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Home , Evolution of the horse, Explore Evolution, Randal Keynes, Skandar Keynes

Vol. 16, No. 2 Wildlife & Parks Spring, 2006 The Scientific Theory of

INSIDE...

What Is A Scientific Theory 2 The Scientific Method 3 Don’t Miss Evolution By 4 Species Spotlight: 8 Our Next Did You Know? 11 Issue: Science Definition 11 Evolution of the Modern 12 The Tree of 13 15 Problem Concepts in Evolution 17 Champions NABT Statement of Evolution 18 of Kansas WHAT IS THE DIFFERENCE BETWEEN A the facts as we know them, that they have become SCIENTIFIC THEORY AND A BELIEF? THAT the cornerstones of modern science for today, but REALLY IS THE HEART OF THE CONTRO- who knows about tomorrow? VERSY OVER THE TEACHING OF EVOLU- It is important to remember that scientific theories are never considered fact and are always TION IN BIOLOGY CLASSES. OUR GOAL open to question and change if new scientific evi- FOR THIS ISSUE OF ON TRACKS IS TO dence says otherwise. EXPLAIN WHAT A SCIENTIFIC THEORY IS AND HOW THE THEORY OF EVOLUTION Public Definition of Theory MEETS THE CRITERIA FOR A GOOD SCIEN- An idea, speculation, or plan as to how TIFIC THEORY. something might be done. Most of us have theories about all kinds of things in our but these are NOT scientific theories WHAT IS A in any sense! Scientific Hypothesis SCIENTIFIC An idea or hunch that is used to form an experiment to determine if it is valid. THEORY? Scientists regularly use an hypothesis to begin a research project. Reprinted with permission from the Roger Tory Institute and the Electronic Naturalist, www.enatu - Scientific Definition of Theory ralist.org Overwhelming evidence in support of a For most people, a theory is an idea, more general principle explaining the operation or less well thought out, that someone has about a of certain phenomena or events that take given event or process. In science, however, noth- place in the world as in the Theory of ing gets labeled “Theory” until it has undergone a Evolution. rigorous process of questioning via research from many different approaches and still holds up. Granted, this process isn’t perfect because humans aren’t perfect, but it does do a good job of helping scientists understand how the world functions. There are many kinds of science, from astronomy to zoology- with botany, chemistry, and physics in between. But science, worldwide and in all its forms, adheres to a rigid set of standards for experimentation and conclusions, called the “scien- tific method.” Conclusions drawn by scientists who did not follow this method are regularly drawn into question by other scientists, and only those conclu- sions that have “passed the test” of the scientific method are accepted by the scientific community. Scientific Law So a scientific “theory” is quite different from a Implies exact formulation of principles “guess” or “hunch.” It is an idea that has been tried operating in a sequence of events in , and tried again, but never disproved (at least not observed to occur with unvarying yet!). Cell theory, germ theory, evolution theory, uniformity under the same conditions as in and molecular theory are all so well supported by the Law of Gravity

On T.R.A.C.K.S. 2 The Scientific Method

The scientific method (different from a sci- If the experiments bear out the hypothesis it may ence methods course) is the process by which sci- come to be regarded as a theory or even a law of entists, collectively and over time, endeavor to nature. If the experiments do not bear out the construct an accurate (that is, reliable, consistent hypothesis, it must be rejected or modified. What and non-arbitrary) representation of the world. is key in the description of the scientific method Recognizing that personal and cultural just given is the predictive power (the ability to beliefs influence both our perceptions and our get more out of the theory than you put in) of the interpretations of the natural world, we aim hypothesis or theory, as tested by experiment. It is through the use of standard procedures and criteria, often said in science that theories can never be to minimize those influences when developing a proved, only disproved. There is always the possi- theory. As a famous scientist once said, "Smart bility that a new observation or a new experiment people (like smart lawyers) can come up with very will conflict with a long-standing theory. good explanations for mistaken points of view." In summary, the scientific method attempts to mini- mize the influence of bias or prejudice when test- ing an hypothesis or a theory.

As stated earlier, the scientific method attempts to minimize the influence of the scientist's bias on the outcome of an experiment. That is, 1. Observation and descrip- when testing an hypothesis or a theory, the scientist tion of a phenomenon or may have a preference for one outcome or another, group of phenomena. and it is important that this preference not bias the results or their interpretation. The most fundamen- 2. Formulation of an tal error is to mistake the hypothesis for an expla- hypothesis to explain the nation of a phenomenon, without performing phenomena. In physics, the experimental tests. Sometimes "common sense" hypothesis often takes the and "logic" tempt us into believing that no test is form of a cause for the phe- needed. nomena or a mathematical Another common mistake is to ignore or relation. rule out data which do not support the hypothesis. Ideally, the experimenter is open to the possibility 3. Use of the hypothesis to that the hypothesis is correct or incorrect. Some- predict the existence of times, however, a scientist may have a strong belief other phenomena, or to pre- that the hypothesis is true (or false), or feels inter- dict quantitatively the results of new observations. nal or external pressure to get a specific result. In that case, there may be a psychological tendency to 4. Repeat of the experiment by several inde- find "something wrong" with data which do not support the scientist's expectations, while data pendent experimenters and properly performed which do agree with those expectations may not be experiments. checked as carefully. The lesson is that all data must be handled in the same way.

On T.R.A.C.K.S. 3 Another common mistake arises from the tion and open communication among members of failure to estimate quantitatively systematic errors the scientific community, the biases of individuals (and all errors). There are many examples of dis- or groups may cancel out, because experimental coveries which were missed by experimenters tests are repeated by different scientists who may whose data contained a new phenomenon, but who have different biases. In addition, different types of explained it away as a flaw in the methodology of experimental setups have different sources of sys- the experiment. Conversely, there are many exam- tematic errors. Over a period spanning a variety of ples of alleged "new discoveries" which later experimental tests (usually at least several years), a proved to be due to flaws in the methods not consensus develops in the community as to which accounted for by the "discoverers." experimental results have stood the test of time. In a field where there is active experimenta-

Scientific methods are means used by scientif- ic communities for building supportable, evi- dence-based understandings of our natural world. Evolution By Natural Selection The following are excerpts from the article, the evidence. They embrace such an explanation “Was Darwin Wrong?” by David Quammen confidently but provisionally—taking it as their found in National Geographic Magazine Online best available view of reality, at least until some Extra, Nov. 2004. www.magma.nationalgeo - severely conflicting data or some better explana- graphic.com/ngm/0411/feature1 tion might come along. Evolution is both a beautiful concept and Evolution by natural selection, the central an important one, more crucial nowadays to human concept of the life's work of Charles Darwin, is a welfare, to medical science, and to our understand- theory. It's a theory about the origin of , ing of the world than ever before. It's also deeply complexity, and diversity among Earth's living persuasive—a theory you can take to the bank. The creatures. If you are skeptical by nature, unfamiliar essential points are slightly more complicated than with the terminology of science, and unaware of most people assume, but not so complicated that the overwhelming evidence, you might even be they can't be comprehended by any attentive per- tempted to say that it's "just" a theory. In the same son. Furthermore, the supporting evidence is abun- sense, relativity as described by Albert Einstein is dant, various, ever increas- "just" a theory. The notion that Earth orbits around ing, solidly interconnect- the sun rather than vice versa, offered by Two big ed, and easily available in Copernicus in 1543, is a theory. Continental drift is , popular books, ideas are at issue: a theory. The existence, structure, and dynamics of textbooks, and a moun- atoms? Atomic theory. Even electricity is a theoret- the evolution of tainous accumulation of ical construct, involving electrons, which are tiny all species, and peer-reviewed scientific units of charged mass that no one has ever seen. studies. No one needs to, natural selection, Each of these theories is an explanation that has and no one should, accept as the main mech- been confirmed to such a degree, by observation evolution merely as a and experiment, that knowledgeable experts accept anism causing matter of faith. it as fact. That's what scientists mean when they that phenomenon Two big ideas, not talk about a theory: not a dreamy and unreliable just one, are at issue: the speculation, but an explanatory statement that fits evolution of all species, as a historical On T.R.A.C.K.S. 4 phenomenon, and natural selection, as the main The evidence, as he presented it, mostly fell mechanism causing that phenomenon. The first is a within four categories: , paleontology, question of what happened. The second is a ques- embryology, and morphology. Biogeography is the tion of how. The idea that all species are descended study of the geographical distribution of living from common ancestors had been suggested by creatures—that is, which species inhabit which other thinkers, including Jean-Baptiste Lamarck, parts of the planet and why. Paleontology investi- long before Darwin published The Origin of gates extinct life-forms, as revealed in the fossil Species in 1859. What made Darwin's book so record. Embryology examines the revealing stages remarkable when it appeared, and so influential in of development (echoing earlier stages of evolu- the long run, was that it offered a rational explana- tionary history) that embryos pass through before tion of how evolution must occur. The same birth or hatching; at a stretch, embryology also insight came independently to Alfred Russel concerns the immature forms of that meta- Wallace, a young naturalist doing fieldwork in the morphose, such as the larvae of insects. Malay Archipelago during the late 1850s. In histor- Morphology is the science of anatomical shape and ical annals, if not in the popular awareness, design. Darwin devoted sizable sections of The Wallace and Darwin share the kudos for having Origin of Species to these categories. discovered natural selection. Biogeography, for instance, offered a great The gist of the concept is that small, ran- pageant of peculiar facts and patterns. Anyone who dom, inheritable differences among individuals considers the biogeographical data, Darwin wrote, result in different chances of survival and repro- must be struck by the mysterious clustering pattern duction—success for some, without off- among what he called "closely allied" species— spring for others—and that this natural culling that is, similar creatures sharing roughly the same leads to significant changes in shape, size, . Such closely allied species tend to be strength, color, biochemistry, and behavior among found on the the descendants. Excess population growth drives same continent the competitive struggle. Because less successful (several species competitors produce fewer surviving offspring, the of in useless or negative variations tend to disappear, Africa) or within whereas the useful variations tend to be perpetuat- the same group ed and gradually magnified throughout a popula- of oceanic tion. islands (dozens This describes one part of the evolutionary of species of process, known as , during which a sin- honeycreepers in gle species is transformed. But there's also a sec- Hawaii, 13 species of Galápagos finch), despite ond part, known as . Genetic changes their species-by-species preferences for different sometimes accumulate within an isolated segment habitats, food sources, or conditions of climate. of a species, but not throughout the whole, as that Adjacent areas of South America, Darwin noted, isolated population adapts to its local conditions. are occupied by two similar species of large, flight- Gradually it goes its own way, seizing a new eco- less birds (the rheas, Rhea americana and logical niche. At a certain point it becomes irre- Pterocnemia pennata), not by ostriches as in Africa versibly distinct—that is, so different that its mem- or emus as in Australia. South America also has bers can't interbreed with the rest. Two species agoutis and viscachas (small rodents) in terrestrial now exist where formerly there was one. Darwin habitats, plus coypus and capybaras in the wet- called that splitting-and-specializing phenomenon lands, not—as Darwin wrote—hares and rabbits in the "principle of divergence." It was an important terrestrial habitats or beavers and muskrats in the part of his theory, explaining the overall diversity wetlands. of life as well as the adaptation of individual Why should "closely allied" species inhabit species. neighboring patches of habitat? And why should

On T.R.A.C.K.S. 5 similar habitat on different continents be occupied resembling stages of the embryo of a reptile? Why by species that aren't so closely allied? "We see in is one of the larval forms of a barnacle, before these facts some deep organic bond, prevailing metamorphosis, so similar to the larval form of a throughout space and time," Darwin wrote. "This shrimp? Why do the larvae of moths, flies, and bond, on my theory, is simply inheritance." Similar beetles resemble one another more than any of species occur nearby in space because they have them resemble their respective adults? Because, descended from common ancestors. Darwin wrote, "the embryo is the animal in its less Paleontology reveals a similar clustering modified state" and that state "reveals the structure pattern in the dimension of time. The vertical col- of its progenitor." umn of geologic strata, laid down by sedimentary Morphology, his fourth category of evi- processes over the eons, lightly peppered with fos- dence, was the "very soul" of natural history, sils, represents a tangible record showing which according to Darwin. All vertebrate animals have species lived when. Less ancient layers of rock lie backbones. Among vertebrates, birds have feathers, atop more ancient ones (except where geologic whereas reptiles have scales. have fur forces have tipped or shuffled them), and likewise and mammary glands, not feathers or scales. with the animal and plant fossils that the strata Among mammals, some have pouches in which contain. What Darwin noticed about this record is they nurse their tiny young. Among these species, that closely allied species tend to be found adjacent the marsupials, some have huge rear legs and to one another in successive strata. One species strong by which they go hopping across miles endures for millions of years and then makes its of arid outback; we call them kangaroos. Bring in last appearance in, say, the middle epoch; modern microscopic and molecular evidence, and just you can trace the similarities still further back. All above, a plants and fungi, as well as animals, have nuclei similar within their cells. All living organisms contain but not DNA and RNA (except some viruses with RNA identical only), two related forms of information-coding species molecules. replaces Such a pattern of tiered resemblances— it. In groups of similar species nested within broader North America, for example, a vaguely horselike groupings, and all descending from a single creature known as was succeeded source—isn't naturally present among other collec- by , then , then , tions of items. You won't find anything equivalent which in turn were succeeded by a variety of if you try to categorize rocks, or musical instru- horsey American critters. Some of them even gal- ments, or jewelry. Why not? Because rock types loped across the Bering into Asia, then and styles of jewelry don't reflect unbroken descent onward to Europe and Africa. By five million years from common ancestors. Biological diversity does. ago they had nearly all disappeared, leaving behind The number of shared characteristics between any , which was succeeded by , the one species and another indicates how recently modern genus of horse. Not all these fossil links those two species have diverged from a shared lin- had been unearthed in Darwin's day, but he cap- eage. tured the essence of the matter anyway. Again, That insight gave new meaning to the task were such sequences just coincidental? No, Darwin of taxonomic classification, which had been found- argued. Closely allied species succeed one another ed in its modern form back in 1735 by the Swedish in time, as well as living nearby in space, because naturalist Carolus Linnaeus. Linnaeus showed how they're related through evolutionary descent. species could be systematically classified, accord- Embryology, too, involved patterns that ing to their shared similarities, but he worked from couldn't be explained by coincidence. Why does creationist assumptions that offered no material the embryo of a pass through stages explanation for the nested pattern he found. In the

On T.R.A.C.K.S. 6 early and middle 19th century, morphologists such legs buried inside their sleek profiles? Why do as and Étienne Geoffroy Saint- certain species of flightless beetle have wings, Hilaire in France and in sealed beneath wing covers that never open? improved classification with their meticulous stud- Darwin raised all these questions, and answered ies of internal as well as external anatomies, and them, in The Origin of Species. Vestigial struc- tried to make sense of what the ultimate source of tures stand as remnants of the evolutionary histo- these patterned similarities could be. Not even ry of a . Owen, a contemporary and onetime friend of Today the same four branches of biologi- Darwin's (later in life they had a bitter falling out), cal science from which Darwin drew—biogeog- took the full step to an evolutionary vision before raphy, paleontology, embryology, morphology— The Origin of Species was published. Owen made embrace an ever growing body of supporting a major contribution, though, by advancing the data. In addition to those categories we now have concept of homologues—that is, superficially dif- others: , biochemistry, molec- ferent but fundamentally similar versions of a sin- ular biology, and, most recently, the whiz-bang gle or trait, shared by dissimilar species. field of machine-driven genetic sequencing For instance, the five-digit skeletal structure known as genomics. These new forms of knowl- of the vertebrate hand appears not just in humans edge overlap one another seamlessly and intersect and apes and raccoons and bears but also, variously with the older forms, strengthening the whole modified, in cats and bats and porpoises and edifice, contributing further to the certainty that Darwin was right. Among most forms of living creatures, evolution proceeds slowly—too slowly to be observed by a single scientist within a research lifetime. But science functions by inference, not just by direct observation, and the inferential sorts of evidence such as paleontology and bio- geography are no less cogent simply because crocodile bat whale mole man they're indirect. Still, skeptics of evolutionary Five-digit skeletal structure of veterbrate hands theory ask: Can we see evolution in action? Can it be observed in the wild? Can it be measured in lizards and turtles. The paired bones of our lower the laboratory? leg, the tibia and the fibula, are also represented by The answer is yes. Peter and Rosemary homologous bones in other mammals and in rep- Grant, two British-born researchers who have tiles, and even in the long-extinct bird-reptile spent decades where Charles Darwin spent Archaeopteryx. What's the reason behind such var- weeks, have captured a glimpse of evolution with ied recurrence of a few basic designs? Darwin, their long-term studies of beak size among with a nod to Owen's "most interesting work," sup- Galápagos finches. William R. Rice and George plied the answer: , as shaped by W. Salt achieved something similar in their lab, natural selection, modifying the inherited basics for through an experiment involving 35 generations different circumstances. of the fruit fly Drosophila melanogaster. Richard Vestigial characteristics are still another E. Lenski and his colleagues at Michigan State form of morphological evidence, illuminating to University have done it too, tracking 20,000 gen- contemplate because they show that the living erations of evolution in the bacterium Escherichia world is full of small, tolerable imperfections. Why coli. Such field studies and lab experiments docu- do male mammals (including human males) have ment anagenesis—that is, slow evolutionary nipples? Why do some snakes (notably boa con- change within a single, unsplit lineage. With strictors) carry the rudiments of a pelvis and tiny patience it can be seen, like the movement of a minute hand on a clock.

On T.R.A.C.K.S. 7 Species Spotlight: Charles Darwin Excerpts from the Darwin Exhibit at the American By this time, geologists had shown that of Natural History www.amnh.org/exhibi - Earth was not static or fixed—clearly it had tions/darwin undergone sweeping changes over time and was, Happiest at home with his notebooks and in fact, still changing. This idea had a huge his microscope, he shunned the public eye. influence on Darwin's thought. Pondering the Controversy made him ill. This brilliant observer long, slow changes in Earth's history would later of nature kept his most original and revolutionary help shape Darwin's ideas about how plant and idea under wraps for decades. Yet today, two cen- animal species, too, had changed over millions turies after Charles Darwin's birth, nearly everyone of years. knows his name. Who was Charles Darwin?

In 1831, Charles Darwin received an Birds' eggs and sea shells, beetles and astounding invitation: to join the HMS Beagle as coins, moths and minerals—as a child, Charles ship's naturalist for a trip around the world. The Darwin collected all of these and more. Born in captain and crew 1809 to a wealthy family in rural England, he spent of the HMS hours watching birds and lying under the dining- Beagle originally room table, reading. He was an indifferent student, planned to spend though, and school bored him. two years on their As a teenager, Darwin was thrilled by trip. Instead, the chemistry, biology, botany and geology. Yet all the voyage took near- while he dutifully pursued the careers his father ly five years, had selected for him: doctor and then clergyman. from December As he studied at the University of Cambridge, 1831 to October though, Darwin was singled out by an elite circle 1836. The pri- of academics who recognized his potential. Finally, mary purpose of Charles Darwin in 1840 his true talent for natural history blossomed. the trip, spon- Darwin's mentor at Cambridge, J. S. sored by the British government, was to survey Henslow, was known for his popular botany lec- the coastline and chart the harbors of South tures and field outings. "It was obvious that America, in to make better maps and pro- Darwin was Henslow's favorite pupil," a fellow tect British interests in the Americas. The posi- student recalled. "Professor Henslow used to say tion of ship’s naturalist, filled by Darwin, was 'What a fellow that Darwin is for asking ques- unpaid. tions!'" The two became so close that Darwin was For most of the next five years, the known as "the man who walks with Henslow." Beagle surveyed the coast of South America, Henslow profoundly shaped Darwin's thinking leaving Darwin free to explore the continent and about the nature of species. islands, including the Galápagos. In fact, two- When Charles Darwin was a student in the thirds of Darwin's time was spent on dry land, 1820s, no science exerted a stronger hold on the largely in the South American wilderness of popular imagination than geology. The public fol- , , Chile and remote areas such lowed the latest theories and discoveries in amaze- as the Galápagos Islands. By any measure, ment. Thousands bought books on the subject, and Darwin's labors were hugely successful. He debates on the history of the Earth and its forma- filled dozens of notebooks with careful observa- tion raged among scientists. tions on animals, plants and geology, and On T.R.A.C.K.S. 8 brought back specimens of more than 1,500 differ- Darwin's growing skepti- ent species, hundreds of which had never before cism about religion been seen in Europe. caused Emma great pain, Darwin later called the Beagle voyage "by which in turn caused her far the most important event in my life," saying it husband deep sadness. "determined my whole career." When he set out, And Darwin began to suf- 22-year-old Darwin was a young university gradu- fer increasingly severe ate, still planning a career as a clergyman. By the and mysterious bouts of time he returned, he was an established naturalist, illness that would plague well-known in for the astonishing collec- his entire working life. tions he'd sent ahead. He had also grown from a promising observer into a probing theorist. The Beagle voyage would provide Darwin with a life- In 1842 Charles Darwin in 1854, at the age time of experiences to ponder—and the seeds of a Darwin and his family of 43. theory he would work on for the rest of his life. fled London in search of Darwin was something of a scientific peace and quiet. They found it in a tiny village 16 celebrity when he got back to England. The strange miles outside the city, and for the next 40 years fossils and unfamiliar animals he had shipped their home—called —was Darwin's home gained him entry into London's learned cir- retreat, research station and the hub of his vast sci- cles. Mere months after he left the Beagle, Darwin entific network. Working in his study, greenhouse presented his first paper—on the uplift of the and garden, corresponding with scientists around Andes—at the Geological Society. the world, Darwin patiently completed the puzzle Determined to earn the respect of the men of evolution by natural selection. he called the "great guns," Darwin threw himself As the years passed, the sprawling house at into work. Sorting his Beagle specimens and Down filled up with children—the Darwins would arranging for experts to analyze them were his first have ten in all—and a series of governesses, nurses priority. What these authorities told him about his and pets. Charles and his wife Emma were relaxed specimens—particularly the fossils and the birds— and affectionate parents whose children, daughter would profoundly affect his developing theories. Henrietta later wrote, felt like "creatures whose opinions and thoughts were important." Since London days Darwin's health had After a year or so in London, following his been fragile. Breaks in the regular routine—even return from the HMS Beagle, the 29-year-old an interesting talk with a visitor—could provoke Darwin began to think seriously about marrying. spells of vomiting and dizziness. But he doggedly But like many an ambitious scientist, he was torn pursued his research program, and on some days between determination to make a mark and desire his work could be an exciting household adventure. to have a family. Would supporting a wife and chil- Children tracked the flight paths of bumblebees, a dren mean abandoning his scientific career? A governess joined in counting the plant species in a methodical man, Darwin drew up a list of the pros meadow, a longtime servant helped Darwin boil and cons of marriage—and what he called the carcasses of small mice and birds to "skeletonise" "nice wife on a sofa" won out. He soon proposed them for study. to a woman he had known since childhood, first cousin Emma Wedgwood. Both parties—and both families—agreed it would be the perfect match. All the research Darwin undertook in 40 Bonds of real affection linked Emma and years at Down revolved around a single grand Charles throughout their long lives, and they would theme: evolution by natural selection. In at least 16 establish a warm, lively and loving family. Yet two books and many papers, Darwin explored variation troubling issues surfaced in those early years. and adaptation. He worked tirelessly to figure out

On T.R.A.C.K.S. 9 how natural selection had acted on variation to pro- from scientists studying cultures worldwide, con- duce the marvelous he saw. vinced him that all humans have the same feelings. But in many cases he couldn't do this What's more, they show directly. Extended studies of wild nature—measur- them on their faces in similar ing and tracking minute changes in fur, feather or ways. flower over generations—were unimagined by any Similarly, Darwin naturalist of the period. So instead Darwin often thought, animals had recog- turned to domesticated species—manageable and nizable emotions. well-documented groups that he, or the experts he Chimpanzees could feel dis- knew, could breed and shape. Pigeons, rabbits, cab- appointment. When they bages, gooseberries—these would be a major were disappointed, they object of study and his window into the workings sulked; and when they of selection. sulked, they stuck out their Darwin was trying to find out how much like pouting children. Darwin in the 1870’s variation existed within a single type of animal in Experts of the time believed, wrongly, that we nature. Breeding animals—selecting and perpetuat- humans had special muscles in our faces so we ing desired traits—was a sped-up version of the could express what they called our "exquisite feel- process that gave rise to new species in nature, he ings." Darwin's work contradicts this. Our emo- thought. tions, and the way we express them, connect us The color, shape and placement of feathers with the rest of life on Earth. in pigeons are the obvious differences between Darwin had made observation and studied pigeon breeds, but the variations in the natural world beginning with his skeletons underneath dif- voyage on the HMS Beagle but for nearly two fer, too. Had these skulls decades Darwin kept his ideas about natural selec- belonged to wild birds, tion secret. Fully aware that others had been Darwin thought, they severely punished for such "heretical" ideas, he would be considered dif- only confided in his closest friends and continued ferent species. And if arti- his research to meet anticipated objections. It took ficial selection could pro- a letter outlining another man's version of natural duce such diversity over selection to push him into print. The letter deliv- decades, what might natu- ered to Down House in June 1858 was sent by the ral selection produce over young naturalist Alfred Russel Wallace and it out- millions of years? lined a theory of evolution by natural selection eerily like Darwin's own. Wallace even cited the Variability in the cabbage family also inter- passage of Malthus (author of Essay on the ested Darwin. The wild cabbage, he knew, had Principle of Population c.1798) that Darwin had given rise to very different-looking varieties, cited in his notebook nearly 20 years before. including Brussels sprouts, broccoli and kale. What Darwin was distraught: after all the years of work accounted for this diversity? "The explanation is and worry, someone else would get the credit. He obvious," Darwin wrote. Because we humans eat hated being scooped—and he hated himself for the leaves of these plants, farmers had been select- caring. ing the "many useful variations in their leaves and Shutting himself in his study, working stems" since prehistoric times. Such strong selec- feverishly, Darwin finally produced the Origin of tive pressure produced those distinct shapes. Species (1859). That book—and its companion When Darwin looked at the expressions on volume, the Descent of Man—would spark a revo- people's faces—and at the body language of dogs lution. They would also make Darwin the most and cats—he saw evidence for evolution. What revered, and controversial, scientist of his time. Darwin himself observed, and what he learned On T.R.A.C.K.S. 10 Did You Know?

Harriet is a Galápagos tortoise (born September 5, 1991 believed to be, at an esti- in London) is a young mated 175 years, the actor best known for star- oldest known living ani- ring as Edmund Pevensie mal in the world. in the 2005 film version of The Chronicles of It was originally thought that Harriet was Narnia: The Lion, the captured by Charles Darwin in 1835 on the Witch and the Wardrobe. Galápagos Islands. DNA testing has in fact Keynes, who attended the Anna Scher indicated her to have been born around 1830. Theatre School from 2000 to 2005, is the However, the story regarding Darwin is most great-great-great grandson of the famous likely apocryphal. Though Darwin caught three scientist Charles Darwin. He has an older tortoises and took them home to Britain, genetic sister, Soumaya, and his parents are Zelfa Cecil tests indicate that Harriet belongs to a sub- Hourani (who is of Lebanese descent) and species endemic to one of the Galapagos Islands . He studies Tae Kwon Do and that Darwin never visited. plays the coronet and the flute and currently attends the City of London All Boys School On November 15, 2005, her 175th birthday was along with Daniel Radcliffe (Harry Potter). celebrated at the Australia Zoo, owned by the Crocodile Hunter’s Steve Irwin

sci·ence- the observation, indentifica- tion, description, experimental investigation, and theoretical explanation of natural phenomenon. (American Heritage Dictionary) sci·ence- 1. The act and embodiment of performing the scientific method in order to discover empiri- cally proven truth. (Wikipedia Dictionary)

On T.R.A.C.K.S. 11 Evolution of the Modern Horse

Equus 3mya

Pliohippus 7 mya

Horse evolution is largely recog- nized as one of the best exam- ples of evolution from the fossil record. Horse species were con- stantly branching off the "evolu- tionary tree" and evolving along various unrelated routes. There's no discernible "straight line" of horse evolution. Many horse species were usually present at the same time, with various numbers of toes and adapted to various diets. In other words, horse evolution had no inherent 25 mya direction. We only have the impression of straight-line evo- Mesohippus lution because only one genus 40 mya happens to still be alive, which deceives some people into thinking that that one genus was somehow the "target" of all the evolution. Instead, that one genus is merely the last surviv- ing branch of a once mighty and sprawling "bush.”

Eohippus 60 million years ago (mya)

On T.R.A.C.K.S. 12 The Tree of Life

Simply stated, biological evolution is deri- relationship between the lineages, not that one is vation from an ancestor; it is the . It “higher” or “more evolved than another. consists of two transformations: Small-scale evo- We use homologous characteristics to build lution which are changes in gene frequency from the phylogeny. An homologous characteristic is one one generation to the next and large scale evolu- that may appear different in two dissimilar species tion which is the descent of different species from but is fundamentally the same and therefore points a common ancestor over many generations. to a common ancestry. An example would be the Transformation is not a simple matter. It is homologous characteristics of four limbs not like the changes trees undergo in the fall or (). Birds, bats, mice and alligators all how a mountain range erodes over millions of have four limbs. Both the ancestor of tetrapods and years. What we are speaking about is the change of their descendents have inherited the feature of hav- genetic inheritance. Genetic material that is ing four limbs; so the presence of four limbs is an changed in minute ways over many, many, many . generations gives rise to the fantastic diversity of Not all characteristics are homologies. life we see today. Birds and bats have wings, but mice and alligators The central ideas of evolution are: all life do not. Does this mean that birds and bats are more has a history, it changed over time, and different closely related to each other than mice and alliga- species share common ancestors. Life has an evo- tors? When one examines the wing of a bird and lutionary “family tree.” By studying a species’ that of a bat, we see some major differences. Bat inherited characteristics and other historical evi- wings have skin stretched between their bones; dence, we can reconstruct evolutionary relation- birds have feathers extending along their arm. This ships and represent them on a “family tree” called suggests they didn’t inherit wings from a common a phylogeny. This “tree” is an hypothesis about the winged ancestor. They are similar in function, but relationships among organisms. It is by no means different in structure. Bird and bat wings are analo- perfect. Scientists constantly reevaluate the gous, having separate evolutionary origins, but hypotheses and restructure them based on new evi- they evolved to serve the same function. dence. For example, evidence discovered in the last Sometimes this is called “.” 50 years now suggests birds may have originated We know these changes in organisms didn’t from . happen overnight. The history of the earth is A phylogeny is similar to reading a family roughly 3.5 billion years old. If we condensed this tree. The roots of the tree represent the ancestral into a single minute, we would have to wait for lineage and the tips of the branches represent the about 50 seconds for multicelluar life to evolve, descendents of that ancestor. When a lineage splits another four seconds for vertebrates to appear, (speciation) it is represented as a branch on a phy- another four seconds for flowers to evolve and logeny. When a speciation event occurs, a single only 0.002 second to first see “modern” humans. . ancestral lineage gives rise to two or more daugh- Time can be represented on phylogenies by draw- ter lineages. ing the branch lengths in proportion to the amount Phylogenies trace patterns of shared ances- of time that passed since that lineage arose. They try between lineages. Each lineage has a part of its can also be adjusted to show when lineages split history unique to itself and parts that are shared and/or went extinct. with other lineages. Before Darwin, biologists organized life forms like the rungs of a ladder, low- est forms to highest forms. Phylogeny shows the

On T.R.A.C.K.S. 13 Darwin’s sketch of an evolutionary tree of related organisms--the first of its kind, appear- ing on page 36 of Notebook B.

This tree of life--or --traces the pattern of descent of all life over mil- lions of years into three major branches: Bacteria, Archaea, and Eucarya. Until 1996, however, scientists had confirmed the existence of only two of those branches. And although Earth's biomass is largely microbial, most previous studies focused primarily on a tiny portion at the tip of the Eucarya branch, the region containing animals and plants.

On T.R.A.C.K.S. 14 Genetic Variation

Just how do the selective forces and can only occur if there is a genetic work that allow evolution to occur? Fundamental difference in the population. A beetle population to the process is genetic variation. Evolution only would remain unaffected by changes if the genes occurs when there is a change in gene frequency were all the same. within a population over time. These genetic differ- Without genetic variation the basic of evo- ences are inheritable and can be passed on to the lutionary change cannot operate. There are three next generation. This long term change is what primary sources of genetic variations: really matters in evolution. Let’s say a population – changes in the DNA: In most of beetles is 90% green in color and 10% brown in situations, evolutionary change is based on the color. Generations later the brown beetles make up accumulation of many mutations. 70% of the population; a change in gene frequency – any movement of genes from has occurred. How did this happen? one population to another. Sex – can introduce new gene combinations Let’s look at these possible events: into a population. Mutations A could have caused parents with A mutation is a change in DNA, the heredi- 1 genes for green to have offspring with a tary material of life. The DNA of an organism gene for brown coloration. affects its looks, behavior, and its physiology. Any change in its DNA could cause a A migration of brown beetles may have change in all aspects of its life. Mutations are ran- 2 entered the genetic pool making the genes dom; it may or may not be useful to the organisms. for brown beetles more frequent in the Not all mutations matter for evolution. Somatic green beetle population. mutations occur in non-reproductive cells and can’t be passed on. Only those that can be passed on to Imagine a fire swept over the beetles, the offspring (called germ line mutations) matter to 3 causing many more green beetles to be large scale evolution. They also have to cause killed than brown ones. The next generation some really important phenotypic changes, like would have more brown beetles. resistance to an insecticide or be lethal to an organ- ism. These chance changes from generation to genera- Persons in farming and animal breeding tion are known as genetic drift. have used the idea of selecting traits in plants and animals for decades. Only those animals or plants What if green beetles were easier for birds with desirable characteristics are allowed to repro- 4 to spot and be eaten than brown beetles? duce. Farmers have cultivated numerous popular The brown beetles are more likely to sur- crops from wild mustard by artificially selecting vive and pass their brown genes to the next for certain desirable traits. Broccoli was developed generation. by suppression of flower development; kohlrabi came about by the enhancement of the lateral This is known as natural selection. meristems. Adaptation All of the above can cause changes in the Adaptations are common in populations and frequency of genes in a population and are mecha- are produced by natural selection. It can take many nisms of evolutionary change. Natural selection forms: The mimicry of leaves by insects is an

On T.R.A.C.K.S. 15 adaptation for evading predators. A bush that pro- evolve under different selective pressures and duces toxins is preventing other plants from grow- experience different random events than the up- ing which reduces its competition for water and stream population. Morphology, food preference, nutrients. Echolocation in bats is an adaptation for and courtship displays change over the course of catching insects at night. many generations of natural selection. Even if the What is a species? two could be rejoined, the difference between them At this point, we need to define species. It makes them incompatible to each other. The line- is often defined as a group of individuals that can age now has split, forming two new species. In interbreed in nature. This definition is not a “cut most “real life” situations, it is difficult to put the and dry” situation. If two lineages of maple trees whole story together from the available evidence; look quite different, but can occasionally form but the known evidence suggests this sort of hybrids, should we consider them as separate process does occur. Scientists believe geographic species? The boundaries of “species” are often a isolation, rivers, mountains, and continental drift blur, maybe because humans invented it for their are common means for the process of speciation to own convenience. begin. Speciation is a splitting event which pro- Scientific evidence supports the central duces two or more separates lineages. When this conclusion of evolutionary theory, that life on happens, genetic changes result in two separate Earth has evolved and that species share common species. For example, let’s say there is a population ancestors. Biologists are not arguing about these of wild, fruit eating beetles laying their eggs on conclusions. They are still trying to determine how ripe peaches. A flood occurs, washing the peaches evolution happens. That is not an easy task. It and beetle eggs several hundred miles downstream. involves collecting data, proposing hypotheses, This population is too far downstream for the indi- creating models, and evaluating the works of other viduals to mate with the population upstream. scientists. These are all activities that we can and Ecological conditions are also slightly different should hold up to a checklist and ask the question: than those upstream. The downstream beetles “Is what we are doing science?”

Explore Evolution, a new multimedia exhibition, will open at the University of Kansas Natural History Museum and Research Center on Nov. 1. The free exhibition, which will be on dis- play for the next two years, gives visitors the opportunity to understand and expe- rience how scientists conduct research on evolution.

On T.R.A.C.K.S. 16 The following article is condensed from an article written by Eugenie C. Scott. Problem Concepts in Evolution: www.ncseweb.org/resources/article/695_prob- Cause, Purpose, Design, and Chance lem_concepts_in_evolution

The manner in which teachers present the con- that if a watch exists, so does a watchmaker. A self cepts of cause, purpose, design, and chance to stu- imposed theory, like natural selection is difficult for dents can make a significant difference to students’ most people to understand. In science, we limit our- acceptance of evolution. selves to natural explanations which guide the process To members of the non-scientific public, these of change. or the idea that you will have a terms can have meanings, such as religious implica- specific “thing” at the end of the process is another tions, beyond those applied in science. Religion is “public” concept for design but not a process of evolu- allowed, by its nature, to recognize supernatural causa- tion. tion. Science is neutral to religion. Science does not Let’s look at the automobile which has under- attempt to promote or denigrate religious explanations gone a number of changes since it first appeared, most for natural processes. Science is an attempt to explain of them to help it do its “job” better. The first automo- natural processes using things observable and testable biles did not look all alike: some were powered by and cannot be altered by rules or beliefs associated with steam, others by a gas engine, and one even used a a nonmaterial or supernatural world. Science requires device like a watch spring. Some were steered by a testing of alternate explanations. In truth, science must stick, others by a wheel, and one by applying a brake be neutral to religion for practical as well as philosophi- device to the opposite set of wheels! The automobile cal reasons. evolved many lines of “cars” to its present form, each Scientific Meaning of Cause: Modern biolo- with many unique features for acheiving its purpose. gists recognize two classes of causes: proximate (or Design in evolution is not going to create an “end for immediate) and ultimate or indirect causes. Goldsmith all times” of a particular life form--it is a continuous describes proximate cause as "what one can see" and process. ultimate causes as invoking "the concept of adaptation Chance: Scientific Meanings In science, of organs to their environment as well as evolutionary chance means it will occur according to a known proba- inferences...” The immediate cause for plumage differ- bility, such as the possibility of a coin landing on ence in male and female birds is hormonal differences, “heads is fifty percent. In evolution, chance is referred but the indirect cause is natural selection . to as changes which may occur due to fluctuations of The public tends to answer most questions genes or traits in a nonselective environment. Random about the natural world through proximate cause-- the is when occurrences are governed by equal probability. causation factors and their interactions--such as why In a bowl of numbers from 1-50, the numbers 59 and 24 storms form? But divine causes may be used to infer have equal probability of being drawn. why the storm occurred at a certain location for a par- Chance: Public Meanings In newspapers, on ticular reason, such as punishment for the inhabitants. television and in other popular media, chance and ran- Only proximate or immediate causes and secondary or dom are more often used nonprobabilistically such as remote causes are what science is concerned with, not when we read about “random violence.” The writers do the philosophical reason behind the event. The goal in not mean that everyone has an equal chance of being presenting science and evolution is to do so in a way sampled, but that such violence is meaningless and pur- that prevents the student from having to choose poseless. It is the most frightening form of violence between science and their religious beliefs. because it is unpredictable — you just don’t know what Scientific Meaning of Design: Scientists use will happen, or why. Ironically, scientists use the con- design in two ways. One definition of design is a struc- cepts of random and chance to make predictions, ture which allows an organism to do something. The which is the direct opposite of their connotation in long, slender bill of a hummingbird used to extract nec- ordinary usage. tar from flowers is an example of design. In this sense, One must be clear that the use of chance is the design refers to parts that work together to accomplish scientist’s probabilistic term, not the public’s “unpre- something. The purpose of a structure is "what it is dictable, senseless” use. In approaching evolution, we good for,” and the design is how it achieves its purpose. will have to be specific about how we use “chance and Design in the public definition is linked with random” and be careful not to leave students with the teleology, as the means by which a goal is achieved, or impression that natural selection is a “chance” process. On T.R.A.C.K.S. 17 National Association of Biology Teachers Statement on Teaching Evolution

This statement has been edited to fit into this space. • Evolutionary theory is significant in biology, Complete text can be found at www.kabt.org among other reasons, for its unifying properties and predictive features, the clear empirical testabil- As stated in The American Biology Teacher ity of its integral models and the richness of new by the eminent scientist Theodosius Dobzhansky scientific research it fosters. (1973), "Nothing in biology makes sense except in the light of evolution." This often-quoted assertion • The fossil record, which includes abundant transi- accurately illuminates the central, unifying role of tional forms in diverse taxonomic groups, estab- evolution in nature, and therefore in biology. lishes extensive and comprehensive evidence for Teaching biology in an effective and scientifically- organic evolution. honest manner requires classroom discussions and laboratory experiences on evolution. • Natural selection, the primary mechanism for Modern biologists constantly study, ponder evolutionary changes, can be demonstrated with and deliberate the patterns, mechanisms and pace numerous, convincing examples, both extant and of evolution, but they do not debate evolution's extinct. occurrence. The fossil record and the diversity of extant organisms, combined with modern tech- •Natural selection-a differential, greater survival niques of molecular biology, taxonomy and geolo- and reproduction of some genetic variants within a gy, provide exhaustive examples and powerful evi- population under an existing environmental state- dence for genetic variation, natural selection, speci- has no specific direction or goal, including survival ation, and other well-established compo- of a species. nents of current evolutionary theory. Scientific deliberations and modifications of these compo- • Adaptations do not always provide an obvious nents clearly demonstrate the vitality and scientific selective advantage. Furthermore, there is no indi- integrity of evolutionary theory. cation that adaptations-molecular to organismal- This same examination, pondering and pos- must be perfect: adaptations providing a selective sible revision have firmly established evolution as advantage must simply be good enough for sur- an important natural process explained by valid vival and increased reproductive fitness. scientific principles, and clearly differentiate and separate science from various kinds of nonscientif- •The model of provides ic ways of knowing, including those with a super- another account of the tempo of speciation in the natural basis such as . Evolutionary the- fossil record of many lineages: it does not refute or ory, indeed all of science, is necessarily silent on overturn evolutionary theory, but instead adds to its religion and neither refutes nor supports the exis- scientific richness. tence of a deity or deities. Accordingly, the National Association of •Evolution does not violate the second law of ther- Biology Teachers, an organization of science teach- modynamics: producing order from disorder is pos- ers, endorses the following tenets of science, evo- sible with the addition of energy, such as from the lution and biology education: sun. • The diversity of life on earth is the outcome of evolution: an unpredictable and natural process of • Although comprehending deep time is difficult, temporal descent with genetic modification that is the earth is about 4.5 billion years old. Homo sapi- affected by natural selection, chance, historical ens has occupied only a minuscule moment of that contingencies and changing environments. immense duration of time. On T.R.A.C.K.S. 18 •When compared with earlier periods, the •Students can maintain their religious beliefs and Cambrian explosion evident in the fossil record learn the scientific foundations of evolution. reflects at least three phenomena: the evolution of animals with readily-fossilized hard body parts; • Teachers should respect diverse beliefs, but con- Cambrian environment (sedimentary rock) more trasting science with religion, such as belief in cre- conducive to preserving fossils; and the evolution ationism, is not a role of science. Science teachers from pre-Cambrian forms of an increased diversity can, and often do, hold devout religious beliefs, of body patterns in animals. accept evolution as a valid scientific theory, and teach the theory's mechanisms and principles. • Radiometric and other dating techniques, when used properly, are highly accurate means of estab- • Science and religion differ in significant ways lishing dates in the history of the planet and in the that make it inappropriate to teach any of the dif- history of life. ferent religious beliefs in the science classroom. Opposition to teaching evolution reflects confusion • In science, a theory is not a guess or an approxi- about the nature and processes of science. Teachers mation but an extensive explanation developed can, and should, stand firm and teach good science from well-documented, reproducible sets of experi- with the acknowledged support of the courts. In mentally-derived data from repeated observations Epperson v. Arkansas (1968), the U.S. Supreme of natural processes. Court struck down a 1928 Arkansas law prohibit- ing the teaching of evolution in state schools. In •The models and the subsequent outcomes of a sci- McLean v. Arkansas (1982), the federal district entific theory are not decided in advance, but can court invalidated a state statute requiring equal be, and often are, modified and improved as new classroom time for evolution and creationism. empirical evidence is uncovered. Thus, science is a Edwards v. Aguillard (1987) led to another constantly self-correcting endeavor to understand Supreme Court ruling against so-called "balanced nature and natural phenomena. treatment" of and evolution in public schools. In this landmark case, the Court • Science is not teleological: the accepted processes called the equal-time statute "facially do not start with a conclusion, then refuse to invalid as violative of the Establishment Clause of change it, or acknowledge as valid only those data the First Amendment, because it lacks a clear secu- that support an unyielding conclusion. Science lar purpose." This decision-"the Edwards restric- does not base theories on an untestable collection tion"-is now the controlling legal position on of dogmatic proposals. Instead, the processes of attempts to mandate the teaching of creationism: science are characterized by asking questions, pro- the nation's highest court has said that such man- posing hypotheses, and designing empirical models dates are unconstitutional. Subsequent district court for research about natural events. decisions in Illinois and California have applied "the Edwards restriction" to teachers who advocate • Providing a rational, coherent and scientific creation science, and to the right of a district to account of the taxonomic history and diversity of prohibit an individual teacher from promoting cre- organisms requires inclusion of the mechanisms ation science, in the classroom. Courts have thus and principles of evolution. restricted school districts from requiring creation science in the science curriculum and have restrict- • Similarly, effective teaching of cellular and ed individual instructors from teaching it. All molecular biology requires inclusion of evolution. teachers and administrators should be mindful of these court cases, remembering that the law, sci- • Specific textbook chapters on evolution should be ence and NABT support them as they appropriately included in biology curricula, and evolution should include the teaching of evolution in the science be a recurrent theme throughout biology textbooks curriculum. and courses. On T.R.A.C.K.S. 19 On TRACKS is pub- Pat Silovsky Alaine Neelly Hudlin lished by the Kansas Milford Nature Center The Center Editor: 3115 Hatchery Dr. 26325 W. 135th St. Department of Wildlife Junction City, KS Olathe, KS 66061 Pat Silovsky & Parks several times (785) 238-5323 (913) 856-7669 during the school year. [email protected] [email protected] Contributing Authors: The purpose of On Alaine Neelly- TRACKS is to dissemi- Hudlin nate information and Roland Stein educational resources Pat Silovsky pertaining to the natural, historic, and cultural Editorial resources of the prairie, Assistant: emphasizing Kansas Shelby Stevens ecology. Information is presented from the per- spective of current sci- Roland Stein entific theory. Pratt Headquarters 512 SE 25th Ave Equal opportunity to participate in and benefit from programs described herein is Pratt, KS 67124 available to all individuals, without regards to their race, color, national origin or (620) 672-0708 ancestry, religion, sex, age, sexual preference, mental or physical handicap, or politi- [email protected] cal affiliation. Complaints of discrimination should be sent to: Office of the Secretary, Kansas Department of Wildlife & Parks, 1020 S. Kansas Ave, Suite 200, Topeka, KS 66612-1327.