andymanec
Eukaryotes and prokaryotes split from their common ancestor long enough ago that a lot of differences and unique traits have popped up. Antibiotics take advantage of these differences by disabling some part of bacterial cells that human cells don't have. In most cases, it's the cell wall - a protective layer that bacterial cells have on the outside of their cell membranes, but that humans lack.
You see a similar effect with antifungal medications. The thing is that fungi and our single-celled ancestors split from a common ancestor much more recently than the split with bacteria. In other words, we're more closely related to fungi than we are to bacteria. There are still differences that we can exploit, but they're not as pronounced. That's why the side-effects of antifungal medications are usually much worse.
Humans and bacteria both evolved from a common ancestor. It's *because* of evolution that antibiotics kill bacteria but not humans.
robin_lionheart
We didn't evolve from bacteria. Bacteria branched off from the tree of life waaaay down near the bottom. Plants and animals actually evolved from eukaryotes.
Also, occasionally antibiotics do kill humans.
?
the same reason that bacteria that used to be killed by antibiotics isn't now - evolution
thank you for proving our point that evolution works
Anonymous
If I were a level 7 user, I'd move this question to Home & Garden.
Anonymous
Because humans are not bacteria