Undeniable (6 page)

I often reflect on what an extraordinary time (pun intended) it is to be alive here in the beginning of the twenty-first century. It took life billions of years to get to this point. It took humans thousands of years to piece together a meaningful understanding of our cosmos, our planet, and ourselves. Think how fortunate we are to know this much. But think also of all that's yet to be discovered. Here's hoping the deep answers to the deep questions—from the nature of consciousness to the origin of life—will be found in not too much more time.

 

6

ON THE ORIGIN OF EVOLUTION

While my family was seated together eating a chicken dinner, sometime back in the 1960s, my father described a scene around his family's table that I like to think of as his version of Darwin's trip to the Galapagos: the moment when he realized that all living things are related. My grandparents lived in a pretty big house in Washington, D.C. To supplement their income during the Great Depression, my grandmother rented rooms to young men, students, or people just starting out in their careers. One of these guys would often sit at the dinner table and remark offhandedly about the close similarities between a chicken's knees and our knees, along with other unsettling anatomical parallels.

According to legend, my grandmother was okay with these observations, and her approval carried with it an acceptance of evolution and natural selection. She was quite the naturalist and spent a great deal of time studying wildflowers. But my grandfather, who attended church regularly, was troubled by all this. A link between humans and chickens flew in the face (or beak) of his churchgoing upbringing. The tenant was very nice and paid his rent on time, but his chicken talk was not-so-subtly influencing the kids—my father, his brother, and their friends. These dinners gave my father food for thought for the rest of his life.

My dad returned from World War II and went to work as a salesman. Nevertheless, he often referred to himself as Ned Nye, Boy Scientist. My mom spent that war as a lieutenant in the Navy. She was recruited because she was good at math and science; she went on to earn a doctorate in education. So I was brought up with a great deal of respect for the human capacity to figure things out and solve problems. As a kid growing up in Washington, I also had access to the Smithsonian Institution. I was often dumped off … er, I mean, I was often given a ride to the downtown bus and encouraged to visit the museums and see the sights. Like any kid, I was utterly fascinated by the ancient dinosaurs. I thought about how cool it would be to see one of those animals in the wild. Evolution was in my bones, you might say. I was immersed in the scientific story of life on Earth pretty much from the time my own life began. It's no wonder I ended up writing this book.

Now consider what things were like when Charles Darwin and Alfred Wallace were formulating their ideas in the first half of the nineteenth century. They lived at a time when few people considered the biological meaning of fossil bones. Nobody knew the true age of Earth, and the majority of the ancient creatures we know about today had not yet been discovered. There were no museums full of dinosaur bones; there were probably never any casual dinner conversations about the physiological parallels between humans and chickens. Darwin lived when the ideas that so captivated me as a kid were just beginning to take shape in academic circles.

For many centuries, people in Europe and elsewhere had taken as gospel (perhaps more accurately,
from
Gospel) that the world had always been pretty much the way it looked right then. But in the late eighteenth century, several thinkers started to question long-held beliefs. The Scottish naturalist James Hutton studied Earth and its natural processes. He is generally regarded as humankind's first geologist. He reconsidered the idea that Earth has always looked the way it does right now. His writing is hard for me to follow sometimes, as it's in florid prose no doubt designed to impress his colleagues, but try this one: “Time, which measures everything in our idea, and is often deficient to our schemes, is to nature endless and as nothing…”

I would rewrite his idea in this way: “Time is part of our thinking in everything we do, and often we seem to have too little of it; in nature, though, there is no limit to the amount of time available…” This insight led Hutton to realize that the landforms he observed were not the product of a creator clocking in for just six days of work and then heading off for a little R & R. Instead, the geology that Hutton observed and documented was clearly the result of countless years of steady change. He rejected the standard story that there had been a great flood, leaving just a few thousand years of history to create everything we see today. Instead, he deduced that there had been slow, continual change of Earth's surface for eons and eons.

Hutton's idea is called “uniformitarianism,” and it was one of the crucial insights on which Darwin built his theory of evolution. Uniformitarianism denotes the idea that the world is uniform, or consistent with one set of natural laws; it connotes another idea that the natural laws we deduce today are the same natural laws that applied eons and millennia ago. It's quite a departure from what Hutton's contemporaries believed (and what creationists today still do). They believed that a creator could change natural laws to suit her, him, or itself. By necessity, then, natural laws and the natural history of Earth could not be uniform. It was to both Ned Nye Boy Scientist and Bill Nye the Science Guy a completely unreasonable point of view. But, we have the benefit of another century of human thought to influence our reasoning.

By the 1830s, the British scholar Charles Lyell elaborated on Hutton's work. I like to say Lyell calibrated the world. He measured how quickly (or slowly) sediments were laid down. He estimated the age of rock layers by measuring them and integrating one age or period of time with another. He was establishing the timescale of Earth. Lyell wrote clearly and with insight into the nature of the enormous spans of time involved. Charles Darwin carried Lyell's
Principles of Geology
with him on his famous voyage around the world aboard the HMS
Beagle
. Several geologists that I know have a copy of Lyell's book on their office bookshelves even today. It stands the test of (deep) time.

Hutton and Lyell were pushing against a strong academic tradition that looked at the world in totally different, static terms. If you visit the Smithsonian Museum of American History today, you'll come across a statue of George Washington by Horatio Greenough, unveiled in 1841. Even as a kid, I thought the statue looked a little odd. I mean, George Washington didn't wear an ancient Greek chlamys (toga thing)—did he? In this statue, he does. So revered were the ancient Greeks that people celebrating the birth of the U.S.'s first president thought it made sense to put an eighteenth-century politician in a minus-fourth-century Greek outfit. As part of that style of thinking, Aristotle's ideas on the relationships of living things persisted well into the age of Hutton, Lyell, Wallace, and Darwin.

Back in that fourth century BC, Aristotle postulated that there is a
scala naturae
, a ladder of nature. In this Latin usage, a ladder is not something you use for climbing. Instead, here, nature's ladder is how things are arranged or displayed from bottom to top. Nothing on the ladder is climbing or descending; each living thing is placed on each step or rung, like books on shelves. Aristotle observed the extraordinary, even exquisite balance of nature and figured that a creator or natural force set each living thing in its exact place, and there they or we each stayed. Everything fits perfectly, like pieces in a vertical puzzle. Along with this arrangement, though, was the idea that things do change with time. Babies grow up to be cowboys (or discus throwers), for example. They have life cycles, during which they grow and change. But in the bigger picture, they remain in their assigned places. These were parts of the perfect ladder of nature.

Taking this perfection into account, Hutton wrote repeatedly that, although he could not help but notice that Earth is ever changing, process, too, was part of a creator's plan. For example: “Nature, everywhere the most amazingly and outstandingly remarkable producer of living bodies, being most carefully arranged according to physical, mechanical, and chemical laws, does not give even the smallest hint of its extraordinary and tireless workings and quite clearly points to its work as being alone worthy of a benign and omnipotent God…”

The perspective of Hutton and Lyell began to take hold. By the late 1830s, people were actively speculating on the philosophical and scientific consequences of a very, very old Earth. It roughly goes like this: If Earth's surface has changed slowly over countless millennia, does that mean living things like us have also changed over time? In turn, that might mean that there is no one—to wit, no god—in charge right now. Instead of animals and plants striving for perfection to take their rightful place on nature's ladder, as ancient philosophers had presumed, we are all just blinks in the slowly moving picture of the long, long stretch of time.

Like my grandmother's tenant, many observant people had noted the connections and morphological relationships between different animals and plants. That's how, in the eighteenth century, the botanist Carl von Linné (Carolus Linnaeus, as it is written in Latinized form) came up with his naming scheme for connecting one type of organism to another. Any living thing could be categorized in a hierarchy each level of which was a binary choice. To place something in a catalog of living things, the naturalist just had to decide, is it animal or plant? Does it have mirror-image symmetrical leaves or long flat leaves? Is it woody or smooth? It's like a game of Twenty Questions. The Linnaean system further encouraged naturalists to think deeply about the relationships between living things. Linnaeus was so influential that the Linnaean Society is going strong still today.

By the time Darwin was born in 1809, a number of naturalists were starting to explore how different varieties of living things were related and how they could change over time. Earth seemed old enough to allow such changes to happen, but nobody knew how one species could become another species, no matter how much time was involved. One person came close but got the main idea wrong—you'll read a whole lot more about him in the next chapter. Then along came Darwin and Wallace and … here we are. Later, people like Estonian explorer Karl Ernst von Baer and philosopher Johann Goethe explored the ideas further; later still came Niles Eldredge, Stephen Jay Gould, and many others, each adding another element to the scientific story.

Darwin's idea of evolution through natural selection sparked a broader fascination with the idea of competition in the natural world. I've got a good deal more about this in chapter 8. The idea of competition inspired “social Darwinism,” which looked at competition among human populations (often in racist ways that were unrelated to what Darwin actually wrote). Meanwhile, Darwin himself got to thinking about populations: not just human populations, but populations of every species observable in nature. He saw that there is a spectrum of variation between species that comes into being slowly, tiny change by tiny change. He realized that variations happen naturally when an organism reproduces. He realized that populations of species compete for resources. And he realized that the traits that are inherited, which benefit the organism, have a greater chance of showing up in that organism's offspring, providing the engine that drives evolutionary change.

Although Darwin and Wallace came upon the idea of evolution at almost the same time, I can see why we associate the theory of evolution solely with Darwin. (I'll tip my hat to Wallace in a later chapter.) Darwin's book is amazing.
On the Origin of Species by Means of Natural Selection
—that's the full title—includes dozens of diligent observations and experiments that Darwin personally conducted. It is also beautifully written. He leaves the reader to draw his or her own conclusions as to whether or not the theory of evolution is the real deal. Just for example: “On the view that each species has been independently created, with all its parts as we now see them, I can see no explanation. But on the view that groups of species have descended from other species, and have been modified through natural selection, I think we can obtain some light…”

In his writings, Darwin makes it clear that he cannot state whether or not there is a creator in charge. The idea was impossible to prove or disprove then, and it still is today. But what emerged from Darwin's steady investigations was a new view of the world that can be appreciated and understood on its own terms. Perhaps there is intelligence in charge of the universe, but Darwin's theory shows no sign of it, and has no need of it. The exquisite variety and balance that we see in nature is a result of nature itself.

I know that this realization still bothers a great many people. For me, it is stunning and uplifting. After 2,400 years of speculation, humankind has finally uncovered this fundamental aspect of nature and our place among living things. Just think what other equally revolutionary discoveries lie right around the corner.

 

7

LAMARCK AND HIS NOT-ACQUIRED TRAITS

By the time Darwin came along there were and had been a great many naturalists—what today we might call biologists—who had been paying attention to the similar shapes and functions they observed among plants and animals. Philosophers had been wrestling with the origin of life since the heyday of the ancient Greeks. Almost all had speculated on how life began, and how living things became so obviously interdependent. They observed and documented patterns in nature. Big fish need little fish. Squirrels need trees. Humans need to eat, and nature provides the groceries. But how did the great variety of living things come to be; how did we all get here?