Levels of organization: we are an ecosystem within ecosystems


Graham Lawton (2020) writes in NEW SCIENTIST:

More profoundly for our definition of self, we are also holobionts: we aren’t individuals, but collectives. Every bit of our body is teeming with microbial life: bacteria, fungi, protists, archaea and viruses. They live on us and in us, on our skin, inside every orifice, and above all in our gut. We are even surrounded by an invisible cloud of them, a bit like Pig-Pen from the Peanuts cartoons.  //  These microbes outnumber our own cells, though not by 10:1 as is often claimed. An average human body is made up of about 30 trillion human cells and 38 trillion microbial ones. By mass, we absolutely dwarf our companions: a 70-kilogram human contains just 200 grams of microbe. //  But they punch well above their weight. The microbiome is different from parasitic freeloaders like lice and intestinal worms: it is an active and vital participant in our lives. Our gut microbiota, for example, do huge amounts of work digesting food that the products of our human genome can’t break down on their own. They are, in fact, the principal determinant of how we respond to food. Our microbiome influences our health in many other ways, contributing to mental well-being and modulating our emotions and cognition, and helping determine how our immune systems function.” (Read more:  


The microbiome is a major new frontier in medicine, but is providing important new insights in ethology: read about the microbiome in animal behavior  and the “psychobiome“–both in the journal SCIENCE [if you are not a member of AAAS the librarian can help you get this article]