Do we not understand enough about the human body? I have heard that we don’t fully understand the mechanism behind aging and this got me wondering. I mean our body seems to be like one of the first things we’d investigate, and yet we seem to know less than I had originally thought.
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>Do we not understand enough about the human body?
We don’t, no, primarily because it’s really, really, really, really complicated.
Here’s a map of [human metabolic components](https://metabolicatlas.org/explore/Human-GEM/map-viewer/endoplasmic_reticulum?dim=2d&panel=0&sel=&search=&coords=-10136.19,-107123.49,0.05,0,0,500&dataTypes=None&dataSources=None&dataSets=None). It’s specific to the endoplasmic reticulum, and not all are even shown. The schematic for metabolic reactions taking place in the cytosol has six parts. You can see the ones for the other organelles of a cell too: the mitochondria, the golgi, lysosomes and peroxisomes. What you’re seeing here, is a map of the chemical reactions that take place to keep life living.
And this is just the metabolism. Each metabolic step has one or more protein enzymes that have to get made in order to allow the chemical reaction to take place. The enzymes have to get transcribed from DNA. There’s a bunch of DNA replication that happens. That’s the genetic level at which life lives.
Every cell has a slightly different selection of all of these happening inside of it, because different cells need to perform different behaviors in order to keep the body functioning. Then there are cell-specific processes that have to happen. Life at the cellular scale has its own rules that are an emergent property of the genes and the chemistry.
And it’s not all about the cell. The cells themselves need to be sewn together in a way that produces functional organs. There’s an entire extracellular matrix that has to stay functioning. And some of these extracellular components are things you know: bones, tendon, skin. Life has to work at the level of organ systems.
If any of these, either the cells or the extracellular matrix or the big extracellular components like bones or skin get damaged, the cells of the body need to perform special functions that heal that damage. The body needs to maintain itself, and the cells need to be constantly adapting and changing their behavior depending on what the body needs. Life needs to heal itself and self-regulate, that’s a core function of staying alive.
To power all of this healing — and not just healing, growth too, ideally, if at the appropriate phase of life for that — we need enough fuel of various different kinds. We need caloric ones like sugars and fats, but also certain vitamins and minerals that you need to eat and they aren’t interchangeable with other food. That’s the nutrition life needs to survive.
The body is immensely, immensely, immensely complicated, and aging *can* cause and be caused by changes in pretty much any and all of that at once. Indeed, aging *usually* involves changes in pretty much all of that at once. Genes start shutting down, changing which chemical reactions take place. Bones get brittle, making tasks more difficult. As muscle mass is lost, the proteins needed to heal reduce in availability. As our digestive system ages, the nutrition we take in changes.
We know lots of mechanisms of aging. But aging is a lot of things happening all at once. That’s why we can say “we don’t know the mechanism of aging”, because the body’s really complicated and we don’t really know for sure why all of the things that happen during aging happen during aging.
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