The last talk of the day (for me, as I had to leave before the final, final talk) made for a great reminder of how far the field of evolutionary biology, wrapped in a relatively simple story told engagingly by Hopi Hoekstra of Harvard. Hoekstra described her research quest as “the hunt for genes that make a difference,” and she uses a really nice model system – the oldfield mice of the southern United States. These mice typically are brown in color, but they have migrated in the recent (meaning thousands) of years to the gulf and atlantic coasts and taken up residence, like a retired couple, on the beach. But a brown mouse on a beach is a target, and their predators, which include birds and coyotes, find it all to easy to locate their brown fur on white sand and make a beachside snack out of them.
Cue natural selection – soon you have brown oldfield mice inland, and predominantly white oldfield mice that live on the beach. Hoekstra tested whether the fur color really does construe an evolutionary advantage with a simple experiment – make a bunch of clay mice colored brown or white, and leave them out on the beach. Sure enough, the brown clay mice quickly showed divots and bitemarks left by attacks from (presumably very frustrated) predators.
That would have been a fine experiment for the 1959 conference, but Hoekstra’s next step was pure 2009 – she took examples of brown and white mice back to the lab, bred them, and searched for the genes that determined fur color. Her laboratory narrowed the gene candidates down to three genes, and in one of them – a receptor called Mc1r – the substitution of a single amino acid flipped the switch from brown fur to white fur. Amazingly, when another group of scientists sequenced the genome of extinct mammoths in 2006, they found the same amino-acid substitution in the same gene, implying that mammoths, like the oldfield mice, came in different color varieties.
After so much high theory and methodological complexity, Hoekstra’s experiment sent all of us (or at least me) home with a warm feeling – not only was her experiments a beautiful example of evolutionary biology that would have been impossible in 1959, it was a great example of teachable science, the kind of story that a 3rd-grader could wrap their head around and begin to see the truth of evolution. The cloud hanging over Darwin/Chicago 2009 was the uneasy feeling that all this scientific progress was still losing out in the arena of public opinion, but Hoekstra’s work and charismatic speaking style (on the heels of similar ambassador figures Neil Shubin and Michael Shue) chased away some of the pessimism, and left me confident that the more examples we find of Darwin’s elegant theory at work in nature, the easier it will be to convince the world that it is true.
And with that, we’re finished. Happy Halloween to those of you who have followed me this far, and thanks very much for reading and perhaps linking to the posts. I’ll be back Monday with a digest post to help navigate the coverage of the last few days, and Jeremy Manier will be here Tuesday with his own thoughts on the conference.
In a packed lecture up on the 3rd floor of the conference, Michael Ruse of Florida State University gave easily the funniest talk this weekend, using Gary Larsen comic strips, comparing slow-moving ancient reptiles to philosophy undergraduates and goofing on PZ Myers in the front row. But between the laughs, he also made a brilliant case for the continued relevance of Darwinism, saying that he was frustrated by magazine, newspaper and scientists eager to emphasize where Darwin was wrong rather than the many places he was right.
In Ruse’s version, Darwin made his convincing argument not by directly doing the science himself (though he obviously collected a lot of observations in his famous voyage on the Beagle) but by drawing upon other scientific discoveries that were well accepted by his audience at the time. Using established 19th century knowledge about animal instinct, paleontology, geographical distribution of species, homology between species and embryology, Darwin was able to construct an over-arching hypothesis that explained all of them. My own impression was that you could think of Darwin like a skilled DJ, grabbing pieces of already popular songs and building them into a wider context enjoyable to everyone. Hmmm, maybe it needs some work, but I’ll try to have it polished up for the 2059 conference.
Anyway, Ruse went on to demonstrate how Darwin’s patchwork evidence was so strong that the major findings in those fields since Origin of Species have only added more weight to the correctness of evolution and natural selection. Discoveries of older fossils, the genetic similarities between fruit flies and humans, the plate tectonics explanation for the movement of continents – all occurred after Darwin’s death, but have done nothing but strengthen his case. To the question posed by his talk, “are we Darwinian or not?, Ruse said the answer was a resounding yes, but only because the field has not stood still since the publication of Origin of Species 150 years ago, and will continue to develop for 100 more years.
“In 2109, we will continue to celebrate Darwin not just because of what he discovered, but because of what we still use from his ideas,” Ruse said.
What do 390-million-year-old fossils have to do with the developmental genetics of how human hands and fingers are formed as fetuses? It sounds like a riddle, but it’s actually the thrust of Neil Shubin’s research, and the topic of his lecture on “Major Transitions in Evolution” this afternoon. Shubin is a paleontologist famous for the discovery of Tiktaalik, an ancient fish with fin bones that resemble the organization of vertebrate limbs – the type of transitional organism that fossil hunters dream about. But Shubin hasn’t stopped with filling an important gap in what we know about the history of life, instead expandingupon his field work in the Canadian Arctic with laboratory work in the sometimes-arctic conditions of Chicago on how limbs develop.
Shubin joked that he felt a bit humbled in light of the massive amounts of genetic data Eric Lander talked about yesterday, since he “spent 6 years collecting one data point.” But that was an over-simplification, as he showed reams of data from his lab showing how primitive fish, such as sharks and skates, use many of the same signaling mechanisms to construct fins and even structures called “gill rays” that have no fin-like function. The commonality of these signals suggests that the program that built the fingers I am currently using to type up the post actually is hundreds of millions of years old, conserved and re-purposed by natural selection. No wonder Shubin’s book is called “Your Inner Fish.”
The greater message of Shubin’s lecture, beyond his very interesting data, answered a dilemma that was starting to grow in my mind this morning. Hearing so many wonderful speakers talk about their field, I was jumping back and forth between disciplines thinking they held the “answer” to evolution – oh, fossils will tell the story! No, it’ll be animal behavior! Perhaps genetics?!? Shubin summed up the real answer perfectly by drawing the connections between ancient, dusty bones and shiny, modern genetic sequencers, describing it as a reciprocal relationship, united “through the profound power of descent with modification and the Tree of Life.”
Finally, more than three-quarters of the way through the conference, we get our first positive mention of Jean-Baptiste Lamarck, the Pete Best of evolution. I expected Pietro Corsi, author of the definitive Lamarck website, to give us some Lamarck love yesterday, but he said he wanted to focus on other, more neglected scientists of the 19th century: “I’m sick and tired of Lamarck,” Corsi said. “Either it’s Darwin or Lamarck, and we keep missing the point.”
But Richard Burkhardt, from the University of Illinois, was happy to pay Lamarck his due as the first scientist to emphasize the importance of animal behavior in biology. Lamarck’s theory supporting the inheritance of acquired characteristics gave behavior its due as both a cause and result of evolution – encapsulated most famously in his example of a giraffe stretching its neck to reach food on tall trees and passing down that elongated neck to its offspring. Amazingly, Burkhardt points out that Lamarck never saw a live giraffe and based his theories entirely on the viewing of dead specimens, making him an unlikely father of the science of animal behavior, but an important ancestor nonetheless for linking behavior to evolution.
Darwin himself conducted animal behavioral experiments at home, and famously used the behavior of social insects such as bees – where worker drones are unable to reproduce – as examples of how natural selection can work on the population level as well as the individual. But the field of studying animal behavior still lagged in part to (we mention again) the difficulty of field studies, which are “notoriously better for the animal than for the observer,” Burkhardt said. One early proponent of animal behavior worked right up the street from today’s conference – Charles Otis Whitman, who built an aviary for studying hundreds of pigeons at his home near the University of Chicago campus in the early 20th century.
But it wasn’t until the 1960’s and 70’s when the field of behavioral ecology truly took flight, Burkhardt said, and in four decades of work it has only scratched the surface of describing how natural selection whittled complex behaviors as animals adapt to their environment. “The field continues to shed light on both the products of evolution and the mechanisms under which it operates,” Burkhardt said.
11:00 a.m. – Redrawing the Boundaries of Evolution
Part of the purpose of a conference is to open up a field of study to outside input, resisting the natural flow of a scientific discipline to become an isolated and insular island. The morning session for the Biological Sciences branch focused on stretching the boundaries of evolutionary biology to incorporate related, but sometimes alienated fields – one new and one old.
Perhaps because the University of Chicago has a Department of Ecology & Evolution, I didn’t realize that the pairing of those two fields was a recent phenomenon. On the surface, it seems more than logical – both are sciences of natural life – but the day’s opening talk by Thomas Schoener from UC-Davis mostly portrayed a courtship between the two disciplines that only goes back about 10 years. The issue, it seems, is that it’s much easier to think about evolution of a species in isolation, with natural selection shaping its features and behavior over time. But no species on Earth is truly isolated, and every significant change in a species should have a ripple effect through all the other species in connects to, either in a food web or a more indirect ecological relationship.
Yet studying the relationship between ecology and evolution is no simple matter; as Schoener put it, there are plenty examples of ecology affecting evolution (think the peppered moths of England, which grew darker as soot blackened their environment), but few examples of evolution affecting ecology. To demonstrate such an effect, one would need to find a case of rapid evolution, on the scale of years instead of millions of years, and study it carefully in the field. Setting up such studies is so difficult that there really haven’t been any satisfying cases as of yet, but Schoener described his ongoing experiments in the Bahamas (must be nice) where researchers are introducing a small lizard on to an island and studying both how it evolves and how that evolution affects other animals and plants in that environment.
The other argument for a bridge between evolution and another discipline was made by University of Chicago’s David Jablonski, who made the case for a “renewed partnership” between paleontology and evolutionary biology. As Paul Sereno noted yesterday, Darwin largely avoided the fossil record in his writings, because the record of his time was very spotty and entirely unpredictable – many a scientific theory has been sunk by the discovery of a previously unexpected fossil. But in the 150 years since Origin of Species was published, Jablonski argued, the fossil record has filled in enough to become a valuable tool for the study of evolution over long stretches of time.
As Schoener noted, scientists studying living creatures are constrained to only study cases of rapid evolution by the fact that we only live 7 or 8 decades – a mere fraction of a blink in evolutionary time. But Jablonski, who studies bivalve fossils, said that the answers to important questions about the rates of extinction and diversification in different species can be answered with careful study of the fossil record, which offers a “trail of mayhem, destruction and heartbreak.”
9:15 a.m. – Day Two Begins
And we’re back for the second full day of Darwin discussion on a gorgeously crisp fall day at the University of Chicago. The speakers and attendees are loading up on coffee and pastries before the program starts at 9:30. I’ll be checking in all day with frequent updates from talks by Thomas Schoener, David Jablonski, Richard Burkhardt, Neil Shubin, and more. Continue to check PZ Myers of Pharyngula and Skip Evans of Wisconsin Citizens for Science for their reports from the conference as well.