Frequently Asked Questions about Evolutionary Biology

Questions asked at the UW Madison, Darwin Day Outreach Symposium, Evidence for Evolution: Updating Darwin’s Case, February 11th 2006

Schedule for February 11, 2006 DARWIN DAY Symposium (click here)

TABLE OF CONTENTS (click on title)

Origin of Life

Religion and Evolution

Human Evolution

Evolution and Complexity

Speciation

Extinctions

Teaching and Philosophical  Issues

Miscellaneous

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Posting of Darwin Day Podcasts

For copyright reasons we discovered that we can only disseminate the 2006 talks to UW personnel to help them prepare for teaching functions, with two exceptions. However, individuals can approach individual speakers who may be able to share materials from their presentations. Please visit faculty page to find contact information about a particular speaker.

David Baum's Introduction podcast

http://evolution.wisc.edu/podcast/Evidence_Evolution.mp4

Origin of Life

I don’t buy the single origin of life….. 

The single origin of life is supported by the large number of traits that are shared by ALL currently known cellular life, including:

• A nucleic acid based information system (RNA and/or DNA) with the same nitrogenous bases (of the almost infinite number of possible nitrogenous bases)

• The use of the same 20 amino acids (of the almost infinite number of possible amino acids)

• The use of only left-handed amino acids (when there is no a priori reason why some origins of life might not have used right-handed amino acids).

• Almost identical genetic codes (despite the fact that there are a huge number of possible genetic codes)

• Ribosomes (complex structures used by all cells to make proteins)

• A similar energy system involving ATP

• Some shared metabolic pathways (e.g., glycolysis – the basis of respiration)

• A large number of shared proteins and the genes that encode them (e.g., ATPase, aminoacyl tRNA synthetase, etc.)

However, it is possible that there were additional origins of life on earth but that they either went extinct or (less likely) they are alive but have yet to be discovered.

…was there reticulate evolution in the beginning of life? 

Yes, and there still is some.  Reticulate evolution occurs when parts or all of an organism’s genome integrates into the genome of a second organism.  Eukaryotic cells are likely the result of reticulate evolution, as there is evidence that mitochondrial DNA is prokaryotic (bacterial) in origin.  Reticulate evolution does not argue against a single origin for life, though it does open the possibility that there were multiple origins with subsequent homogenization by lateral transfer.

If all living species trace to a single common ancestor, where did that ancestor come from? and

Can you provide a brief discussion of current theories of the evolution of RNA/DNA in the precellular world?

It is believed that life emerged when complexes of organic molecules in particular geological settings became organized into self-replicating consortia (that may or may not have already acquired a cell membrane).  The problem of the origin of life, or as I like to view it, the transition from geochemistry to biochemistry is a real challenge.  However, a number of circumstantial lines of evidence have been converging on a convincing, if speculative, scenario.  It is known that organic molecules accumulate spontaneously in sea-water that contains carbon dioxide, other dissolved gases, and minerals.  These would be most stable deep in the ocean where they would not be broken down by light, and would tend to become concentrated on mineral surfaces that were appropriately charged.  In such settings, theory allows that assemblages of organic molecules would begin using energy (obtained from inorganic chemical reactions) to build yet more organic matter.  Eventually some collections of organic molecules are proposed to have acquired the ability to synthesize of a similar set of molecules.  At this point this consortium became self-replicating and would be subject to natural selection for improved stability and more accurate replication. 

              There is good circumstantial evidence that these early precellular life forms used RNA and perhaps other nucleic acids to catalyze (promote) specific chemical reactions, but that gradually they enslaved proteins to do much to catalysis.  Sometime thereafter, DNA, which is more stable than RNA (but not good at catalysis), became the long-term storage medium for the genetic information.

              You might find this Scientific American article interesting: http://www.americanscientist.org/template/AssetDetail/assetid/48545

Religion and Evolution

Creationists claim that there are many scientists who doubt Darwin’s theory.  Do any of the panelists know of any scholar who fits that description? 

There are indeed a few anti-evolutionary biologists – but they represent a tiny number compared to the overwhelming support for evolutionary theory.

How come there are still anti-evolutionists if it is such an open-and-shut case?  

Good question!  I think this is largely due to the fact that people have a hard time accepting the existential implications of viewing humans as products of nature just like other living species.  People want to not believe evolution – and this is pretty easy if you don’t take the trouble to learn about the scientific evidence.  In addition, some people accept the Bible as the infallible word of God, and thus, believe in Genesis as literal.

Can you reconcile religion and evolution? 

Yes.  Many evolutionary biologists are religious.   Likewise a majority of major religious groups (Catholics, Anglicans, Conservative Jews, Mormons) accept much or all of modern evolutionary biology. It may not be possible to be a biblical literalist and accept evolution, but such people represent only a small segment of the religious world.

Human Evolution

If humans evolved from chimps, why are they still around? 

Humans did not evolve from chimps.  The common ancestor of a human and a chimpanzee was neither a human nor a chimpanzee.  It may, or may not, have resembled a chimp more than a human – but it most certainly was not a living chimpanzee!

Are we more closely related to orangutans or chimpanzees? 

Chimpanzees. This relationship is based on biochemical and molecular evidence.

See also http://news.bbc.co.uk/1/hi/sci/tech/3042781.stm

                 http://www.genome.gov/15515096

                M.C. King and A.C. Wilson. April 11, 1975. Science pg. 107.

Does intelligence confer survival benefits? 

In humans it appears to have done so – though it is unclear which aspects of intelligence were acted-upon by natural selection:  problem-solving; tool-use; language; social intelligence, or….?

How did human intelligence arise “so suddenly”? 

We do not know how many genes had to change to go from a level of intelligence typical of other living great apes to that found in humans.  Thus, it is very difficult to assess whether the rise of human intelligence was especially fast.  There is reason to think that selection for brains that could learn complex tasks quickly could be very strong.  Thus the real question is how come there was sufficient genetic variation for selection to act upon.  But, again, the lack of genetic data make this hard to answer.

Evolution and Complexity

How do you explain evolution in light of the thermodynamic principle that entropy increases in the Universe? 

The second thermodynamic principle assumes a closed system in which entropy will accumulate. The sun and, to a lesser extent, radiation in the earth’s core, are sources of energy that flow into and through the biosphere.  The biosphere is, thus, not a closed system so there is no reason why entropy cannot decrease.  Life is just like an air-conditioner, which uses energy to decrease entropy.

How does complexity relate to the age of a lineage? 

Life necessarily started simple, and the average complexity of life has tended to increase over time.  However, because all species alive today, whether simple or complex, have been evolving for the same amount of time, there is no relationship between age of a lineage and degree of complexity.  For example parasites are often simpler than their more complex ancestors because of their way of life.

In Carol Lee’s talk, the salt-water organisms that invaded freshwater lost the ability to live in salt-water.  With pesticides, if an insect becomes resistant to pesticide A and we then use pesticide B, does the insect then become vulnerable again to pesticide A? 

An important evolutionary principle is that it impossible to remain good at everything: if a mutation arises to suit you better to your current environment, it will tend to increase in frequency even if that same change makes you less able to live in some other possible environment.  This explains the fact that adaptation to freshwater comes at the cost of an ability to survive in salt-water.  The situation with pesticides is closely related but somewhat different.  In this case the important issue is not the use of pesticide B but the cessation of use of pesticide A.  In almost all cases studied, pesticide resistance has a “cost,” such that resistant individuals are less fit in the absence of pesticide.  As a result, stopping the use of A will tend to cause the frequency of susceptible individuals to increase.  It is possible that the application of a different pesticide, B, will speed-up this process (e.g., by stressing individuals so that the cost of resistance to B will be greater) or will slow it down (e.g., if B and A are chemically related such that the same resistance trait helps with both pesticides). 

It may be of interest that cyclically applying or withholding anti-viral agents is now a common strategy for treating AIDS – and that is was guided by evolutionary considerations.

How might the concept of evolution apply to non-carbon-based biological forms? 

Natural selection will occur in any self-replicating entity.  Whether you will see species and speciation might depend on the ecology and reproductive biology of these replicators (e.g., Do they show ecological specialization?  Does sexual reproduction arise?)

Is there a connection between evolution of life and evolution of the universe?

Not really. Darwin and modern evolutionary biologists focus on the evolution of life rather than the evolution of the universe, which is left to astrophysics. 

What do you think of John McFadden’s theory of quantum evolution? 

Quantum evolution is the hypothesis that genetic mutation is adaptive, or directed through quantum effects.  McFadden provides a scientific hypothesis to explain the phenomenon of “directed mutations”, equated with adaptive mutation. “The mechanism proposed by quantum evolution is to imagine that the configuration of DNA in a cell is held in a quantum superposition of states, and that "mutations" occur as a result of a collapse of the superposition into the "best" configuration for the cell.” (http://en.wikipedia.org/wiki/Quantum_evolution_%28alternative%29) However, most biologists doubt the experiments that purported to show directed mutations, in which case there is no need to invoke quantum evolution.  This is a good thing because I for one find it hard to imagine that a DNA molecule can simultaneously have two different bases at a single position and can “choose” between them depending on its environmental “needs”! 

See also http://en.wikipedia.org/wiki/Quantum_evolution,        http://www.genetics.org/cgi/content/abstract/131/4/783     

Why are mules sterile and are there evolutionary reasons for mules (and animals like mules) to exist in nature? 

Mules arise by hybridization between a horse and an ass/donkey.  The two parents represent lineages that have been isolated genetically for a very long time and have consequently come to be very different from each other.  As a result, the hybrid has chromosomes in its cells that do not pair-up in meiosis, and this means that it cannot make sperm or eggs properly.  The notion of “reason to exist” is alien to a biologist – what does it mean to you?

How does chromosome number change and how are chromosomes altered?  Chromosomes change number is several ways, including: (1) chromosomes can fuse, thereby reducing the number; (2) chromosomes can break into two, thereby increase the number, (3) they can double in number (euploidy) by a failure of meiosis, (4) they can be lost (but usually only after a euploid doubling because otherwise essential genes are likelyto be lost).

If genes for structures that are found in insects, amphibians, reptiles, and mammals are consistent, why do these animals have such different numbers of chromosomes? 

First off it is important to be clear that chromosome number has little relationship to gene content.  Genes often move between chromosomes without any major change in their function and chromosomes often fuse and split (see above).  The reason that an overlapping set of genes can yield such different organisms involves the following: (1) the number of genes of a given type may vary between species; (2) the genes can be slightly different in mode of action; (3) the genes can be turned on and off in different patterns; (4) some basically new genes can arise (e.g., when pieces of two ancestral genes get fused together).

In HIV, if reverse transcriptase cobbles together strands of DNA without much accuracy, why doesn’t the same thing happen in all cells?  What is so special about HIV? 

Only RNA viruses routinely use reverse transcriptase to replicate DNA.  We use a much more accurate enzyme called DNA polymerase.

What evidence is there that genomes were created by adding pieces of DNA from other organisms?  For example, have viruses introduced new pieces of DNA into organisms? 

There is abundant evidence of the transfer of DNA between species, called horizontal transmission.  Nonetheless, the vast majority of a genome is transmitted vertically, i.e., from parents to offspring.

Did ancestral populations who domesticated plants understand the principles underlying domestication?

In general, no.  That is to say the people involved seemed primarily to have chosen to propagate those crops that provided the best and most reliable yields.  However, there is some evidence that the Hopi Indians used hybrid breeding strategies for corn, similar to those used by modern seed companies, some 8000 years ago (http://www.unlv.edu/faculty/landau/maize.htm)

Why is there a high mutation rate in reverse transcriptase?

There are no correction mechanisms for this enzyme, as there are for DNA polymerase and DNA replication. By way of general interest, reverse transcriptase was discovered by UW Scientist and Nobel laureate Howard Temin.

Is it beneficial for HIV to have a high mutation rate?

There is strong selection for the virus to escape detection by the host immune system.  The region of the virus that is detected by the immune system has the highest mutation rate in the viral particle. 

What is the relation between virulence of a virus and its probability of transmission?  Generally, the higher the transmission rate, the higher the virulence of the virus and hence the more likely it is that the host will die quickly.  This follows because in viruses with low transmission rates, the host must not die too quickly or the virus has a low chance of finding another host.  If transmission rates are high, then selection for more competitive viral strains within a host can lead to increasing virulence.

Discuss whale phylogeny

See

http://www.indiana.edu/~ensiweb/lessons/wh.ph.os.html

http://www.indiana.edu/~ensiweb/lessons/wh.il.in.html

http://www.ucmp.berkeley.edu/mammal/cetacea/cetacean.html

http://www.talkorigins.org/features/whales/

http://www.nhm.org/research/mammals/phylogen.htm        

What explains persistence of vestigial structures?

Vestigial structures are often those that are present but have no current function.  In almost all cases, related species have the structure in a functional form suggesting that the structure has been retained from an ancestor that had and used the structure.  During development an organism will form the same structures regardless of whether they will be used.  However, those individuals that experience mutations that reduce the size of an unused structure will suffer no detriment and may gain an advantage due to avoiding the energetic cost of making a useless structure.  Thus, over time selection will favor reductions in the vestigial structure.  However, this will take time because it may be rare to have a mutation that reduces the organ in question and does not have other detrimental consequences.  Also, as the organ gets smaller the potential energetic benefit to a further reduction is reduced.  So, it may take a very long time for a vestigial organ to be fully lost.  Examples of vestigial structures in humans include ear muscles, pointy canine teeth, possibly goose bumps (when we were hairier, these functioned to raise hair which served as a social signal and also increased air held between hairs to insulate us).     

Can you recommend a video that presents the overwhelming evidence for evolution?

I have heard that the best option is the PBS series “Evolution” (http://www.pbs.org/wgbh/evolution/).  I only saw a few clips, but these were fine.

Speciation

Is there evidence for macroevolution and the origin of species?

Yes.  Scientists have created reproductive barriers between populations of fruit flies and plants in one to several years.  Selection for reproductive barriers between populations is probably the most rapid way to achieve speciation. 

Also see examples

http://www.talkorigins.org/faqs/faq-speciation.html#part5   

Can the fresh water copepod breed with the salt water copepod? 

This is what Carol says: “They might, but they can no longer survive in each other's environment unless you select on them for tolerance. So they are different "evolutionary species" on separate evolutionary trajectories.”

In speciation events, does one observe intermediate forms?

Yes, one can.

Extinctions

Can you please place in historical context the extinctions during the “Holocene Holocaust” relative to other mass extinction events? 

Some information can be found at: http://www.pbs.org/wgbh/evolution/extinction/massext/index.html

Here is Dana Geary’s response:

Absolute numbers or percentage extinct is tricky because we are so ignorant about how many species are alive today.  However, most estimates of the current extinction trajectory (your "Holocene Holocaust") put it in the ballpark of four of the five major mass extinctions.  Extinctions in the Late Ordovician, Late Devonian, end-Triassic, and end-Cretaceous all resulted in the loss of 11-14% of families, with estimated species extinction rates ranging from 50-80%.  If we continue on our current trajectory, most people think we will see this magnitude of extinction in the next few decades.  The most major mass extinction ever was in the Late Permian, when 50% of all families died (80-95% of species).  We are not to that level yet.

Important to note is that the major mass extinctions, particularly the Late Permian, but also the end-Cretaceous, were not caused by a single factor but by a concatenation of catastrophes (e.g. climate change, impacts, volcanism, etc.).  Today's ecosystems are also faced with a multitude of problems (pollution, habitat loss, invasive species, climate change) whose combined effects are very serious indeed. see: http://cbc.amnh.org/symposia/archives/expandingthearc/speakers/transcripts/jackson-text.pdf

Were “indigenous” people (e.g., Maoris, Polynesians) more responsible for the extirpation of native species than Europeans? 

There is clear evidence that many large animals were driven extinct by indigenous human populations.  However, the effect of indigenous peoples was primarily on large, terrestrial animals.  In contrast, technologically advanced humans have the capacity to cause the extinction of a much wider variety of animals and plants.

Opponents of evolution are always talking about gaps in the fossil record.  What are they referring to?

When we have a group of living organisms that is differentiated from its nearest relatives by a whole suite of traits, evolution predicts that there were formally ancestral organisms that had some but not all of these traits.  These are called “transitional fossils.”  In some cases we lack fossils that document all the steps in the evolution of the suite to traits found in a living group.  Such missing steps are “gaps.”  Over time the number of such gaps has been reduced greatly. For example, many intermediates have been discovered, such as vertebrates with some but not all the features of the land-dwelling tetrapods, dinosaurs with some but not all the features of birds, land plants with some but not all the features of vascular plants.  Nonetheless, there are still some cases where we would very much like to find additional transitional fossils: for example in the origin of bilaterally symmetrical animals and the origin of flowering plants.

See also http://www.talkorigins.org/faqs/faq-transitional/part1a.html#gaps   

Teaching and Philosophical Issues

What efforts are evolutionists making to avert the teaching of Intelligent Design as science in schools?

• Terese Berceau and Spencer Black have introduced a bill in the Wisconsin

Legislature to ban teaching of ID as science. (http://www.ncseweb.org/resources/news/2006/WI/736_anticreationism_legislation_in_2_8_2006.asp)

• The National Center for Science Education (http://ncseweb.org/) defends the teaching of evolution in our schools.

• Darwin Day is also another effort by scientists to reach out to the public so individuals can understand the substance of evolution.

•American Astronomical Society

http://www.aas.org/governance/council/resolutions.html          

• American Institute of Biological Sciences

http://www.aibs.org/public-policy/teaching_evolution.html

• Botanical Society of America

http://www.botany.org/newsite/announcements/evolution.php

• Federation of American Societies for Experimental Biology

http://opa.faseb.org/pages/PolicyIssues/evolutionresources.htm

•National Academy of Sciences

http://fermat.nap.edu/html/evolution98/        

•Society for Neuroscience

http://opa.faseb.org/pages/PolicyIssues/evolutionresources.htm

•Joint Letter of Scientists and Teachers

http://www.agiweb.org/gap/legis107/evolutionletter.html          

• National Association of Biology Teachers statement http://www.nabt.org/sub/position_statements/evolution.asp  

• In addition, over 400 churches across the U.S. participated in Darwin Sunday, February 12, 2006 and over 10,000 clergy have signed a letter stating that religion is not incompatible with evolution (see Clergy Letter Project http://www.uwosh.edu/colleges/cols/clergy_project.htm)

See also http://www.pandasthumb.org/

Google on “evolution and teaching”

Isn't it important to teach the controversy between ID and evolution?

Yes, but not in a science class and not in a way that takes time away from teaching evolutionary biology.  It's clear that many people do not understand evolution, and that may be linked with the too little time it is given in the classroom.   We need to teach the distinction between science as rational inquiry and religion as faith in history of science or philosophy classes, so that people appreciate the difference between science and religion and can make informed choices.

If biodiversity arose spontaneously, why worry about human impacts on biodiversity?  Won't it evolve again?

Remember, it takes millions of years for the oceans to be replenished with diversity after the end of the Permian extinction.  From a practical viewpoint, humans may go extinct as loss of biodiversity impacts on our existence. From an aesthetic viewpoint, loss of species we revere (polar bears, birds, frogs, plants) impacts our human experience profoundly.  From an ethical/spiritual viewpoint, many people hold that we are the stewards of the Earth, and have a moral obligation to pass on resources to future generations.

See also http://www.actionbioscience.org/biodiversity/wilson.html

http://cbc.amnh.org/symposia/archives/expandingthearc/speakers/transcripts/jackson-text.pdf    

Why use the term "believe in evolution?"

“Believe” construes a leap of faith. It’s better to substitute "accept."

How does Evolutionary Theory inform ethics?

It does not.  Evolution is the study of biology (life), whereas Ethics studies the moral values underlying a culture. Although evolutionary theory has been used to support Social Darwinism, there is no implicit ethical agenda inherent in the theory.  It is worth noting that ethics and morality cannot simply be seen as being the products of religious belief either.  This is laid out in an excellent and accessible book, What Ever Happened to Good and Evil? by UW-Madison philosophy professor, Russ Shafer-Landau.

What is Brassica?

Brassica is the genus that includes cabbages, kale, and mustards.  Paul Williams has selected several species for rapid cycling (from seed to seed in about 30 days) for use in classrooms to teach biology in an academic year.

What are FAST plants?

FAST plants are rapid cycling Brassica species that can be adapted to use in a  classroom for teaching purposes.  Moreover, because they go from seed to seed in about 30 days, students can do repeat experiments on them.

http://www.fastplants.org/     

Should teachers still teach one gene-one enzyme hypothesis and the Central Dogma?

The one-gene-one-enzyme hypothesis does not hold: many enzymes are the product of multiple genes and many genes encode for multiple proteins. Also, there are RNA gene products (e.g., microRNA) that never get transcribed into proteins. The central dogma, while fraught with exceptions (e.g., reverse transcriptase) may nonetheless be an important principle to introduce to our students.

Is there a limit to scientific inquiry at which point we must turn to religion?  How far back to our origins can science take us?

Logically, there must be a point beyond which we cannot obtain scientific data. 

For example, under the Big Bang hypothesis we cannot make inferences as to the state of the universe before the Big Bang.  Nonetheless, just because science does not allow us to collect data (for now anyway), that does not mean one should automatically resort to non-scientific modes of reasoning (e.g., the intervention of a supernatural being) – though in the absence of data it does not matter much if one does resort to supernatural or religious modes of understanding.

Miscellaneous

Link to pictures of plate tectonics

              http://www.ucmp.berkeley.edu/geology/tectonics.html    

Who was Joseph Hooker?

Joseph Hooker was a botanical confidant of Darwin.  He specialized in plants of the Southern Hemisphere.  He is noted for having downplayed dispersal as a mechanism explaining the present distribution of plants, preferring  mechanisms such as continental bridges or geological events to explain plant distributions.

What is your opinion of The Ancestor’s Tale? Were you pleased with it?  

I was very pleased to see a popular book on the tree of life and a renewed emphasis on the principle of common ancestry (I think there has been disproportionate attention paid to natural selection).  I worry that it might bore some readers – but it will be helpful for teaching.

Darwin always gets the “blame,”  what about Robert Chambers’ “Vestiges…”?

Vestiges did offer an evolutionary (transmutationist) worldview, but failed to develop a compelling theory and did not wield scientific data anywhere nearly as effectively as Darwin.  Still, Darwin felt that Vestiges helped “soften-up” the public to allow them to accept his views.   

Why were the members of the anthropology department not represented here?….Are the anthropology instructors here at UW crypto-creationists? 

Not that I know of!  Two members of the Anthropology department have joined the evolution faculty group (John Hawks and Karen Strier) and others conduct research on humans (e.g., Karen Steudel, Bret Payseur).

John Hawks http://www.news.wisc.edu/12160.html

Karen Strier http://www.zoology.wisc.edu/faculty/Stri/Stri.html

Karen Steudel http://www.zoology.wisc.edu/faculty/Ste/Ste.html

Bret Payseur http://www.genetics.wisc.edu/faculty/profile.php?id=471

Is there government funding for studying evolution? 

Yes – primarily through the National Science Foundation, but also through the National Institutes of Health (NIH) and occasionally through National Aeronautics Space Administration (NASA), Department of Energy (DOE), and the United States Department of Agriculture (USDA).

What are the chances of the speakers turning their talks into articles and generating a published symposium volume? 

Slim.  However, there is talk of a book targeted at teachers on evidence for evolution that might be put out jointly by three scholarly societies: The Society for the Study of Evolution, The Society of Systematic Biologists, and the American Society of Naturalists.  If that happens it is likely that UW faculty will contribute.