(9:55pm) Greg: Alright you have the choice to only work on or teach one scientific finding for the next twenty years. What would it be and why?

Mrs Peebles: Genetics at the cellular and genome level - how fascinating it is to better understand the workings of our bodies and those of all living things!

Professor Williamson: Evolutionary theory at the synthesis level---it permeates all of life and human societal systems....

Dr Hewlett: How frightening! OK...I'll try. For me as a scientist/philosopher it would be to follow the new field of systems biology to see where the philosophical foundations of our field will be at the end of that period. I have the sense that things will be very different from what we have seen for most of my career.

Dr. Miller: Oh, that's easy. I would work on RNA interference. It's the newest, hottest, and most exciting discovery about the ways in which cells use and process genetic information -- and, of course, it has profound evolutionary implications. (And I would consider myself very luck to be able to carry out 20 more years of scientific work!)

(9:33pm) Greg: You are all scientists - do you see any validity in claims made by creationists about dinosaurs and humans roaming the earth together or that the earth is younger than what traditional scientific thought suggests?

Dr Miller: Nope. There isn't a shred of evidence (except, maybe, for Fred Flintstone) that humans and dinos coexisted, and those people who construct museums to tell people otherwise should, quite frankly, be ashamed of themselves.

The age of the earth is a geological question, and I know enough geologists to know that they couldn't care less about what we biologists think. If any geologist had genuine scientific evidence that the current picture of earth history were fundamentally wrong, they wouldn't be shy about publishing it, believe me - it would make their career. And, as you know, that hasn't happened. No, there is no credible evidence of a young earth.

Dr Hewlett: Dr. Peters took a "pilgrimage" of sorts to that river bed in Texas where footprints of men and dinosaurs are said to be found together. Hmmm? I wonder what he thinks? Never mind...I think I know. There's really no credible evidence for this. On the other hand, so what if there were? What would that do? It would merely suggest that some sort of dinosaurs remained in some pocket of our planet and overlapped with our human ancestors. I've never understood why this would present any problem for biological evolution. Like any other scientific finding, it would just mean that we would figure out what it actually says and how it fits into our naturalistic understanding of our biosphere.

Dr Peters: It's rather widely accepted that dinosaurs disappeared about 60 million or more years ago, long before our humanoid ancestors began to walk upright on the African savannah. Neverthteless, I find interesting the fact that prehistoric animals such as mastedons were contemporary with Native Americans; and they went extinct only a few thousand years ago. I kinda like the Paluxy River bed in Texas. Here in lime stone one can discern what looks like human footprints in proximity to sauropod footprints. Now, more than one interpration is given of these footprints, to be sure. Yet, one might surmise: if the climate north of Texas (Utah, Montana) became uninhabitalbe due to the ice age, perhaps large creatures migrated south to Texas in order to collect profits from oil revenues. Perhaps some survived long enough to walk with humans.

Even if this scenario becomes credible, it in no way supports the creationist denial of speciation or an old earth. It only would claim that a few animals from the dinosaur period survived longer than is generally accepted.

Yes, this is controversial. I also find it an enjoyable topic for speculation.

Professor Williamson: No--not in the realm of scientific understanding. These claims are always paired with incredible mental gymnastics that attempt to incorporate known evidence to contradict the current scientific understanding. At this point with the multitudes of plain, incontrovertible evidence their counter claims would require extraordinary evidence....

Mrs Peebles: If there was any such evidence, the ID and creationists groups would have publicized it to the hilt! Of course, the evidence doesn't exist, and since we rely on scientific proof, we must not give validity to such speculation. If this unlikely evidence was found, then the scientists would duly analyze it and integrate it into the body of knowledge.

(9:17pm) Greg: Much controversy has been made about teaching creationism along side evolution - Edwards vs Aguillard, Kitzmiller et al vs Dover, etc.- can you please tell our viewers the importance of these cases? Has there been on court case that has been pivotal in evolution education? What are the current disputes being considered by circuit courts today?

Mrs Peebles:All of the court cases have been pivotal in defining what should and should not be taught in science class. Each has defined a little better the parameters, and the Kitzmiller et al vs Dover really made clear that the intelligent design movement of today is the creationism movement of yesterday. There is a basic misunderstanding in the public eye today. They think "Intelligent Design" is the middle ground in the controversy, and merely represents those who think that God had a role in starting life on earth. That is a misrepresentation. The ID movement seeks to discredit the scientific understanding of evolution, and create a disequilibrium in students' mind which will cause them to reject scientific evolution. The Discovery Institute has partnered with organizations in many states to introduce legislation to allow discussion of "different theories" or to allow "critical thinking", which is what science classes are actually already teaching. It is telling that this legislation and these movements have NOT come from science teachers or research scientists. In my own state, the scientists and science teachers fought hard against the legislation. We do not need politicians to tell us how to teach! The national science education standards and the state standards do a good job of defining what should be taught, and there is a unified assault against them, as witnessed in Texas. The citizens of this country should be vigilant in watching what is legislated and what is taught in their own area. Apathy will lead to pseudo-science being taught in the classrooms of America.

Dr Hewlett: The issue is that the proponents wish for creationism or intelligent design to be taught in the science classroom as scientific alternative explanations against biological evolution. The problem, as revealed in these court cases, is that both creationism and intelligent design are ultimately forms of theological explanation. As a result, they do not belong in the science classroom, but rather in the religion or philosophy classroom. In order to understand this statement, you only need to ask what the basis of explanation is for creationism and intelligent design. In both cases, a theological commitment is required. I'll let Dr. Peters expound on this point.

Dr Miller: As far as I know, there are no cases being considered today in the Federal Circuit Court system on this issue. The last important court case was Kitzmiller v. Dover, which will be reviewed Tuesday night (2/10) at 8 PM on PBS ("Judgment Day"). One of the interesting thing about this and other court cases is that the side promoting evolution has won each and every one of the cases -- and they've prevailed in front of both liberal and conservative justices. The reason is that in each of these cases one of the first things to come out is the religious motivation of the creationist (or "intelligent design") side. In the Kitzmiller case, for example, the "intelligent design" textbook purchased for use by schoolkids started its publishing life as a "creation science" book. When the US Supreme Court (in 1987) ruled that creationism was inherently religious, they too the text and simply re-named the "Creator" a "designer." That move, which was clearly made to conceal the religious nature of the text, impressed the judge (a Republican appointed by George W. Bush), and led to his decision that "intelligent design" simply was not science - and that it could not disentangle itself from its religious roots. The biggest current battle in the US is now taking place in Texas, where creationist members of the State Board of Education are seeking to undermine evolution by rewording the state's science education standards. So far they have fallen a vote or two short of their goals, but they keep trying.

Professor Williamson:Each federal case has been pivitol in evolution education--The law and human culture can be seen to have a trajectory or path. Each of the significant cases represent an answer from society and the legal system to strategies developed by those consider science and evolution in particular such a threat to their way of thinking that they seek legal remedies. So far the courts are firmly on the side of science but we have to change how society understands and supports science and evolution before any long term solution is apparent. To me the ridiculous aspect of this controversy is the incredible amount of wasted time and energy of our teachers and scientists as they have to enter this struggle....

(9:05pm) Greg: In Morphed: From Dinosaur To Turkey, it touches upon the intermediate gliding stage in some species. Can you please explain why there may be controversy, if any, related to the origins of flight in species?

Dr Miller: Much of the controversy stems from the incorrect assumption that all of the organs and structures associated with flight, such as the feathers, limbs, flight muscles, and hollow bones of birds, must be assembled at once. The sheer improbability of that has led many to argue that flight couldn't have been a product of evolution by natural selection. As the current show (on NGEO) points out, feathers, which are really modified scales, appeared first in dinosaurs that clearly were not capable of flight. The capacity for flight came later, and the beauty of the fossil record is that many of the intermediates in this transformation have been discovered and analyzed.

(8:53pm) Greg: Since we announced that we were going to be doing this discussion, many comments have talked about "Micro-Evolution" versus "Macro-Evolution". Now for some of viewers that may not understand these concepts, can you please discuss why there is a debate going on between these two interpretations.

Dr Peters: This distinction is scientific, but it has a religious pay off for creationist Christians who are also laboratory researchers.

Macroevolution refers to speciation, where over time one species gives way to a subsequent species. Creationists deny that macroevolution has ever occurred. The species we observe today are fixed, and have been fixed since the dawn of creation.

Microevolution refers to genomic changes and the evolution of heritable traits within a species. Creationist researchers rely upon microevolution, of course; because they can watch it under their microscopes. Macroeolution takes such a long time that it is not directly observable, even if the fossil record and other evidence supports it.

Creationists do not deny all evolution, only macroevolution.

Dr Hewlett: The critics of the evolutionary model believe that microevolution deals only with mutational changes within a species (creationists call these "kinds"), whereas macroevolution requires changes that convert one species (or "kind") into another. Our scientific understanding of these two terms is that small, sometimes gradual, changes in the informational content of an organism (so-called microevolution) ultimately lead to variants that, over geological time, can result in speciation (macroevolution). This does not mean that one species "suddenly" becomes another, but rather that a common ancestor might lead to divergent pathways, resulting in related but different species.

Dr Miller: I will be frank about this. I think that very often those who make a distinction between "microevolution" and "macroevolution" are using a debating strategy to avoid the wealth of evidence for evolution. The strategy is label anything that can be directly demonstrated in the lab or in the field as "micro." Then, you pretend that "macroevolution," which is required to explain the profound changes we see in the fossil record, has never been observed. When I see this micro-macro distinction invoked, I usually ask the individual to explain to me exactly what the boundary is. What percentage of the genome must change? How large a change in morphology would count as "macro?" 2% 5% 10%. No one ever has given me an answer, and I think I know why.

Once a definite value is given for a threshold of "macro" change, some diabolical scientist (I mean that ironically) will go into the lab or field and demonstrate it. It's very much in the strategy of evolution-deniers to pretend that all evidence amounts to "micro," and thereby find a way to deny that there is any evidence for evolution that matters.

The fact of the matter, however, is that we have excellent examples of evolutionary mechanisms producing new biochemical pathways, new genes, and new capabilities that separate species and allow organisms to survive under new environmental conditions. To call all of these "micro" is to distort the term beyond all meaning. Macroevolution is really nothing more than the sum of well-understood genetic processes that divide species and produce evolutionary novelty.

(8:46pm) Greg: What is the future of teaching evolution? Is it teaching human genome mapping? Are schools funded enough to properly educate students in these areas?

Mrs Peebles:Evolution should not be taught only as a separate "unit" in science. It can't be taught in isolation because it is the commonality in biology - the uniting idea that makes it all make sense. You have to teach it integrated into everything in biology, and of course you still have to teach the specifics. Modern findings and developments in genomics are fascinating and underscore the truth of evolution. Education funding is always an issue, and there is never enough, but I don't think there is enough funding of basic scientific research either! We have thousands and thousands of wonderful biology teachers in this country and most of them do the right thing by our students no matter what the funding is. The scientific community has come together and supported science education in a terrific way in recent years and I hope that continues.

Dr Miller:I think that the future of "teaching evolution" is neither more nor less that the teaching of biology. As biology rapidly becomes a more unified science, it becomes very clear that evolution is the glue that ties it all together. One cannot investigate the human genome without running into the marks of evolution on each and every chromosomes. One cannot study the development of the body's organs and systems without being struck by the way in which our own body is a modification of the basic body plan of all vertebrates -- we possess, in a striking way, modified fish skeletons, and the nature of those modifications defines the differences between today's fish and the mammals that emerged from common ancestors hundreds of millions of years ago.

I don't think that schools are supported or funded well enough to teach science in general, and that increasing support for science education is vital to our survival as a nation. I would like to see science education given a much, much higher priority. To some extent, exactly this happened in the early 1960s as a reaction to the Soviet Sputnik successes, and scientists of my generation were the beneficiaries of that emphasis. I'd like to see us do it again!

Dr Hewlett:I believe that evolution will remain one of the central features of biological thinking for the foreseeable future. This means that as biology changes in some of the ways I've discussed, from considering only the parts to a more holistic view, it will still be that descent with modification from a common ancestor will be the best explanation for how we scientifically perceive the biological world around us. A more important question, as Bruce Alberts (editor-in-chief of Science) pointed out recently, we need to move science education into a mode that teaches the process of science, rather than just the collection of facts. This will require a deep rethinking of our process, and likely substantial funding to facilitate this change.

Professor Williamson:Neils Bohr said it best: Prediction is very difficult, especially if it's about the future.

But that won't stop me from a bit of discussion...

Evolution by its very nature is perhaps the hardest topic to teach--and not just because of the societal controversies. For most of biology education we have a series of well-thought out inquiry based laboratories that let the students experience some aspect of the doing of biology. As generally, taught evolution has been a bit different. Often the instruction is film, or lecture based with activities such as simulations rather than labs--for many evolution instruction can quickly devolve into a discussion about evolution instead of providing the student with strong evidence that they havegenerated themselves. Today's students have a pretty good deficit in understanding organisms in general and this just makes the instruction that much more challenging. My own class features quite a bit on quantifying actual population variation, artificial selection, microbial evolution and in recent years more and more molecular analysis, and tree building with public databases. What I'm really hoping for is some evo-devo lab develoments that will translate into accessible laboratory experiences for pre-college courses--I do expect to see just such a lab in the future. And I don't want to sound disrepectful on Darwin's anniversaries but I'm thinking that high school classrooms that focus first on the molecular basis of evolution (rather than Darwin) and then on whole organism with a heavy dose of tree thinking.....before introducing the history of the idea will be more the rule than the exception in the future.

(8:28pm) Greg: A viewer asks: "My understanding is that one school of thought has evolution happening in bursts of dramatic change across many species in a relatively short period, over time -- as opposed to small, gradual changes over time as proposed by Darwin. First, is this correct, and second, if so, what would account for this?"

Professor Williamson:Evolution doesn't proceed in a linear fashion--and certainly not in the example of hominid evolution you cite. It is true that one of the most pervasive misunderstanding of evolution is that it is "progressive" and "linear". I truly believe that if any of the other hominid lines were still extant so that we weren't the only living example we humans wouldn't be so prone to think this way.

Dr Hewlett:It's important to realize that evolution does not "leap" from one species to another. Rather, two species (say chimpanzees and humans) represent two divergent evolutionary pathways from a common ancestor. These pathways take place over geological time frames, where even Gould's punctuated model, involves thousands of years and many generations. I think that Dr. Miller will have much more to say about this.

Mrs Peebles:We have finally gotten rid of the wonderful old picture in the textbooks about "The Evolution of Man" showing that seemingly direct evolutionary line from apes to modern humans. There are a lot of us still around who have seen it and been confused by it though! Modern research, especially DNA analysis, has provided much illumination in this area, and shown the many BRANCHES of evolution. It answers that question always posed by the creationists, "If we evolved from apes, why are there still apes?" Of course we didn't evolve from apes, but we had common ancestors. As for present and future evolution, I will leave that answer to the scientists.

Dr Miller: The course of evolution isn't predictable in the strict sense, so the most direct answer to your question is "we can't know for sure." What we do know is that evolutionary pressures on our species continue, and therefore we aren't at a "dead end" where no further evolution is possible. So long as a species shows variation and differential reproductive success, evolution will continue -- and we humans display both. So do our primate relatives, many of which are under tremendous selective pressure. The very small existing populations of gorillas and chimps in nature suggest that these species are at the very edge of extinction -- but they also guarantee that genetic changes within each species, if beneficial, could come to dominate the population in relatively sort order.

My own view, which is an opinion and not a scientific claim, is that the evolution of a large, highly developed nervous system could happen again if we were to disappear from this planet. I don't think we can be sure in which part of the living world that might take place -- it could be in cetaceans (whales and dolphins), it could be in primates (again), or it could even be in birds. The conditions that would allow it to happen? Right now, we aren't sure about the conditions that led to our own evolution, and therefore we can't be sure which conditions might drive it in the future.

(8:19pm) Greg: It seems like a lot of the resistance around the scientific proof of evolution is, to put it plainly, is religious thought. Is there a place for science in religion? Or vice versa?

Dr Miller: Sure, there is a place for science in religion. Science is the best, indeed, the only tool we have to investigate the natural world. Scientific knowledge can inform religious belief, and I would argue that it can expand our appreciation for God's work. It's also true that to the extent that religious doctrines make specific testable statements about nature, they can themselves be subjected to scientific tests. One that comes to mind, of course, is the age of the earth and the other is the claim that all species appeared simultaneous during a 6-day creation week. Both of these claims can and have been disproved by scientific means. Religion, therefore, needs to accommodate what we know about the natural world from science. But religious faith can inform science as well -- not by telling scientists what they should discover, but by giving us a reason to explore and appreciate the natural world, and a set of values that respects human creativity and prefers knowledge to ignorance.

Dr Peters:The religious mind--especially the mind of the theologian--loves science. It is no accident that in Western Europe that the midwives of at the birth of modern science were very interested in theological matters. Isaac Newton wrote more pages of theology than he did of science. Even today the Vatican sponsors an observatory that scans the heavens looking among the stars for, among other things, signs of extraterrestrial life. So, it is misleading to read in the media that the relationship between science and religion is simply one of warfare.

Quite specifically, since the nineteenth century a battle has been waged over the scientific veracity of Darwin's theory of evolution; and some critics have use their religious conviction as a basis. In particular, Darwin challenged tradtional Christian beliefs regarding divine purpose discernible in nature. Darwin's appeal to random variations in inheritance combined with natural selection in order to explain speciation elicited a religious problem, because this seemd to evacuate biological history of any divine purpose or direction or design. This struggl has been intense, at times. But, this struggle ought not to suggest that the overall relationship between science and faith is one of antagonism.

When my colleague Marty Hewlett and I put together a couple books on the evolution controversy, we wresteled with the above question. Marty is a Roman Catholic and I am a Lutheran, and we boh believe that God has a purpose for the cr eation. So, this is what we said: God has a purpose for nature, even if we cannot discern a purpose in nature when looking at nature through scientific lenses. We need to allow the research scientist to employ "methodological naturalism"--that is, a method of research that looks for natural explanations--and not require the scientist to come up with transcedental explanations. Even so, we can construct a theology of nature that affirms a divine purpose; and we can look forward to nature's redemption as God has promised it in the Bible.

(8:08pm) Greg: As Morphed: When Whales Had Legs is about to premiere here on the channel at 9p e/p, I find it fascinating that we are finding new species every day and that science is uncovering links between species every year, my own question to you all is what has been the most fascinating concept or finding that you have studied?

Dr Hewlett:As a scientist, a molecular virologist, I would have to say that the objects of my study, viruses, are most fascinating. Here are inhabitants of the biosphere that exist at the limits of what we call living. I have been continually surprised by what these entities have led us to understand about how living systems operate. However, my current area of study is philosophy of science. In this new venue, I'm still learning. But one of the most surprising things was to learn how little scientists actually understand about the philosophical assumptions under which they work. In biology, those assumptions have changed dramatically a number of times, and are in the process of changing once more. Darwin's theory represented one of these major shifts in our understanding, as did the molecular biological revolution of the middle twentieth century. We are now in the midst of a shift from thinking that the whole organism is simply the sum of its chemical parts, to considering the organism as a whole emerging from a complex interaction of those parts. This change will undoubtedly alter how future biologists carry on a conversation.

Dr Miller:To me, as a cellular biologist, the single most fascinating finding comes from the molecular exploration of the human genome, and its comparison with the genomes of other organisms. Roughly 20 years ago, cell biologists studying yeast and sea urchins identified the proteins that controlled the cell cycle -- a basic process that is also important in cancer and in human development. The stunning aspect of these discoveries wasn't that we had figured out how yeasts know when to divide -- but that the very same collection of proteins also controls the cell cycle in humans and other mammals. In effect, that organisms as different as humans and fungi share a set of control mechanisms that help to make the most fundamental decisions of cellular life and death. These discoveries not only confirmed Darwin's view of a universal tree of life -- but they provided a practical experimental way to investigate the molecular mechanisms that all living things share.

Professor Williamson:My son's work as one of the computational biologists that are developing new tools to read the history in the genomes of organisms...including our own story.

Mrs Peebles:I have to say that as a biology teacher rather than a laboratory or field scientist, the latest discovery is always the most exciting and fascinating. I just love learning about the newest findings and sharing it with my students - that is WHY I am a teacher! And that is where National Geographic and all the scientists come in - to help teach US so that we can teach our students!

(7:54pm) Greg: A viewer asks: My understanding is that one school of thought has evolution happening in bursts of dramatic change across many species in a relatively short period, over time -- as opposed to small, gradual changes over time as proposed by Darwin. First, is this correct, and second, if so, what would account for this?"

Dr Peters: What you're talking about is the theory of punctuated events in natural selection that mark relatively rapid evolutionary change. Punctuated developments do not stand in oppostion to Darwin's notion of gradualism, however. Speciation remains a step by step process, regardless of whether speciation takes place slowly or rapidly. Regardless of whether you regularly contribute a small amount of federal withholding from your monthly pay check or pay estimated tax in giant quarterly payments, at the end of the year Uncle Sam still gets the same amount of your earnings. Punctuated leaps in development are still gradualist.

Dr Miller: The school of thought you have in mind is most likely "punctuated equilibrium," an idea developed by Niles Eldredge and the late Stephen Jay Gould. Eldredge and Gould argued that the actual fossil record of most species shows little change for long periods of time, and then changes suddenly ("punctuating" the "equilibrium" of stasis) to give rise to new species and evolutionary novelties. On its face, this sounds very different from Darwin's idea that "nature does not like to jump." However, if one reads both Darwin and Gould carefully, there really isn't much of a conflict. Darwin was very clear that species might remain essentially unchanged for long periods of time, and Gould once admitted that when he describes such changes as "geologically instantaneous," he meant something on the order of 25,000 years -- a very long time, but a period that really would appear instantaneous in the fossil record.

In the past several decades, we been able to gain a new appreciation of how quickly important genetic changes can appear, and these have indeed provided support for the notion that evolutionary change can be quite rapid. I'd recommend that you read Sean Carroll's wonderful new book "The Making of the Fittest" to see how far we have come in understanding the pace and the basis of evolutionary change.

Professor Williamson: The punctuated equilbria model described by Ken so well generally refers to punctuated bouts of evolutionary change within a specific lineage. Your question seemed to imply that you were applying the model across many lineages at various time periods in evolutionary history. You could be referring to adaptive radiations such as that that occured in the mammal line after the Cretaceous--the PE model does not preclude this type of event be generally as I understand it would be focused on the evolutionary paths of specific lineages. The varying rate of evolutionary change is an open area of research--we still have a difficult time measuring the rate of evolution--depending on what level of organism we are looking at.

(8:19pm) Greg: It seems like a lot of the resistance around the scientific proof of evolution is, to put it plainly, is religious thought. Is there a place for science in religion? Or vice versa?

Dr Miller: Sure, there is a place for science in religion. Science is the best, indeed, the only tool we have to investigate the natural world. Scientific knowledge can inform religious belief, and I would argue that it can expand our appreciation for God's work. It's also true that to the extent that religious doctrines make specific testable statements about nature, they can themselves be subjected to scientific tests. One that comes to mind, of course, is the age of the earth and the other is the claim that all species appeared simultaneous during a 6-day creation week. Both of these claims can and have been disproved by scientific means. Religion, therefore, needs to accommodate what we know about the natural world from science. But religious faith can inform science as well -- not by telling scientists what they should discover, but by giving us a reason to explore and appreciate the natural world, and a set of values that respects human creativity and prefers knowledge to ignorance.

Dr Peters:The religious mind--especially the mind of the theologian--loves science. It is no accident that in Western Europe that the midwives of at the birth of modern science were very interested in theological matters. Isaac Newton wrote more pages of theology than he did of science. Even today the Vatican sponsors an observatory that scans the heavens looking among the stars for, among other things, signs of extraterrestrial life. So, it is misleading to read in the media that the relationship between science and religion is simply one of warfare.

Quite specifically, since the nineteenth century a battle has been waged over the scientific veracity of Darwin's theory of evolution; and some critics have use their religious conviction as a basis. In particular, Darwin challenged tradtional Christian beliefs regarding divine purpose discernible in nature. Darwin's appeal to random variations in inheritance combined with natural selection in order to explain speciation elicited a religious problem, because this seemd to evacuate biological history of any divine purpose or direction or design. This struggl has been intense, at times. But, this struggle ought not to suggest that the overall relationship between science and faith is one of antagonism.

When my colleague Marty Hewlett and I put together a couple books on the evolution controversy, we wresteled with the above question. Marty is a Roman Catholic and I am a Lutheran, and we boh believe that God has a purpose for the cr eation. So, this is what we said: God has a purpose for nature, even if we cannot discern a purpose in nature when looking at nature through scientific lenses. We need to allow the research scientist to employ "methodological naturalism"--that is, a method of research that looks for natural explanations--and not require the scientist to come up with transcedental explanations. Even so, we can construct a theology of nature that affirms a divine purpose; and we can look forward to nature's redemption as God has promised it in the Bible.

(8:08pm) Greg: As Morphed: When Whales Had Legs is about to premiere here on the channel at 9p e/p, I find it fascinating that we are finding new species every day and that science is uncovering links between species every year, my own question to you all is what has been the most fascinating concept or finding that you have studied?

Dr Hewlett:As a scientist, a molecular virologist, I would have to say that the objects of my study, viruses, are most fascinating. Here are inhabitants of the biosphere that exist at the limits of what we call living. I have been continually surprised by what these entities have led us to understand about how living systems operate. However, my current area of study is philosophy of science. In this new venue, I'm still learning. But one of the most surprising things was to learn how little scientists actually understand about the philosophical assumptions under which they work. In biology, those assumptions have changed dramatically a number of times, and are in the process of changing once more. Darwin's theory represented one of these major shifts in our understanding, as did the molecular biological revolution of the middle twentieth century. We are now in the midst of a shift from thinking that the whole organism is simply the sum of its chemical parts, to considering the organism as a whole emerging from a complex interaction of those parts. This change will undoubtedly alter how future biologists carry on a conversation.

Dr Miller:To me, as a cellular biologist, the single most fascinating finding comes from the molecular exploration of the human genome, and its comparison with the genomes of other organisms. Roughly 20 years ago, cell biologists studying yeast and sea urchins identified the proteins that controlled the cell cycle -- a basic process that is also important in cancer and in human development. The stunning aspect of these discoveries wasn't that we had figured out how yeasts know when to divide -- but that the very same collection of proteins also controls the cell cycle in humans and other mammals. In effect, that organisms as different as humans and fungi share a set of control mechanisms that help to make the most fundamental decisions of cellular life and death. These discoveries not only confirmed Darwin's view of a universal tree of life -- but they provided a practical experimental way to investigate the molecular mechanisms that all living things share.

Professor Williamson:My son's work as one of the computational biologists that are developing new tools to read the history in the genomes of organisms...including our own story.

Mrs Peebles:I have to say that as a biology teacher rather than a laboratory or field scientist, the latest discovery is always the most exciting and fascinating. I just love learning about the newest findings and sharing it with my students - that is WHY I am a teacher! And that is where National Geographic and all the scientists come in - to help teach US so that we can teach our students!

(7:54pm) Greg: A viewer asks: My understanding is that one school of thought has evolution happening in bursts of dramatic change across many species in a relatively short period, over time -- as opposed to small, gradual changes over time as proposed by Darwin. First, is this correct, and second, if so, what would account for this?"

Dr Peters: What you're talking about is the theory of punctuated events in natural selection that mark relatively rapid evolutionary change. Punctuated developments do not stand in oppostion to Darwin's notion of gradualism, however. Speciation remains a step by step process, regardless of whether speciation takes place slowly or rapidly. Regardless of whether you regularly contribute a small amount of federal withholding from your monthly pay check or pay estimated tax in giant quarterly payments, at the end of the year Uncle Sam still gets the same amount of your earnings. Punctuated leaps in development are still gradualist.

Dr Miller: The school of thought you have in mind is most likely "punctuated equilibrium," an idea developed by Niles Eldredge and the late Stephen Jay Gould. Eldredge and Gould argued that the actual fossil record of most species shows little change for long periods of time, and then changes suddenly ("punctuating" the "equilibrium" of stasis) to give rise to new species and evolutionary novelties. On its face, this sounds very different from Darwin's idea that "nature does not like to jump." However, if one reads both Darwin and Gould carefully, there really isn't much of a conflict. Darwin was very clear that species might remain essentially unchanged for long periods of time, and Gould once admitted that when he describes such changes as "geologically instantaneous," he meant something on the order of 25,000 years -- a very long time, but a period that really would appear instantaneous in the fossil record.

In the past several decades, we been able to gain a new appreciation of how quickly important genetic changes can appear, and these have indeed provided support for the notion that evolutionary change can be quite rapid. I'd recommend that you read Sean Carroll's wonderful new book "The Making of the Fittest" to see how far we have come in understanding the pace and the basis of evolutionary change.

Professor Williamson: The punctuated equilbria model described by Ken so well generally refers to punctuated bouts of evolutionary change within a specific lineage. Your question seemed to imply that you were applying the model across many lineages at various time periods in evolutionary history. You could be referring to adaptive radiations such as that that occured in the mammal line after the Cretaceous--the PE model does not preclude this type of event be generally as I understand it would be focused on the evolutionary paths of specific lineages. The varying rate of evolutionary change is an open area of research--we still have a difficult time measuring the rate of evolution--depending on what level of organism we are looking at.

(7:41pm) Greg: A viewer asks: "I am catholic, but also a biology student. When explaining Darwin's theory of Evolution and the fact that there is very much evidence to date to substantiate this theory from esteemed biologists all over the world, what would you/do you say to the religious community to try and soften this blow? This is a devastating realization that the scientific community is asking them to come to grips with. Do you try to introduce this with tact, keeping those and their life's work and beliefs in mind, or do you present it with arrogance, as it seemed in the last article that I read 2 weeks ago in NG regarding Darwin did?"

Mrs Peebles: I don't think this is devastating at all. There is no basic conflict between religion and science. We have to be careful to distinguish between the two. Science must be testable, and must be tested, and cannot be accepted on "faith". Religion relies on faith, and does not require testing in the scientific sense in order to be believed. I don't have to prove my God in order to accept him. There is sometimes arrogance on both sides of this issue, and that is unfortunate. As a teacher, I never presume to tell my students what to believe, but only what scientific evidence shows us. And for most of them, that is not a conflict.

Dr. Peters:Just what is the reason, do you think, that an adherent to the Darwinian model of biological evolution would need tact? Is the present form of Darwinian theory good science? Yes, indeed; the Darwinian model continues to generate a progressive research program. Christians in general, and Roman Catholics in particular, celebrate good science. If Darwinian evolution can be shown to be good science, then it would be natural for people of faith to embrace it.

Or, is the problem one of religious authority? Does Darwin contradict the Bible by offering natural selection rather than design as an explanation for speciation? No. Despite how scientific creationists expand on the word "kind" in Genesis 1:1-2:4a, the Bible has no investment in the fixation of species.

It might be interesting to note that in the late 19th century that some Roman Catholic intellectuals at Notre Dame and some leading Reformed theologians at Princeton found they could adopt the original Darwinism into their theologies of creation. The Princeton theology led directly to the birth of American fundamentalism in 1910. American fundamentalists did not find themselves originally at odds with science, but rather with liberal Protestantism. The battle over evolution began in the 1920s, and it focused more on cultural values (eugenics, Social Darwinism, militarism) than it did on Biblical authority. So, again: just what requires tact, in your question?

Marty Hewlett is a biologist with considerable experience teaching undergraduates. He has striven to provide a warm and welcoming invitation for religious people to come into the home of science. Perhaps he can add to what I've said here.

Dr Hewlett:I, too, am a Roman Catholic, and, in fact, a lay member of the Dominican Order. It is important to keep in mind that the science of evolution does not require any kind of theological commitment, either theistic or atheistic. Most modern Catholic theologians understand this. John Haught, at Georgetown, argues that we need to take Darwin seriously and then use this scientific information for a new theological reflection. Pope John Paul II in a major communication to the Papal Academy of Science, wrote that the Darwinian model is the most likely scientific explanation of what we observe in the natural world. Darwin's model does not speak to the existence of God, nor does it address the spiritual nature of humankind. These are not scientific questions. Now it is true that some evolutionary biologists choose to step outside of science and comment on these philosophical or theological issues. However, the science of evolution does not require this. It is true that evolution can challenge a literalist approach to scripture. This merely means that we have to follow St. Augustine's advice when he warned against this in the 5th century.

Dr Miller: As a fellow Catholic, I don't think that you need to write ".. BUT a biology student." As you know, there are distinguished departments of Biology at universities like Georgetown, Notre Dame, Boston College, Holy Cross, etc... An appreciation of science, including evolutionary biology, is part of the Catholic tradition - and I would point out that our two most recent Popes (John Paul II and Benedict XVI) have endorsed both the validity of the scientific evidence for evolution, and the view that it is compatible with a Catholic understanding of nature. I don't think that scientists need to "soften" the blow to the religious community to make evolution acceptable. Rather, I think that we need only to act like true scientists, and to emphasize that our work applies to the natural world - not to questions of theology and philosophy. Ultimately, what evolution tells us is that we are a product of the natural world, and that we are made, as Scripture once told us, from "the dust of the earth." Several years ago I wrote a book ("Finding Darwin's God - a Scientist's Search for Common Ground between God & Evolution") to make exactly that point. And more recently, this point of view has been expressed by any number of scientists who are also Christians, including geneticist and human genome project director Francis Collins ("The Language of God") and physicist Karl Gibberson ("Saving Darwin"). Scientists who pretend that evolution amounts to a rejection of the very idea of God are making (in my opinion) a serious error of logic. And they should not pretend to speak with the authority of science when the practice theology without a license. Any religious faith worth its name should recognize that faith and reason are both gifts from God, and should embrace the findings of science at every opportunity - including evolution.

Professor Williamson: As a long time high school teacher I've always worked very hard to "soften this blow". Unfortunately, I have at least one hand tied behind my back. As a public school teacher, any religious instruction on my part that might help my more devout students reconcile the science and their religious beliefs is off limits. By design, by statute and by the court it is not my place (nor would I want it) to provide the kind of religiously based instruction to fully "soften the blow." For this very reason, I tell my students from the outset--this is a science class---we'll cover the science--not the religious interpretations of that science. If you find that you are having difficulties with reconciling your spiritual understandings and beliefs with the science in this class you should ask your parents or your clergy for guidance.

(7:31pm) Greg: A viewer asks: "With all the millions of years inbetween these major transformations, there would obviously be hundreds of millions of transitional fossils in between. I have never seen one (let alone millions), which I find unusual and hard to explain. Can you offer some ideas on this?"

Dr Hewlett:Given the fragility of most organic forms, it's amazing that we have any examples of fossil remains from which to work. In fact, major fossil examples of transitional forms do exits. For example, the intermediate forms leading from a land dwelling creature to the modern whale have been discovered. However, it should be noted that evolutionary theory does not rest entirely on paleontology. All sorts of other evidence leads us to conclude, as did Pope John Paul II, that evolution is the best scientific explanation for the observations.

Professor Miller: If you've "never seen one," I suspect that you haven't been following the past several decades of paleontology. Let's start with two famous findings. The first concerns a large series of transitional fossils documenting the way in which land-dwelling mammals evolved into present-day whales and dolphins. Scientists like Phillip Gingerich (U Michigan) and Hans Thewissen (Northern Ohio U) have unearthed a score or so of distinct intermediate species showing stages in this evolutionary transition. Notable individual fossils include Ambulocetus, Pakicetus, Indohyus, and most recently an extraordinary fossilized pregnant female now called Maiacetus. Carl Zimmer wrote a wonderful book about this called "At the Water's Edge."

The other series that immediately comes to mind is an even more fundamental evolutionary transition, the evolution of tetrapods, the first land-dwelling vertebrates, from fish in the Devonian period, about 350 million years ago. Neil Shubin and his associates (in 2004) discovered several nearly complete fossils of a species they named Tiktaalik. This organism was clearly intermediate between lobe-finned fish of the period and the very fish land-dwelling amphibians. It was highlighted in the PBS program "Judgment Day," which will air again Tuesday (2/10) on the NOVA series on most PBS stations at 8 PM. I'd recommend you watch it - and also that you real Neil Shubin's best-selling book "Your Inner Fish," which describes the discovery and its relevance to human physiology.

Professor Williamson: Two things, here---

One, I'm not sure about the millions of years between major transitions---It would seem that if as Darwin did---prior to any fossil evidence---predict that the ancestors to whales once lived on land that one could predict some aspect of the nature of the transitions necessary for that major transition to take place. Legs would have to be lost (based on living whales), adaptations to drink salt water would be needed, and the nostrils would need to move--one would expect various transitional forms to have some different combinations of such trends---with some trends moving faster than others.....

Sure enough as the work in tonight's film shows there are a number of candidate transitional fossils that have been found in recent years (the latest just announce this month)--some with legs--some with rudimentary legs---in time sequence. Which brings us to point 2

Two: Often when a new transitional fossil candidate (I say candidate because generally no one can establish with certainty that this particular population of organism was ancestoral to specific later forms) for some it essentially opens up two new gaps in the evolutionary record. I can't imagine the joy that would be on Darwin's face if he had any inkling about how extensively documented the fossil record is, today--especially in light of how incredibly improbable any specific fossil discovery is.

(7:27pm) Greg: What is your reaction to Darwin's statement that "All the organic beings which have ever lived on this earth have descended from some one primordial form."

Professor Williamson:This statement in today's world is the type of statement that I feel is difficult to appreciate. There is no scientific dispute of the main thrust of this idea---it is accepted fact. (with some modification how horizontal contributions to descent might play into the overall thrust of evolutionary history) This fact is so obvious that it's significance for tying all of life together into a framework for understanding and prediction is usually underappreciated. This is the story that binds all living things together and helps make of biology.

(7:14pm) Greg: It wasn't the work on the Galapagos that was insignificant, but it was his time spent in Argentina mining for fossils and work done in Punta Alta that led to significant findings, please explain the scientific significance of what he found.

Professor Miller: Actually, I think that BOTH were significant. But Punta Alta fossils, which included gigantic extinct animals like Toxodon and Glyptodont, particularly fascinated Darwin for two reasons. They were clearly of extinct organisms, and yet they were closely related to living organisms (the Capybara and Armadillo, respectively) that were also native to South America. Why should these strange animals, some extinct and some living, be found on the same continent. Gradually, it dawned upon Darwin that the most sensible explanation was that the extinct forms were the ancestors of the living - accounting for the clear relationship between them and also the fact that they were both unique to the same continent. In his book "The Voyage of the Beagle" he wrote:

"This wonderful relationship in the same continent between the dead and the living will, I do not doubt, throw more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts."

Clearly, these fossils got him think about the true origins of their living relatives -- which is the foundation upon which the theory of evolution is built.

Professor Williamson: The Punta Alta fossil work did indeed lead to significant insights for Darwin and helped put Darwin's name on the mind of the scientific establishment back in England. The significance of the fossils is biogeographical. It was fairly well known at the time that South America's mammal fauna had several unique representatives--not as unique as say Australia but certainly unique mammals like sloths, anteaters, and armadillos. The Punta Alta fossils provided examples of exinct examples of the same unique groups. How would someone like Darwin or anyone else suspect the fossils respresented extinct lineages? Presumably the gigantic size of the fossils suggested that any extant or living representatives would be well known--even in the early 1800's. Today, this doesn't seem to be more than a "well of course that makes sense" type of observation but in the background of the dominant early 1800's thinking this observation presented serious challenges.

I would disagree that the work in the Galapagos was not as important--just another type of puzzle piece to the problem--one that you could argue was more essential to the theory of natural selection whereas you could argue that the Punta Alta work was more critical to the arguements of shared common descent.

(6:55pm) Greg:How do studying DNA sequences advance medical theories such as advancing stem cell research, causes of diseases such as cancer and autism or birth defects? What are some of the future studies that we can expect?

Dr Miller: Cancer and birth defects results from the failure of cells to control the cell cycle, or the failure of cells and tissues to develop normally, respectively. Changes in DNA are at the heart of both problems, and understanding deep connections at cellular and molecular level is the only way to get to the root of both. Autism, involving complex behaviors, is a more vexing problem, but I believe that it, too, will eventually yield its secrets to approaches that combine modern genetics, neurobiology, and behavioral psychology.

Dr Hewlett: We are actually moving away from studying just DNA sequences. The more current analysis focuses more on the gene products themselves, the proteins, for instance. More importantly, it's really about how those gene products interact in complex networks with properties that emerge and are greater than the sum of the interacting parts. This "holistic" approach, called interactome analysis, really paves the way for a new kind of biology that we will see more and more in the future.

Dr Peters: I've heard my good friend Marty Hewlett say, "thank God for the Darwinian model of evolution!" As a virologist whose research could lead to the saving of countless lives, he must rely upon an understanding of evolution to pursue his laboratory work. I can't imagine that the CDC in Atlanta, mustering an initiative against a major virus threat, asking creationist or ID scientists to head up the research.

Professor Williamson: One area that I expect some work on in the future is the nature of the evolution of the population of cells in cancer tumors. These cells are some of the fastest evolving cells known--the population of cells that are metastasizing have very different genetic characteristics than the earlier population that first started the tumor growth. We have some of the tools now to characterize these cell populations as more are developed I expect we'll develop a greater understanding of the evolutionary trajectories that tumor cell populations take---likewise I think that similar approaches will shed significant light on the HIV....

(6:39pm) Greg:The first question that I'll ask is with as much respect as Charles Darwin has had, and rightfully so, what was his biggest mistake?

Dr Hewlett: Darwin did not make a mistake, per se, but he did not have the information he needed about heredity. The prevailing view of his time was that inheritance took place by a blending of traits from the parents into the offspring. Mendel's experiments, published in 1868, were not appreciated until the beginning of the 20th century. As a result, Darwin had not real explanation for how inheritance could work. This became the source of one of the main scientific criticisms of his model. Fleeming Jenkin, a British engineer, critiqued his model because, Jenkin wrote, there would be no way for selective traits to survive the blending in subsequent generations.

Dr Miller: I think that his biggest mistake was the gradual retreat on the importance of evolutionary novelties (mutations) he made as he revised "on the origin of species" for its later editions. Since he was unaware of the work of Gregor Mendel, Darwin did not appreciate that a beneficial gene could be passed along from one generation to the next without being "diluted" by blending with other genes. Had he understood this - which is a basic principle of genetics - he would have been able to weave that into the theory. And that would have made his theory nearly complete as a story of change over time.

Dr Peters: Marty has gotten us off to a good start. Let me leap to the question interpreting, "All the organic beings which have ever lived on this earth have decended from some one primordial form?"

For a follower of Darwin, it appears that life began on planet Earth only once; and we all are related. New knowledge of DNA seems to confirm: DNA is DNA is DNA. Whether we like it or not, we humans need to invite to our family reunions field mice, mosquitos, and peat moss.

Professor Williamson: Darwin made lots of mistakes--however, his work was characterized by extreme care and attention to detail. He did not shy from correcting assertions made in earlier editions of his work. In fact some have argued that such attention might have been "his biggest" since he took so long to document his long argument before being shocked into making it public.

As far as the main components of his arguments I'd propose that his understanding that evolutionary change was generally very slow and took more time than one generation of humans could observe would be one idea that he might wish he could retract if he knew what is known today....As careful and meticulous as he was I doubt that he had much of an inkling at just how fast evolutionary change could happen in short generation organisms.....If he had I'm sure he'd have tried to document such change such as the change in the peppered moth populations that were taking place in his lifetime.

(6:23pm) Greg:Greetings Everyone! Four days from now people around the world will mark Charles Darwin's 200th birthday. National Geographic Society and Channel are no different. Tonight we gather scientists, teachers and theologians to discuss Charles Darwin's legacy, where scientific thought is progressing and the current debate of the science in the nation's education system.

Please join us and submit your questions now!