Recent comments in /f/askscience

PhyrexianHealthDept t1_j1r7l1j wrote

Reply to Maybe a simple question, but why are proteins structural? by danrthemanr

>I know proteins are important as structural elements, my question (as ever) is just why?

A couple things. First, a lot of "why" questions in biology are unanswerable, and the explanation you get will come down to quirks of life's evolutionary history.

Second, if I may, I'd like to reframe your question as "Why do we see proteins playing structural roles in the places that we do?" Proteins are just one type of structural molecule, and nature uses many.

Arguably lipids are the most critical structural component for all life since they can form membranes. Cellulose and chitin are polysaccharides (i.e. many sugars linked together) that have structural functions in plants and fungi/arthropods respectively. Lignin is another plant cell wall component, but it is actually a polyphenol. Some organisms even use inorganic compounds to provide structure - bones are obvious, but for a microscopic example look at the silica frustules of diatoms. Even in these examples, it gets messy. You can have several different types of molecules that together form some structural component.

You can think of evolution as a process of blindly stumbling into "solutions" for "problems". In some cases, evolution reaches different solutions for similar problems. Things like hair and fingernails are made of keratin (a structural protein) while insect exoskeletons are made of chitin (a structural polysaccharide). In other cases like the cytoskeleton, you only see protein being used. That brings me back to my reformulation of your question. You can make hypotheses about why this is the case, but they are very hard to test.

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Game_Minds t1_j1r5o47 wrote

Reply to comment by sciencedthatshit in What is the currently-accepted theory for how the moon was formed? by CopperGenie

Ahhh, okay. I remembered the 1.5 inches per year but in the wrong direction-- I think i mixed up decaying orbits / Lagrange points for closer satellites that are impacted by atmospheric friction. I had forgotten that the weird phenomena of rotation and tidal gravitational forces combine to speed up the moon's orbit, functionally the same thing as escaping. And yes, explode was a convenient fill in word for "expand into a red giant, assimilating most of the inner bodies in the solar system, then shed the outer layers in a not-quite-explosion, leaving a white dwarf core", but you're right, that's incomplete

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perta1234 t1_j1r33h3 wrote

Reply to comment by Jacquesatoutfaire in What does it mean for a population to be "genetically diverse"? by MysteriousLeader6187

By the way, famines used to be very common just 200 years ago, or even less. There were several per generation, also but not only in Finland. Basically that is why agricultural subsidy systems were created. Either there was way too little food or there was way too much food. Trade was not able to balance things enough.

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perta1234 t1_j1r2aau wrote

Reply to comment by thegagis in What does it mean for a population to be "genetically diverse"? by MysteriousLeader6187

These are side effects of HOW Finns lost variation, and what variation was there in the beginning. This is not result of low variability itself, but impact of what variability was left. Basically inbreeding depression. A very slow population decline could result in quite different end result, more akin to purging less advantageous gene variant combinations out of the population.

Effect of low variability is that the population is slow in adapting genetically (by selection on existing variation). Need to wait for suitable mutations.

Generally, many inherited diseases are adaptations to other environments. I guess the last one I saw, was suggestion that many autoimmune disorders are related to survivability over plague.

[Added: By the way, Finns lack many genetic diseases that are common elsewhere]

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