The Universe Within: Discovering the Common History of Rocks, Planets, and People

by Neil Shubin

  In our past, long-term success came from spreading one’s genes and traits, often in response to changes to the environment. The major source of information passed from one generation to the next was written in DNA. The situation now is not so simple. The American scientist Norman Borlaug and his wife had three children, five grandkids, and six great-grandchildren. We can look at his entire family tree and assess the extent to which his genetic traits have been passed from generation to generation. If we transport to the future, we could assess the success of his biological traits in the gene pool: hair color, ability to curl his tongue, susceptibility to diseases, and so on. But how much will traits like those really matter for our future as a species? In addition to passing on his genes, Borlaug was the widely acclaimed father of the “green revolution,” whose work on corn and wheat increased their pest resistance and yield. He is responsible for bettering or saving the lives of millions of people around the world. His ideas live in the ways others have used them and improved them and in an entire planet changed by his genius. From the people saved by agricultural and medical breakthroughs to the lives changed by great literature, philosophy, and music, the success of our species resides inside the offspring of our minds.

  Like a sixty-year-old person on actuarial charts, the habitable Earth is three-quarters of the way through its calculated life expectancy. Earth is about 4.57 billion years old, and the laws of stellar physics tell of another billion years before the sun expands to the point that it bakes the possibility for life off the planet. Looking back, life got going quickly after Earth’s formation—within a paltry few hundred million years. Bodies took roughly 2.5 billion years to come about. Then, one after another, heads, hands, and consciousness arose in ever more rapid succession. As in Moore’s law, which famously describes the doubling power of silicon chips every twenty-four months, the biological world has witnessed exponential rates of change: it took most of the expected life span of our planet for the origin of a big-brained species using stone tools; then merely thousands for the origin of the Internet, gene cloning, and schemes of geo-engineering the atmosphere of the planet itself. Planetary and biological change have brought about a transformative moment—one in which ideas and inventions shape our bodies, the planet, and the interactions between them. Before our species hit the scene, trillions of algae took billions of years to transform the planet; now change is driven by single ideas traveling at the speed of light.

  Ours is a species that can extend its biological inheritance to see vast reaches of space, know 13.7 billion years of history, and explore our deep connections to planets, galaxies, and other living things. There is something almost magical to the notion that our bodies, minds, and ideas have roots in the crust of Earth, water of the oceans, and atoms in celestial bodies. The stars in the sky and the fossils in the ground are enduring beacons that signal, though the pace of human change is ever accelerating, we are but a recent link in a network of connections as old as the heavens.

  FURTHER READING AND NOTES

  Excellent works for a general audience on the history of the universe, planet, and life grace the literature. Carl Sagan’s Cosmos (New York: Ballantine Books, 1985), while superseded by decades of scientific discovery, remains one of the clearest and most evocative accounts of the universe and its connection to us. The story from the big bang to the formation of the planet has been told by several scientist-authors, including Lawrence Krauss, Atom: A Single Oxygen Atom’s Journey from the Big Bang to Life on Earth … and Beyond (Boston: Back Bay Books, 2002); and Neil deGrasse Tyson and Donald Goldsmith, Origins: Fourteen Billion Years of Cosmic Evolution (New York: Norton, 2005). Richard Fortey, with his characteristic elegance, covers the history of the planet in Earth: An Intimate History (New York: Knopf, 2002). Fortey’s book joins Tim Flannery’s Here on Earth: A Natural History of the Planet (New York: Atlantic Monthly Press, 2011), Michael Novacek’s Terra: Our 100-Million-Year-Old Ecosystem—and the Threats That Now Put It at Risk (New York: Farrar, Straus and Giroux, 2007), and Curt Stager’s Deep Future: The Next 100,000 Years of Life on Earth (New York: Thomas Dunne Books, 2011) as forward-looking and richly described histories of the planet and the processes at work on it. For general and lively overviews of the history of life, see Richard Dawkins’s Ancestor’s Tale: A Pilgrimage to the Dawn of Evolution (New York: Mariner Books, 2005), Andrew Knoll’s Life on a Young Planet: The First Three Billion Years of Evolution on Earth (Princeton, N.J.: Princeton University Press, 2004), and Brian Switek’s Written in Stone: Evolution, the Fossil Record, and Our Place in Nature (New York: Bellevue Literary Press, 2010).

  ONE ROCKING OUR WORLD

  Using the predictions of evolutionary and geological history to find fossils means employing the tools of historical geology, especially the fields of stratigraphy, sedimentology, and structural geology. Generally speaking, stratigraphy works to piece together the layers of rock in Earth to understand their ages and their relationships to one another. Sedimentology centers on elucidating the conditions that led to the formation of rocks such as the sandstones, shales, and siltstones that occasionally contain the fossils of interest to paleontologists like myself. Were the rocks originally deposited by the action of lakes, streams, or oceans, or by some other earthly process? Structural geology seeks to make sense of the movements and forces at work on the rocks relative to one another during the millions of years from their deposition as sediments to their presence as layers today. General references on these fields abound. For a captivating primer that requires absolutely no prior knowledge, see Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth (New York: Basic Books, 2005). Fortey’s Earth also fits into this category. See also Walter Alvarez’s excellent The Mountains of St. Francis: Discovering the Geological Events That Shaped the Earth (New York: Norton, 2008).

  Bill Amaral’s insight into the fossil-bearing potential of the Triassic-age rocks in Greenland began with the Shell Oil Guide to the Permian and Triassic of the World. The library discard saved from the trash was K. Perch-Nielsen et al., “Revision of Triassic Stratigraphy of the Scoresby Land and Jameson Land Region, East Greenland,” Meddelelser om Grønland 193 (1974): 94–141. This reference ultimately led Bill, Chuck, and Farish to the elegant sedimentological work of Lars Clemmensen, a Danish sedimentologist. These papers—L. B. Clemmensen, “Triassic Lithostratigraphy of East Greenland Between Scoresby Sund and Kejser Franz Josephs Fjord,” Grønlands geologiske undersøgelse (1980), and L. B. Clemmensen, “Triassic Rift Sedimentation and Palaeogeography of Central East Greenland,” Geological Survey of Greenland, Bulletin, no. 136 (1980): 5–72—became a kind of Rosetta stone because they revealed the fossil potential of the rocks and their similarity to those of eastern North America (described in P. E. Olsen, “Stratigraphic Record of the Early Mesozoic Breakup of Pangea in the Laurasia-Gondwana Rift System,” Annual Reviews of Earth and Planetary Science 25 [1997]: 337–401). This was a eureka moment in the library.

  Coming to grips with the past inside the rocks is as much about practical matters—food, boot selection, and learning to see—as about great ideas at stake. The first of these considerations is derived from one of Napoléon’s insights: armies run on their stomachs. You can have the best scientific preparation on the planet, but if the food is terrible, things can go awry very quickly. When a field crew eats well and meals become an event to anticipate, folks can endure privations of weather, boredom, and the drudgery of failure that a new fossil hunt brings. Long days spent wet and cold, finding nothing, can be rescued by comfort foods awaiting people when they return to the tent at night. Before departing for the Arctic, we prepare by dehydrating many of our own vegetables and fruits to devise menus that have a diversity of tastes, textures, and smells. Come to my lab in April before a field season and you might smell kiwis, strawberries, or San Marzano tomatoes in the dehydrator. We even bake bread in the field, knowing that the smell of a rising loaf can not only sell a house but also soothe a surly field crew. In the field
, the bread tastes like the finest French baguette. Unfortunately, our creations, having the consistency and density more of a building material than of an edible substance, would be an insult if served at home.

  We knew few of these tricks the first season in 1988. The meals were all prepackaged dehydrated affairs with fancy labels to make one salivate and sumptuous names such as veal scallopini, chicken marsala, and turkey tetrazzini. After two weeks of gorging on these bags in the field, we noticed that they all tasted the same. A depressing confirmation came when I read the ingredients lists: all our fancy dinners were essentially the same meal with a different label, in a different-colored bag, with a different-shaped pasta. Revealing this discovery to my colleagues did not help matters; the ensuing run on hot sauce and spices left us with no way to vary tastes. Needless to say, I lost a lot of weight that year.

  Our recipes for dehydrated meals can be found at http://tiktaalik.uchicago.edu. They do the trick after a day of slogging through tundra or clambering over scree, use a minimum of fuel and water during preparation, can be modified for everyone from a vegan to a ravenous carnivore, and aren’t heavy to pack or ship. You can even serve the meals at home to company you never wish to see again.

  For a good nontechnical introduction to the geological history of eastern North America, see Chet Raymo and Maureen E. Raymo, Written in Stone (Hensonville, N.Y.: Black Dome Press, 2007). The story of Lull’s dinosaur in the bridge abutment can be found in Edwin H. Colbert, Men and Dinosaurs (New York: E. P. Dutton, 1968).

  The Greenland discoveries are described in F. A. Jenkins Jr. et al., “A Late Triassic Continental Fauna from the Fleming Fjord Formation, Jameson Land, East Greenland,” in The Nonmarine Triassic, ed. S. G. Lucas and M. Morales (Albuquerque: New Mexico Museum of Natural History and Science, 1993), 74; F. A. Jenkins Jr. et al., “A New Record of Late Triassic Mammals from the Fleming Fjord Formation, Jameson Land, East Greenland,” in Lucas and Morales, Nonmarine Triassic, 94. The most important of the mammals we found is described in F. A. Jenkins Jr. et al., “Haramiyids and Triassic Mammalian Evolution,” Nature 385 (1997): 715–18.

  General references on the origin of mammals and the relevance of little teeth to our own branch of the evolutionary tree can be found in Zofia Kielan-Jaworowska, Richard L. Cifelli, and Zhe-Xi Luo, Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure (New York: Columbia University Press, 2004); and Z.-X. Luo, “Commentary on Mammalian Dental Evolutionary Development,” Nature 465 (2010): 669.

  TWO BLASTS FROM THE PAST

  The relative numbers of the atoms in the human body were taken from Robert W. Sterner and James J. Elser, Ecological Stoichiometry: The Biology of Elements from Molecules to the Biosphere (Princeton, N.J.: Princeton University Press, 2002), chap. 1. This is of course not a true chemical formula, as the ratios of elements in us compose not a single unique molecule, like a crystal of salt, but a body consisting of numerous different kinds of them.

  The notion of a tree of life that connects all creatures living and extinct is one of the insights of the Darwinian revolution. It makes specific and testable predictions and allows us to formulate hypotheses. Background discussion of these methods written for a general audience is found in Dawkins’s Ancestor’s Tale. For those who wish a treatment written for practitioners, try E. O. Wiley et al., The Compleat Cladist: A Primer of Phylogenetic Procedures, special publication no. 19 (Lawrence: University of Kansas, Museum of Natural History, 1991), http://www.archive.org/stream/compleatcladistp00wile#page/n5/mode/2up. To get a real taste for the discipline with its applications and vigorous debates, try some of the journals in the field: Cladistics and Systematic Biology.

  The story of Henrietta Leavitt’s work is published in E. C. Pickering, “Periods of 25 Variable Stars in the Small Magellanic Cloud,” Harvard College Observatory Circular 173 (1912): 1–3. The story of her work, and that of the other women in the observatory, is in Nina Byers and Gary Williams, eds., Out of Shadows: Contributions of Twentieth-Century Women to Physics (New York: Cambridge University Press, 2006); and Jacob Darwin Hamblin, Science in the Early Twentieth Century: An Encyclopedia (Santa Barbara, Calif.: ABC-CLIO, 2005), 181–84.

  General discussion of the big bang and its consequences can be found in Krauss, Atom; Tyson and Goldsmith, Origins; Simon Singh, Big Bang: The Origin of the Universe (New York: HarperCollins, 2005); and Steven Weinberg, The First Three Minutes, updated ed. (New York: Basic Books, 1993).

  Operation Ivy Mike, the first test of the Teller-Ulam device, is described in Richard Rhodes, Dark Sun: The Making of the Hydrogen Bomb (New York: Simon & Schuster, 1995).

  THREE LUCKY STARS

  In the days since the “nebular hypothesis” of Swedenborg, Kant, and Laplace, the origin of the planets of the solar system has been an active area of research, discovery, and debate. General background can be found in Tyson and Goldsmith, Origins. A general review of the dynamics of the formation of Earth is found in R. M. Canup, “Accretion of the Earth,” Philosophical Transactions of the Royal Society A 366 (2008): 4061–75. For those with a quantitative background who want to immerse themselves in the field by reading original scientific papers, go to the main scientific journal of the field, Icarus: The International Journal of Solar System Studies, the official publication of the Division of Planetary Sciences of the American Astronomical Society.

  Harry McSween has written wonderful books on the solar system, meteoritics, and cosmochemistry. See in particular Stardust to Planets: A Geological Tour of the Solar System (New York: St. Martin’s Press, 1993). For an excellent review of the dynamics of the solar system, see J. Kelly Beatty, Carolyn C. Petersen, and Andrew Chaikin, The New Solar System, 4th ed. (Cambridge, Mass.: Sky Publishing, 1999).

  The field of cosmochemistry is concerned with the chemical analysis of meteors, lunar rocks, and other extraterrestrial materials. On November 29, 2011, the Proceedings of the National Academy of Sciences (PNAS) ran a special issue with a number of excellent reviews. The opening review is a useful overview of the field and the special issue: G. MacPherson and M. H. Thiemens, “Cosmochemistry: Understanding the Solar System Through Analysis of Extraterrestrial Materials,” PNAS 108 (2011): 19130–34.

  Studies of the age of Earth have, themselves, a rich history. A source now several decades old but a resource for history, detail, and method, is G. Brent Dalrymple, The Age of the Earth (Stanford, Calif.: Stanford University Press, 1991). For a more recent treatment, see G. B. Dalrymple, “The Age of the Earth in the Twentieth Century: A Problem (Mostly) Solved,” in The Age of the Earth: From 4004 B.C. to A.D. 2002, Geological Society, London, Special Publication 190, ed. C. L. E. Lewis and S. J. Knell (London: Geological Society, 2001), 205–21. This special publication from the London Geological Society contains a veritable feast of papers on the age of Earth, the history of this field of study, and the methods used.

  Zircons are magnificent windows into early Earth. See J. W. Valley, W. H. Peck, and E. M. King, “Zircons Are Forever,” Outcrop, University of Wisconsin-Madison Geology Alumni Newsletter (1999), 34–35. For a scientific paper on this, see S. A. Wilde et al., “Evidence from Detrital Zircons for the Existence of Continental Crust and Oceans on the Earth 4.4 Gyr Ago,” Nature 409 (2001): 175–78. For a general treatise on the hunt for and meaning of the oldest rocks on the planet, see Martin Van Kranendonk, R. Hugh Smithies, and Vickie C. Bennett, eds., Earth’s Oldest Rocks (Boston: Elsevier, 2007). That volume has an enormous amount of information written by and for specialists in the field.

  Geologists tell time in rocks in two ways: relatively and absolutely. See Doug Macdougall, Nature’s Clocks: How Scientists Measure the Age of Almost Everything (Berkeley: University of California Press, 2008). Relative time is a matter of understanding the relationships between different layers—layers above are generally younger than those below. The situation gets challenging when the layers are highly altered. Piecing together the layer history comes from understanding the faults and movements that shifted
rocks and layers about.

  Calculating absolute time in rocks and minerals depends on understanding the radioactive decay of atoms. Some atoms have an unstable configuration of electrons, neutrons, and protons, causing them to lose or gain components. As they do this, their atomic weights can change, and they become new forms. The important point is that this transformation happens at rates that are physical constants, known as the half-life. The half-life of an atom is the time required for one-half of a sample to decay, or transform, into its daughters. If you know the amounts of parent atoms, daughter atoms, and the half-life, then you can calculate the time that the atoms have been decaying. A number of atoms are useful to geologists: uranium 238, argon 39, and carbon 14, for example. In general, you try to match atoms for the job: atoms with the slowest decay rates are useful for the oldest rocks, whereas those that decay faster are useful for more recent ones. Uranium 238, with its long half-life, is useful for questions about the most ancient phases of Earth. Carbon 14 has such a rapid decay rate it is useful for more recent events, such as those of human history and culture.

  In zircons, such as those from the Jack Hills, the isotopes (atomic versions) of uranium and lead are most useful. Uranium 238 decays into a stable daughter isotope, lead 206, with a half-life of 4.5 billion years. When uranium was incorporated in the zircon when it was formed, the clock started ticking: the slow transformation to lead 206 began. Looking at that zircon now, we make the reasonable assumption that all of the lead 206 has come from the decay of uranium. Knowing the ratios of parent and daughter isotopes and the half-life allows the age of the zircon to be calculated.

  A general timescale for the major events in the history of the solar system and Earth is in F. Albarede, “Volatile Accretion History of the Terrestrial Planets and Dynamic Implications,” Nature 461 (2009): 1227–33.