world constraints will be a huge improvement. Even better, death will become an outdated concept. If someone should somehow die, they could simply be recreated from a back-up file. Even if they lived in a physical shell and just kept a few backups in various, widely-spaced locations, they would be protected against almost every possible disaster. Life span would increase exponentially with the number of backups, because the probability of all of them being destroyed drops off rapidly.
Technological advancements are already pointing in this direction. The best avenue for engineering these improvements appears to be nanotechnology, with which atoms can be manipulated individually to create nearly any physically-possible structure. This is rapidly becoming one of the hottest fields in modern science, especially because of the enormous potential benefits of such a technology.