For example, why did zinc, of all things, start getting utilized by brain and prostate tissue in humans?
Metal ions can perform interesting chemical reactions that organic molecules cannot. A positively charge metal ion can also naturally bind to negatively charged proteins. So the organisms that more successfully took advantage of these chemical reactions reproduced more effectively than the organisms that didn’t.
The answer is almost certainly “because it was available” but that doesn’t exactly explain much.
Animals whose biology that used the metals reproduced more successfully is the explanation. It could longer lives, better reproductive outcomes, or a ton of other reasons but it all comes down to reproduction.
Well, genes, if we want to get really technical. Otherwise you can find counterexamples where genes are detrimental to the organism, but manage to spread anyway do to some quirk.
Theoretical biologist here. I’m going to push back on that just a bit. I think that you might have mentioned Selfish Gene, too. That was not the best book even at the time of publication (most biologists had a number of problems with it oversimplifying in a way that’s probably similar to what anthropologists think about Guns Germs and Steel). It also has been getting worse the more we learn.
Evolution acts on the phenotype, not the genotype. It affects the gene makeup of the population through differential reproduction rates. “Fitness” can be measured as a value relative to the rest of the population specifically by using the number of offspring. So what I’m saying here is that all factors that affect phenotype, whether genes or other factors, affect evolution.
So, of course genes are important. But you have epigenetic factors, too. link here You also have extensive non-coding regions that regulate transcription. You have rna editing. And so on.
If you’re interested, I would highly recommend a book called How Life Works by Phillip Ball. It was just published in November and is an outstanding summary of how much our understanding of life has evolved (heh) in the last 20 years or so.
Well, you would know a lot better. And thanks for the reading recommendation.
What are your thoughts on viruses as a form of life? Asking what natural selection is in exact terms is pretty closely related to asking what life is, since life is probably some subset of things that can do natural selection.
Personally, I do think of viruses as a form of life, and although it’s not universally held by any means, I think there’s a growing consensus around the idea.
That’s probably as minimalistic as I would go, though. I mean, you can make a similar argument to some extent about prions, but prions are too close to being “just chemistry” for me.
Viruses on the other hand cooperate and compete in complex ecosystems, which in my opinion magnifies the complexity of a virus as an element of a complex adaptive system. They don’t have a metabolism as such (which is why so many don’t consider them living), but their ability to conduct theft of resources of more complex and obviously living systems makes me push them to group of living things.
One of the nearest things about biology is that there’s always an exception to the rules and examples, and the simplifications we make when teaching bio 101 are really best learned as rules of thumb. Things like what a “gene” really is, the operation of selection, and even what constitutes a “species” can lead to some really interesting discussions.
A few fields are a bit like that. I remember my chemistry teacher in high school saying something similar.
As mostly a math person, it kind of bugs me. There definitely is one set of rules that a field obeys, and while it’s usually necessary to simplify I’d really like to know how not to. Sure, water is mostly incompressible, but it’s not exactly so, and that’s how sound works and can translate to other mediums. And then once you get down to small scales, high energies or low pressures you start seeing the individual water molecules being relevant and doing all kinds of different things. Those factors were always there, even if they weren’t relevant.
Sorry, maybe that’s a bit of a rant, but all that to say I’m sure you can find a consensus on these questions eventually.
Generally they don’t impact the reproduction rate enough.
Let’s take reproductive cycles as an example of there being no single benefit or negative. Some species reproduce in mass quantities and that works for them, while others are slower. The fast one having genes that slow reproduction would probably die out because their adaptation of mass reproduction is what keeps them around. A slower reproducing species won’t necessarily benefit from higher rates as they might overpopulate their range. So what looks like a detriment could just be a thing that neither benefits nor is a detriment depending on the complex context of the species and where they live.
And sometimes detriment are offset by other benefits, like sickle cell anemia having some terrible outcomes but it also protects against malaria so in the context of somewhere with a high rate of malaria it is beneficial to survive to a reproductive age, which would explain it sticking around.
Ah, so you haven’t heard about this thing. It’s not really lucky 10,000 territory, but it’s still cool.
There are situations, where in sexually reproducing organisms, an unambiguously bad gene can spread through the population, just by ensuring it’s more likely to appear in the next generation. As long as it’s not so bad it kills the species off, you’re still likely to observe it a lot in a future population. We’ve actually harnessed this idea technologically, with genetically modified mosquitoes that crash their local population by skewing all offspring malewards.
Richard Dawkins wrote a pop-sci book about it. Here’s a list of examples on Wikipedia.
That is one example of ‘not detrimental enough to impact reproduction’ which I meant in the context of a population and not an individual, but I guess that my wording wasn’t clear enough.
But that’s all that can be said. Life is random. There is no “why”. The body uses zinc because it can.
Depends how you’re using “why”. In Russian, they actually have two words for why, one of which implies teleology, and one which doesn’t, and merely requests some explanation for a phenomenon. I wish we had that in English.
In this case, it’s such a general question you can’t do much better, but you could, for example, talk about why oxygen-carrying proteins pretty much always incorporate an ion of something, in a merely cause-and-effect way. (And I actually don’t know the answer to that one)
In English we can use “How”.
The answer to the question, “How did this evolve?”, is the same as the answer to a non-teleological “why”. People just need to learn to use “how” because “why” is such a loaded word.
When using “how” in this sense and “why” in the non-teleological sense, they have the exact same meaning (at least to my ear), but then the “how” version isn’t ambiguous.
If I say to myself, “How did this evolve?”, the question feels good. It feels clear, and my mind leaps into thinking about the function of the mineral in the body and the chain of evolutionary steps that could have caused it.
If I say to myself “Why did this evolve?”, I just can’t get the teleology sense of the word out of my head. If someone didn’t want a teleological answer, why did they say “why” when “how” is clearly better? So I assume they mean why.
I feel like even if I answered their question, the next one would be, “Yeah, but why?” Making me feel like I wasted my time explaining the “how”.
That’s might be an option too, I guess, but in some situations it’s a different question. If I make a mistake and you ask “how”, you might just get more details. If you ask “why” I might respond with “I was tired”, which doesn’t really imply teleology. As I understand it почему would be more specific to cause rather than just means, but then again my Russian is pretty basic. The word “how” would be как, and it even works as an intensifier the same way.
Yeah, I was focused on science questions since this is a science questions community. It’s not universal advice.
Also, metals can easily accommodate varying number of electrons in the electron shells of their atoms and still be stable. That makes them very good to quickly store and release electrons which means they can help say transfer molecules around (iron for transport of gasses), scavenge free radicals (e.g. manganese) etc.
I’m guessing the main reason is “why not”. It’s in the environment, and one day some critter mutated a new process that involved it.
It’s not just complex life, either. Bacteria use all kinds of strange elements in various enzymes and complexes.
