Where Did Modern Humans Evolve?
Young Earth creationists have a ready-made answer to this question—the Garden of Eden—and they accept the biblical story of Adam and Eve as factual history instead of mythic saga. IDers, by comparison, avoid all such biblical references and argue simply that there is no evidence for human ancestry and thus there must have been a divine spark of humanity miraculously inserted into one hominid species. The evolutionary story is more complex, says University of Cambridge professor Peter Forster, an expert in archaeogenetics, who demonstrated how prehistoric human migrations can be traced by mitochondrial DNA (mtDNA) through the maternal line of modern humans.
Forster outlined our migrational history over the past 200,000 years as follows: Between 190,000 and 130,000 years ago, a single female, known formally as the “mitochondrial coalescent” but dubbed “mitochondrial Eve,” gave rise to every living human today. Between 80,000 and 60,000 years ago, a large population from the center of Africa migrated to all areas of Africa, as well as the area of present-day Saudi Arabia. This migration may have taken two routes, a northern one up the Nile and around the Red Sea and a southern one across the narrow strait at Yemen which during the last ice age would have been only five kilometers across (Forster thinks the southern route was the more likely). Between 60,000 and 30,000 years ago there was a great migration to Southeast Asia, Northern Asia, and Europe. Between 30,000 and 20,000 years ago, people spread throughout most of the rest of the world, including Australia, and between 20,000 and 15,000 years ago they migrated into North America, making their way into South America between 15,000 and 2,000 years ago. The final migration over the past 2,000 years saw the settlement of the Pacific islands.
Creationists who take comfort in the “Eve” part of this account should know that other scientists believe that we arose from a single population, not one individual, and still other scientists opt for the multiregional theory of human origins, in which different human groups arose from different ancestral groups who migrated out of Africa at different times. And in any case, this is just the story of our most recent ancestors; our lineage goes back at least as far as six million years ago to the common ancestor of apes and humans.
What Direct Evidence Is There
for Natural Selection and Evolution?
Every year for the past three decades the husband and wife team of Peter and Rosemary Grant, both from Princeton University, have parked themselves on the Galápagos island of Daphne Major, a tiny volcanic plug 120 meters high and a kilometer long, to study the evolution of Darwin’s finches.
We now have extensive evidence from both fossils and genes that three million years ago a single group of finches flew out to the Galápagos during a time of very active plate tectonics and the creation of the island archipelago. When this founder population arrived, it encountered a permanent El Niño that made the islands warm and wet, which helped to trigger an explosion of speciation.
First came the warbler finch, then the tree finch (of which there are now five species), and then the ground finch (of which there are now six species). Following Ernst Mayr’s theory of allopatric speciation (in which a founder daughter population breaks away from the parental population), the first finches landed on San Cristóbal, then migrated to Española, then to Floreana, then to Santa Cruz, and finally made their way back to San Cristóbal. Along the journey the finches adapted to local conditions. Finches in highlands developed larger beaks to break hard beetles and seeds. Finches in lowlands evolved smaller beaks for eating small seeds and succulents. As an opportunistic species, some of these finches also ate sea turtle eggs and sucked the blood from blue-footed boobies. Different adaptations to different islands led to the origin of new species.
The Grants provide one of the strongest examples of observing evolution as it unfolds, which they did in tracking thirty years of environmental changes on Daphne Major and how the finch species responded. Arriving in 1973, the Grants immediately witnessed a drought that wiped out 85 percent of the population of two species of finches (the ground finch Geospiza fortis and the cactus finch Geospiza scandens). From 1975 to 1978 there was almost no rainfall and natural selection operated rapidly to change beak size. In 1983, an El Niño rainfall produced an abundance of plants and trees and cactus fruit, but two years later the island dried out and the large seeds were replaced by small seeds. Throughout this cycle, beak shape, beak size, and body size of the finches all changed in parallel.
What Is the Difference between
Natural Selection and Sexual Selection?
On the heels of Margulis’s pronouncement of the death of neo-Darwinism, Stanford University evolutionary biologist Joan Roughgarden proclaimed the demise of Darwin’s theory of sexual selection. Darwin said that males have stronger passions than females, that females are coy, and that females choose mates who are more attractive, vigorous, and well-armed. “People are surprised to learn how much sex animals have for purely social reasons (including same-sex sexuality in over 300 species of vertebrates),” Roughgarden explained, “and how many species have sex-role reversal in which the males are drab and the females are colorfully ornamented and compete for the attention of males, and that most plants and perhaps a quarter of all animal species have individuals that cannot be classified as male or female.”
In response to Roughgarden, University of Georgia evolutionary biologist Patricia Gowaty noted that Roughgarden is right in identifying the exceptions to Darwin’s theory and that there is much we still do not know, but added that since Darwin’s time much has been learned about mate selection and competition that should not be dismissed.
What Is Right in Evolutionary Theory?
At the end of the Evolution Summit the evolutionary biologist Douglas Futuyma, who wrote the book on evolution (literally—he is the author of the bestselling textbook on evolution biology), summed up the state of evolutionary theory today: “I am tempted to quote from Gilbert and Sullivan’s The Mikado: ‘I am right and you are right and all is right as right can be.’ ” Futuyma explained that he had agreements with everyone on some aspects of the various debates and controversies under discussion, but that in the end more research and more data will resolve some issues and open up new ones.
Here are a few additional controversies that are well within the borders of mainstream evolutionary science and that are experiencing vigorous debate:
1. If natural selection is the primary mechanism of evolution, what is the role of chance and contingency in the history of life?
2. What was the origin of organic molecules?
3. If DNA came from RNA, what was the first replicator that became RNA?
4. What is the target of natural selection? (Strict Darwinians believe that the individual organism is the sole target of selection; others hold that selection may occur below the individual at the level of genes, chromosomes, organelles, and cells, and above the individual at the level of groups, species, and multispecies communities.)
5. What is the relationship between evolution and embryological development (evo-devo)?
6. How much of modern human behavior can be explained by our evolutionary history (evolutionary psychology v. learning psychology; nature v. nurture)?
7. How much of modern society, culture, politics, and economics can be explained by our evolutionary past (evolutionary economics, Darwinian politics)?
Science’s greatest strength lies in the ability not only to withstand such buffeting, but actually to grow from it. Creationists, IDers, and outsiders contend that science is a cozy and insular club in which meetings are held to enforce agreement with the party line, to circle the wagons against any and all would-be challengers, and to achieve consensus on the most contentious issues. This conclusion cannot have been proposed by anyone who has ever attended a scientific conference. The World Summit on Evolution, like most scientific conferences, revealed a science rich in controversy and debate as well as data and theory. After a century and a half of such disputation, t
he theory of evolution has never been stronger.
EPILOGUE
Why Science Matters
I worry that, especially as the Millennium edges nearer, pseudoscience and superstition will seem year by year more tempting, the siren song of unreason more sonorous and attractive. Where have we heard it before? Whenever our ethnic or national prejudices are aroused, in times of scarcity, during challenges to national self-esteem or nerve, when we agonize about our diminished cosmic place and purpose, or when fanaticism is bubbling up around us—then, habits of thought familiar from ages past reach for the controls. The candle flame gutters. Its little pool of light trembles. Darkness gathers. The demons begin to stir.
—Carl Sagan, The Demon-Haunted World, 1996
Many millennia ago, the Esselen Indians of the California coast frequented natural hot springs just south of what later Spanish explorers would name Monterey Bay. The near-boiling waters of the hot springs cascaded out of the cliffs and into the crashing waves of the Pacific Ocean below. The Esselen found the sulfur-rich waters relaxing, the morning mist and afternoon sun rejuvenating, and the spectacular views of mountains and beaches breathtaking. It was a spiritual center, a place to go to renew one’s soul.
In 1910, with the Esselen Indians long ago extirpated by European guns, germs, and steel, Dr. Henry Murphy purchased the land and constructed tubs to capture the hot springs for the restoration of his patients’ health. In 1962, Dr. Murphy’s grandson, Michael Murphy, and an associate named Richard Price transformed the site into a center for the nascent human potential movement, calling it the Esalen Institute in honor of the original residents. Today, Esalen is a cluster of meeting rooms, lodging facilities, and architecturally elegant hot baths all nestled into a stunning craggy outcrop along the Pacific Coast Highway.
Over the decades Esalen has hosted a veritable Who’s Who of savants and gurus, including Alan Watts, Aldous Huxley, Abraham Maslow, Paul Tillich, Arnold Toynbee, B. F. Skinner, Stanislav Grof, Ida Rolf, Carl Rogers, Linus Pauling, Buckminster Fuller, Rollo May, Joseph Campbell, Susan Sontag, Ken Kesey, Gregory Bateson, John C. Lilly, Carlos Castaneda, Fritjof Capra, Ansel Adams, John Cage, Joan Baez, Robert Anton Wilson, Andrew Weil, Deepak Chopra, and even counterculture icon Bob Dylan. I had long wanted to visit Esalen, ever since I read Surely You’re Joking, Mr. Feynman, in which the Nobel laureate Caltech physicist Richard Feynman recounted his experiences in the natural hot spring baths there. In one particularly amusing tale, a woman was getting a massage from a man she just met: “He starts to rub her big toe. ‘I think I feel it,’ he says. ‘I feel a kind of dent—is that the pituitary?’ I blurt out, ‘You’re a helluva long way from the pituitary, man!’ They looked at me horrified and said, ‘It’s reflexology!’ I quickly closed my eyes and appeared to be meditating.”1
With this background to the mecca of the New Age movement, I was delighted to receive an invitation to speak at a conference there on evolutionary theory that featured an eclectic mix of participants: an anthropologist, a philosopher of religion, a Buddhist monk, a biophysicist, a philosopher of mind, an evolutionary biologist, a psychologist, a complexity theorist, a business entrepreneur, and a skeptic. The lectures and discussions were wide-ranging and diverse, but focused on the philosophical, religious, social, and spiritual implications and applications of evolution. My talk on the evolutionary origins of morality led to an invitation to teach a weekend seminar on science and spirituality at Esalen the following summer. Given my propensity for skepticism when it comes to most of the paranormal piffle proffered by the prajna peddlers meditating and soaking their way to nirvana at Esalen, I was surprised that the hall was full. Perhaps skeptical consciousness is rising!
The workshop was enriching for all of us, but it was in the extracurricular conversations—during healthful homegrown meals served cafeteria style with informal group seating, and while soaking in the hot tubs—that I gleaned a sense of what people believe and why. Once it became known that Mr. Skeptic was there, for example, I heard one after another “how do you explain this?” story, mostly involving angels, aliens, and the usual paranormal fare. But this being Esalen—ground zero for all that is weird and wonderful in the human potential movement—there were some singularly unusual accounts.
One woman explained the theory behind “bodywork,” a combination of massage and “energy work” that involves adjusting the body’s seven energy centers called chakras. I signed up for a massage, which was the best I’ve ever had, but when another practitioner told me about how she cured a woman’s migraine headache by directing a light beam through her head, I decided that practice and theory are best kept separate. Another woman warned about the epidemic of satanic cults throughout Europe and America. “But there’s no evidence of such cults,” I countered. “Of course not,” she explained. “They erase all memories and evidence of their nefarious activities.” Of course.
One gentleman recounted a lengthy tantric sexual encounter with his lover that lasted for many hours, at the culmination of which a lightning bolt shot through her left eye followed by a blue light-being child entering her womb, ensuring conception. Nine months later, friends and gurus joined the couple in a hot house, sweating their way through their own “rebirthing” process (to cleanse the pain of one’s own childbirth so that it is not passed on to the child) before the mother gave birth to a baby boy. Right then and there the father informed this infant that he would need to become an athlete in order to get into college; two decades later, the father told me as I slipped deeper into the hot tub, this young man became a professional baseball player. “How do you explain that?” he queried. I quickly closed my eyes and appeared to be meditating.
People have and share such spiritual experiences, and impart larger significance to them, because we have a cortex large enough to conceive of such transcendent notions, and an imagination creative enough to concoct fantastic narratives. If we define the spirit (or soul) as the pattern of information of which we are made—our genes, proteins, memories, and personalities—then spirituality is the quest to know the place of our essence within the deep time of evolution and the deep space of the cosmos.
There are many ways to be spiritual, and science is one in its awe-inspiring account of who we are and where we came from. “The universe is all that is, or ever was, or ever will be,” began the late astronomer Carl Sagan in the opening scene of Cosmos, filmed just down the coast from Esalen. “Our contemplations of the cosmos stir us. There’s a tingling in the spine, a catch in the voice, a faint sensation as if a distant memory of falling from a great height. We know we are approaching the grandest of mysteries.” How can we connect to this vast cosmos? Sagan’s answer is both spiritually scientific and scientifically spiritual: “The cosmos is within us. We are made of star stuff,” he said, referring to the stellar origins of the chemical elements of life, which are cooked in the interiors of stars, then released in supernova explosions into interstellar space where they condense into a new solar system with planets, some of which have life that is composed of this star stuff. “We’ve begun at last to wonder about our origins, star stuff contemplating the stars, organized collections of ten billion billion billion atoms contemplating the evolution of matter, tracing that long path by which it arrived at consciousness here on the planet Earth and perhaps throughout the cosmos. Our obligation to survive and flourish is owed not just to ourselves but also to that cosmos, ancient and vast, from which we spring.”2
That is spiritual gold, and Carl Sagan was one of the most spiritual scientists of our epoch.3
How can we find spiritual meaning in a scientific worldview? Spirituality is a way of being in the world, a sense of one’s place in the cosmos, a relationship to that which extends beyond oneself. There are many sources of spirituality. Unfortunately, there are those who believe that science and spirituality are in conflict. The nineteenth-century English poet John Keats, for example, lamented that Isaac Newton had “destroyed the poetry of the rainbow by reducing it to
a prism.” Natural philosophy, he complained in his 1820 poem Lamia,
will clip an Angel’s wings,
Conquer all mysteries by rule and line,
Empty the haunted air, and gnomed mine—
Unweave a rainbow.
Keats’s contemporary Samuel Taylor Coleridge similarly averred, “the souls of 500 Sir Isaac Newtons would go to the making up of a Shakespeare or a Milton.”4
Does a scientific explanation for the world diminish its spiritual beauty? I think not. Science and spirituality are complementary, not conflicting; additive, not detractive. Anything that generates a sense of awe may be a source of spirituality. Science does this in spades. I am deeply moved, for example, when I observe through my Meade eight-inch reflecting telescope in my backyard the fuzzy little patch of light that is the Andromeda galaxy. It is not just because it is lovely, but because I also understand that the photons of light landing on my retina left Andromeda 2.9 million years ago, when our ancestors were tiny-brained hominids roaming the plains of Africa.
Why Darwin Matters Page 16