When I was younger, I was walking through the NorCal redwoods with my family. It was a clear and crisp day, maybe 65F. I strolled ahead of the group by 30 or 40 feet, lost in thought, but enjoying the dim light and the smell of pine needles and duff. After a few minutes along the trail, I began to smell something else. It was...musky. Foreign to the place. A few minutes more and I realized I was smelling human.
Sure enough, we caught up to a slower group. After we passed them, the smell was gone. I'll never forget it.
I've heard many an anecdote of soldiers deployed for months in male-only settings who could smell that a woman had arrived on base. They weren't able to describe what they smelled, or how they knew it was a woman, but they just knew.
In the books of the former Navy SEAL Richard Marcinko (he sadly died in Dec 2021), it is repeatedly stressed that soldiers shouldn't use any cologne or indeed any perfumed soap, because these smells carry a long way in the wild. The plainest soap possible and that's it.
In About Face: The Odyssey of an American Warrior (1989), David Hackworth mentions about being on patrol in the Korean war:
None of us used repellent (Chinks could smell it as easily as after-shave, soap, tobacco, and toothpaste); we couldn’t slap at them (noises traveled loud and far at night). So we waited and reluctantly contributed our blood.
and about poor discipline in Vietnam:
Guys were using soap, toothpaste, and shaving cream before operations. They were smoking and wearing mosquito repellent on patrol.
I went on a weeks-long sailing expedition as a teenager and realized after my first couple days at sea that I could smell land from over the horizon.
If we were passing downwind of a landmass I could smell it even if I couldn't see it!
Both trees and regular dirt have a smell that carries for miles and miles and when you've been on a fiberglass boat with no trees and dirt for days the smell really, really, stands out.
I imagine that ancient maritime explorers, at sea in the vast oceans for weeks not days, would have been able to smell remote forested and guano-covered islands for hundreds of miles.
I used to occasionally fill in for my professor to run labs in a biology class, and I'd encourage the students to smell and such saying, "you do science with all of your senses."
Sure enough, we caught up to a slower group. After we passed them, the smell was gone. I'll never forget it.