Column: From dust to us

Our planet is a very interesting place. I understand that arguments could be made against my stance, but I happen to have a substantial bias — I live here. Many things make the Earth objectively uninteresting: it’s neither remarkably large nor small, there’s a single moon, there aren’t any rings or many extreme atmospheric conditions like on Saturn or Jupiter and it orbits a fairly ordinary star made up of hydrogen and helium. Despite being an ordinary planet, in an ordinary solar system, in an ordinary galaxy, Earth has a few characteristics that make it extraordinary in its own right.

Possibly the most noteworthy of these characteristics is the repeated violation of the second law of thermodynamics. Newton’s second law states that no system can increase in order without decreasing the order of another system. Living things represent an incredibly intricate ordering of particles; cell membranes, proteins and nucleic acids are very ordered and precise arrangements of molecules that entropically might prefer to be scattered about somewhere instead of being bundled into double helices or sheets or whatever form they happen to take within us and our fellow living things.

(A disclaimer to the angry physicists who’ve just read that previous passage and happen to be particular about definitions: the physical laws are not actually being broken, because living systems are not truly isolated. Through thermodynamic exchanges with electromagnetic radiation from the sun and other interesting things, disorder increases elsewhere, but that’s beside the point I’m making: life as we understand it today is something extraordinary).

From the Earth’s point of view, life appears to makes things happen incredibly quickly.  The current going theory popular among many geologists, astronomers, biologists and others within the scientific community goes as such: 4.6 billion or so years ago, some of the dust orbiting our fair star condensed through gravity into a sphere. Then it was bombarded with some meteorites and there was a great deal of volcanic activity. Things cooled down and stabilized a little more, and then life began to emerge.

This life was dramatically different from you and I — they didn’t even breathe oxygen. Fortunately for us and other beings, these ancient stromatolites photosynthesized and released a great deal of oxygen into the planet’s atmosphere. During that time and for a billion or two years after that, the living organisms were perfectly successful existing as isolated units. Some non-motile individuals aggregated into sheets or mats because they couldn’t move, and as they divided, they stayed right next to one another. Each cell was still independent of the rest of the group.

Eventually, something extraordinary happened. Some groups of cells began to increase their success by cooperating — and boom! Suddenly, there was multicellular life (It’s worth mentioning that since then, multicellularity has evolved several times across different groups, but doesn’t it sound much more fun to talk about the first time as a big moment?).

From there, living things could increase odds of surviving by aggregating in different arrangements, and organisms like sponges and algae started to arise. From there, the animals rapidly diversified with new traits like cnidocytes (the specialized stinging cells of creatures like sea jellies and anemones), or segmentation of the body plan in arthropods (lobsters, millipedes, etc.) which eventually allowed for the evolution of tagmatization: the specialization of sets of segments into different regions for different functions, as seen in beetles and shrimp.

As life became more prevalent, more evolutionary niches opened up, and more traits evolved to fill them. Traits like the endoskeleton, pharyngeal gill slits and the dorsal nerve cord gave rise to a relatively small, but conspicuous group: the chordates. These beings spread far and wide, moving from sea to land via the development of heavier skeletal structures in the outer appendages, and then eventually to the air, as those same skeletal features were selectively reduced in weight to facilitate flight.

Moving on to a few million years ago after a large rock collided with our planet and Earth had a bit of time to recover, some of those surviving land-going pioneers developed outwardly practical traits like fangs or fur. Some were selected for other structures, like a highly developed frontal cortex in the brain. While a frontal cortex wouldn’t allow these life forms to chew through tougher prey, or shield them from cold, it allowed for a much richer diversity of social interactions, cooperative behaviors and problem-solving skills. It enabled more sophisticated manipulation of tools. Eventually, the improved frontal cortex would allow for many spectacular things to transpire. The manipulation of stone and clay to form a wall visible from space, great buildings that convert the mechanical energy of rivers into electrical energy to power refrigerators and computers, precise control over plant genetics to ensure a stable supply of food, the rocket-propelled journey to the earth’s only natural satellite and back. Tectonic activity builds Mt. Everest a few centimeters every year. Our great brains allow us to build thousands of miles of roads and digital networks every day.

The development of the frontal cortex could even allow narcissistic writers to churn out drivel on evolutionary history. It is an absolutely marvelous adaptation.

ALAN LIN can be reached at science@theaggie.org.

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