first time that what went around came around "a quid
pro quo with bacteria"
We humans love old saws, old adages, and the like. The best ones
persist indefinitely because, at their core of meaning, they embody
great truth. One of these adages, in an older form, is "quid
pro quo". A more contemporary version is "you scratch
my back, I'll scratch yours", and more recently still: "what
goes around, comes around". I think you will immediately
agree that the concept is ubiquitous in both nature (termed symbiosis)
and human behavior (affectionately known as mutually beneficial
relationships) which is really nothing more than a subset of nature.
I contend that the first meaningful quid pro quo "happened"
some few billion years ago, involved bacteria and an early form
of Eukaryote cell, and that we humans owe our very existence to
this reciprocal back scratching.
is a story of the evolutionary origin of the eukaryotic cell,
described by the Theory
The Eukaryota include the organisms that we are most familiar
with - all animals, plants, fungi, and protists. They also
the vast majority fossilized animals. Despite their mind-boggling
diversity in form, Eukaryota share fundamental characteristics
of cellular organization, biochemistry, and molecular biology.
A critical characteristic they share is the presence of mitochondria,
a small organelle is the cell that produces energy. Plants
cells contain chloroplasts that function similar to the mitochondria.
are the cell's "powerhouses," the sites where aerobic
respiration breaks down food in the presence of oxygen into water
and carbon dioxide, generating energy. Plants and many protists
also contain plastids, where photosynthesis takes place, allowing
these organisms to manufacture their own food from carbon dioxide
and water. Chloroplasts and mitochondria are curious organelles
indeed; they contain their own DNA and replicate independently.
In fact, these organelles are descendants of symbiotic bacteria
living inside the eukaryote host. They have become so dependent
on their host that they can no longer live outside. Eukaryotes
- including humans - are, in a very real sense, not individual
organisms but colonies, and living proof that evolution frequently
does not proceed according to the violent stereotypes of continuous
struggle, of "nature red in tooth and claw." Sometimes
the winning strategy is cooperation.