>> This makes it sound as if "evolution" is some magical process whereby
>> each time we reproduce, our DNA gets optimised to our situation, so that
>> as generations pass, everybody slowly improves...
>
> Indeed, genes do not "try" to do anything. They just change slightly with
> each individual that's born.

If anything, the only thing "deciding" what genes will go into the next 
generation is YOU - when you decide who to **** with. ;-)

> Another thing that many people don't understand is that a change in a
> gene can have several consequences.

Again, just like a fractal. But then, if you look at molecular biology, 
you discover that cortisol is a hormone, and also just happens to be a 
neurotransmitter too - how random is that? That's like making a 
telephone that's also a video camera - oh, wait...

> I have been thinking that humans have evolved to a point where rather
> than becoming better, we may in fact be becoming worse. Because of
> progress in healthcare, nutrition, and all other kinds of things that
> help people survive, all kinds of detrimental changes to our genes are
> not being removed from the gene pool, which means that over time our
> genes will become more and more trash. I'm expecting that as further
> thousands and thousands of generations pass, the number of genetic
> disorders and diseases will only increase in prevalence, simply because
> there's nothing removing them from the gene pool.

That's the idea I get too.

> Actually, for humans to evolve to be less fat would require
>
> 1) for obesity to be an inherited trait (that can change without causing
>     ancillary side-effects that are worse), and

I think it already is.

It is obvious that how fat you are depends on what you eat. But it is 
equally obvious that some people have more of a tendency to retain fat 
than others, or more of a drive to eat more. As with most things, it's 
partly genetic and partly environmental.

> 2) for people with this trait to never reach a reproductive age.

Well, technically we just need them to not reproduce - either by dying, 
or by failing to find a mate, or whatever.

But yes, I share your conclusion. Not likely.

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