The Craziest Creatures on Earth
What Weird Earth Life Tells Us About Aliens
Life on Earth is wild.
It’s honestly pretty easy to take it all for granted, given that we’re living things and we’re surrounded by living things. But if you just sit back for even just a moment and think about all of the things life has done on this planet, and continues to do on a regular basis, it’s all pretty bizarre. Even more: some of the weird stuff that life does might be the most important for our considerations of what alien life might be like.
Since its inception very early in Earth’s history, life has come to be intertwined with the geochemistry of our world. Life has altered the evolution of minerals and rocks and changed the gas composition of the atmosphere. Life has provided kindling for fires, intercepted star light for energy, consumed elements in the Earth’s crust, and has altered the carbon chemistry of our world such that life takes up over 500 Gigatons in our carbon atoms alone (what we call biomass). Living things have gone quite a long way in all of their work to consume resources, use energy, build biomass, excrete waste, and reproduce. And we have reproduced a whole lot.
There’s no way to know how many generations of living things have come and gone on Earth. Some things can reproduce really fast. Some microbes can double their populations in less than 10 minutes (when resources aren’t limiting). Those of us who take a little bit longer are still pretty quick in the scheme of things. Birds do it, bees do it, and even educated fleas do it. I asked ChatGPT to try to estimate how many generations of animals alone have come and gone since the Cambrian Radiation some 541 Million years ago. Even though it has to be a little “hand wavey” due to all of the variations in reproduction times and many unknowns, the best estimate was likely 100-500 million generations of animals. That’s a whole lot of offspring doing a whole lot of things on this planet.
Life has diversified to fill so many ecological niches and to perform a humongous array of functions. While microbial life has always dominated the diversity of living things, multicellular organisms and the advent of sex really kicked evolutionary diversification and adaptation into gear. I honestly am flummoxed by those who find no pleasure in thinking on the variety of living things that share our world with us.
And among the great diversity of functions and behaviors that life has, there are some things that life does that honestly seems kind of bizarre.
Early in my career in science communication and astrobiology, I started keeping small notes on some of the weird things that life does that I found amusing or intriguing. Just to have little tidbits to share with others.
That sharing slowly grew, and one day, when I was sitting with my friend Morgan Rehnberg—who then led a series of scicomm lectures at the Fiske Planetarium in Colorado—and talking about my idea for a planetarium lecture to share ideas about weird livings things and what they could even teach us about alien life, Morgan suggested the title “The Craziest Creatures on Earth” to share the concept.
That planetarium show turned into just the first of many, including talks at museums and community colleges and more. I turned my thoughts into a blog post on A Cosmobiologist’s Dream back in 2015. I shared the concept for the Low Orbit podcast some years back. And, now, I figured it might be fun to write a little about weird living things and alien life here on The Cosmobiologist.
Here are a few of the weird things about life on Earth that can inspire our thinking about the possibilities for aliens out there:
Hummingbirds have some of the most bizarre metabolisms on Earth, consuming food at a rate that would require a human to eat over 150,000 calories daily if we were the same. Hummingbirds can hover, fly backward, and beat their wings up to 200 times per second. What happens if we meet aliens who have metabolisms and behaviors much closer to hummingbirds than humans? Can’t imagine we’d be able to manage having them over for dinner very easily.
Blue Whales, the largest animals on Earth in our modern day, can consume up to 4 tons of krill daily during feeding seasons. Their immense size necessitates one of the most energy-demanding diets in the animal kingdom. In case you were wondering, the Blue Whale dietary equivalent of krill when measured instead by the weight of tacos (assuming ~100 grams per taco) would be something in the ballpark of 36,000 tacos per day. Joey Chestnut’s best was 126 tacos in one sitting. He’s got some catching up to do.
There are an estimated 1030 to 1031 viruses on Earth. Though they are small, they are mighty, as those little biological machines can drive evolutionary change through their injections of genetic material in other organisms to take over their biological functions. Here’s a crazy stat: if all of the viruses on Earth were organized in a single-file fashion, they would stretch for over 100 million lightyears—which, according to genome.gov, is four times the distance from Earth to the Canis Major dwarf galaxy (that checks out if you assume an average size of a virus around 100 nm and use 1031 viruses—I did the math!).
The Mariana snailfish, living at depths of over 26,000 feet, is the deepest dwelling fish and thrives in pressures that would crush most terrestrial animals. They’ve evolved gelatinous bodies to survive without gas-filled swim bladders, much like the blobfish and other dwellers of the deep. In case you were wondering, the pressures on the bodies of the Mariana snailfish are in the range of 1,100 times greater than surface pressure for us—they face the equivalent of 8 tons per square inch. If there are fully ocean worlds out there with their own biospheres, we can only begin to imagine life at even greater depths than what we have on Earth.
Organisms like naked mole rats create elaborate tunnel systems for social organization and temperature control. Some marine worms and shrimp construct undersea burrows that influence entire ecosystems. One of my favorites, the Giant Ground Sloth, created humongous burrows so big that humans can walk through them now as caves. Might there be alien worlds out there with criss-crossing tunnel systems all throughout the planetary crust?
Microorganisms like Pseudomonas syringae have been found at altitudes of up to 8 miles above Earth. Some bacteria and fungi can survive extreme cold and radiation during long trips through the atmosphere, and some might even be expelled from our planet into space. There’s so much we don’t really know yet about the actual ways that organisms can be transported to the upper atmosphere. But this alone makes me wonder about alien words that might not develop space programs, but might be able to slough off some biological material to the cosmos all the same.
The hydra, a freshwater organism, shows no signs of aging and may be biologically immortal due to its regenerative abilities. It continually replaces its cells, avoiding senescence. Even now, many of us are wondering if we might soon extend our own lifespans to become technically immortal. And, if we could do it, then maybe aliens have already done it. What happens if our first meetings with an alien civilization are with one where individuals exist that have lived for thousands or even millions of years? Would our behaviors and attitudes be in any way understandable for them?
The adult mayfly lives for only 24 to 48 hours, just long enough to mate and reproduce. This brevity contrasts with larval stages, which can last up to a year, but still one must wonder what it’s like to only have a day or two of being an adult. We might one day meet aliens that have very different stages of their own lives, and might even only survive their adulthood in a window of time that appears fleeting to us.
Horseshoe crabs have existed for over 450 million years with little morphological change. They’ve adapted to various environments while retaining ancient biological features. I have to wonder if there might be alien beings out there who generally have a much slower evolutionary pace in their biosphere, such that adaptation comes much slower and the life there is rooted in a slowness that will at first be hard for us to understand.
Deep-sea creatures like the anglerfish use bioluminescence to lure prey. Some species of fungi and fireflies use light for communication or predation. What if there are worlds out there where bioluminescence has been taken to even great extremes? We might one day meet aliens who want to communicate by lighting up their bodies. They might not use any form of vibration reception (using voices or hearing) the way we do at all.
This is just a small smattering of some of the cool things that life does that seems a bit bizarre and makes me think about possible alien life out there.
What are some of your favorite adaptations of life as we know it? Are there any creatures that you think fit the bill of being bizarre or weird and yet might have some things to tell us about alien life?