Our Special Relationship with Ancestral Bacteria

By Dr. Neela Sandal

Human beings have a very special relationship with bacteria. In a fundamental sense, humans wouldn't exist without bacteria. We have co-evolved with bacteria for so long that they are literally a part of every single one of our cells.

There are an enormous amount of bacterial cells living in anyone's body at any time, yet bacteria get a bad rap. We think of them as disease harbingers, but there are an enormous amount of bacteria that help us digest foods, provide unique nutrients, and maintain hormones we could not produce without them. Bacteria helps us cycle toxins as well as fight off infections from other bacteria, fungus, and viruses that would be damaging.

We have an incredibly long and cooperative relationship with specific kinds of bacteria. With any system of adaptation, we have become more finely attuned to each other over time. The bacteria that works well for us, our immune system learns not to fight off. We exist in this balance with bacteria, and we have for millennia. Naturally, bacteria is always changing somewhat, but our beneficial bacteria has less evolutionary pressure because it has a comfortable niche already. The furthermost example of that is mitochondria, which merged with our cell lines so long ago that it's a critical part of how we form and function. Every cell has this bacterial ancestor.

What we've done recently is to shake up this long-standing peaceful cooperation between bacteria and human communities, the co-adapted bacteria and human cells. We've come to fear bacteria so broadly that we have begun to damage our allies. We've begun to sterilize everything – and there's a lot of hyper-sterilization in our culture. We no longer interact with bacteria the way our ancestors did, so what was once a comfortable niche for certain species of bacteria no longer is.