eli5 How does such a small difference in human body temperature make such drastic differences? Ex:98° compared to 102°

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eli5 How does such a small difference in human body temperature make such drastic differences? Ex:98° compared to 102°

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the biggest benefit from being warm-blooded is controlling your body temperature. A lizard might have its body temp go between 50⁰ and 100⁰ from day to night. Everything in every cell runs differently at different temperatures. Certain chemical reactions don’t happen if it’s too cold, or certain molecules that work well in the cold fall apart when they’re too hot. Bacteria in the gut need to be able to survive big swings in temperature, and can’t be specialized.

“Warm-blooded” animals aren’t so much about being warm as being the exact same temperature, all the time. This means everything is tuned to run really well, at the **exact** temperature it’s tuned for. The benefit is that everything in our bodies can work faster, more efficiently than a lizard’a, but the cost is that our bodies get thrown out of whack *fast* if that temperature changes even a relatively small amount.

Believe it or not your body temperature can vary through the day (and your lifetime) without major impact. When we are younger a higher temperature is actually more common and our average lowers as we age. Individuals vary a bit from each other too, but between 98° and 99° seems to be the sweet spot. Why, you ask?

Fungus. No seriously. Scientists looked into it and found that our body temperature is actually balanced between being high enough to be in hospital to most fungal infections but low enough not to require greater caloric intake. Mammals evolved to avoid fungal infections which are far more prevalent in our cold blooded distant cousins such as reptiles and amphibians.

However our body chemistry also evolved around that temperature too so getting too far off, either too high or too low has increasingly bad consequences. You will generally be fine with a slightly higher or lower temperature for a short time, but if it persists or if it becomes more extreme your bodies processes start to malfunction or break down. Millions of years of evolution have found a sweet spot so it’s better to stay like that for now.