A New History of Life: The Radical New Discoveries about the Origins and Evolution of Life on Earth

354 Pages·2015·3.69 MB·English

by  Peter Ward

From PW: For Dr. Howard Leonard and Dr. Peter Shalit, life historians, and to
the great Robert Berner, Yale University

From JK: To the memories of Dr. Eugene M. Shoemaker, Dr. Heinz A.
Lowenstam, and Dr. Clair C. Patterson of Caltech. They and many others left
fingerprints all over my brain.
Contents
Introduction

CHAPTER I
Telling Time

CHAPTER II
Becoming an Earthlike Planet: 4.6–4.5 GA

CHAPTER III
Life, Death, and the Newly Discovered Place In Between
CHAPTER IV
Forming Life: 4.2(?)–3.5 GA

CHAPTER V
From Origin to Oxygenation: 3.5–2.0 GA

CHAPTER VI
The Long Road to Animals: 2.0–1.0 GA

CHAPTER VII
The Cryogenian and the Evolution of Animals: 850–635 MA
CHAPTER VIII
The Cambrian Explosion: 600–500 MA

CHAPTER IX
The Ordovician-Devonian Expansion of Animals: 500–360 MA
CHAPTER X
Tiktaalik and the Invasion of the Land: 475–300 MA

CHAPTER XI
The Age of Arthropods: 350–300 MA

CHAPTER XII
The Great Dying—Anoxia and Global Stagnation: 252–250 MA
CHAPTER XIII
The Triassic Explosion: 252–200 MA

CHAPTER XIV
Dinosaur Hegemony in a Low-Oxygen World: 230–180 MA
CHAPTER XV
The Greenhouse Oceans: 200–65 MA

CHAPTER XVI
Death of the Dinosaurs: 65 MA

CHAPTER XVII
The Long-Delayed Third Age of Mammals: 65–50 MA
CHAPTER XVIII
The Age of Birds: 50–2.5 MA

CHAPTER XIX
Humanity and the Tenth Extinction: 2.5 MA to present
CHAPTER XX
The Knowable Futures of Earth Life

Notes
A Note on the Authors
Introduction
History in almost any form is the academic subject perhaps most hated by school
kids. One of the most thoughtful examinations was by James Loewen, in Lies
My Teacher Told Me.1 His conclusion can be summarized in one word:
“irrelevance.” Loewen wrote, “The stories that history textbooks tell are
predictable; every problem has already been solved or is about to be solved …
Authors almost never use the present to illuminate the past—the present is not a
source of information for writers of history texts.”
Loewen’s message is quite clear. As American history is now taught in high
schools, the past and present are disconnected, such that history has no effect on,
or relevance to, our day-to-day lives. Yet that conclusion is so untrue, especially
for the history of life, so ancient it is written in rocks, molecules, models, and on
the DNA strands found within our every cell. Its relevance is that it gives us
place and context. The history of life also just might save us from near-term
extinction, if we take note of it and heed its warnings.
In the early 1960s the great American writer James Baldwin wrote: “People
are trapped in history, and history is trapped in them.”2 He was speaking to race
when he penned those words. But the statement is equally true if the word
“people” is replaced with “all of life on Earth, present and past,” for each strand
of DNA, in each of our cells, is an ancient record of biological history, written in
simple code and passed down from generation to generation. One could say that
DNA is nothing but history, one with a physical manifestation that was slowly
melded and accumulated over countless eons by the most pitiless of all
phenomena—natural selection. DNA is a history that is inside us—and yet one
that is our master as well, the blueprint for our bodies, and dictator of what we
will pass on to our children, gifts that can be blessings—or deadly time bombs.
We are indeed trapped in this particular vehicle of history as much as it is
trapped in us.
The history of life gives us the answers to so many of the perplexing questions
confronting us all: How did we humans come to inhabit this thin, late-occurring,
and very marginal twig on the giant tree of life? What wars did our species have
to pass through? What calamities mark the human branch of life’s 4-billion-year-
old tree? The past can help us understand our place among the twenty or more
million species now living—and the untold billions now extinct. When a species
is no longer extant, what is also destroyed is the as yet unrealized future
evolution of untold species.
In the pages to come we will look at the long road to our present and the
distant trials our long-ago ancestors had to pass through: fire, ice, hammer blows
from space, poison gas, the fangs of predators, pitiless competition, lethal
radiation, starvation, enormous changes of habitat, and episodes of war and
conquest amid a relentless colonization of every habitable corner of this planet—
each an episode that left its mark in the total sum of DNA now extant. Each
crisis and conquest was a forge that changed genomes by adding or subtracting
all manner of genes, each of us the descendant of survivors tempered by
catastrophe and quenched by time.
There is a second and perhaps even greater reason to pay attention to the
history of life encapsulated in this quote from Norman Cousins: “History is a
vast Early Warning System.”3 This wisdom dates back to near the end of the
Cold War. Newer generations of humans have little sense of what it was like to
grow up in the 1950s and 1960s, when weekly noontime siren tests told us
children of that dark time that Armageddon was but one terrifying siren scream
away, and that every faint sound of a late-night jet might be the start of the end.
Human warfare has repeatedly, and seemingly incessantly, exacted a hideous
toll on humanity—physically, economically, and emotionally. In many ways the
history of life has undeniable similarities to human conflict and warfare. The
coevolutionary development of offensive weapons by predators (better claws,
teeth, gas attack, even poison-tipped barbs to catch and kill food species) caused
equally rapid countermeasures in the predators’ prey, including better body
armor, speed, hiding ability, and sometimes defensive weapons as well—all of
which is technically called the biological arms race. Many of the great events of
evolution cannot be repeated; evolution has had a long period to fill the
biosphere with highly competitive and efficient organisms, making it unlikely to
repeat, for instance, the Cambrian explosion when all of the basic body plans of
animals came into being. But what can be repeated are things antipodal to living
and diversifying, such as extinction, or extinction writ larger—the dreadful past
catastrophes of deep time, the mass extinctions.
With every molecule of carbon dioxide we pump into the atmosphere we are
ignoring the early warning sirens that rapid rises in carbon dioxide are the
commonality between more than ten mass extinctions of the deep past and what
is happening today. Those extinctions were caused not by asteroid impact, but
from rapid increases in volcanically produced atmospheric greenhouse gases and
the global warming they produced. A terrifying new paradigm of mass extinction
has arisen this century: “greenhouse mass extinctions,” a name overtly chosen to
describe the cause of the vast majority of species killed off by mass extinctions
in the past.4
Evidence of when, where, and how these greenhouse extinctions took place
now blares at us from a wide variety of data. To those hearing these siren calls,
the danger seems real enough. Yet too many have ignored or missed vast
moralities from the past, and what is a possible future. The history of life
provides an early warning system that tells us we must reduce human-caused
greenhouse gas emissions, but it is human history that tells us that we probably
will not heed the warnings and reverse the damage until a succession of climate-
induced mass human mortalities gives us no choice.
Scientific information from so-called deep time is the single most ignored
aspect of the climate change debate. George Santayana wrote the most oft-
repeated aphorism about history, one so commonly used that it is trite: “Those
who ignore history are condemned to repeat it.”5 With regard to a clear history
of mass extinction brought about by atmospheric carbon dioxide levels rapidly
approaching in the near future, however, we should especially take heed of the
most important word in Santayana’s prophecy: the word “condemned.”
WHAT IS NEW IN THIS “NEW HISTORY OF LIFE”
No single book could ever do justice to the history of life. Choices had to be
made, and those choices were largely dictated by our directive around the word
“new.” The last “complete” single-volume history of life was written in the mid-
1990s: the exquisite and bestselling Life: A Natural History of the First Four
Billion Years of Life on Earth,6 by the British paleontologist and science writer
Richard Fortey. His “takes” were marvelous and the book remains a joy to read,
or in our case, to reread nearly two decades after its publication. But because
science advances so quickly, there is much that was not known then compared to
now. There are even two new scientific disciplines that barely existed in the mid-
1990s: astrobiology and geobiology. The advances in instrumentation have led to
entirely new understanding, while outcrops of strata containing fossils from
times or taxa previously unknown have come to light. Even the sociology of how
science is done has changed, for now the most important scientific
breakthroughs are acknowledged to take place between the boundaries of the
previously august and familiar disciplines of geology, astronomy, paleontology,
chemistry, genetics, physics, zoology, and botany—each symbolically separated
into their own buildings on most university campuses, each with not only a
faculty with its own rules and boundaries, but entire fields with their own
vocabularies and favored methods of disseminating information coming from
research.
We have used three themes in the pages to come as lodestones for the history
we have chosen to feature. First, we posit that the history of life has been more
affected by catastrophe than the sum of all other forces, including the slow,
gradual evolution first recognized by Charles Darwin—based on his training by
the dominant teachers of uniformitarianism. The guiding principle of geology for
more than two centuries—the Principle of Uniformitarianism—was first
developed by James Hutton and Charles Lyell in the late 1700s.7 It was taught to
and ultimately became the prime scientific influence on generations of young
naturalists, including Charles Darwin.8 The discovery of the dinosaur-killing
asteroid that hit our planet 65 million years ago was the start of this paradigm
shift toward one that has been sometimes called neocatastrophism,9 a take on
catastrophism, the paradigm that preceded uniformitarianism.
As we will show in this book, uniformitarianism, as it applies to ancient
worlds as well as the mode and tempo of evolution, is outmoded and largely
refuted. The modern world is not the best tool for explaining many times and
events in the deep past that indeed were sudden—not gradual. For example,
there are no modern examples that can explain the “snowball Earths,” or the
“great oxygenation event,” or the sulfur-rich “Canfield oceans” that lasted for
more than a billion years and in all that time impeded the first evolution of the
animal grade of complexity. Even the dinosaur killing K-T Cretaceous Period–
Tertiary Period mass extinction (now termed the K-Pg, or Cretaceous-Paleogene
Period, but we hope our colleagues forgive us if we stick to the better sounding
and better known K-T) has no parallel today; nor the type of atmosphere and
ocean that allowed life to form on Earth; or an atmosphere with carbon dioxide
levels so high that there is not a scrap of ice anywhere on the planet. The present
is not a key to most of the past; in fact, it is barely a key to the Pleistocene.
Making it so has limited us in our vision and understanding.
Second, while we may be carbon-based life, composed of “long-chain” carbon
molecules (carbon atoms strung together to form proteins), it is the influence of
three different kinds of molecules, simple molecules that exist as simple gases,
that have had the greatest influence on the history of life: oxygen, carbon
dioxide, and hydrogen sulfide. Sulfur, in fact, may have been the single most
important of all elements in dictating the nature and history of life on this planet.
Finally, while the history of life may be populated by species, it has been the
evolution of ecosystems that has been the most influential factor in arriving at
the modern-day assemblage of life. Coral reefs, tropical forests, deep-sea “vent”
faunas, and many more—each can be viewed as a play with differing actors but
the same script over eons of time. Yet we know that on occasion in the deep past
entirely new ecosystems appear, populated by new kinds of life. The appearance
of life that can fly, for instance, or life that can swim or walk—each was a major
shift in evolutionary innovation that changed the world, and in each case helped
create a new kind of ecosystem.
WHAT WE BRING
An author’s background affects the biases inherent in any written history. Peter
Ward has been a paleobiologist since 1973, and has published extensively on
modern and ancient cephalopods as well as on mass extinctions of vertebrates
and invertebrates. Joseph Kirschvink is a geophysical biologist who began his
work on the Precambrian-Cambrian transition, but then expanded to looking at
older times (the great oxidation event) as well as being the discoverer of the
snowball Earths—major parts of life’s history. Together we have subsequently
worked on the Devonian, Permian, Triassic-Jurassic, and Cretaceous-Tertiary
(this time interval recently renamed the Paleogene Period) mass extinctions.
We have worked together in the field since the mid-1990s. These trips
included study of the Permian mass extinction in South Africa, from 1997 to
2001; the study of Upper Cretaceous ammonites in Baja California, California,
and the Vancouver Island region; the study of the Triassic-Jurassic mass
extinction in the Queen Charlotte Islands; the study of the K-T mass extinction
in Tunisia, Vancouver Island, California, Mexico, and Antarctica; and the study
of the Devonian mass extinction in Western Australia.
The voice we bring to this book is meant to be a seamless duet, but there are
passages where one or the other of us self-identifies because of the nearness of
the topics to some particular interest we have, or because we were integral in the