This humid ball of mud we call earth has been bubbling with life for about 3.5 billion years, and during that time the blue whale is the clunkiest creature Mother Nature could squeeze out.
To be honest, we’re a little disappointed.
Don’t get us wrong; a 180-ton, 30-meter-long mammal is not exactly trivial. There is still a lot to embrace.
But raised on a diet of Hollywood’s Kong-sized creatures and Tokyo-destroying Gaiju, we’re curious to know – what would it take to really oversize life in the universe?
How big could a single cell get?
Okay, let’s start small. Big things grow out of small things, so why not just make bigger things out of bigger cells?
With a few exceptions, most self-replicating cells in the entire biosphere cannot be seen without the help of a microscope. There is a good reason for that. As a matter of fact, a number of reasonsall based on principles hardwired into chemistry and geometry.
Take, for example, the ratio of the surface area of an object to its volume. As 3D objects (like cells) get larger, this ratio gets smaller, which means that the goo in the center expands faster than its outer layer.
Having less surface area per cubic micron cell is like having a mouth that can’t keep up with a growing body – it limits the speed at which vital nutrients and gases can cross the border to get to the expanding plots.
That’s not the only limitation. There are also questions of structure. Even large cells have to break apart their membrane and DNA at some point if they are to replicate.
In most living things, the mechanics of this process are based on thread-like structures, the so-called microtubules, which act like a skeleton and give the cell structure and freedom of movement. These also help limit cell size.
Of course, evolution could come up with solutions to push the boundaries of biotechnology. To take Caulerpa taxifolia for example. This invasive, fast growing alga I threw out the whole rule book In cell theory, choosing multicellularity was just not their style.
Even though C. taxifolia (above) has the temporary appearance of a water fern with fronds up to 80 centimeters long, it’s effectively a giant cell … if you play around with the definition of cell quickly and easily. For example, it still has multiple nuclei and is home to a swarm of endosymbiotic bacteria that help it absorb nutrients.
Still, as far as unicellular organisms are concerned, it is a real monster.
Speaking of monsters, the algae known as sailor eyes (Valonia ventricosa) also deserves a mention as a giant solitary cell.
And then there’s Acetabularia. Although it only reaches about 10 centimeters, it is one of the largest unicellular organisms that contains only a single nucleus.
So cells can get pretty big if we are willing to rethink what counts as a cell.
How big can a plant get?
About two and a half thousand years ago, a seed sprouted in what would one day become known as Tulare County, California. Today, that sapling is just over 80 meters tall and made up of nearly 1,500 cubic meters (about 52,500 cubic feet) of wood.
Even the old general is compared to the giant who is called Lindsey Creek French Tree.
The Lindsey Creek French Tree was a coastal sequoia (Sequoia sempervirens); an ancient species that dates back to the beginnings of the dinosaurs.
With a whopping 2,550 cubic meters in volume and 118.87 meters high, it has a place in the history books as the largest tree ever recorded. Unfortunately, a storm destroyed it in 1905, or it could still be the king of plants today.
To support such formidable crowds and reach dizzying heights, sequoias came up with a few tricks to help overcome limitations.
One limitation on the size of a system is that it can direct water from the basement to the roof. Fortunately, sequoias are incredibly well suited to their cool, humid habitats on the west coast of North America, with more than half of their moisture drawn from the churned mist via their leaves.
Although their roots are typically flat, their broad bases are made up of a ‘Fairy Ring’ root structure, gives them broader, more solid support.
Paired with a complex genome allowing them to push higher and higher for centuries and withstand the plague and occasional fires with relative ease, sequoias like these are true survivors who can take their time to approach the sky.
Nature might one day bring out something bigger, but it probably won’t be that fast. Even the old sequoia would have seen his day as climate changes reduce humidity and threaten forests with hotter fires.
In order for something even bigger to develop on earth, it would have to overcome some of the technical problems our skyscrapers face.
The 828 meter high Burj Khalifa in Dubai is currently the tallest building in the world. It is possible that we could build higher and break a kilometer, but that would require ever wider buttresses.
A larger tree would face similar soil support challenges, not to mention water and nutrient transport and longevity of growth.
If we’re not worried about height and are ready to reconsider what makes up a single plant, then sequoias are just toothpicks compared to the truly god-like being known as pando.
Utah’s 107-acre Fishlake National Forest is a natural wonder made up of tens of thousands of trembling aspen trees (Populus tremuloides) Trees, each genetically identical to the last. For most purposes this forest can be made up of connected, identical trunks as an organism, a male aspen affectionately known as Pando.
Weighing nearly 6,000 tons (about 13 million pounds), the vast mass of roots, trunks, and branches is essentially one of the largest organisms on earth. As with the sequoias, his time may be running out. Although it’s been around for 80,000 years, there doesn’t seem to be much new growth recently, which makes researchers wonder if poor old Pando’s days are numbered.
Plants are not the only contenders for the largest single organism on earth. Extensive hyphae networks that connect a network of honey mushrooms (Armillaria ostoyae) are up there with the giants.
A specimen in Michigan covers 90 acres and weighs approximately 400,000 kilograms (880,000 pounds). Not quite as big as Pando, but an impressive demonstration of the potential of mushrooms to reach truly gigantic proportions. And who knows if we have overlooked other such giants underground.
Okay, but what about my godzilla?
Compared to the challenges of developing a mountain-sized beast, skyscraper plants and mega-mushrooms are easy. It is likely that we saw as big as animals could get.
The largest land animals we have records of belong to the sauropod branch of the dinosaur pedigree – giant quadrupeds with a long neck balanced by a long tail that can exceed 40 meters and weigh 70 tons … if not more.
How much more? When an animal doubles in volume, its mass increases by a factor of 8. Bones have to find ways to keep that extra weight off the floor – by increasing density, for example – and then the muscles have to pull everything. This not only requires more energy, but also puts additional strain on the heart and lungs.
Sauropods found an efficient body plan that made good use of their plant material diet and wandered their rotatable heads for food while their mass stood in place.
But if we don’t want our kaiju to live on spinach, he has to hunt for prey.
The largest of the carnivorous dinosaurs was arguably not much larger than Spinosaurus. As it was, at 15 to 16 meters in length, this maximum size predator seemed more inclined to float around in rivers, waiting for a large fish to slip by.
Spinosaurus however, had the correct idea of the ultimate plus-size predator. Let the water hold up your bulky bum and the food comes to you.
Whales have perfected this strategy over the past ten million years, expanding their length and girth to basically become long gulping tubes of plankton death. Powered by seawater, their bones have been spared the trauma of holding all that mass, and their muscles can focus their energies on pouncing on schools of nutritious crustaceans.
Larger lunges are well worth the effort as they may send lots of calories through the hatch. But only if the calories are there to swallow. The density and availability of krill goes only so far and sets limits even for the enormous size of the whale.
Even with more food, it’s possible that we can (based at least on existing physiology) have animals as big as animals, with blue whale hearts is already working overtime while foraging for food.
To grow a real megabeast, we would need a world with low gravity, deep oceans or a dense atmosphere. We’d need a dense supply of calories nearby, maybe we even need a whole new way of imagining how vital substances are transported through this mass.
In other words, based on what we know about life on earth, our Godzilla-sized life form would be remarkably un-Godzilla-like.
Might at least make it safer to hug.
All explainers are determined by fact checkers to be correct and relevant at the time of publication. Text and images can be changed, removed, or added as an editorial decision to keep the information current.