3 ms·

It appears humans are more sensitive to fresh rain on dry soil than sharks are to blood in the water. Fun to think of the evolutionary pressures there. From th

It appears humans are more sensitive to fresh rain on dry soil than sharks are to blood in the water. Fun to think of the evolutionary pressures there. From the wiki, humans detect at 0.4 ppb and it appears sharks are at about 1 ppm. I can't find a proper source, but several articles say about a teaspoon of blood to an olympic swimming pool. https://www.sharktrust.org/shark-senses https://www.sharktrust.org/shark-senses

Scalene2 4y ago
Maybe we like the smell and are sensitive to it due to its association with arable land?
082349872349872 4y ago
> Fun to think of the evolutionary pressures there. Savannah hominids obviously needed to run to the parking and put up the tops on their convertibles as soon as they scented rain? By etymology, I'd consider magma to be a good referent for petrichor. Or at least the salty deposits left along contact surfaces of strike-slip faults?
- jeroenhd 4y ago
  Hominids traveling deserts may need to quickly climb when rain starts falling. If you're not prepared, you can get swept away and even drown by flash floods in the dryest places on earth. The "more people drown in deserts than die of thirst" factoid is not entirely made up; flash floods are incredibly deadly, especially so in areas where it doesn't rain much. Modern humans are quite good at surviving such events but I can definitely see (early) mammals struggle to survive them.
- maxerickson 4y ago
  It's a neologism. I imagine the evolutionary benefit of the sensitivity is in avoiding drinking stagnant water, where the compound is also present: https://en.wikipedia.org/wiki/Geosmin https://en.wikipedia.org/wiki/Geosmin
addaon 4y ago
Real question: Are individual scent receptors evolutionary preserved, or is there enough "cross-encoding" either at the genetic level or the receptor level itself that preservation of a small number of survival-correlated scent receptors will, coincidentally, cause preservation of other receptors as well?
MadcapJake 4y ago
Could this just be the fact that air is less dense than water so (due to the densities of particulate) sensitivities must be tuned differently?

Scalene2 4y ago

Maybe we like the smell and are sensitive to it due to its association with arable land?

082349872349872 4y ago

> Fun to think of the evolutionary pressures there. Savannah hominids obviously needed to run to the parking and put up the tops on their convertibles as soon as they scented rain? By etymology, I'd consider magma to be a good referent for petrichor. Or at least the salty deposits left along contact surfaces of strike-slip faults?

jeroenhd 4y ago
Hominids traveling deserts may need to quickly climb when rain starts falling. If you're not prepared, you can get swept away and even drown by flash floods in the dryest places on earth. The "more people drown in deserts than die of thirst" factoid is not entirely made up; flash floods are incredibly deadly, especially so in areas where it doesn't rain much. Modern humans are quite good at surviving such events but I can definitely see (early) mammals struggle to survive them.
maxerickson 4y ago
It's a neologism. I imagine the evolutionary benefit of the sensitivity is in avoiding drinking stagnant water, where the compound is also present: https://en.wikipedia.org/wiki/Geosmin https://en.wikipedia.org/wiki/Geosmin

addaon 4y ago

Real question: Are individual scent receptors evolutionary preserved, or is there enough "cross-encoding" either at the genetic level or the receptor level itself that preservation of a small number of survival-correlated scent receptors will, coincidentally, cause preservation of other receptors as well?

MadcapJake 4y ago

Could this just be the fact that air is less dense than water so (due to the densities of particulate) sensitivities must be tuned differently?