Scientists think microbes may have evolved to make humans act more altruistically.

For all our faults, we humans are pretty nice to each other. We go out of our way to save children from burning buildings, rescue kittens stuck in trees and cook dinner for our roommates.

Since people are altruistic around the world and have probably been so for a long time, you might assume all this inspiring humanitarianism is written into our DNA. But a group of scientists from Tel Aviv University is proposing a kind of reverse horror sci-fi: that our microbes are making us act nice to each other.

"I believe the most important aspect of the work is that it changes the way we think about altruism from centering on the animals (or humans) performing the altruistic acts to their microbes," Lilach Hadany, one of the researchers, explained to Phys.org.

It sounds incredibly weird, but all animals are full of microbes, and we already know that microbes can make animals act differently – that's what rabies is all about. Perhaps microbes can make animals help each other, too.

The theory goes like this: Some microbes naturally make you more likely to help others. So when you rescue that kitten, you touch it. Your microbes spread to the kitten, and all of a sudden, these altruistic microbes are spreading throughout a population. Like a monster virus that just wants you to hug people.

Genetics are still probably responsible for a lot of our good behavior (not to mention cultural norms). But if microbes also play a role, then we've got a lot to think about. For instance, are antibiotics making us meaner?