5:00 p.m. – Biomedicine and Bracketology
Here’s the final report from today’s session, join us again tomorrow for a full Halloween day of evolutionary science and philosophy! Also, continue to follow PZ Myers of Pharyngula and Skip Evans of Wisconsin Citizens for Science for their reports on the conference.
Both talks in the final session of the day focused on how the incredible advances in gathering genetic information over the last decade have done much to shake up the worlds of genetics and evolutionary biology. As we’ve written about previously, the 1959 conference helped solidify what’s known as the modern synthesis of evolution that incorporated the then-new information about DNA, genes and molecular mechanisms of inheritance, an arrangement that forever married the two fields. Well, could the participants in that conference have predicted that 50 years later we would have a reasonably complete genome for humans, not to mention 43 other vertebrate species? And did they know how much trouble it would cause?
Eric Lander, who was one of the leaders of the Human Genome Project, said he felt slightly out of place at a conference about Darwin, but the modern synthesis marriage sometimes makes strange bedfellows! Regardless, Lander’s talk was a great primer on how the dogma of genetics has been forever altered by what we learned from the HGP and the genomes of other animals: that we have far fewer genes than we thought (~20,000 vs. previous estimates of 100,000), that much of what is handed down between generations is “non-coding” DNA that doesn’t make proteins, that those “non-coding” sections may create important regulatory elements that help organisms develop. Lander, who described himself as a biomedical scientist, said much of what has been found since the explosion of genetic data has been bad news for medical geneticists – many disease-associated alleles have been found, but most have very marginal effects on the probability of a person developing that disease. But Lander said it was a glass half-full/half-empty situation:
“Those people who want to do personal genomics – take your DNA and tell you your risk of diabetes – they’re in trouble. This is not going to be the best way to do that,” Lander said. “But if I want to understand what diabetes is about…I start to get clues to the pathways that matter to diabetes.”
The final talk of the day covered how genetics has caused a similar reshuffling in the field of phylogeny – the science of organizing life into “trees” that show the evolution and relationships of species. Philip Ward, from UC-Davis, talked about the durability of the “Tree of Life” simile, which Darwin readily used in Origin of Species – the only figure in the book is an early phylogenic tree. Modern phylogeny produces beautifully complex trees that look like 10,000-team basketball tournaments run in reverse, with the winner being life’s common ancestor. But as biologists have turned to genetics to build these trees, they’ve found that they lead to completely different trees than the ones built from morphology, the physical characteristics of organisms.
One reason for this is a tricky effect called convergence – two species that are not closely related and live continents apart could form a resemblance because they evolved in similar environments. Ward studies a type of ant that is found in both Asia and America, and morphology would suggest that they are closely related species despite being so far apart geographically. However, genetic data showed the ants were more distantly related than previously could have been estimated from their looks, suggesting they evolved to look similar due to their similar environments, without a recent common ancestor.
But the Tree of Life remains a strong structural model, Ward said. So strong, in fact, that it has been adopted by creationists, who describe an “orchard of life” of animals that evolved after Noah’s flood. As with most mentions of creation “science” at the meeting, Ward’s slides about these theories drew mostly giggles from an audience decidedly on the side of Darwin, even as genetics reveals a world more complex than he ever could have imagined.
Our own Jerry Coyne is known for not shying away from an argument; his recent book Why Evolution Is True is a 300-page smackdown of creationist arguments, and he’s continued the battle on his blog of the same name. At Darwin/Chicago 2009, he’s among friends (he was one of the co-organizers, after all), but he still chose to go to battle in his lecture on speciation – arguing that a form of speciation currently gaining popularity in the field of evolutionary genetics is possible, but not significant to natural life.
As I mentioned in my preview, how species form was the major question that Darwin did not provide an answer to – how individuals from one species evolve far away from each other that they can no longer interbreed was a mystery to him. Darwin, Coyne said, settled on a “sympatric” theory of speciation, where two species can erupt from one even when they are still exchanging genes and living in the same area. But a more commonly observed form of speciation is called allopatric, and results from forced reproductive isolation. The classic example is when a physical barrier, such as a glacier, splits a population of organisms in half for millions of years – that population would be expected to eventually split into two different species.
Coyne is a supporter of the allopatric form of speciation as an explanation for the vast majority of species creation that has occurred on Earth. The one criticism of that form is that it doesn’t happen often enough to have populated the planet with millions of different species, but he demonstrates in his book with some mathematical modeling that it is possible. This afternoon, Coyne spent most of his time dispelling the idea that sympatric speciation could have been an important contributor to the diversity of life, arguing that many of the examples cited from nature are “ecological and genetic trickery.” One example is the parasitic indigobird, which lays its eggs in the nest of other species, tricking those foreign birds into raising their young. When the parasitic birds develop, they hear the songs of their “adoptive” parents, and because bird song is conducive to mating in many bird species (a process Rosemary Grant described beautifully this morning), they become reproductively isolated from their own species. Sure enough, a multitude of indigobird offshoot species have been observed in the same habitats.
Near the end of the talk, Coyne acknowledged, despite his admission that “I’m known for being hyper-critical,” that there have been honest cases of sympatric speciation observed in crater lakes of Cameroon and Nicaragua. But his conclusion was that these were merely rare cases, the exception to the rule of allopatric speciation. Unfortunately, there was no time for questions – I was spoiling for a fight myself, should there be any sympatric speciation advocates in the crowd.
(In an ironic move, I heard John Hedley Brooke’s lecture on the history of religious opposition to Darwin immediately before Coyne’s talk. Ironic, because much of Brooke’s talk focused on thinkers who had no issue reconciling belief in evolution with religious beliefs, a subject Coyne has often railed against on his blog, particularly as regards new NIH Director Francis Collins.)
You might have thought Paul Sereno would be out of his element when popular demand pulled his lunchtime lecture out of his fossil lab and into the relatively sterile Max Palevsky Theater. But Sereno, uncharacteristically dressed in a suit instead of his usual jeans and leather vest field outfit, appeared to relish the opportunity to dig into the details of his field instead of showing off his latest dinosaur fossil find to the cameras. Oh, he still brought an amazing fossil with him – confuciusornis, the second-oldest known bird fossil – but as he pointed out, Darwin didn’t talk much about dinosaurs, even though he secretly was “delighted” with the discovery of Archaeopteryx, the oldest bird.
Instead, Sereno discussed his recent paper proposing a new language of morphology – very technical stuff, but clearly a passion of the dinosaur hunter. The field of phlyogenetics, which uses gene sequences to organize animals into a “tree of life,” threatens to steer biologists’ attention away from what organisms actually look like towards the ingredients of their genome. Scientists who study the “morphology,” or physical characteristics of fossils or living organisms, are falling behind, Sereno said, because the language used to discuss those features is too subjective and not standardized. Sereno pointed out one case where two papers published by the same author disagreed by more than 10% on how its terminology was deployed – “can you imagine a genetic paper where the sequence in 10% wrong?” Sereno asked. The way forward was for morphologists to agree on a common grammar of how to describe physical features of specimens, so that computer programs could be designed to enable comparisons previously scuttled by inconsistency. Because as Sereno said, genes are fine and good, but we don’t just care about molecules.
On the schedule, the title of Robert Richards talk is “Darwin’s Moral Reconstruction of Nature.” But at the start of his lecture, Richards announced its title was instead “Darwin’s Biology of Intelligent Design,” a thesis more in keeping with the controversy the conference’s lead organizer hoped to stir among a roomful of evolutionary biologists. Richards’ argument – almost blasphemy among evolution experts – is that Darwin was, at heart, a teleologist, believing that natural selection was not a impartial, mechanical shaper of organisms but a “discerning mind” with the ultimate purpose of creating human beings.
Part of why that assertion is so combustible lies with the history of teleology, which has often been used as a justification for the supremacy not just of humans over the rest of life, but the supremacy of Caucasians over other races. Richards did not go so far as to ascribe those repulsive ideas to Darwin, but did say it was important to realize that “while Darwin is indeed valued in the modern world, his values were formed in the pre-modern world.” To illustrate that point, Richards read several excerpts of Darwin’s writing before The Origin of Species, passages from notebooks where the biologist worked out the problems his theory must answer.
Because Darwin received some inspiration for the process of natural selection from observing how animal breeders can selectively increase the frequency of beneficial traits, Richards argued that much of what he wrote about natural selection seemed to imply the presence of a guiding hand. He also uses language that suggests natural selection is a force for “improving” species – not the cruel destroyer of unfit species we think of today – with the creation of a moral animal, humans, as the realization of this beneficial pruning process. Darwin didn’t think of natural selection as an emotionless machine, Richards argued, but thought of nature as a benevolent entity – “purpose” and “object” appear 63 times in Origin of Species, “mechanism” appears only 6 times.
The few questions for which there was time before the rush to get lunch all offered examples from later in Darwin’s life where he firmly rejected teleology and proclaimed his agnosticism. But Richards’ final argument lingered with me, poignantly driving home the importance of understanding Darwin’s words in the context under which they were written. At the time when Origin of Species was published, its readers (and its writer) could not have conceived of a “machine” capable of the work that natural selection does in driving evolution of complex organisms. In the middle of the 19th century, a controlling “mind” was an easier metaphor for readers to swallow, and whether Darwin still believed in “purposeful” natural selection or not at the time, it was the quickest way to help the world understand and accept his radical ideas.
Peter and Rosemary Grant are well known to even casual Darwin scholars thanks to the 1994 book by Jonathan Weiner, The Beak of the Finch, which profiled their field work on Darwin’s Finches in the Galapagos Islands. As described in the book, their studies of the islands’ 14 different finch species are a gorgeous living example of evolution at work – when a drought hit the islands in 1977, the Grants observed the beak size of one finch species increasing rapidly, natural selection favoring birds with large beaks able to crack the hard seeds that were the only remaining food source.
The Grants’ research didn’t stop with the publication of Weiner’s book, and Peter Grant said this morning they have now been tracking the birds for 37 years. Thus, they were for another recent environmental shift that again illustrated the complex changes that the wonderful simplicity of natural selection can produce. In 2004 and 2005, Peter Grant said, another drought hit the Galapagos Islands that was as severe as the 1977 drought they observed. But this time, the average beak size of the finch species they study decreased, rather than increased. A puzzle, to be sure, until Grant explained that in the years between 1977 and 2004, another finch species had invaded the island of Daphne Major. This species was large in size and had a large beak, and when hard seeds again dominated the food supply in drought conditions, they outcompeted the large-beaked individuals of the “native” species, forcing the average beak size of the original species downward. Another great example of natural selection, borne of tireless work – which, I was thrilled to see now also includes components of developmental biology in collaboration with other laboratories to find the specific genes and cellular signals that underlie these remarkable adaptations.
Charles Darwin’s The Origin of Species is often portrayed as having suddenly popped into existence and changed the world of science and the science of the world. But Pietro Corsi, of Oxford, wanted to tell us all how wrong that idea was – even if he knew that this particular audience was probably already aware that there was a science of how life begins and changes before Darwin. Armed with a Powerpoint filled with lists of names and publications that showed the multitude of people thinking about the history of life on Earth before Darwin was even born, Corsi emphasized that “debate on life is a constant.”
Only having 45 minutes to speak, Corsi ripped through the history at lightning speed, and it was hard to grab onto details. But I was impressed with how technology has enhanced even a dusty field like history of science, as Corsi talked about scanning Google Books and using search words in electronic journals to build his reconstruction of this historical debate piece by piece. Combing through medical dictionaries from the 1820’s and religious texts from the 1830’s from the comfort of his computer, Corsi could make the case that there’s no excuse for a simplified view of pre-Darwin biology. “Once you widen the spectrum and look…you realize how poor is our view of who is evolutionist before Darwin,” Corsi said.
Today’s program starts at 9:30 am, and I hope to file my first dispatch during the first break around 11:00. In the meantime, here’s a recap of last night’s opening session, which we live-blogged here.
If a vengeful deity wanted to keep the evolutionists away from His chapel on Thursday night, He certainly tried His best, sending down sheets of rain on Chicago during the opening session of Darwin/Chicago 2009. Yet hundreds of people still risked a little moisture to pack the pews at Rockefeller Chapel, eager to hear from three past and present superstars of evolutionary biology. And in the spirit of a conference that is less about continuing to celebrate Darwin’s 200th birthday and more about getting back to the work of expanding his vision, all three talks struck a dark tone that matched the stormy weather outside.
Richard Lewontin, who Jerry Coyne described in his introduction as “Mr. Population Genetics,” said this was the only Darwin conference invite he had accepted this year, due in part to the persistence of Coyne, his former graduate student. Lewontin (who was in the crowd at the 1959 conference) used his time to scold his peers for buying into “two bad metaphors” for explaining evolution and natural selection: the idea that “genes make organisms” and the concept of organisms adapting to fit an environment “niche.” The truth is much more complex, Lewontin repeatedly emphasized – a mix of genes, environment and randomness create the organisms we see, and plants, animals, bacteria and humans are not passive victims of their environment, but do whatever they can to shape the environment around them. Perhaps, Lewontin suggested, we should move away from using the term “adaptation” in favor of a better term “so that an organism is understood as being not just influential, but in some sense determining the elements of its world and how they’re put together in relation to itself.”
Moving from science to society, Ronald Numbers gave a quick history lesson about anti-evolution movements in America, focusing on the differences between today’s advocates of intelligent design and the more moderate movement of the 1920’s led by William Jennings Bryan. Bryan (made famous by the Scopes Monkey Trial) and his followers had no quarrel with the idea that the Earth was billions of years old or even that other organisms had evolved, Numbers said – their opposition was solely to the idea that humans evolved as well. But over the 20th century, what was once a minority view of a young-earth, literal reading of Genesis began to overtake the evangelical mainstream, leading to the frequent challenges to evolution we see today. Numbers warned that this movement is growing worldwide and across religious lines, cautioning “Across the world, there is a booming interest in creationism…I come with a sobering message: There is yet a lot of work to do.”
Marc Hauser ended the night with what could have been an optimistic message – the idea that evolution and biology is crossing over to explain concepts of human behavior previously ascribed to religious upbringing. His talk about the neurobiological origins of morality was both inspiring and depressing, however, showing as it did a relatively immutable “moral grammar” present in all of his test subjects regardless of religious or political affiliation, gender, and other social factors. The one way you could change a person’s perception of a moral dilemma was borderline sci-fi – magnetic stimulation of a brain area called right temporal-parietal junction shifted people’s perception of a case study where a woman either intentionally or accidentally poisoned her co-worker’s coffee. But Hauser ended his talk with an encouraging conclusion; if we can learn to understand the structure of this “universal moral grammar”, we can concentrate on the moral values that are sensitive to change to make a better world.