I. Evolution is the most important concept in all of biology. None of biology makes sense except in the context of evolution. Just why is evolution so important to biologists? A few examples’
A. Taxonomy: Evolution makes sense of the similarities and differences and provides a rational explanation for the distribution of taxa. It also supplies explanations for the sometimes wild exceptions we see (eg cacti and euphorbs, which look so similar but are clearly only very distantly related to each other. The explanation is convergent evolution).
B. Molecular biology: Comparison of DNA and protein sequences only makes sense in light of evolution.
C. Medicine: Our understanding of infectious organisms and our tactics to combat them are entirely based upon understanding of evolution.
II. No idea comes from thin air. The historical perspective helps to understand where the concepts behind evolutionary theory came from. Here are some of the basic historical issues.
A. The typical view of the nature of species at the beginning of the nineteenth century is often described as the Doctrine of Fixed Species. This concept had its primary roots in Greek philosophy: Aristotle’s Scala Naturae (The ‘Great Chain of Being’) and Plato’s essentialism.
B. During the eighteenth century, Carolus Linnaeus (1707-1778) developed the basis for our nested, hierarchical classification system, or Taxonomy. This system is also a ‘natural’ system, meaning that, regardless of the characters of organisms chosen as the basis for the classification, species almost always end up classified in the same pattern, an oddity which didn’t escape early 19th century naturalists, and which led to all kinds of evolutionary thinking.
C. The geologic discipline of stratigraphy was developed during the late eighteenth and early nineteenth centuries. Though this accomplishment was shared by many geologists throughout Europe, the name most commonly associated with developing the concept of stratigraphy is William Smith (1769-1839), who was an engineer engaged in building canals all over England.
D. George Cuvier (eventually Baron George Cuvier) (1769-1832) was a scientist of the late 18th and early 19th centuries. His specialty was vertebrate anatomy. He developed the important technique of comparative anatomy, which is based upon the understanding that the parts of an animal aren’t just unrelated bits stuck together’they reflect the life style and type of the animal, and are thus all related to each other. Because of his expertise in anatomy, Cuvier was the obvious person to ask to examine strange remains found during reconstruction after a major Paris fire. These remains turned out to belong to extinct organisms, and led to the development of the field of study we call Paleontology. Cuvier was the first to reconstruct dinosaurs. Cuvier is also remembered for coming up with the concept of Catastrophism, as an attempt to reconcile his religious beliefs with the evidence he discovered as a scientist.
E. Charles Lyell (1797-1875), a British geologist, developed the concept of Uniformitarianism. This theory of geology is often summarized by the catch phrase, ‘The present is the key to the past.’ The meaning of this phrase is that, if you can understand how geological features are being shaped and formed today, you can look at the formations from a long time ago and assume that they were created in the same way. In other words, the forces acting upon and shaping the Earth today are the same as the forces that acted upon and shaped the Earth in the past. Uniformitarianism is a central tenet of modern geology.
III. Charles Darwin (1809-1882) and the Origin of Species
A. Who was Charles Darwin?
1. Darwin was born in the first century of the nineteenth century to a wealthy family. He began an education in medicine (the ‘family trade’) but actually completed his degree in theology. His hobby was natural history. He collected beetles, went on geological field trips and became very friendly with the natural history faculty at his universities.
2. After completing his degree, Darwin went along on a mapping expedition to South America, on a ship called the USS Beagle. During the five-year trip, he collected tons (literally) of specimens of animals, plants and fossils, which he shipped back to England for later analysis.
3. Upon returning to England, he officially became a naturalist. Almost all of his specimens were sent to experts for analysis. He kept the barnacles for himself, setting out to become an expert in barnacles. It was the analyses that were returned to him from his experts that started him thinking along revolutionary pathways.
4. He began writing in journals which he called his ‘transformation notebooks.’ This is where he worked out the specifics of his theory (which he called ‘descent with modification. He never liked the name ‘evolution’ for his theory, because this term was already used for the development of an embryo from a fertilized egg, a process strictly controlled and predictable, which Darwin’s theory says is not true for the history of life’s diversity.
5. Darwin read Thomas Malthus’s Essay on Populations. Malthus (1766-1834) was an economist who wrote that people always tend to over-reproduce, but that the resources they depend upon don’t reproduce fast enough to continue to provide for the extended population. Thus, he said, if it weren’t for things that control population size (like war, plague, and other pleasant things), there would never be enough resources to go around. Thus, in order for humans to continue to survive, some have to die.
6. Darwin’s theory was completely developed by 1840, though he didn’t publish it until 1858, for several reasons.
7. One reason he finally published in 1858 (and then published Origin of Species in 1859) was that he discovered that another man, Alfred Russell Wallace (1823-1913), had independently discovered and was about to publish exactly the same theory Darwin had been working on for 20 years.
B. What exactly is the theory of evolution? Darwin’s theory has two novel concepts.
1. Darwin saw a clear pattern of common descent among the species of life. Examining the expert analyses of all of the specimens from the Beagle expedition, it was clear to Darwin that the various forms of life were all descended from one, or many from a very few, common ancestral species. Additional evidence since Darwin’s time provides very powerful support for the idea of a single ancestral species for all life on Earth.
2. The mechanism Darwin figured out by which species could change from one thing into something different was natural selection. He’d spent virtually all of his life in the country, and was very aware of how radically artificial selection by plant and animal breeders could alter organisms. He saw environmental competition as providing the selective pressure in nature. Natural selection was partially derived from Malthus’s ideas. Here’s the reasoning:
a. Observation: All living things tend to over-reproduce.
b. Observation: Resources are finite.
c. Conclusion: There will be competition over resources, and not all members of any generation can survive.
d. Observation: There is variation in all species’a more profound statement than you might think
e. Observation: Variations in species can influence who can and who can’t get enough resources to survive and reproduce.
f. Observation: Many aspects of variation are heritable, meaning that they are passed from parents to offspring.
g. Conclusion: Each new generation will tend to be more like the successful parents and less like the unsuccessful parents. Given enough time (meaning enough generations), these changes can produce brand new species, especially if the environmental pressure is strong.
IV. What is the evidence in support of the theory of evolution? This question could take weeks to answer. Observations of a wide variety of phenomena demonstrate evolutionary action and consequences. Here are some examples:
A. Artificial selection among plants and animals, as described above.
B. Adaptive radiation, which Darwin saw abundantly demonstrated among the species he observed and collected while on the Beagle. Adaptive radiation is the phenomenon in which a single species splinters into many daughter species. This phenomenon is very commonly observed among species living on off-shore islands like the Galapagos Islands to the west of South America.
C. The fossil record abundantly demonstrates evolutionary change. Transitional sequences show, for instance, the emergence of mammals from reptiles in the Permian Period, and the emergence of Cetaceans from terrestrial mammals in the early Cenozoic Era.
D. Biogeography (the distribution of species geographically) abundantly supports evolution, specifically island biogeography, which shows us that the resident species of islands are always derived from the species on the adjacent mainland.
E. Signatures of History are abundant in virtually all species. These are physical or behavioral features which clearly show that the modern species is descended from a species that lived a different kind of life cycle.
F. Molecular sequencing is an area of evidence that Darwin could never have predicted. Our modern biotechnology allows us to compare DNA and protein sequences among living organisms. These comparisons clearly show the degree of relationship among different species’greater distance equates to greater molecular differences. Molecular sequencing has provided a superb method of directly testing the predictions of evolutionary theory.
V. What is the modern status of Darwin’s theory of evolution?
A. All of the basic concepts have remained sound, and have survived extensive challenge and testing. There was a great deal of evidence in support of Darwin’s theory when he published it, and it has gained in acceptability and supportive evidence for nearly 150 years.
B. Do we agree with Darwin’s original theory on all points? Of course not. 150 years of gathering and examining evidence has led to some greater understandings than were possible in Darwin’s time.
1. One of the areas in which our available information is much greater is in the fossil record. We have many times more fossil evidence than Darwin did, and some things have become more clear with the greater abundance of physical evidence of extinct species. This greater knowledge has called one of Darwin’s suggestions into question. Darwin felt that, to a large extent, new species arose from old species by the gradual accumulation of tiny changes, a pattern of change that has come to be called ‘Darwinian gradualism.’ If this were the typical pattern of new species production, we would predict that the fossil record would contain a very high percentage of transitional forms. In reality, though there are many transitional fossils, they don’t occur in nearly the abundance predicted by gradualism. Niles Eldredge and Stephen Jay Gould proposed an alternative view, which has come to be called ‘punctuated equilibrium.’ They suggest that most species remain in stasis for long periods of time, and that when new species arise, they do so relatively rapidly (geologically speaking).
2. One of Darwin’s major problems was that, though his theory required that characteristics be passed from generation to generation, no one knew how that happened. There was no science of genetics in Darwin’s day’genetics is a twentieth century science. Darwin suggested a method of heredity which involved the production of what he called ‘gemules’ by various parts of the body, but it was incorrect. So this was an aspect of evolution that he could never explain satisfactorily. In the year 1900, the science of genetics was ‘born.’ Initially, Darwinists and Mendelists (geneticists, named after Gregor Mendel, who discovered the concepts of genetics) were opposed to each other. Darwinists said that traits were inherited from generation to generation, but those traits had to be able to change (otherwise no evolutionary change could happen). Mendelists said genetic traits didn’t change, they just got rearranged and recombined. Growing understanding of mutation, which does change genes, allowed the two battling factions of biologists to come to an agreement. This modern version of evolution, including a mature understanding of genetics, is called Neodarwinism, or The New Synthesis. It is our modern theory of evolution’Darwin, only better.
VI. Some have greatly misused Darwin’s ideas, particularly the concept of natural selection, to support their own notions of how humans should interact with each other. The theory of evolution is a theory about how the diversity of living things has come to be; it has nothing to do with human social systems, and should never be applied in these ways.
A. Social Darwinism is not actually ‘Darwinism’ of any kind. Charles Darwin himself was not a social Darwinist. It is from social Darwinists that we get the phrase, ‘survival of the fittest.’ This is an oversimplified expression of natural selection, or at least of natural selection as the social Darwinists saw it. Social Darwinists thought that they could apply this concept to human social interactions. Thus, in human interactions, the guy who could win was clearly innately superior. In war, the victory would go to the superior nationality. In business, the guy who could come out on top, no matter the strategies used, was obviously superior to the one who ended up on the bottom. Evolutionary theory has nothing to do with this sort of thing; this is just human politics and human philosophy at work, and trying to give itself legitimacy by dressing up in the trappings of science.
B. Eugenics was a specific expression of early twentieth century social Darwinism. The word literally translates as ‘good origins.’ The eugenics movement was based upon the idea that, as scientists finally understood both genetics and evolution, they could take control of the evolutionary future of the human species. Unfortunately, actual understanding of the complexities and realities of genetics and evolution was not really available. It still isn’t available today. The primary concern of most eugenicists was the ‘problem’ of ‘feeblemindedness,’ which was felt to be at the root of all kinds of social ills. Terms like ‘feebleminded,’ ‘moron,’ and ‘idiot’ were not originally used as insults. They were technical terms given to particular ranges on the I.Q. ‘bell curve.’ The feebleminded were those in the segment one standard deviation below 100’those who were of ‘substandard’ I.Q., but who could function in the world’hold down jobs, marry, have children. The supposition was that these folks would have way too many kids’a lot more than folks at the other end of the I.Q. scale, and would thus drag the whole human species down with their ‘stupid’ genes. So the eugenicists advocated doing something about limiting the reproduction going on in this segment of the population. In the U.S. the preferred approach was sterilization. In Nazi Germ
Darwin and Evolution
Dr. C. George Boeree
Charles Robert Darwin (1809-1882)
Charles Darwin was born in Shrewsbury, England, on February 2, 1809. His father was Robert Waring Darwin, a physician and son of the famous Erasmus Darwin, also a physician, as well as a respected writer and naturalist. His mother was Susannah Wedgewood Darwin. She died when Charles was eight.
Charles was educated in the local school, taught by Dr. Samuel Butler. In 1825, he went to Edinburgh to start studying medicine, but he soon realized that he did not have the stomach for it! So he switched to Cambridge, ostensibly to become a clergyman. He was actually more interested in entomology -- especially beetles -- and in hunting. He graduated from Christ’s College in 1831.
It is said that even when he was a young man, he had a patient and open mind, spending many hours collecting specimens of one sort or another and pondering over new ideas. The idea of evolution was very much in the air in those times: It was increasingly clear to naturalists that species change and have been changing for many millennia. The question was, how did this happen?
One of his mentors, John Henslow, encouraged him to apply for the (unpaid!) position of naturalist on a surveying expedition on the now-famous vessel, the Beagle, under the command of Capt. Robert Fitz-Roy. Charles left England for the first time in his life on December 27, 1831. He wouldn’t return until October 2, 1836!
Most of the ship’s time was spent surveying the coasts of South America and nearby islands, but it would also visit various Pacific islands, New Zealand, and Australia. It was the Galapagos Islands that most impressed him. There he found that finches had evolved a variety of beaks -- each suited to a particular food source. Natural variation had somehow been selected to fit the ecological niches available on the tiny islands.
Upon returning, Darwin wrote several books based on his surveys on geology and the plant and animal species he had observed and collected. He also published his journal as Journal of a Naturalist. He notes that he was most impressed by the ways similar animals adapted to different ecologies.
From early on, Darwin recognized that selection was the principle men used so successfully when breeding animals. What he needed now was an idea as to how nature could perform that task without the benefit of intelligence!
In 1838, he read a book by Malthus called Population. Malthus introduced the idea that competition over limited resources would, in nature, keep populations stable. He also warned that human populations, when straining resources, would suffer as well!
On January 29, 1839, Darwin married Emma Wedgewood, a cousin. They lived in London for a few years, then settled in the village of Down, 15 miles outside London, where they lived the rest of their lives. Darwin began suffering from an illness he had probably contracted from an insect bite in the Andes many years before. Darwin’s son, Francis, later could not say enough about his mother’s dedication to his father’s well-being. Without her, he would have been considerably less productive. They would go on to have two daughters and five sons.
Darwin wrote a sketch of his theory in 1842. In 1844, he wrote in a letter “At last gleams of light have come, and I am almost convinced (quite contrary to the opinion I started with) that species are not (it is like confessing a murder) immutable.”
He was about half done with a full exposition of his ideas when he received an essay from A. R. Wallace, with a request for comments. The essay outlined a theory of natural selection! Wallace, too, had read Malthus, and in 1858, while sick from fever, had the whole idea come to him in one flash. Darwin, in his reluctance, had postponed revealing his ideas to the scientific public for 20 years!
Darwin forwarded the essay to his friend, Sir Charles Lyell of the Geological Society, as Wallace had requested. Lyell sent the essay on, with an essay by Darwin, for presentation at a scientific conference.
The point they jointly made was clear: Just like men can exaggerate one or another minor variation by selectively breeding dogs or cattle, so nature selects similar variations -- by only permitting the most successful variations to survive and reproduce in the struggle over limited resources. Although the changes would be slight and slow, the millennia would permit the obvious diversity of nature! Darwin named this natural selection.
In 1859, Darwin finally published his master work, on the Origin of Species by Means of Natural Selection. The book was an instant success. There was also, of course, a great deal of debate -- mostly concerning the contrast with traditional religious explanations of the natural world.
Natural selection was often confused with an earlier idea of the French naturalist Lamarck. He suggested that characteristics acquired during an animal’s life were passed on to its offspring. The famous example is how the constant stretching of the neck over many generations explains the giraffe’s unlikely physique. This theory -- Lamarckianism -- was natural selection’s major competitor for decades to come!
In 1868, he published The Variation of Animals and Plants under Domestication. Then, in 1871, he came out with The Descent of Man, and Selection in Relation to Sex. This was really two books in one. The second part is about sexual selection. This is what accounts for, for example, the bright colors of many male birds: Both the males' coloring and the attraction to the coloring on the part of the females during courtship are selected for because these variations benefit the offspring.
The Descent of Man portion of the book is a brief introduction to the idea that we, too, are the results of natural selection. This part would lead to a lot of heated arguments!
In 1872, The Expression of Emotion was published. This time, Darwin talks about the evolution of the signals that animals use to communicate -- and relates those signals to human emotional expression. This is the first step towards what we now call sociobiology (and evolutionary psychology).
In addition to these influential books, Darwin also enjoyed studying and writing about plants. In 1862, he wrote Fertilization of Orchids. In 1875, he came out with both Climbing Plants and Insectivorous Plants. In I877, came Different Forms of Flowers on Plants of the Same Species. In 1880, he wrote, with his son Francis, The Power of Movement in Plants. And in 1881, he published the famous Formation of Vegetable Mould through the Action of Worms!
Charles Darwin died April 19, 1882. He was buried in Westminster Abbey. He was apparently a kind and gentle man, beloved by his family and friends alike. Outside of his voyage on the Beagle, he rarely left his home in Down. Reluctantly, he surrendered his religious beliefs and settled into an agnosticism that did not prevent him from participating with his parish in charitable works.
Alfred Russel Wallace
Alfred Wallace was born in 1823 in the village of Usk in Monmouthshire, England. His options were limited as his father died when Alfred was still a young man. So, taking advantage of a natural talent, he became a drawing teacher.
He went on an expedition to South America with his friend Henry Bates. He spent four years in the jungles of Brazil. On his way home, the ship caught fire and sank -- with four years of notes and specimen collections. The crew and passengers were fortunately rescued by a passing vessel. These adventures were the basis of Travels on the Amazon and Rio Negro, published in 1853.
Soon afterwards, he left on a second voyage, this time to Malaysia. This one would last eight years! It was during this expedition that he, sick with fever, had the idea for natural selection, and in two days, wrote an essay on the topic and sent it off to Darwin. After his return from Malaysia, he published The Malay Archipelago, a detailed journal on the plants, animals, and people of the islands.
He died November 7, 1913. Although offered a place at Westminster Abbey, his family preferred that he be buried near his home. His grave is appropriately marked by a fossilized tree trunk.
Thomas Henry Huxley
Thomas Henry Huxley was born May 4, 1825, the son of George Huxley, a schoolmaster, and Rachel Huxley. He received two years of formal education at his dad's school, and was for the rest self-educated.
Although he was raised Anglican, he became interested in Unitarianism and its naturalistic thinking. This interest led him to begin studying biology with his brother in law. His studies led to a scholarship to Charing Cross Hospital in London, where he won awards in physiology and organic chemistry.
He served as assistant surgeon on the HMS Rattlesnake. which was surveying the waters around Australia and New Guinea. To pass the time, he began investigating the various forms of sea life.
Huxley met and fell in love with Nettie Heathorn in Sydney in 1847. He then continued his biological research in that part of the world. After returning to England, he was elected to the Royal Society in 1850, but could not find an academic position. Depressed and angry, he began taking on controversial stands -- including denial of the Christian version of geology.
In 1854, he began teaching at the Government School of Mines. Finally established as a gentleman, he brought the patient Nettie to England and they married in 1855.
Huxley met Darwin in 1856, and they developed a long and close friendship. He took it upon himself to begin a campaign for Darwin's theory, which earned him the nickname "Darwin's bulldog." In particular, he fought against the church and for the concept of human evolution from apes. All the while he was a great promoter of science in general and scientific education in particular.
Huxley was responsible for a great deal of research, from his original work on sea creatures to later work on the evolution of vertebrates. He also came up with the idea of agnosticism -- by which he meant the belief that ultimate reality would always be beyond human grasp. And he is responsible for the popular metaphysical point of view known as epiphenomenalism.
In 1882, his daughter went mad. She would die five years later under the care of Jean-Martin Charcot, the great French psychiatrist. He became very depressed and retired from his professorship. For a while, he promoted Social Darwinism (see below), but backed away years later to say, with Darwin, that humanity is best served by promoting ethics, rather than instincts.
He died of a heart attack during a speech, June 29, 1895.
Herbert Spencer was born April 27, 1820, in Derby, England. His father was a schoolmaster, and both his parents were "dissenters" (i.e. religious non-conformists). Spencer was clearly gifted and was mostly self-educated.
An excellent writer, he wrote articles on social issues for various magazines of the day and even became editor of The Economist for several years. In 1855, he published The Principles of Psychology. This became part of a series of books, which he called The Synthetic Philosophy, and included biology and sociology as well as psychology.
Originally believing in the inheritance of acquired characteristics (Lamarckianism), he became a follower of Darwin's theory. It was, in fact, Spencer who coined the phrase "survival of the fittest" But he also transformed Darwin's theory into a social theory that encouraged extreme individualism and laissez-faire economic policies, called Social Darwinism.
Basically, survival of the fittest was to apply to people competing against people as well, and he implied that it was something of a social duty to accept the fact that some would be rich and some poor -- and that the consequences of poverty should not be interfered with. Even whole societies -- such as England -- were engaged in a struggle for survival that did not allow for weakness of will or sentimentality.
Social Darwinism is not something Darwin would have approved of. It has in it the fallacy of false analogy: Human society is not a neat parallel to the non-human biological world. Unfortunately, Social Darwinism seems to be here to stay, and can be found within Fascist, Conservative, and Libertarian political agendas, and in personal philosophies such as that of Ayn Rand.
Spencer is, nevertheless, considered one of the great productive thinkers of his day. He died Dec. 8, 1903, in Brighton, Sussex.
© Copyright 2000, Dr. C. George Boeree
(A major resource for Darwin's biography was the 11th edition (1910/1911) of the Encyclopedia Britannica, available online at http://www.gennet. org/darwin.htm)