Holy fuck.

From Wikipedia:

Biological dark matter is uncategorized genetic material found in humans and throughout Earth that does not fall under the three existing domains of life: bacteria, archaea and eukaryotes. Its presence suggests that a possible fourth domain of life may yet to be discovered.^[1]

According to research by US virologist Nathan Wolfe, 20% of the genetic material in a typical human nasal swab is biological dark matter that cannot be attributed to any of the existing categories of living organisms on Earth. Biological dark matter accounts for up to 40% to 50% of the genetic material in the human gut and between 1% and 2% of genetic material in the relatively sterile human blood.^[2]