Tamolitch the Blue Pool, Oregon. Photo: Bonnie Moreland
What’s an organism?
We have a basic concept of an organism as being an individual life form, the smallest discrete level of life. And this concept works decently well for human-sized scales — no one disagrees that a single human is an organism, or a single hippo, or a single pine tree. But just like nearly everything else, once you get too far outside that human scale, our ways for filtering and categorizing our world starts to break down.
Small Stuff
Thanks to COVID-19, more people seem to know these days that viruses technically don’t count as forms of life — and are therefore not organisms. Viruses are protein coated sacks of genetic material, absolutely tiny even compared to bacteria and completely incapable of producing its own energy or reproducing outside of a host cell. This latter one is why viruses have been generally considered nonliving — without a host to infect and leech off of, viruses are incapable of reproducing, evolving, and making more virus.
But these days, scientists are a little less sure. Back in 2003, some researchers announced that an organism originally discovered in 1992 wasn’t a large bacterium, as had been thought; instead, they announced it was the largest virus (by orders of magnitude) that had ever been found. The virus still couldn’t reproduce on its own, though it did a lot more of the job than any virus discovered before, attaching its own replication machinery to the host cell rather than just hijacking the cell’s normal processes. Plus, this virus could actually get viruses of its own, something that had never been observed before.
The giant virus — mimivirus — on the July 2011 cover of American Scientist.
This sparked a hunt for giant viruses, leading researchers to try and identify new strains in sea water, in water towers, in animals, and eventually even in human guts. Giant viruses were everywhere, it seemed — and some of them even had the basic equipment necessary to make their own proteins, something that hadn’t been observed in viruses before and hinted that these viruses may have once been able to make their own energy, not being dependent on other cells.
And as more of these giants are being discovered, researchers have had a bold new idea — what if these viruses are actually evolved from cellular life, which has leaned so far into parasitism that they’ve lost the ability to reproduce on their own? What if these giant viruses represent a fourth domain of life — one which was once able to do all the things we think of life as requiring, but abandoned the pieces they no longer needed? And what if there are other, normal-sized viruses which are further along this path of evolution — if there are legions of viruses that come from life forms which learned how to survive while doing a little less work?
Can life evolve to no longer be life? Or does our classification system need some reexamination?
I should note, this is still an active debate in virology. There’s not a strong consensus here. But soon enough we might just be reconsidering the fun fact everyone knows about viruses.
Big Boy
If you clone yourself, and your clone goes and has a kid, is that child your kid? That is, is your clone still you?
For some species of plant, this isn’t a hypothetical question. A lot of plants can reproduce asexually, cloning themselves and creating large colonies of genetically identical individuals, connected to one another through a dense root network that allows them to share resources between individuals.
These colonies are generally viewed as a single organism, with each individual more like a limb — doing a job, contributing to the survival of the collective — than an extant being. This mostly makes sense — all the strawberry plants scattered throughout your grass are sharing resources under the table, so we count them all as a single plant. But there are some places this begins to break down.
Pando. Photo: John Zapell
For instance, take a forest out in Utah named Pando. 107 acres in total, this forest has more than 47,000 trees dotting its hillsides. Every single one of those stems is a quaking aspen, all attached to the same 80,000 year old root system and all a part of the same massive, ancient organism.
If you believe that this forest is all one organism, Pando is the oldest living thing that we have ever identified. Sure, there’s no cells or root hairs that have lasted the full 80,000 years, but that’s nothing new — even in humans, most of your cells die and get replaced every 16 years or so, except for a few brain cells that only formed when you were two. And each of these trees is contributing to the survival of the forest as a whole, sending nutrients back into the root network to prop up ailing stems. On the other hand, there aren’t too many organisms which provide habitat for entire populations of other species, or take up over a hundred acres of space. You get the sense that we’re asking the wrong question altogether, trying to force this forest into the wrong classification.
So these are neat, but… what’s the point?
Personally, I’m interested in how quickly our understanding of the world, how we sort things into categories and comprehend the rules of the universe we live in, deteriorates as we move further away from human-scale systems. The vast majority of our scientific understanding sits on top of fundamentals that date back centuries, before we had developed the tools that have enabled us to fully explore the vast majority of the world which exists outside of our natural size and timespan. In the modern era we’re coming up with more precise microscopes and measurement tools every day while simultaneously learning how to collect massive amounts of data on a landscape scale and process it faster than has ever been possible. What counts as “human scale” is expanding every day, and a lot of our basic assumptions about the world are going to need to change to match.
I like to look at the world and wonder what things we’ll be laughed at for believing. It wasn’t that long ago, even on a human time scale, that we thought giraffes got that way because they stretched more in the mornings. It wasn’t that long that cutting edge medical practice involved grave robbing and bloodletting. And as we rapidly realize just how much world there is left to understand, I’m guessing that we won’t fare much better than those who came before us.
It’s an exciting time to be alive. We’re going to learn that we’re wrong about an unprescedented number of things in an incredibly short period of time, and need to fundamentally rewrite the way we understand our world. And it might be starting off with what we use as the very definition of life itself.