How Did We Get Here?

M106 Galaxy,
M106 Galaxy,

Over the last few months I took a fascinating on-line course from Coursera, “Origins – Formation of the Universe, Solar System, Earth and Life.” The lectures I heard at Chautauqua in 2013 about “Our Elegant Universe” and my visit to the McDonald Observatory in West Texas last April primed me to study our Universe in greater depth. Seventeen outstanding English-speaking professors at the University of Copenhagen made use of Denmark’s amazing collection of fossils and their exemplary scholarship to explain the latest findings about how our world came to be. From sixty hours of study and sixty pages of notes, here are some of the concepts I want to remember:

  • The Big Bang was 13.6 billion years ago. In the 1920s a Belgian priest named Georges Lemaître suggested this concept, which subsequently received major boosts from Edwin Hubble’s observations on galaxies, and from the discovery of cosmic microwave radiation by Arno Penzias and Robert Wilson. In 1983, the Nobel Prize in Physics went to  Subramanyan Chandrasekhar “for his theoretical studies of the physical processes of importance to the structure and evolution of the stars” and William Alfred Fowler “for his theoretical and experimental studies of the nuclear reactions of importance in the formation of the chemical elements in the universe”. Their model is the standard used today for explaining the origin of the Universe, though many questions remain.
  • Our Solar System originated 4.56 billion years ago from elements that had formed from the original two, Hydrogen and Helium (the pillars of the Periodic Table of the Elements) through nucleosynthesis. New stars formed from giant molecular cloud discs composed of dust and gas. Planets grew by attracting solid material from the disc. Embryonic planets attracted more and more dust and merged with other planets.
  • Meteorites contain clues. Chondrites, silicate spheres orbiting the sun, are the most common type of meteorite. When they fall to Earth, the radioactive isotopes they contain allow dating and reveal conditions that existed during the first phases of Solar System development. How fascinating it was to hear Henning Haack, the lead professor of the course, discuss how NASA’s missions to Mars have helped us identify the large number of Mars fragments that fall to Earth as meteorites. I met a man in Novato CA whose wife found a meteorite in her yard in 2012. Will I ever be so lucky?
  • The Giant Impact Hypothesis was formulated in the 1970s on the basis of data collected by the Apollo missions to explain how our Moon was formed. The University of Copenhagen scholars explained it as having coalesced from the debris orbiting the earth after the grazing impact of a Mars-sized body many million years ago. Here is a recent video that discusses alternate theories.

Confused about geological periods? Here’s a chart that will answer all your questions, but you’ll need a print-out the size of a billboard. The six days of creation described in Genesis were easier for earlier generations to remember.

  • Life on Earth. First a definition: Living organisms are things that use energy to build molecular structures (metabolism) and to reproduce or replicate. They do both activities with a set of embedded instructions contained in proteins. Did life begin in venting hydrothermal systems in deep oceans? Or was it delivered to earth by comets or asteroids? The jury is still out, but tiny microbes were surely the first organisms.
  • The Cambrian Explosion, 541 millions years ago, refers to the rapid rise of multi-cellular life due to tectonic activity, glaciations, the steady increase of atmospheric oxygen and changes in ocean phosphates over a period of just 21 million years. Some animals became predators; others hardened their skeletons and evolved defenses in an escalating arms race.
  • Five Major Mass Extinctions (and several lesser ones) have occurred since life began. The worst was 250 million years ago at the end of the Permian, when 90% of all species perished in a relatively short time.  Volcanic eruptions in Siberia and India  led to a dead zone in the median latitudes. Recovery took 100 million years, but after millennia of fungus thriving on the desolation, there was a resurgence of biodiversity. The Cretaceous-Tertiary Mass Extinction about 66 million years ago, began when an asteroid 10 kilometers in diameter hit the earth near the Yucatan peninsula. The ash blotted the sun’s rays completely and caused the extinction of 65% of all species, including the reigning dinosaurs. Guess who survived? sharks, crocodiles, and certain dinosaur ancestors of birds and mammals, which then had an advantage over the less agile dinosaurs.
  • Factors governing Earth’s climate:  plate tectonic migration/ocean spreading; solar radiation/retention; volcanic activity; sea level fluctuations; atmospheric composition (especially the amount of greenhouse gases). The upthrust of the Himalayas led to weathering that removed CO2 from the atmosphere. Wind systems and ocean currents changed with the positioning of the continents. Ice sheets grew and retracted until modern patterns were in place five million years ago. Thermohaline circulation, which distributes heat around the globe from cold deep water at the poles to surface currents through the tropics, shifted over time. The Gulf Stream, for example, resulted from the closing of the Panama isthmus as North and South America bridged a previous gap. The canal built one hundred years ago didn’t affect the Gulf Stream (as far as I know), but it’s an example of how man has changed the Earth.
  • Defining Characteristics of Primates:
    1. Fingernails in place of claws
    2. Opposable thumbs
    3. Shoulder girdles that are highly mobile and can rotate
    4. Bone cover behind eye socket
  • Anatomically Modern Humans (AMH) emerged 200,000 years ago. If the history of Earth were compressed to a single year, modern humans would appear on December 31st at about 11:58 pm. They are distinguished by these cognitive traits:
    1. Development of tools
    2. Sophisticated behaviors
      1. Burial of the dead
      2. Making of clothes
      3. Hunting techniques
      4. Rock paintings
    3. Abstract thinking
    4. Planning
    5. Innovating
    6. Undertaking symbolic behavior (?)
  • Most evidence indicates that humans originated in Africa, where DNA samples reveal the most genetic diversity. Humans began to leave Africa 100,000 years ago to populate other continents.

From astrophysics and paleobiology to DNA analysis, this course stretched my mind and helped cause the crisis of faith I described in Lazarus: Life, Death and Faith. That crisis has resolved somewhat as I have realized that science and religion can co-exist and learn from each other. I am grateful to Henning Haack and all the real rock stars in Copenhagen for giving me new incentive to look up and reach for the stars.

Son David observed that this account ends 100,000 years ago and suggested my next book, Sapiens: A Brief History of Humankind by Yuval Noah Harari. It picks up just where Origins left off and explains why Homo Sapiens prevailed over other proto-humans. My first glance tells me that Sapiens haven’t been very kind to the Earth. Stay tuned.

Download (PDF, 259KB)

Leave a Reply

Your email address will not be published. Required fields are marked *