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Does modern theory of evolution include modification of physical environment?


Does any branch of modern evolution theories include aspects of evolving organisms modifying the physical environment?

An example from the evolution of life could be early stage introduction of oxygen and carbon dioxide to the atmosphere from single cell bacterial growth, thereby establishing a basis for growth of more complex organisms.

See also somewhat related question: https://physics.stackexchange.com/questions/22771/does-the-universe-follow-a-general-physical-and-computational-principle-of-evolu


Yes, such processes are considered but there is still a lot of work to be done in this field.

Because the question is open-ended I will just define two concepts of interest and let you go through papers if you want to understand how such processes are modelled.

Niche Construction

Niche construction is the process in which an organism alters its own environment. Sometimes, niche construction takes a broad definition and it then refers more globally to any environment change that is induced by an organism regardless of whether the individual/lineage experiencing the environment is the same one than the one causing the modification. Under this broad definition, niche construction has the meaning as ecological engineering to my understanding.

Some obvious examples are bird nests, beaver's dam and humans's houses. The process of niche construction gets really interesting when the niche is inherited by future generations.

Ecosystem engineering

Ecosystem engineering is the process in which an organism alters the its environment and the environment of other lineages/species. Ecological facilitation is one class of examples.

Ecosystem engineering vs Niche Construction

To my understanding, the term niche construction is more often used in the evolutionary ecology literature, while the term ecosystem engineering is more often used in the ecology literature. Note again that (in my understanding) niche construction in its broad sense takes the same definition as ecosystem engineering but not in its narrow sense.

Models of niche construction in evolutionary biology

There are a number of models of niche construction in evolutionary biology. I am not expert in this field and am not able to make a good summary (would take a while even for an expert anyway). Here are a few papers (that I haven't fully read) that you may want to consider

Note that depending on your level of understanding of evolutionary biology, these papers may be a bit complicated to fully understand.


The Mathematics of Evolution: Q&A with Biologist Marcus Feldman

Marcus Feldman never planned to end up on the front lines of evolutionary biology. &ldquoI always wanted to do mathematics, as much as I could,&rdquo he said. &ldquoThere was a little bit of time when I flirted with the idea of being a psychiatrist.&rdquo

More than anything else, Feldman is a polymath. His desk at Stanford University, where he has been a professor for 46 years, is tiled with stacks upon stacks of journal articles, most teetering above coffee-cup height. Each stack is dedicated to a topic somehow related to his work in evolutionary theory: the origins of behavioral disorders, the epidemiology of tuberculosis, the way modern humans overrode Neanderthals.

Feldman&rsquos openness to unexpected lines of thinking has allowed him to carve out a contrarian niche in a field where established ideas typically rule the day. Along with a group of similarly unorthodox colleagues, Feldman has developed a proposal called the extended evolutionary synthesis (EES). The EES argues that while the existing framework of evolutionary theory, known as the &ldquomodern synthesis,&rdquo is basically solid, it needs to be expanded to account for newly recognized drivers of evolution. One such driver is epigenetics &mdash gene-expression changes that stem from exposure to, say, pesticides. While these epigenetic changes are not encoded in an organism&rsquos genes, they do give rise to physical and behavioral differences that natural selection can act upon.

The EES also stresses the importance of culture and behavior in evolution. When prairie dogs construct burrows, for instance, selection pressures may begin to favor behaviors like burrow guarding to keep predators out. And both humans and animals direct their evolution through the social and cultural environments they construct for themselves &mdash a phenomenon Feldman thinks is not well reflected in the modern synthesis.

Quanta Magazine spoke with Feldman at Stanford about how mathematical models can illuminate evolution, his contributions to the extended evolutionary synthesis, and his role in redressing China&rsquos sex-ratio imbalance. An edited and condensed version of the conversation follows.

QUANTA MAGAZINE: When you were a young man in Australia, would you ever have pictured your career unfolding the way it has?

MARCUS FELDMAN: No! I went to work in Melbourne when IBM opened its offices. I didn&rsquot like working for IBM, so I tried to do a master&rsquos degree in mathematics and statistics at Monash University, which of course involved an enormous cut in pay. I was lucky that my adviser had just come back from America. He introduced me to using mathematics on genetics problems. I had never done a biology course in my life, but I started to work on this class of problems.

The first two years of my Ph.D. at Stanford, I still hadn&rsquot done any biology. But I got so interested in some of the problems I was working on that I decided I&rsquod better take some courses. I became immersed in the application of mathematics to genetics questions. From then on, it was just trying to formalize in mathematical terms the kinds of questions that biologists would ask.

You joined Stanford&rsquos biology department as a faculty member in 1971. What happened after that?

Very soon after my arrival, I met a famous geneticist, Luigi Luca Cavalli-Sforza. He is what I call the consummate Renaissance man. He was interested in the statistics of human genetic and cultural variation &mdash why different people in different parts of the world behave differently, have different rules in their societies and were genetically different from one another. He and I immediately hit it off.

The first thing we did was develop mathematical models to describe cultural differences. What would happen to the old style of genetic evolution if there were also cultural factors that influenced what was happening to the genes in the populations? For example, IQ &mdash if there happened to be genetic contributions to IQ, but also culturally determined contributions to IQ, how would you combine the two of them in a dynamic system?

How do these models reveal how evolution takes place?

One of the nice things about models is you can ask what conditions have to change to make the results change. As Murray Gell-Mann says, models are prostheses for the imagination. They help you think about ways in which you might interpret data, even complicated data.

If you think about use of milk, dairy in itself is culturally transmitted. But there&rsquos a gene called the lactase persistence gene, which allows some people to digest milk. Suppose that people who drink milk get enough extra protein that they can survive better. If those same people are learning from somebody to use cows for the purpose of getting milk, any gene which allows you to drink more milk without getting sick is going to have an advantage in the situation where cows are used for milking.

If the cows weren&rsquot there, that gene wouldn&rsquot have any advantage at all. Using the cows for milk production is not part of your genetics it&rsquos part of your culture. The spread of that culture had the effect of spreading the lactase persistence gene.

Other cultural things have huge effects on other organisms, not just on us. I&rsquom thinking of the period when everybody was using antibiotics &mdash you took the kid to the doctor, you had a sore throat, you would get an antibiotic. We humans have had a huge effect on the growth of antibiotic resistance. It&rsquos a straightforward predictable consequence of evolution. If there are resistant genes there, they&rsquoll succeed.

Did culture alter humans&rsquo evolutionary course in the distant past, too?

We can construct a model for the movement of modern humans out of Africa into Eurasia and the competition that they&rsquore going to have with the Neanderthals who were already there. We formulated it like a diffusion. You have these people diffusing across the continent, and within the population is a level of culture that could be more advanced than that of the residents. The question we came up with is: Could a smaller population with a lot of culture overcome a bigger population that didn&rsquot have very much culture?

We found that a smaller number of people could invade a population that&rsquos quite a lot bigger if they had a sufficiently developed culture. The way in which the populations grew depended on the level of culture. That group that had the most culture &mdash the modern humans &mdash would be the winner.

In your view, what are some of the shortcomings of the classical model of evolution &mdash the so-called &ldquomodern synthesis&rdquo?

The modern synthesis developed in the 1930s and 1940s and basically had finished by the 1950s. At that time, little was known about the molecular biology of development &mdash how what&rsquos going on in the development process itself influences what can happen to the evolutionary trajectory of cells and organisms. Although some of its originators were interested in behavior, many were steeped in the eugenics tradition. They would have thought that the majority of behaviors were determined by genes. The inclusion of other forms of inheritance totally changes evolutionary dynamics.

What was your involvement in the early stages of the EES?

My colleagues and I started to build the first quantitative models for &ldquoniche construction,&rdquo which is an idea that had been around, but peripherally, from writings of the evolutionary biologist Richard Lewontin. What Lewontin had proposed was that individuals don&rsquot only react to their environments, they actually contribute to making them. Rather than solving problems, they construct the environment, which they then have to exist in, and their offspring have to exist in the environment that they changed. Humans do it all the time, but other organisms do it too. The classic example is dams made by beavers it changes the environment for everything around. You have beavers having offspring that are going to live in the dams their parents and grandparents built. It can affect the behavior of the subsequent generations.

And some of those environmental changes might affect which traits confer fitness, then?

Yes, exactly. After we had written a book on niche construction, I started to think about how the cultural evolution work and the niche construction work would interact. When you&rsquore a scientist and you work on a lot of different things, you can&rsquot separate them &mdash the thoughts cross over. It made it natural to think this was an extension of the evolutionary synthesis.

Ina commentary in Nature, you and your co-authors wrote, &ldquoWe hold that organisms are constructed in development, not simply &lsquoprogrammed&rsquo to develop by genes.&rdquo What does &ldquoconstructed in development&rdquo mean?

It means there&rsquos an interaction between the subject and the environment. The idea of a genetic blueprint is not tenable in light of all that is now known about how all sorts of environmental contingencies affect traits. For many animals it&rsquos like that. Even plants &mdash the same plant that is genetically identical, if you put it in this environment, it&rsquos going to look totally different from if you put it in that environment.

We now have a better picture of the regulatory process on genes. Epigenetics changes the landscape in genetics because it&rsquos not only the pure DNA sequence which influences what&rsquos going on at the level of proteins and enzymes. There&rsquos this whole other stuff, the other 95 percent of the genome, that acts like rheostats &mdash you slide this thing up and down, you get more or less of this protein. It&rsquos a critical thing in how much of this protein is going to be made. It&rsquos interesting to think about the way in which cultural phenomena, which we used to think were things by themselves, can have this effect on how much messenger RNA is made, and therefore on many aspects of gene regulation.

How can these epigenetic changes affect the traits that natural selection can act on &mdash and therefore the future course of evolution?

We&rsquove just submitted a paper on epigenetic contributions to longevity in hunter-gatherers. There is increasing evidence of important associations between the level of methylation [which affects how strongly your genes are expressed] and features of your environment such as diet, stress and poverty.

If those things are culturally transmitted, those effects on evolution are going to be longer term. Simple notions of the ways in which traits are formed are going to be thrown out the window.

The EES has gotten pushback from many biologists who think that things like cultural evolution and niche construction are already accounted for in evolutionary theory, and that therefore the EES is unnecessary. How do you respond?

I don&rsquot think they are accounted for. You can&rsquot predict, using old theory, what the influence of these newly important phenomena are likely to be on evolution. They don&rsquot fit the framework of all the models that were used to make those original predictions.

People who make models like I do for a living don&rsquot actually believe they&rsquore describing reality. We aren&rsquot saying that our model is more probable than another model we&rsquore saying it exposes what is possible. The EES includes more of these phenomena, that now we have a better handle on biologically, in thinking about evolution.

You&rsquove been looking into the imbalance in the sex ratio in China and the potential long-term consequences that imbalance could have. How has your background in evolution and modeling informed that research?

The first paper we wrote on that was really about genetics. The idea was to use the standard idea of sex determined by sex chromosomes &mdash XX for female and XY for males &mdash and to ask what would happen if culture affected the different numbers of each being produced. One of my colleagues in China saw this stuff. He said, &ldquoLet&rsquos talk about son preference in the sex ratio.&rdquo So we started to make models for a cultural preference for sons, a preference that could be learned and hence transmitted. We made models where a given couple would decide they would prefer to have sons, and they would pass on that preference to their children.

What we were able to do was to make a projection of what would happen in China if they continued on this path. We really were able to get a lot of stuff published, some things that might have influenced government policy. The government finally woke up and saw that not only was it having a bad effect on females, but it was going to affect the economy because the number of marriages was going down. You have these 30, 40 million men who can&rsquot find wives and the long-term outlook for the labor market and social security was not promising.

How do you think the EES will change the direction of biology research?

I think it&rsquos a bit hard to tell yet. We still have &mdash I&rsquom going to put on my mathematical hat &mdash very few models for how development and evolution interact. They&rsquore based in models from the 1920s. That needs to change, in my view. We have very few models that integrate gene regulation and genic evolution they&rsquore really quite limited in scope.

I&rsquom always excited about the subject getting more complex. It means there&rsquos more and more room for the people who are well-trained quantitatively. It&rsquos a bit selfish, but there you are.

Reprinted with permission from Quanta Magazine, an editorially independent publication of the Simons Foundation whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.

ABOUT THE AUTHOR(S)

Elizabeth Svoboda is a science writer in San Jose, Calif., and author of What Makes a Hero?: The Surprising Science of Selflessness (Penguin Group, 2013).


Does modern theory of evolution include modification of physical environment? - Biology

Resource Type: Web Activity

Resource Type: Web Activity

Resource Type: Web Activity

Field of Genes
These images of Bt and non-Bt corn show the result of inserting the genes of a bacterial species into the corn to act as a pesticide.

Pesticide Resistance
This series of images shows how pesticide acts as a selective pressure on a population of insects, allowing only individuals that happen to be resistant to its effects to survive and reproduce. From NOVA: "Insect Alternative."

About BIO
This site provides information on this industry group's position on food and agricultural biotechnology. Hosted by Biotechnology Industry Organization.

Cats! Wild to Mild
Follow the link from this site to "Egypt & Domestication" to learn how artificial selection and domestication of a wild cat produced the number one pet in the United States today. Hosted by Natural History Museum of Los Angeles County.

Cotton Picking Blues
Written by a geneticist, this article warns against rampant engineering of crop plants, arguing that natural selection pressures will stimulate the evolution of tougher pest species. Hosted by New Internationalist Online.

Does the World Need Genetically Modified Foods?
In this interview, Dr. Margaret Mellon of the Union of Concerned Scientists turns a skeptical eye on the genetic modification of crop plants, suggesting alternatives and offering some cautions about as-yet-unknown risks of GM foods. Hosted by Scientific American.

Evolution, Science and Society: Evolutionary Biology and the National Research Agenda
This comprehensive article details the relevance of evolutionary biology to basic research, as well as to science applications, in a wide variety of fields. Hosted by Rutgers University.

Here We Go Again: Bt Corn and Monarch Butterflies
This site includes the abstract of (and a link to) the research paper that raised alarm about Bt corn, a crop that has been genetically modified to produce a bacterial pesticide. Readers will also find the official rebuttal by the Biotechnology Industry Organization and some hype-free comments by the author of the page. Contains technical jargon. Hosted by the University of Illinois.

Is GM Safe?
This site includes the transcript of a 2000 BBC program on the genetic modification of crops. The site is a bit hard on the eyes, but the information and opinions are very interesting and offer many different perspectives. For further discussions, follow the link to the chat at the bottom of the page. Hosted by the BBC.

Mendel
This site includes a challenging game which helps develop an intuitive understanding of genetic inheritance, just as Mendel did more than 130 years ago. Follow the "All About Genes" link for an explanation of the processes that underlie inheritance. Designed by Agon Design, hosted by the University of Birmingham.

Mendel's Paper in English
This translation of Gregor Mendel's 1865 "Experiments in Plant Hybridization" supplements the original text with links to a glossary of troublesome terms, additional notes, discussion questions (for classroom use), a fairly current bibliography, and a "live" annotation page where you can add your own remarks for all to see. Hosted by MendelWeb.

Online Mendelian Inheritance In Animals (OMIA)
This up-to-date searchable catalog describes the genes that influence phenotypic traits of animals, from alpacas to zebrafish. Search by species or traits/disorders. Hosted by the Australian National Genomic Information Service.

Origin, Adaptation, and Types of Corn
This site is a compendium of research summaries (primary sources are not cited on the page) detailing the evolutionary history of corn, as well as the varieties that currently exist throughout the world. Hosted by the University of Maryland.

Resistance Fighting
This short article describes how natural selection may defeat one of the most successful "natural" pesticides genetic engineers have come up with by producing insects resistant to the toxic pesticide that are even more damaging to crops. Hosted by Scientific American.

The Domestication and Evolution of Wheat
This page illustrates the evolution of wheat from wild, weedy ancestors to its current form through a combination of natural hybridization and artificial selection. Hosted by the University of Birmingham.

The Domestication of Plants and Animals
This article provides an enlightening history of human domestication of plants and animals from a geographic perspective, including a section describing some traits which were artificially selected. In addition, you'll find information about how domestication has affected human cultures. Hosted by the University of Oklahoma.

The Food and Environment Program
Select "biotechnology" from the Features menu to read the Union of Concerned Scientists' view on genetically engineered crops and reasons for modifications, as well as information on antibiotic resistance. Hosted by the Union of Concerned Scientists.

Variation Under Domestication
This site includes chapter 1 of Charles Darwin's On the Origin of Species, in which he explains heritable variations seen among domesticated plant and animal species. Hosted by literature.org.

Western Corn Rootworms Adapt to Crop Rotation
This article is targeted toward a more advanced audience and gives a complete account of the coevolutionary counterplay between an important crop plant and one of its principal pests. The lessons learned here apply equally as well to other pest-crop plant groups. Hosted by Washington State University Tri-cities.

Genetically Modified Pest-Protected Plants: Science and Regulation
This is a book for agricultural, scientific, and policy professionals interested in the processes and consequences (pros and cons) of genetic modification of crop plants, as well as related policy issues. Case studies of several plants, notably Bt transgenics, are presented. By National Research Council Committee on Genetically Modified Pest-Protected Plants [Washington, D.C.: National Academy Press, 2000].

Plant Evolution under Domestication
An excellent resource for the advanced reader, this book chronicles the origins of agriculture, the evolution of crop plants and weeds under artificial selection, and wild sources of genetic diversity that agriculture may take advantage of in the future. By Gideon Ladizinsky [Dordrecht, Netherlands: Kluwer Academic Publishers, 1998].

Plant Resistance to Herbivores and Pathogens: Ecology, Evolution, and Genetics
Targeted toward an advanced scientific audience, this book provides a review of plant resistance to phytophages gathered from many fields, including evolutionary biology. Mechanisms and consequences of resistance are discussed, along with methodologies for study. Edited by Robert S. Fritz, and Ellen L. Simms [Chicago: University of Chicago Press, 1992].

Who Harnessed the Horse?: The Story of Animal Domestication
Written for a younger audience, this book explains how various animal species were domesticated and selectively bred by humans to suit a wide variety of purposes. By Matgery Facklam [Boston: Little, Brown, 1992].

Nothing in Biology Makes Sense Except in the Light of Evolution
The oft-quoted title says it all. Dobzhansky succinctly explains how evolutionary theory unified all other field of the biological sciences.

Evolution and the Nature of Science Institutes
This site encourages the teaching of evolutionary theory in the greater context of modern scientific thinking and the nature of science.

BioForum: Evolution Introduction
The site was produced for teachers but is also suitable for a general audience. It includes a clear discussion of how principles of evolution underlie -- and, more importantly, unify -- everything biologists have learned about living things. Hosted by AccessExcellence.

Contributions of Evolutionary Biology to the Biological Sciences
This section of Evolution, Science and Society explores how an understanding of evolution fosters progress in the various fields of biology. A partial bibliography is provided. Hosted by Rutgers University.

Teaching About Evolution and the Nature of Science
Available online, this book is an invaluable reference for grade 5-12 biology teachers. It provides a compendium of essential information and activities for teaching evolutionary biology. By the Working Group on Teaching Evolution, National Academy of Sciences [Washington, D.C.: National Academy Press, 1998].

The Architecture of Life
This article explains how all organic forms, from simple molecules to complex organisms, are built according to the same design rules, rules which are themselves products of evolution. Hosted by Scientific American.

Evolutionary Biology, 3rd ed.
An excellent college-level textbook for the serious student of modern evolutionary theory. By Douglas J. Futuyma [Sunderland, Mass.: Sinauer Associates, Inc., 1998].

The Evolutionary Synthesis: Perspectives on the Unification of Biology, 2nd ed.
A collection of essays by the scientists who forged the modern synthesis, this work discusses how the modern synthesis unified all of biology, not just the evolutionary field. By Ernst Mayr [Cambridge: Harvard University Press, 1998].

Theory of Population Genetics and Evolutionary Ecology: An Introduction
This classic text describes the field of evolutionary ecology, combining population biology and genetics for a more integrated view of species interactions over both short- and long-term periods. By Jonathan Roughgarden [New York: MacMillan, 1979].


Teaching About Evolution and the Nature of Science (1998)

Teachers often face difficult questions about evolution, many from parents and others who object to evolution being taught. Science has good answers to these questions, answers that draw on the evidence supporting evolution and on the nature of science. This chapter presents short answers to some of the most commonly asked questions.

Definitions

What is evolution?

Evolution in the broadest sense explains that what we see today is different from what existed in the past. Galaxies, stars, the solar system, and earth have changed through time, and so has life on earth.

Biological evolution concerns changes in living things during the history of life on earth. It explains that living things share common ancestors. Over time, evolutionary change gives rise to new species. Darwin called this process "descent with modification," and it remains a good definition of biological evolution today.

What is "creation science"?

The ideas of "creation science" derive from the conviction that God created the universe&mdashincluding humans and other living things&mdashall at once in the relatively recent past. However, scientists from many fields have examined these ideas and have found them to be scientifically insupportable. For example, evidence for a very young earth is incompatible with many different methods of establishing the age of rocks. Furthermore, because the basic proposals of creation science are not subject to test and verification, these ideas do not meet the criteria for science. Indeed, U.S. courts have ruled that ideas of creation science are religious views and cannot be taught when evolution is taught.

The Supporting Evidence

How can evolution be scientific when no one was there to see it happen?

This question reflects a narrow view of how science works. Things in science can be studied even if they cannot be directly observed or experimented on. Archaeologists study past cultures by examining the artifacts those cultures left behind. Geologists can describe past changes in sea level by studying the marks ocean waves left on rocks. Paleontologists study the fossilized remains of organisms that lived long ago.

Something that happened in the past is thus not "off limits" for scientific study. Hypotheses can be made about such phenomena, and these hypotheses can be tested and can lead to solid conclusions. Furthermore, many key aspects of evolution occur in relatively short periods that can be observed directly&mdashsuch as the evolution in bacteria of resistance to antibiotics.

Isn't evolution just an inference?

No one saw the evolution of one-toed horses from three-toed horses, but that does not mean that we cannot be confident that horses evolved. Science is practiced in many ways besides direct observation and experimentation. Much scientific discovery is done through indirect experimentation

and observation in which inferences are made, and hypotheses generated from those inferences are tested.

For instance, particle physicists cannot directly observe subatomic particles because the particles are too small. They must make inferences about the weight, speed, and other properties of the particles based on other observations. A logical hypothesis might be something like this: If the weight of this particle is Y, when I bombard it, X will happen. If X does not happen, then the hypothesis is disproved. Thus, we can learn about the natural world even if we cannot directly observe a phenomenon&mdashand that is true about the past, too.

In historical sciences like astronomy, geology, evolutionary biology, and archaeology, logical inferences are made and then tested against data. Sometimes the test cannot be made until new data are available, but a great deal has been done to help us understand the past. For example, scorpionflies (Mecoptera) and true flies (Diptera) have enough similarities that entomologists consider them to be closely related. Scorpionflies have four wings of about the same size, and true flies have a large front pair of wings but the back pair is replaced by small club-shaped structures. If Diptera evolved from Mecoptera, as comparative anatomy suggests, scientists predicted that a fossil fly with four wings might be found&mdashand in 1976 this is exactly what was discovered. Furthermore, geneticists have found that the number of wings in flies can be changed through mutations in a single gene.

Evolution is a well-supported theory drawn from a variety of sources of data, including observations about the fossil record, genetic information, the distribution of plants and animals, and the similarities across species of anatomy and development. Scientists have inferred that descent with modification offers the best scientific explanation for these observations.

Is evolution a fact or a theory?

The theory of evolution explains how life on earth has changed. In scientific terms, "theory" does not mean "guess" or "hunch'' as it does in everyday usage. Scientific theories are explanations of natural phenomena built up logically from testable observations and hypotheses. Biological evolution is the best scientific explanation we have for the enormous range of observations about the living world.

Scientists most often use the word "fact" to describe an observation. But scientists can also use fact to mean something that has been tested or observed so many times that there is no longer a compelling reason to keep testing or looking for examples. The occurrence of evolution in this sense is a fact. Scientists no longer question whether descent with modification occurred because the evidence supporting the idea is so strong.

Why isn't evolution called a law?

Laws are generalizations that describe phenomena, whereas theories explain phenomena. For example, the laws of thermodynamics describe what will happen under certain circumstances thermodynamics theories explain why these events occur.

Laws, like facts and theories, can change with better data. But theories do not develop into laws with the accumulation of evidence. Rather, theories are the goal of science.

Don't many famous scientists reject evolution?

No. The scientific consensus around evolution is overwhelming. Those opposed to the teaching of evolution sometimes use quotations from prominent scientists out of context to claim that scientists do not support evolution. However, examination of the quotations reveals that the scientists are actually disputing some aspect of how evolution occurs, not whether evolution occurred. For example, the biologist Stephen Jay Gould once wrote that "the extreme rarity of transitional forms in the fossil record persists as the trade secret of paleontology." But Gould, an accomplished paleontologist and eloquent educator about evolution, was arguing about how evolution takes place. He was discussing whether the rate of change of species is constant and gradual or whether it takes place in bursts after long periods when little change occurs&mdashan idea known as punctuated equilibrium. As Gould writes in response, "This quotation, although accurate as a partial citation, is dishonest in leaving out the following explanatory material showing my true purpose&mdashto discuss rates of evolutionary change, not to deny the fact of evolution itself."

Gould defines punctuated equilibrium as follows:

Punctuated equilibrium is neither a creationist idea nor even a non-Darwinian evolutionary theory about sudden change that produces a new species all at once in a single generation. Punctuated equilibrium accepts the conventional idea that new species form over hundreds or thousands of generations and through an extensive series of intermediate stages. But geological time is so long that even a few thousand years may appear as a mere "moment" relative to the several million years of existence for most species. Thus, rates of evolution vary enormously and new species may appear to arise "suddenly" in geological time, even though the time involved would seem long, and the change very slow, when compared to a human lifetime.

Isn't the fossil record full of gaps?

Though significant gaps existed in the fossil record in the 19th century, many have been filled in. In addition, the consistent pattern of ancient to modern species found in the fossil record is strong evidence for evolution. The plants and animals living today are not like the plants and animals of the remote past. For example, dinosaurs were extinct long before humans walked the earth. We know this because no human remains have ever been found in rocks dated to the dinosaur era.

Some changes in populations might occur too rapidly to leave many transitional fossils. Also, many organisms were very unlikely to leave fossils, either because of their habitats or because they had no body parts that could easily be fossilized. However, in many cases, such as between primitive fish and amphibians, amphibians and reptiles, reptiles and mammals, and reptiles and birds, there are excellent transitional fossils.

Can evolution account for new species?

One argument sometimes made by supporters of "creation science" is that natural selection can produce minor changes within species, such as changes in color or beak size, but cannot generate new species from pre-existing species. However, evolutionary biologists have documented many cases in which new species have appeared in recent years (some of these cases are discussed in Chapter 2). Among most plants and animals, speciation is an extended process, and a single human observer can witness only a part of this process. Yet these observations of evolution at work provide powerful confirmation that evolution forms new species.

If humans evolved from apes, why are there still apes?

Humans did not evolve from modern apes, but humans and modern apes shared a common ancestor, a species that no longer exists. Because we shared a recent common ancestor with chimpanzees and gorillas, we have many anatomical, genetic, biochemical, and even behavioral similarities with the African great apes. We are less similar to the Asian apes&mdashorangutans and gibbons&mdashand even less similar to monkeys, because we shared common ancestors with these groups in the more distant past.

Evolution is a branching or splitting process in which populations split off from one another and gradually become different. As the two groups become isolated from each other, they stop sharing genes, and eventually genetic differences increase until members of the groups can no longer interbreed. At this point, they have become separate species. Through time, these two species might give rise to new species, and so on through millennia.

Doesn't the sudden appearance of all the "modern groups" of animals during the Cambrian explosion prove creationism?

During the Cambrian explosion, primitive representatives of the major phyla of invertebrate animals appeared&mdashhard-shelled organisms like mollusks and arthropods. More modern representatives of these invertebrates appeared gradually through the Cambrian and the Ordovician periods. "Modern groups" like terrestrial vertebrates and flowering plants were not present. It is not true that "all the modern groups of animals" appeared during this period.

Also, Cambrian fossils did not appear spontaneously. They had ancestors in the Precambrian period, but because these Precambrian forms were soft-bodied, they left fewer fossils. A characteristic of the Cambrian fossils is the evolution of hard


What is Biology? (with pictures)

Biology is, quite simply, the scientific exploration and study of life. At the highest level, it includes categories based on the type of organism studied: zoology, botany, and microbiology. Each field has contributed to humanity in numerous ways such as improvements in agriculture, greater understanding of livestock and ecological systems, and the study of diseases. Modern biological studies largely center on the concepts of cell theory, evolution, gene theory, and homeostasis.

Three Major Categories

There are three major categories of study within biology, each related to a different type of life form. Zoology is the study of animals and includes just about anything from insects and fish to birds and human beings. Botany, on the other hand, focuses on plants of all types and sizes, including underwater forests, fungi, and trees. Microbiology is the study of microorganisms too small to be plainly seen and which escape categorization in the other two fields, such as viruses.

Other Subcategories

Besides classifications based on the type of organism being studied, biology contains many other specialized sub-disciplines, which may focus on just one type of organism or consider life from different categories. This includes biochemistry, which combines biological and chemical studies, and molecular biology, which looks at life on the molecular level. Cellular biology studies different types of cells and how they work, while physiology looks at organisms at the level of tissue and organs. Experts in ecology study the interactions between various organisms themselves within an environment, and those in ethology study the behavior of animals, especially complex animals in groups. Genetics, which overlaps somewhat with molecular studies, looks at the code of life, Deoxyribonucleic Acid (DNA).

Four Major Foundations of Study

The foundations of modern biology include four components beginning with cell theory, which states that fundamental units called cells make up all life. Evolution is the theory that life is not deliberately designed, but evolves incrementally over a great deal of time through random mutations and natural selection. Gene theory states that tiny molecular sequences of DNA dictate the entire structure of an organism, which pass from parents to offspring. Finally, homeostasis is the idea that each organism’s body includes a complex suite of processes designed to remain in harmony and preserve it against the entropic or destructive effects outside of the organism.

20th Century Developments

Much of the modern approach to biology started with the use of x-ray crystallography in the 1950s to capture a concrete image of DNA. Since then, there have been numerous refinements to the theories put forth, since life is complex and new information is almost constantly being discovered. In the late 20th and early 21st Centuries, a great deal of excitement centered on the sequencing of genomes and their comparison, called genomics. These advances have led to the creation of organisms or living tissue through custom-written DNA programming, called synthetic biology. Such fields are sure to continue grabbing attention as new developments push the limits of what is possible.

Michael is a longtime InfoBloom contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Michael is a longtime InfoBloom contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.


Secret code

Darwin was able to establish natural selection, without any understanding of the genetic mechanisms of inheritance, or the source of novel variation in a population. His own theory on the transmission of traits, called pangenesis, was completely wrong.

It was not until Gregor Mendel and the start of the 20 th century that the genetic mechanism of inheritance began to be revealed. We now know that most traits, such as skin colour, eye colour and blood group are determined by our DNA and genes. During the 20 th century, evolutionary biologists such as Ernst Mayr, J.B.S. Haldane, Julian Huxley, and Theodosius Dobzhansky combined Darwinian evolution with our emerging knowledge of genetics to produce the “modern synthesis” that we call evolutionary biology today.

Most genes come in a variety of forms, one inherited from each parent. The varieties are known as alleles, and encode slightly different traits. The incidence of different traits, or alleles, in a population is driven by natural selection and genetic drift, which can randomly reduce genetic variation. Today, evolution is defined as the change in the frequency of alleles in populations over time.

New traits are introduced into populations by gene flow from other populations or by mutation. Mutation is a change in the structure of a gene and can be caused by errors in copying DNA, carcinogenic chemicals, viruses, UV-light and radiation. Most mutations are neutral, having no effect on gene function others are harmful, such as the ones that cause inherited diseases like cystic fibrosis. Rarely mutations can lead to beneficial new traits, such as increased resistance to malaria.

Today evolutionary biologists are largely divided into two camps. The pro-selectionists such as Richard Dawkins, Stephen Pinker, Edward O Wilson, Matt Ridley, Mark Ridley and Jared Diamond believe in the primacy of natural selection as the principle guiding evolution. Others such as Niles Eldredge, Stephen J. Gould, Brian Goodwin, Stuart Kauffman and Steven Rose argue that we are still missing something big, and that natural selection does not explain the full complexity of evolution.


Contemporary beliefs

According to a Gallup poll, 46% of US citizens believed in creationism in 2012, including 52% of those with only a high-school education or less and 25% of those with post graduate education. 25% of those who do not attend church believe in creationism, while 67% of those who attend church weekly believe. Outside of the US, most contemporary Christian leaders believe that Genesis is allegorical and support evolution.

Notable supporters of Evolution

Evolutionary biologist Richard Dawkins is a notable and vociferous critic of creationism.

The Catholic church's unofficial position is an example of theistic evolution, also known as evolutionary creation, stating that faith and scientific findings regarding human evolution are not in conflict. Moreover, the Church teaches that the process of evolution is a planned and purpose-driven natural process, guided by God. Catholics regard the creation descriptions in the Bible as parables written to provide moral instruction rather than as literal history, and therefore see no conflict between these accounts and the Theory of Evolution. The Church has deferred to scientists on matters such as the age of the earth and the authenticity of the fossil record. Papal pronouncements, along with commentaries by cardinals, have accepted the findings of scientists on the gradual appearance of life. The Church's stance is that any such gradual appearance must have been guided in some way by God, but the Church has thus far declined to define in what way that may be. [1]

Notable supporters of Creationism

Many Protestant, and particularly Evangelical, churches, on the other hand, reject Evolution in favor of a literal, rather than figurative, interpretation of the book of Genesis. However, it is typically not specified which version of the creation account is being considered divinely inspired and hence "literally true". This is problematic since there are two such accounts in the Bible (Gen1:1 - Gen2:3 vs. Gen2:4 - Gen50:26) , and they contradict each other in numerous ways. For instance, order in which Adam vs. the Beasts were created differs [2][3] between the two accounts.


Alfred Russel Wallace

Alfred Russel Wallace (1823-1913) was born near Usk, Monmouthshire (now part of Gwent), Wales as the eighth child of the family. His father was employed as librarian in Hertford, an English county town not too far distant from London. Unfortunately Mr. Wallace lost much of his remaining property through ill advised dealings in 1835 resulting in real hardship for the family - Alfred Russel Wallace, then barely into his teenage years, had to cut short his formal education late in 1836.
Family contacts in the form of an older brother, William, owning a surveying business led to Wallace embarking on a career as a surveyor where a growing interest in Natural History could also be followed up, to some extent, between daily tasks.

It happened, however, that William Wallace's business fell on hard times causing Wallace to lose his place in 1844. He was now successful in gaining a position as a teacher of Surveying in the Collegiate School in Leicester where he had access to a library where there were several reliable books on Natural History.

In 1844 Wallace made the acquaintance of another young man seriously interested in Natural History named Henry Walter Bates, who, although only nineteen years of age, was a well-recognised proficient in the then fashionable pursuit of beetle-collecting and who had already been able to get some scholarly work in Entomology printed in the learned journal, Zoologist.

Other formative developments in his life in these times included attendance at a demonstration of mesmerism - Wallace found that he could himself reproduce the same effects as the mesmerist demonstated and, more seriously, the death of his brother, William, in February 1845 which was followed by Wallace returning to surveying and his brother, John, joining him in the business. Wallace found his adminstrative responsibilities particularly arduous. After the failure of the business Wallace worked as a surveyor in connection with a proposed railway in the Vale of Neath. He also found time to give lectures on science and engineering at the Mechanics' Institute of Neath and to act as a curator of the Neath Philosophical and Literary Institute's museum.

His interest in Natural History continued and he entered into a regular correspondence with his friend Henry Bates. During thes times Wallace seems to have read, and to have corresponded with Henry Bates about, Charles Darwin's journal on the Voyage of the Beagle, Charles Lyell's Principles of Geology which offered to demonstrate how long-term change, in Geology in this instance, could be effected through the operation of slow, long-term processes, and an anonomously published work Vestiges of the Natural History of Creation, (later known to be by Robert Chambers), which was an early, popular, and notably controversial effort at arguing pursuasively against both Creationism and Lamarckism as full explanations of the existence of the solar system, the earth, and the diversity of species.
The latter two of these works might be thought to have almost prepared Alfred Russel Wallace's mind for an acceptance of evolutionism.

In a letter to Bates dated November 9th, 1845, he concludes by asking, "Have you read 'Vestiges of the Natural History of Creation,' or is it out of your line?" and in the next (dated December 28th), in reply to one from his friend, he continues, "I have a rather more favourable opinion of the 'Vestiges' than you appear to have, I do not consider it a hasty generalisation, but rather an ingenious hypothesis strongly supported by some striking facts and analogies, but which remains to be proved by more facts and the additional light which more research may throw upon the problem. It furnishes a subject for every observer of nature to attend to every fact," he observes, "will make either for or against it, and it thus serves both as an incitement to the collection of facts, and an object to which they can be applied when collected. Many eminent writers support the theory of the progressive development of animals and plants. There is a very philosophical work bearing directly on the question - Lawrence's 'Lectures on Man'. The great object of these 'Lectures' is to illustrate the different races of mankind, and the manner in which they probably originated, and he arrives at the conclusion (as also does Prichard in his work on the 'Physical History of Man') that the varieties of the human race have not been produced by any external causes, but are due to the development of certain distinctive peculiarities in some individuals which have thereafter become propagated through an entire race. Now, I should say that a permanent peculiarity not produced by external causes is a characteristic of 'species' and not of mere 'variety,' and thus, if the theory of the 'Vestiges' is accepted, the Negro, the Red Indian, and the European are distinct species of the genus Homo.

"An animal which differs from another by some decided and permanent character, however slight, which difference is undiminished by propagation and unchanged by climate and external circumstances, is universally held to be a distinct species while one which is not regularly transmitted so as to form a distinct race, but is occasionally reproduced from the parent stock (like albinoes), is generally, if the difference is not very considerable, classed as a variety. But I would class both these as distinct species, and I would only consider those to be varieties whose differences are produced by external causes, and which, therefore, are not propagated as distinct races."

Again, writing to Bates some months later, in 1847: "I begin to feel rather dissatisfied with a mere local collection little is to be learnt by it. I should like to take some one family to study thoroughly, principally with a view to the theory of the origin of species. By that means I am strongly of opinion that some definite results might be arrived at." And he further alludes to "my favourite subject - the variations, arrangements, distribution, etc., of species."

Wallace had read Charles Darwin's book about the Voyage of the Beagle and his admiration for the adventures and the observations of natural phenomena that Darwin wrote about as having occured during the Beagle voyage and also those related in a book by William H. Edwards entitled A Voyage Up the River Amazon which came into Wallace's hands resulted in his suggesting to his friend Bates that they set themselves up as professional collectors of Natural History specimens to supply the needs of institutions and gentlemen naturalists. The two young men, they were both in their early twenties, sailed for the mouth of the Amazon in April, 1848. In South America Wallace and Bates worked independently of each other with Wallace travelling and collecting samples in the Amazon basin for several years until, early 1852, ill health led him to decide to return home to England.

His activities as a collector of Natural History specimens, and his authorship of academic papers and of his two books that were fairly well received brought him a little bit of notice in the then somewhat fashionable Natural History circles of society and, during these times he became introduced to many interested persons including one Charles Darwin.

Wallace is considered to have been something of a convinced evolutionist but without seeing how such evolution might be driven.

In September 1855 a paper entitled On the Law which has regulated the Introduction of New Species by ALFRED R. WALLACE, F.R.G.S. (i.e. Fellow of the Royal Geographical Society) appeared in a scientifically inclined publication Known as the Annals and Magazine of Natural History.

In this paper Wallace sets out his "Law" which he claims to have discovered some ten years previously and which he has since then been subject to testing. This possible Law being that:-

This paper was read by Sir Charles Lyell who found its contents to suggest strongly that Species were not fixed creations of God, but were in fact naturally mutable.

Darwin's work in this area had been on-going for a long time. He had returned from his five years of voyaging and observation on the HMS Beagle in 1836 with a newly critical attitude to Biblical explanations of Creation and much personal observation of nature and of the operation of natural forces to consider.

Although trained as a clergyman Charles Darwin, in accordance with his passionate interest in Natural History, had sent home papers of considerable scientific merit to his influential friends in England during the course of his voyaging in HMS Beagle.
Some of these influential friends had made Darwin's discoveries quite widely known of amongst scientific circles in England and, unknown to himself, Darwin was gaining a reputation, back home, as an notable contributor to knowledge about several scientific areas.

This reputation was sufficient for Darwin's wealthy father to be persuaded to give Charles Darwin an allowance such as to allow the freedom to attempt to establish himself as a gentleman naturalist.

Some milestones in this unexpected new path followed by Charles Darwin include:-

On the return of the Beagle (October 1836) Charles Lyell invited Darwin to dinner and from then on they were close friends.
At this dinner on 29 October Charles Lyell introduced Darwin to the up-and-coming anatomist Richard Owen.

On 17 February 1837, Lyell used his presidential address at the Geographical Society to present Owen's findings to date on Darwin's fossils, noting particularly the unexpected implication that extinct species were related to current species in the same locality.
At the same meeting Darwin was elected to the Council of the Society. He had already been invited by FitzRoy to contribute a Journal based on his field notes as the natural history section of the captain's account of the recent Beagle voyage.
When FitzRoy's account was published in May 1839, Darwin's Journal and Remarks was a great success. Later that year it was published on its own, becoming the bestseller today known as The Voyage of the Beagle.

When HMS Beagle had called at Cape Town, on the southern coasts of Africa in 1836 on the return leg of its famous voyage, Captain Robert FitzRoy and the young naturalist Charles Darwin visited the famous English scientist John Herschel, (who was engaged in astronomical survey work there), on 4 June of that year.

Herschel had as recently as February, 1836, written to Charles Lyell concerning Lyell's book Principles of Geology - published in 1830, which had set out the idea of the extremely gradual formation of landscapes through natural processes.

In this letter Herschel apologised to Lyell for not previously acknowledging Lyell's making a presentation, to himself, of a copy of this book:-

Back in England Herschel's letter to Lyell was widely discussed in scientific circles and even appeared in an appendix to Charles Babbage's Ninth Bridgewater Treatise, published in 1837. An entry in Darwin's Notebook E dated 2 December 1838 reads - "Babbage 2d Edit. p. 226 - Herschel calls the appearance of new species the mystery of mysteries, & has grand passage upon the problem.! Hurrah - 'intermediate causes' ".
In the opening lines of The Origin of Species, Darwin writes that his intent is "to throw some light on the origin of species - that mystery of mysteries, as it has been called by one of our greatest philosophers."

During the last few months of the voyage of the Beagle, Darwin spent most of his time tidying up his extensive scientific notes with the aid of Syms Covington.
The animal notes were finished by the time the Cocos Keeling Islands, (in the South Pacific), were reached in April 1836, and the bird notes at Ascension Island, (in the South Atlantic), in July 1836.

By far the most important were the bird notes, for they contained the expansion of the brief account, written in the Galapagos in September 1835 of the three species of Mocking Birds (Thenca) found in the islands, into Darwin's realisation that these birds might provide the first example of island endemism, (or distinct specific type island by island), and hence of evidence that new species had been created.

The key, September 1835, section of these Ornithological Notes - in which specimen reference numbers appear - reads:-

These birds are closely allied in appearance to the Thenca of Chile (2169) or Callandra of la Plata (1216). In their habits I cannot point out a single difference - They are lively inquisitive, active run fast, frequent houses to pick the meat of the Tortoise, which is hung up, - sing tolerably well are said to build a simple open nest. - are very tame, a character in common with the other birds: I imagined however its note or cry was rather different from the Thenca of Chile? - Are very abundant, over the whole Island are chiefly tempted up into the high & damp parts, by the houses & cleared ground.

I have specimens from four of the larger Islands the two above enumerated, and (3349: female. Albermarle Isd.) & (3350: male: James Isd). - The specimens from Chatham & Albermarle Isd appear to be the same but the other two are different. In each Isld. each kind is exclusively found: habits of all are indistinguishable. When I recollect, the fact that the form of the body, shape of scales & general size, the Spaniards can at once pronounce, from which Island any Tortoise may have been brought. When I see these Islands in sight of each other, & [the word "but" deleted here] possessed of but a scanty stock of animals, tenanted by these birds, but slightly differing in structure & filling the same place in Nature, I must suspect they are only varieties.

The only fact of a similar kind of which I am aware, is the constant asserted difference - between the wolf-like Fox of East & West Falkland Islds.

- If there is the slightest foundation for these remarks the zoology of Archipelagoes - will be well worth examining for such facts [the word would inserted here] undermine the stability of Species.

The direction of Darwin's thoughts can perhaps be illustrated by this famous sketch:-

Charles Darwin's Tree of Life sketch from his Notebook B dating from 1837-8, (and deemed by editors of Darwin's papers to be concerned with his thoughts about the Transmutation of Species), shows his early theoretical insight of how a genus of related species might originate by divergence from a starting point (1).

An accompanying text annotation reads:-

Case must be that one generation then should be as many living as now. To do this & to have many species in same genus (as is) requires extinction.

Thus between A & B immense gap of relation. C & B the finest gradation, B & D rather greater distinction. Thus genera would be formed. - bearing relation (page 36 ends - page 37 begins) to ancient types with several extinct forms.

From Darwin's notebook B now stored in Cambridge University library


THE EVOLUTION OF HUMAN PHYSICAL ATTRACTIVENESS

AbstractEverywhere the issue has been examined, people make discriminations about others’ physical attractiveness. Can human standards of physical attractiveness be understood through the lens of evolutionary biology? In the past decade, this question has guided much theoretical and empirical work. In this paper, we (a) outline the basic adaptationist approach that has guided the bulk of this work, (b) describe evolutionary models of signaling that have been applied to understand human physical attractiveness, and (c) discuss and evaluate specific lines of empirical research attempting to address the selective history of human standards of physical attractiveness. We also discuss ways evolutionary scientists have attempted to understand variability in standards of attractiveness across cultures as well as the ways current literature speaks to body modification in modern Western cultures. Though much work has been done, many fundamental questions remain unanswered.


Microevolution and Macroevolution

Changes in gene frequency that occur within a population without producing a new species are called microevolution. As microevolution continues, a population may become so different that it is no longer able to reproduce with members of other populations. At that point, the population becomes a new species. As the new species continues to evolve, biologists might eventually consider it to be a new genus, order, family, or higher level of classification. Such evolution at the level of species or higher is called macroevolution.

Microevolution can occur very quickly indeed, it is probably always occurring. For example, in less than half a century after the discovery of antibiotics, many bacteria evolved resistance to them. Resistance to antibiotics evolves when antibiotics are used improperly, allowing the survival of a few bacteria with mutated genes that confer resistance. Natural selection then leads to the evolution of antibiotic-resistant strains. Pesticide-resistant insects and herbicide-resistant weeds are additional examples of rapid microevolution.

Macroevolution occurs over much longer periods and is seldom observed within the human life span. Occasionally, however, scientists do see evidence that new species have recently evolved. There are species of parasitic insects, for example, that are unable to reproduce except in domesticated plants that did not even exist a few centuries ago. The pace of evolution can be quite variable, with long periods in which there is little change being punctuated by relatively brief periods of tens of thousands of years in which most changes occur. This idea that the pace of evolution is not always slow and constant is referred to as punctuated equilibrium . It was first proposed by paleontologists Niles Eldredge and Stephen Jay Gould in 1979, and it is one of many examples of how scientists' views of evolution are continually changing.

Several possible mechanisms exist for rapid evolution. Chromosomal aberrations, such as breakages and rejoining of chromosomal parts, can introduce large changes in genes and the sequences that regulate them. This may lead to changes much larger than that brought about by simple point mutations.

Environmental catastrophes can set the stage for rapid evolution as well. It is thought that the extinction of the dinosaurs was triggered by a large comet impact. This rapid loss of the dominant fauna in many ecosystems opened up many new niches for mammals, which at the time were a small group of fairly unimportant creatures. The sudden appearance of many new opportunities led to rapid and widespread speciation, in a process called adaptive radiation .

Other areas of biology are also continually changing under the influence of evolution. For example, as Charles Darwin predicted in The Origin of Species, classification has become more than simply the grouping of organisms into species, genera, families, and so on based on how physically similar they are. Classification now aims to group species according to their evolutionary history. Thus two species that diverged recently from the same ancestor should be in the same genus, whereas species that shared a more distant common ancestor might be in different genera or higher taxonomic levels.

Until the 1980s, evolutionary history, or phylogeny, of organisms could only be inferred from anatomical similarities. Since that time, however, it has been possible to determine phylogeny from comparisons of molecules. Often this molecular phylogeny agrees with the phylogeny based on anatomy. For example, about 99 percent of the sequence of bases in the deoxyribonucleic acid (DNA) of chimpanzees and humans is identical. This finding confirms the conclusion from anatomy that chimpanzees and humans evolved from the same ancestor only a few million years ago. Such agreement between anatomical and molecular phylogeny would not be expected if each species were a totally different creation unrelated to other species, but it makes sense in light of evolution. It is one of many examples of the famous saying by the geneticist Theodosius Dobzhansky (1900�): "Nothing in biology makes sense except in light of evolution."