it's consequently a little deflating to observe how primitively our biology can utilize these metals; it will substitute any of a dozen metals into any number of reactions, some of which will contribute to the necessary chemical processes that make up the procedure of cellular respiration and some of which will stimulate production of cancerous clumps of cells in the midst of that process. your body cannot tell which is which in uptake; it cannot differentiate between the helpful zinc and the harmful mercury and it will trip into any myriad of wrong reactions if provided with dangerous inputs. the only solution is avoidance; you're hardwired to fuck it up.
we have evolved, at least, to put these metals away for later when we find them, and that's something that is apparently about as old as organized cells are. plants & fungi do it, too. so, we want the metals, we just lack the ability to select the right ones. but, that's sort of curious, itself. is that observing a primitive response to the environment that could be improved upon or is it observing a sink of genetic variation in most organized cells? and, is that an efficient way to utilize all of these electrons, after all?
for now, my concern is trying to figure out if we need some of these extra metals - vanadium, cobalt, nickel - and the best answer i'm coming up with is that your body sometimes substitutes these metals in for others, like iron and copper. so, it seems like we should focus on the other reactions, then. but, is that arbitrary? should we be looking at these metals as being interchangeably provided to meet a wide array of diverse requirements, rather than as being specifically provided to meet particular requirements? instead of having rdis for iron & copper & zinc, might we have a general rdi for a type I transition metal? & does your body really have the ability to interpret these metals more specifically?
cobalt is really weird in that sense. we need cobalt at the core of vitamin b12, which we have to eat animals to get. so, we don't just need this transition metal to produce the vitamin we use to make red blood cells, but we need this transition metal to be prepared for us in the cells of other creatures first, and then consume the modified transition metal for use in the dna-guided red blood cell production process. if we consume free cobalt, we just mistake it for iron or zinc and try to put it to use in some iron or zinc centered process. so, it's only via external processing of the transition metal that we can determine a way to differentiate it as a distinct entity.
it's the answer to what we do with half an eye; our ability to isolate these metals seems like it's a work in progress, despite being quite a lengthy work. even our most basic chemistry is really that fragile. and, maybe we'll have this figured out better in another 5 billion years - or maybe that's a problem that life on this planet never effectively solves, beyond the introduction of the chemistry lab as a total solution to our chemical inadequacies.
so, we don't seem to need these extra metals for anything specific, although we seem to be able to make use of them in a more general sense if we do succeed in consuming them.