An recent example of evolution observed on an animal, not just bacteria

[fun4alll]

http://www.bbc.co.uk/news/science-environment-22611143

A strain of cockroaches in Europe has evolved to outsmart the sugar traps used to eradicate them.

American scientists found that the mutant cockroaches had a "reorganised" sense of taste, making them perceive the glucose used to coat poisoned bait not as sweet but rather as bitter.

[sudo]

Then again it could that these roaches have always been mixed in with the ones that liked sugar but were so few in number. But when the sugar loving ones started dying off, these sugar hating roaches were the ones that predominated.

sudo

[MemphisBill]

That's evolution

[Robert]

Unfortunately, from the perspective of the evolution-denier, this is only a
micro-evolutionary change, not macro. Intelligent design folks allow for
natural selection as long as it does not involve speciation; organisms can
change within their species but do not evolve into a different organisms at
some point. The biological species concept can be hazy at the edges because
it is often difficult to observe the point at which a species and an
offshoot actually stop reproducing with each other, ultimately leading to
two divergent species.

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[sudo]

No, evolution is one organism giving rise to another organism, Bill. I postulated that there were two distinct species living the whole time. One thrived on sugar and the other didn't. When the sugar loving roaches started dying off in huge numbers the only ones left were the sugar hating ones.. which had been there all the time in such few numbers they hadn't been observed to even exist. 

sudo

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[fun4alll]

I think that's too narrow a definition of evolution sudo. There are not two distinct species here, only variation within one spices that's being accentuated by an environmental influence that exerts a filtering process. A significant change in the relative frequency of a given set of genes within a population still qualifies as 'evolution', even though it falls far short of the creation of a new species.

As far as witnessing that process is concerned, the closest thing I've ever read about concerns populations of squirrels on adjacient islands in the Philippines. On one island, male squirrels can breed with females on both of two adjacent islands. But in the other population, interbreeding always produces infertile off-spring. Are they sepearate species? Well, this discovery has stressed our very definitions! There is an active flow of genetic information in only one direction; in the other direction it's cut-off. This is now recognized as an intermediary step in the creation of a new species. After all, it has to happen at some point, and in the case of these squirrel populations, we've caught the process at mid-step. Evidently a rather short-lived half-step, which shows how this process takes place; snipping the connection one side at a time.

Our definitions of species is being stressed. Firtle offspring is not a requirement any longer. If the offspring are Ill suited to survive, or will not come into being in nature, then sepearate spices exist. For example, the liger and tigon are both firtle, but lions and tigers are reguarded as sepearate species. Also, there are dolphin/whale hybrids that are furtle, but they don't exist in nature, so they are also reguarded as separate species. There are butterfly's that can breed with subspecies on the other side of mountain ranges... But the offspring can't fly, so they are doomed. That's sufficient in the newer definitions of what it means to be a species, but, ironically perhaps, our definitions themselves are continuing to 'evolve'.

[sudo]

Too narrow a definition? If both of these strains had been present for millions of years living side by side... then due to a change of food source one of them dies off leaving only the other one... how can the one that survived be said to have evolved from the other?

sudo

[fun4alll]

Sudo, they were not separate species to begin with. It was described as a single population with a glucose intolerent tendency that ramped up over time, not a binomial population that switched from one mixture ratio to another. The same trend had previously been identified in rats that developed an insensitivity to DDT. These so called super rats of NYC were larger, had a faster metabolism, and developed as DDT usage was in effect. They disappeared back into the rat population after DDT usage stopped. Generally, it's best to assume that peer reviewed published results don't suffer from trivial logic errors like the one you assume.

On a side note, the mixture model you suggested has been used before. it was used to defend the notion that cigarets don't cause cancer. Rather, being cancer prone makes one tend to enjoy cigarets. You see, people are of two types, a single population is actually a mixture. In one sub-population, we have cancer prone cigarette fans and in the other we presume the existence of another sub-population of less cancer prone people that tend to not enjoy cigarets. A convenient mixture model like the one you suggest is contrived, essentially reverse engineered specifically to argue that the researchers are foolish, and have been misled, and thus no signs of evolution are taking place, and cigarets are actually healthy to use... I'm not sure why you're motivated to fabricate a contrived explanation like this, but to each his own.