Week+2+-+History+of+life+on+earth

Geochronology all starts with the eon - or the supereon to be exact. This is the overarching descriptor of time, broken down into smaller and smaller subsets: eons can be divided into eras, which can be divided into periods, which can be divided into epochs. In the history of the universe, we have identified four eons and ten eras, thus far. We presently live in the Holocene epoch of the Quaternary period. **How have this week’s resources improved your understanding of the history o** **f the earth and of life?**
 * Write brief notes, a sentence or two in your own words, on the meaning of eon, era, period and epoch. What epoch are we living in now?**

Is it human nature that we view time on such a tiny scale? Whether it is the pressure of racing to catch a bus, our plans for the day, dreams for our future, even an appreciation of generations within our families, all of these views take in infinitesimally small periods of time when considering the greater picture of the history of life and our planet, earth.

This week I found myself yawning like the ancient clam, as my brain literally struggled at times to fathom the enormity of life and its fascinating rhythms and variations. More than 99% of species to have lived on earth are today extinct - the result of many natural forces including massive drops in oceanic oxygen levels (anoxia), global cooling, comet and asteroid collisions, oceanic volcanism and simple cyclic decreases in speciation.

It somehow challenged the foundations of my reality on anthropogenic global warming: This too, threatens the survival of many species. Is it that we must stop the progress of this dramatic shift in habitat conditions because it has occurred at our instigation? Are we responsible for the survival of species other than our own? Can I view our climate crisis dispassionately as a by-product of a dominant species running its course, precipitating yet another in a series of mass extinction events?

Perhaps most fascinating to me this week, were repeated illustrations of the constant and almost frantic evolutionary process. Nature has taken on a whole new meaning, this marvel of existence and the microscopic yet furious pace with which the natural world is driven to evolve. From the universe’s chemical to biological evolution, from outpourings helium and hydrogen, to the simplicity of the universe’s building blocks - a mere 21 amino acids make up all of life’s proteins while just four nucleotides comprise the coiled strands that form DNA, to theories like The Great Leap Forward, clay theory and alien visitation leading to accidental contamination, I gained powerful insight into the phenomenal complexities nature has woven from such simple beginnings.

And then to life. The fact is, all living organisms on earth share a single, universal ancestor - estimated to have emerged some 3.5 to 3.8 billion years ago, diversifying into three evolutionary branches - archaea, bacteria and eukaryota. On a microscopic level these organisms have not simply landed and set up camp. Their design is so exquisite and complex, that they need no encouragement. They are furiously multiplying, developing, interacting, superceding, co-existing, encroaching, counter-manouvering, and evolving with the passage of time.

We humans are so anthropocentric. We see ourselves as the centre of the universe, the dominant species, the saviours and destroyers, the superior intelligence, and at times, the deciders of all others’ fate. We have awarded ourselves Godlike status and yet, we are so inconsequential!

This week’s micro view has offered me not only a deeper respect for life as a whole, but a greater humility about my own existence. Though our lineage extends back possibly some 7 million years to //Sahelanthropus// //tchadensis,// our modern form as humans is in its infancy. While the material from this week encompasses the vastness that is universal history, it is equally fascinating to contemplate the universe’s future. And within that, the tiny, yet unavoidably compelling future of humankind.