While many Americans tend to think of bad breath as little more than a chronic odor of the mouth, oral hygienists, bacteriologists and microbiologists around the world often see halitosis as a complex web of interdependent variables, all of which rest on one thing - bacteria. Bad breath is caused by microorganisms. Microbes have been on this Earth for far longer than humans have. Therefore, it's a reasonably safe bet that halitosis has existed for all of human history.
That is not to say that it has gotten better or worse over the millennia. Oral bacteria don't exist in a vacuum. They excrete volatile sulfur compounds (VSCs) after consuming food particles in our mouths. They eat what we give them to eat, and what humans eat has changed over time.
The diet eaten by early humans was surprisingly broad. A report released in the journal Science suggested that paleolithic pre-humans called Paranthropus robustus ate a foraged diet of meat, fruits and even sedges or grasses.
Subsequent inquiry, which appeared in the journal Proceedings of the Royal Society B: Biological Sciences, stated that the evidence of a grass-based diet - which was taken from isotopic analysis of fossilized tooth enamel - probably actually pointed to the consumption of roots and bulbs.
The point so far is that ancient humans ate a wide variety of foods, including meat, roots and bulbs, all of which are known today to cause bad breath. Think of garlic breath, onion breath, licorice breath or halitosis caused by savory meat.
Unlike us, though, ancient hominids did not have specialty breath fresheners or oral care probiotics rinses with which to clean their dirty mouths out. Imagine eating a paleolithic diet without access to a toothbrush, and it may dawn on you that pre-humans were likely to have some seriously bad breath.
The consumption of meat in particular can lead to the production of some atrociously scented odors in the mouth. An article in Scientific American ran down the most common VSCs and compounds created by oral bacteria, as well as their attendant smells.
Coming in first is hydrogen sulfide, by far the most common VSC. The article notes that this compound gives bad breath the disagreeable scent of rotten eggs - or, if you like, give rotten eggs an unbelievable ramped up odor of bad breath.
Other common halitosis compounds include methyl mercaptan, skatole, cadaverine, putrescine and isovaleric acid. Respectively, these molecules smell like human waste, human waste (again), corpses, decaying meat and foot odor.
To avoid having paleolithic breath, individuals with halitosis may consider rinsing with a specialty breath freshener.