That resistance to toxins we don't encounter often enough to constitute selective pressure, we carry around only if it's the accidental byproduct of another selected-for trait. Otherwise entropy would take care of it, sooner or later. Parent is right, evolution doesn't pay an annual subscription fee for some service which was useful in the past and might come in handy in the future.
You may just be trying to disagree with the author for sport.
> we carry around only...
Not true. We can carry resistance to some ancestral pressure which isn't part of the current environment.
> sooner or later...
Yes, sooner when it's costly, later when it's less so, through normal evolutionary pressure (entropy and all).
The point is, most species at time T do carry traits that aren't that useful to them anymore. The costlier ones yield enough negative fitness points in evolutionary game theory to rid the gene pool of them quicker. It brings us right back to the author's original argument.
It would be interesting to see how toxic these newts would remain if the garter snakes were eradicated. If this was indeed a costly trait, we should see a drop in toxicity over a long period of time (possibly evolutionary time). To rule out coincidence, you could follow multiple lineages as they speciated.
In fact, looking at related newts whose ancestors were toxic (assuming the trait is not novel in these ones) would give us some idea as well.
In the context of TFA, are you sure it's not GP who's arguing for sport? Maybe this clarifies the issue: one way to reword the root (critical) comment is "of course there is a cost, since entropy is always exacting a price". There's constant upkeep necessary for any trait if it is to be preserved. It points out a glaring blind-spot in the article.
(I agree with you)
It’s funny how often this sort of thing comes up. I’ve always felt that “biology” as a field was unique in the way that it is often taught. Bio 101, etc. - most of undergraduate biology - is often taught with this sort of sweeping worship of the process of evolution in a way that leads to it transcending rational thought. Natural selection is very real, and it’s also such a sorry excuse for an evolutionary algorithm :D
It’s been a long time since my first bio classes so I can’t remember the way I was first taught it, but I do remember all more advanced bio literally being told to unlearn what we had already been taught.
You really seem to lack any understanding of how evolution or biology work :(