[3,400 words, 9 footnotes]

Who are you? A doctor? A farmer? A father, mother, son, daughter? You may be any of these or a few, but it isn’t even close to describing who you really are in total. You aren’t even a single entity, but a collection of living things that work in unison, mostly symbiotically. Inside each and every one of us is a world so bizarre, so strange and alien, that we couldn’t even begin to fabricate a story so implausible. It’s science, not fiction—and the unison of the two is ironically less strange.

To make sense of it, we often call it nature, a sort of catch-all. Or, we punt in various ways, invoking superstition. Doing so is probably nature and natural, too.

LET’S JUST SAY LOTS AND LOTS

There’s about 40 million bacterial cells in a gram of soil and about a million bacterial cells in a milliliter of fresh water. In total, there’s estimated to be about five million trillion trillion, or 5 × 1030 (5 nonillion) bacteria on Earth with a total biomass equaling that of plants. Some researchers believe that the total biomass of bacteria exceeds that of all plants and animals.¹

Inside of every human organism are armies of microorganisms with DNA that are entirely different from our human cells. That microbiome not only outnumbers your human cells by a factor of ten to one but in total, it outnumbers every individual human that has ever lived on Earth. Your intestinal microflora numbers an estimated 100 trillion! Compare that with the total estimated 110 billion humans who have ever been born. You’ve got 900 times as many microorganisms as that. Your internal civilization of gut bugs comprises up to 1,000 different species with 3 million non-human genes, compared to your own 24,000.

But, perhaps large numbers aren’t your thing. After all, the U.S. National Debt in 2021 now stands at over $27,000,000,000,000, and that doesn’t appear to alarm too many; and many even seek to double it. Perhaps the numbers are just too big to comprehend. So let’s look at it another way. Suppose all of your human tissue cells (organs, blood, bone, etc.) were the same size as your bacteria. They would all fit in one coffee can. However, you would need 10 cans to store your bacteria. And did you realize that dead bacteria make up approximately 60% of your stool? So, yea: lots and lots of the little buggers.