Why Are We Here

Why Are We Here? takes us on a journey from the Big Bang to the origin and evolution of complex, intelligent life in a search for the meaning of human existence. How did chemistry come to life? How did the release of oxygen by cyanobacteria change the natural history of life? How did mass extinctions reset the clock and reshape the course of biological evolution? Why are we Homo sapiens so dominant? We share over 98% of our DNA with chimpanzees, yet we build vast civilizations, while chimps are confined to forests and sadly to experimental laboratories and zoos. How come? How will cultural and technological evolution, which have now transcended biological evolution, shape the future of life on our planet? Can we escape the many existential threats that hover over us? Bruce Brodie takes us on an educational and deeply fascinating journey that will give us new perspectives about how we think about our world, our place and purpose in the cosmos, and the future of humanity. 

PART I: PerspectivesPART IV: From Sea to Land
Chapter 1. Our Common Heritage……………………………………………..5
Chapter 2. Darwin’s Theory of Evolution…………………………………….12
Chapter 15. The Greening of Earth…………………………………………..143
Chapter 16. Invasion of the Continents…………………………………….156
Chapter 17. Dinosaurs Reign – Mammals, Birds Emerge…………..164
Chapter 18. The Mass Extinctions……………………………………………175
PART II: OriginsPART V: Human Evolution
Chapter 3. In the Beginning………………………………………………………23
Chapter 4. Chemistry Comes to Life………………………………………….33
Chapter 5. The Universal Energy System…………………………………..45
Chapter 6. Solar Powered Bacteria……………………………………………56
Chapter 19. Out of Africa………………………………………………………..188
Chapter 20. Homo Sapiens Rise to Dominance………………………..195
Chapter 21. Cultural Evolution…………………………………………………201
Chapter 22. Evolution of Morality…………………………………………….218
Chapter 23. The Greatest Mystery……………………………………………244
Chapter 24. Aging, Death, and Evolution…………………………………..231
PART III: Evolution of Complex LifePART VI: The Present and the Future
Chapter 7. The Great Historic Rendezvous………………………………..66
Chapter 8. The Cambrian Explosion………………………………………….104
Chapter 9. Multicellular Life……………………………………………………..73
Chapter 10. The Great Lottery…………………………………………………..82
Chapter 11. Sperm, Eggs, Fertilization, and Sexual Selection………92
Chapter 12. Evolution of Organ Systems…………………………………..113
Chapter 13. Evolution of the Eye………………………………………………123
Chapter 14. Evolution of the Nervous System…………………………..132
Chapter 25. Are We Alone?……………………………………………………..289
Chapter 26. Climate Change…………………………………………………..260
Chapter 27. The Sixth Extinction……………………………………………..276
Chapter 28. Technological Evolution……………………………………….299
Chapter 29. Existential Threats……………………………………………….322
Chapter 30. A New Species of Man…………………………………………314
Epilogue………………………………………………………………………………..336

Seven years ago, I retired from a busy cardiology practice and set out on my own journey in an attempt to understand how we got here, how our evolutionary past has shaped human nature, and where we might be headed. Why Are We Here? is the culmination of that research and that journey.

I have a general science and biochemistry background. I hold a degree in electrical engineering from Purdue University and a medical degree from Washington University in Saint Louis, and I have had an active and productive career in medicine and interventional cardiology. But I am certainly not an expert in the many fields encompassed by this book, which include cosmology, physics, chemistry, biochemistry, genetics, geology, paleontology, psychology, evolutionary biology, evolutionary psychology, neuroscience, anthropology, computer science, and more. Rather than an expert, I regard myself more as a reporter and a scientific writer. What I have tried to do in more than seven years of study and research is draw from scientific publications and books written by many experts in these diverse fields, develop a synthesis of their knowledge and ideas, and present these ideas with a unified perspective for a general audience.

Eclecticism has limitations in the pursuit of new knowledge and new theories, but it may be a requirement for the synthesis of a field as broad as the origin and evolution of life. My goal in this book is to educate the reader about how life may have started and how the evolutionary process has led us to the diverse life that inhabits our planet today. I hope to give the reader an appreciation of how science has helped us to understand the process of evolution, while leaving the reader with an appreciation of the limitations of our knowledge. I hope to provide a perspective of how our species at this point in time fits into the big picture of a universe that is infinite in time and space, and I hope this story will leave the reader with a lasting sense of wonder at the amazing mystery of life and our universe. An understanding of our evolutionary past and an appreciation of possible scenarios for our future provides a basis for seeking answers to the existential questions of life. Why are we here?

Some of the material in the book is detailed and technical, but I have tried to present it in a way that is understandable, educational, and, I hope, entertaining. The book is divided into six parts. Part 1 provides perspectives on our common heritage and evolutionary theory; part 2 chronicles the origin of the universe and our solar system and the origins of life on Earth; part 3 details the evolution of complex life; part 4 recounts the migration of life from sea to land; part 5 chronicles human evolution; and part 6 deals with the present and future of life on our planet. The text is punctuated with photos, figures, and sidebars to help provide interest and clarity. Each chapter is self-contained and can be read in isolation from the other chapters. So, the book can be taken and digested in pieces, used as a reference, or tackled in continuum from cover to cover. The story of the origin and evolution of life is the greatest, most mysterious, and most miraculous story of all time. Let’s get started on the journey.

PART I: Perspectives
Chapter 1. Our Common Heritage…5
Chapter 2. Darwin’s Theory of Evolution…12
PART II: Origins
Chapter 3. In the Beginning…23
Chapter 4. Chemistry Comes to Life…33
Chapter 5. The Universal Energy System…45
Chapter 6. Solar Powered Bacteria…56
PART III: Evolution of Complex Life
Chapter 7. The Great Historic Rendezvous…66
Chapter 8. The Cambrian Explosion…104
Chapter 9. Multicellular Life…73
Chapter 10. The Great Lottery…82
Chapter 11. Sperm, Eggs, Fertilization, and Sexual Selection…92
Chapter 12. Evolution of Organ Systems…113
Chapter 13. Evolution of the Eye…123
Chapter 14. Evolution of the Nervous System…132
PART IV: From Sea to Land
Chapter 15. The Greening of Earth…143
Chapter 16. Invasion of the Continents…156
Chapter 17. Dinosaurs Reign – Mammals, Birds Emerge…164
Chapter 18. The Mass Extinctions…175
PART V: Human Evolution
Chapter 19. Out of Africa…188
Chapter 20. Homo Sapiens Rise to Dominance…195
Chapter 21. Cultural Evolution…201
Chapter 22. Evolution of Morality…218
Chapter 23. The Greatest Mystery…244
Chapter 24. Aging, Death, and Evolution…231
PART VI: The Present and the Future
Chapter 25. Are We Alone?…289
Chapter 26. Climate Change…260
Chapter 27. The Sixth Extinction…276
Chapter 28. Technological Evolution…299
Chapter 29. Existential Threats…322
Chapter 30. A New Species of Man…314
Epilogue…336

Timeline

13.8 Billion Years Ago
The Big Bang and the Origin of the Universe.
13.8 Billion Years Ago
4.5 Billion Years Ago
Formation of the Sun, Earth and Our Solar System.
4.5 Billion Years Ago
3.8 Billion Years Ago
Bacterial Life First Appears On Planet Earth. Fossils of ancient filamentous microorganisms were discovered on the coast of Hudson Bay in Quebec, Canada in 1993, dated 3.8 billion years ago.
3.8 Billion Years Ago
3.7 Billion Years Ago
Cyanobacteria learn the process of photosynthesis to capture energy from the Sun and produce oxygen as a byproduct.
3.7 Billion Years Ago
2.1 Billion Years Ago
The first complex nucleated cell is formed in a “fateful encounter” – an unlikely merger of two microorganisms, an ancient bacterium and an ancient archaeon.
2.1 Billion Years Ago
540 Million Years Ago
The Cambrian Explosion ushers in the sudden appearance of diverse marine animal life and algae in Earth’s oceans.
540 Million Years Ago
470 Million Years Ago
Land plants evolve from algae and begin to colonize the landscape.
470 Million Years Ago
423 Million Years Ago
Arthropods (tiny millipedes) become the first animals to invade the landscape.
423 Million Years Ago
375 Million Years Ago
Tiktaalik, the iconic fish-a-pod, crawls out of water onto dry land and becomes the first vertebrate to invade the landscape.
375 Million Years Ago
363 Million Years Ago
Amphibians evolve from lobed-finned fish and become the dominant land animals during the late Carboniferous period and much of the Permian period. Mastodonsaurus, the giant amphibian predator shown above, ruled the land.
363 Million Years Ago
320 Million Years Ago
Reptiles emerge and become the dominant creatures on the planet during the Permian period.
320 Million Years Ago
251 Million Years Ago
Volcanic eruptions trigger the End Permian extinction, which wipes out greater than 90% of all species on the planet.
251 Million Years Ago
230 Million Years Ago
Dinosaurs emerge and dominate the landscape for 135 million years during the Jurrasic and Cretaceous periods.
230 Million Years Ago
195 Million Years Ago
Small rodent-like mammals emerge in the shadows of the dinosaurs during the Jurassic period.
195 Million Years Ago
159 Million Years Ago
Archaeopteryx, a bird-like dinosaur, is an iconic symbol of the transition from dinosaurs to birds during the Jurassic period. Birds evolve and become a lasting legacy of the dinosaurs.
159 Million Years Ago
66 Million Years Ago
A giant asteroid collides with earth and wipes out the Dinosaurs and 75% of Earth’s species in the End Cretaceous extinction.
66 Million Years Ago
55 Million Years Ago
The first primate, an ancient relative of current-day lemurs and tarsiers, appears on Earth.
1st
55 Million Years Ago
7 Million Years Ago
Our hominin lineage and chimpanzees split from a common ancestor.
7 Million Years Ago
3.2 Million Years Ago
Lucy, a transitional figure between apes and humans, is part of our hominin heritage. The discovery of her fossil remains in 1974 in Ethiopia established that we humans descended from apes.
3.2 Million Years Ago
2.8 Million Years Ago
Homo habilis, whose fossil remains were discovered in Tanzania and Ethiopia dated as early as 2.8 million years ago, emerges as the first human to inhabit our planet.
2.8 Million Years Ago
1.9 Million Years Ago
Homo erectus, whose fossil remains were dated as early as 1.9 million years ago, emerges and becomes the longest-living human species, surviving 1.8 million years.
1.9 Million Years Ago
300 Thousand Years Ago
Homo sapiens, emerge in Africa for the first time. Fossil remains of Homo sapiens were discovered in Ethiopia dated 195,000 years ago and in Morocco dated 300,000 years ago.
300 Thousand Years Ago
60 Thousand Years Ago
Homo sapiens distinguish themselves from other species with the evolution of advanced culture – art, religion, tool use, and trade.
60 Thousand Years Ago
12 Thousand Years Ago
The Agricultural (Neolithic) Revolution begins as Homo sapiens learn to farm, domesticate livestock, and join together in villages.
12 Thousand Years Ago
250 Years Ago
The Industrial Revolution begins as Homo sapiens learn to use machines and produce goods in factories through mass production. As a result, Sapiens produce large cities and advanced civilizations, as this 1941 skyline of Manhattan exemplifies.
250 Years Ago
73 Years Ago
The first atomic bomb is deployed as a weapon of mass destruction in 1945 in World War II.
73 Years Ago
36 Years Ago
Genetic engineering bursts into the mainstream with the synthesis of human recombinant insulin through genetic manipulation of bacteria.
36 Years Ago
22 Years Ago
Artificial Intelligence reaches public awareness when IBM’s chess playing computer Deep Blue defeats chess champion Garry Kasparov.
22 Years Ago
Today
Cultural and Technological Evolution surpass the slow pace of biological evolution and now drive future change.
Today
Close Menu