So Many Critters

Suppose you started with one self-replicating life form. It’s a really, really slow moving life form, but it’s capable of reproducing. After literally forty million years, it’s finally able to double, and now there are two critters.

Another forty million years go by, and now those two critters multiply by two… only that’s not quite what happens, because some of them die off and then are replaced by others, and so on. The important thing to know is that at the end of that second forty million year period, there are now four critters, whereas there were two of them forty million years ago, and one of them eighty million years ago.

This happens again, as another forty million years go by. Lots of critters are being born and dying, but the population is eventually able to stabilize, and now there are eight critters.

Lather, rinse, repeat. How many critters do you have after four billion years?

Before you answer, and assuming you’re not already doing the math in your head, let’s consider the actual planet Earth for a moment. We have actual fossils of life from about 3.5 billion years ago, and there is a reasonable consensus of conjecture that 4 billion years is a reasonable close guess for when life first appeared on Earth.

Given that Earth itself is only about four and a half billions years old, picking 4 billion as a good working number seems very reasonable. So, four billion years ago, you start with one single-celled critter, and that little cutie doubles in forty million years, and so on.

This is where the power of exponentials really comes to bear, going against every fiber of instinct we have in our bones (and brains). Starting with one and doubling every 40 million years gives you a stupefyingly large number. Today, that number is a one followed by 30 zeroes.

Now, 1,000,000,000,000,000,000,000,000,000,000 is no kajillion-jillion, but it is a number that’s well outside of what our brains are wired to process. There are a thousand thousands in a million, and there are a thousand millions in one billion. 10³⁰ is a thousand billion billion billion.

Anyway, I bring that number up because that’s how many individual life forms there are on the planet today, give or take a bunch.

I’m not sure how it all started, exactly—nobody is! But it does seem as though there were single celled life forms for some time, and then gradually more complex and diverse forms over time.

All of this exponential growth has led to the incredible diverse life we have here on the only planet anyone has ever lived on, at least as far as we know… and all you had to do to get to this insanely big number is to double every 40 million years or so.

All this exponential growth now amounts to about 450 billion tons of biomass, and a truly unbelievable range of diversity. Life seems to be everywhere.

There are zombie ants whose minds are taken over by fungus, like the plot of the Last of Us. Speaking of kingdom fungi, there’s something akin to a fungus internet, made up of a vast interconnected web of fungal filaments called mycelium.

There’s life at the bottom of the ocean, where pressures are more than enough to crush an SUV in an instant. Life tends to find a way to reach equilibrium, no matter what the circumstances are, and it seems to keep on doubling every forty million years or so.

There are tiny critters who can survive travel in space.

There are giant mammals, like us, who swim underwater almost all the time and produce a sound louder than a jet engine to communicate across vast distances. There are dogs and boogers, too (and some dogs I like to call “booger”).

There are quasi-immortal jellyfish. There are creatures that glow in the dark, including us (but only a tiny bit). One animal even makes cube-shaped poop.

Then, there’s the utter efficiency of nature and life. She recycles designs that work, like the way hands and wings are built incredibly similarly. Mammals get roughly the same number of heartbeats, no matter how big or how fast their hearts beat. Even if it seems like an idea is put to rest, sometimes nature allows it to propagate underneath the surface, like how birds are living dinosaurs.

And that’s only the living stuff I’ve written about here!

There’s such an absurd number of individual life forms on this planet, and such a wild amount of diversity here, that it’s hard to imagine ever getting bored with studying life. If you spent a second greeting every critter—micro- and macroscopic—you’d need 10³⁰ seconds to “get to know” all life forms on earth, or about 2 trillion times older than the age of the universe.

I’m imagining a never-ending line of life forms, where I walk up and metaphorically shake everyone’s hand. It seems like a Sisyphean struggle, a never-ending task of meeting and greeting over all those billions of trillions of years, but there are an awful lot of critters on our planet today.

I had better get started shaking those pretend hands. The heat death of the universe is right around the corner!