An instructional on species
step one: definition
Figure 1: An individual
what is a species?
do you know?
Can you look up the definition?
Go ahead. Do it now.
i’ll wait here.
Figure 2: A lineage
have it? Read it out loud
for both of us to hear.
Figure 3: Two descendants, one ancestor
now, things get fun.
imagine the definition in your mind,
like on a piece of paper.
Take it, tear it up,
And toss it into the wind.
make a mess.
Figure 4: A mess
step Two: mess
The truth is, a species is messy.
it’s messy just like the scattered paper
That now makes up our definition.
you may have looked at animals and thought,
“This duck is different than a cat,
which is different than a deer or a bat.
All different species.”
Figure 5: Shared ancestry
And you’re right.
we can tell very different things apart.
but what about this bat and that?
This lizard and that?
The closer the two animals get together,
The harder to say they’re a different species.
Figure 6: Species complex, wherein ring species interbreed
we biologists like to say if animals don’t breed,
meaning they can’t make offspring together,
They’re different species. Separate.
but there are species of lizards that blend,
from one place to another.
Able to breed with neighbors,
but not neighbors-neighbors-neighbors,
And more distant.
so where does one species start,
And another end?
hard to say.
Figure 7: Interbreeding fails at ring edges
step Three: mix
or look at bacteria,
That make offspring only by dividing.
how do you decide a species
in a thing that does not mate for offspring?
who is to say bacteria A is a species itself,
isolated and separate from bacteria B?
Figure 8: Asexual reproduction
well, we tell ourselves that it’s in the DNA,
The genetic information that makes all life.
we look at two bacteria,
And if the DNA is different enough,
(we say 1%, but where does that come from?)
we say Bacteria A and B are different species.
but it gets even messier in the bacterial world,
like the pieces of our definition swirling in the wind.
because bacteria can mate,
They just don’t make offspring.
They mate across species,
Across close relatives and distant friends
not to make more of themselves,
but to swap DNA,
The very basis of our definition!
Figure 9: Horizontal gene transfer
They share DNA in mating,
Copying and swapping like teenage pirates,
a gene here, sequence there.
Copy, cut, share, paste, repeat.
each action blurring lines:
is the new cell, now carrying a bit of species A
still species B, or something new?
who’s to say.
Figure 10: Which species, none, or both?
step four: matrimony
And then there’s you.
The collection of cells you think you know
All descended from a first.
but beside your human cells are the others,
A collection of millions by millions of bacteria,
on your skin, in your gut,
on every open inch of body.
The unseen multitudes of multitudes,
different between each person.
They make you, become you,
so you are what?
Figure 11: Human and microbiome
And where do you come from?
who are your ancestors,
your mother’s mother’s mothers
stretching back into unconscious unmemory.
A secret, hidden in you
Thousands by millions of years ago.
Chance cast her lot,
As one cell engulfed another.
A normal act of eat to live,
but this time the infinitely unlikely,
Completely unguessable happened.
The devourer did not kill to sate its hunger
And embraced instead the cell within it
As a host would a guest in their home.
The guest, sealed and safe from the surrounding world,
gave energy for life in return.
if you seek within your cells,
you find these once-guests still today.
making, providing, trading
Their energy for a home.
The two working together,
Creating life from mice to men.
That is the strangest thing about you,
descendent of that accidental chance.
you are a marriage of not one form of life,
Figure 12: Endosymbiotic theory
step five: reality
As you can see, the definition of a species
diverges between flat paper and life.
our paperbound sentence is just convenient shorthand
hiding a stout, immovable truth.
for it’s impossible to encompass the chaos of life
of even for an individual in a word.
A name, a handle, a term,
And life’s lineage stretches long.
Figure 13: The lineage of life