Our bacterial passengers don’t outnumber us after all

Ever hear that we have vastly more bacterial passengers than cells? Yeah, me too. Ever blithely repeat that myth to a large Internet audience? Yeah, me too. But now corrected, in two articles: We Are Full of Critters and Ten Trillion Cells Walked Into a Bar. For an explanation of how the myth was busted, see Scientists bust myth that our bodies have more bacteria than human cells.

Although I have repeated the myth, I have frowned at it suspiciously several times. I’ve always thought it was obvious that mass had to be considered for it to be meaningful, which is why I particularly like this diagram.

I also always assumed that most of the bacteria surely had to be in the poop chute, which isn’t such a fun fact. The idea that we have more bacteria than cells sort of implies symbiosis on a vast scale, bacteria everywhere, which is true in a way … but the bacterial populations outside the gut are really quite small compared to our own cell populations.