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Comment by xwdv | Hacker News Reader

Given the amount of microplastics humans consume, could humans one day evolve to eat and digest plastic?

I'd guess we'd end up hosting bacteria that do that first. I think mitochondria themselves started that way with early cells.

It doesn't even need to be so intimate/permanent as our relationship with mitochondria, gut bacteria are just little mercenaries who are here to help with digestion. Maybe some of them will figure out plastic (although I suspect they'll produce some bad byproducts while doing so).

There's no cause and effect like "my parents consumed a lot of plastic, so I will be able to digest them", if that's what you're asking.

For humans to evolve to be able to eat & digest plastics, we'd probably have to be in a situation where we'd die or be unable to reproduce if we didn't. There's probably been some interesting research around gluten/lactose tolerance that might be related (or maybe not).

> For humans to evolve to be able to eat & digest plastics, we'd probably have to be in a situation where we'd die or be unable to reproduce if we didn't.

That's really not how it works. If you get dumped into a desert you don't become able to eat sand.

You first need to luck out on the ability to digest the thing, before it can become an evolutionary advantage. Because we're so big and we evolve so slowly, the thing in question would have to be a micro-organism colonising our guts. But we consume so little microplastics compared to our size and the rest of our feeding that it's unlikely to happen.

There are much better odds for large seaborne life e.g. seabirds, as not only do they ingest a good amount of plastics (macro and micro both) it accumulates and becomes deadly as they can ingest pieces large enough that they can't excrete or vomit the bits, and it fills their stomach. Likewise sea turtles for instance.

Still not great odds though.

Rate of population evolution is proportional to generational turnover rate.

Microbes can cycle through generations in minutes. Humans these days 2-3 decades.

https://www.quora.com/Why-do-living-things-die/answer/Vas-Su...

It's possible but unlikely. There really isn't any selective pressure on humans to do this. It's much more likely that we will figure out how to handle microplastics before our bodies evolve to digest them.

I would imagine the more probable scenario is that, if plastics truly have a deleterious effect on human health, as many people say, then we will evolve to have more plastic-resistant bodies. But this can only really occur if we incur so much damage due to plastic that it broadly effects our reproductive potential at a relatively young age--a very high bar, and at which point it is probably much too late.

It can work more subtly than that, but takes admittedly a much longer time. If being slightly more plastic tolerant give you a slightly longer reproductive window, then those genes will become more common. Simple as that.

Yea - the thing that a lot of comments seem to be missing here is that evolutionary pressure comes in the form of mass die offs of those unfit for the new environment. If some people just have a higher incidence of cancer when they're 40+ there will be essentially no evolutionary pressure unless it's socially enforced (aka eugenics which is a really bad idea).

I don't think we could possibly evolve fast enough to keep up with the rate at which we change the environment (downside to having giant brains -- we can change the world at an incredible rate, but our generations iterate at a glacial pace compared to, say, bacteria)

It could be more subtle than that. If someone feels depressed and low-energy, they're less likely to find a mate and reproduce, and less likely to be able to take good care of their kids.

Maybe not evolve, but perhaps bio-engineer? Brings to mind this awful story - people choose to evolve to eat anything, and it doesn't go well for all other life on earth:

https://windupstories.com/books/pump-six-and-other-stories/p...

the bacteria really have an advantage with generation time and population and the lack of a society keeping the 'less fit' members procreating.

but maybe they'll get integrated into our gut biome since we do eat the stuff

> society keeping the 'less fit' members procreating

Society is part of the ecosystem within which fitness is determined.

We're not doing most of the digestion ourself, rather delegate it to bacteria. And bacteria are learning to do that - either the existing gut bacteria or new strains that we would collectively acquire.

We can already eat plastics, even if it is usually a bad idea.

Digesting them is another matter. For us to digest it ourselves is very unlikely, I think. Breaking down protein is already a big challenge for our stomachs without help.

Much better to get help, in the form of digestive bacteria with the right enzymes.

Not humans that have access to conventional nutrients. There's no selection pressure to encourage that kind of mutation. There's less and less selection pressure in general, these days.

Indeed. So many things that would have killed off our ancestors are now surviable and managable today, it seems likely to me that we are probably "de-evolving" i.e. more and more undesireable traits are surviving and being passed along to our offspring.

What evolutionary pressure is giving an advantage to humans who can digest plastic? The article is talking about "bugs" as in microbes, bacteria. Not animals.

My first assumption would be lack of food

Cancer and other health issues that make you either die early or affect your health/lifestyle enough where it becomes more difficult to find a mate to reproduce with.

Depends on evolutionary pressure. If it improves your chances of procreation and survival.

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