“Who am I?” is one of the most meaningful questions you can ask yourself, and the assumed answer to this all-elusive question usually comes in the form of automatic thoughts that “you” are Mr. or Ms. so-and-so who graduated from the University of Blah Blah, works as a Bleh Bleh, experienced various other events at some point in the past, and so on.

However, a recent scientific review will make you re-think who “you” truly are, also calling into question whether you actually make the decisions that you do in your daily life.

On the surface level at least, who “you” are is, in reality, a continuous flow of thought, feeling, and sensation that has been solidified into a mental construct and static entity, and slapped with a “me” label. And beyond that, researchers have now found that many of these thoughts and feelings are actually a product of alien species living in your body.

In January 2016, a group of biologists from the Weizmann Institute of Science published their review of more than 40 years of research into the human microbiome and established that the average male between the age of 20 and 30, standing an average of 5’7 tall and weighing an average of 154 pounds, hosts around 39 trillion bacterial cells with a completely different type of DNA than that of the human that hosts them, while that same person only has around 30 trillion human cells in their body.

The fact that your body contains more alien DNA than it does human DNA begs one to reconsider the “Who am I” question. But it gets even stranger when you consider that those foreign bacteria often crave certain substances, such as glucose (sugar) or carbohydrates, and in turn, influence your brain, thoughts, and actions.

What this means is that, in a very literal sense, humans are controlled by a foreign species, or more accurately, a multitude of species.

So…Who exactly are “you” again?

The scientists summarized their findings:

“We critically revisit the ‘common knowledge’ that bacteria outnumber human cells by a ratio of at least 10:1 in the human body. We found the total number of bacteria in the ″reference man″ to be 3.9·1013, with an uncertainty (SEM) of 25%, and a variation over the population (CV) of 52%. For human cells we identify the dominant role of the hematopoietic lineage to the total count of body cells (≈90%), and revise past estimates to reach a total of 3.0·1013 human cells in the 70 kg ‘reference man’ with 2% uncertainty and 14% CV. Our analysis updates the widely-cited 10:1 ratio, showing that the number of bacteria in our bodies is actually of the same order as the number of human cells. Indeed, the numbers are similar enough that each defecation event may flip the ratio to favor human cells over bacteria.”