Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
In an earlier post, I’d noted that I was unable to see the new Hall of Human Origins exhibit at the Smithsonian’s National Museum of Natural History when it opened in March. As promised at the time, I was able to see it this summer, and will provide a review here soon. But in addition to seeing the human evolution exhibit, I also stopped at the gift shop, and am happy to report that WEIT is not only for sale, it is a Curators’ Choice!
WEIT, a Curators' Choice at the USNM, August 2010.
The USNM (as the natural history museum is known to biologists) is one of the nation’s largest non-university research institutions specializing in evolutionary biology, and the curators are the professional scientific research staff of the museum, so it’s an honor to be singled out in this way (even though Neil Shubin’s book is up there too!).
There is a section of the Sierra Nevada in California called The Evolution Range, which includes appropriately named peaks like Mount Mendel, Mount Wallace, Mount Haeckel, and Mount Spencer, and inappropriately named ones like Mount Lamarck. (A new peak, not yet formally named, will be called Mount Gould. I suggest Mount Improbable for the next name.)
The highest peak in the range is, of course, Mount Darwin, at 13,831 feet. It was first scaled in 1908 and, unlike higher peaks like Mt. Whitney, is a technical climb. My friend Andrew Berry, who teaches at Harvard, just undertook a mini-expedition to Mount Darwin with a former member of the Harvard Mountaineering Club, Dunbar Carpenter. I asked them, by way of bicentennial homage to the old man, to place a copy of my book at the summit. Sure enough, they did. Here’s the photographic proof.
Fig. 1. Mount Darwin, with its flat summit.
Fig. 2. Nearly at the summit.
Fig. 3. “I’m the king of the world.” Andrew Berry on the summit with the goods.
Fig. 4. Dunbar Carpenter, too absorbed in reading to climb.
Fig. 5. Now it belongs to the ages. Inscription in the copy left at summit.
o.k., Richard, you may sell a million copies, but let’s see you get The Greatest Show on Earth up there!
Big H/T to Andrew and Dunbar!
_________________
okay, okay, Mount Lamarck is fine. But I draw the line at Mount Lysenko!
Last Monday I spent a few hours at the Smithsonian‘s National Museum of Natural History (originally known as the United States National Museum, and still known as the USNM to scientists, even after the Smithsonian began collecting art, airplanes, tchotchkes, etc., and thus gave its museums more specific names), and came across WEIT in their gift shop.
I moved this copy about two feet to the right to photograph it, because I thought Jerry would appreciate the surroundings: it’s almost a diorama.
The great natural history museums, such as the USNM, are among the world’s premier scientific institutions. The mission of the Smithsonian Institution, bequeathed to it by its founding benefactor, James Smithson, is the “increase and diffusion of knowledge”, and it is a fitting mission, encompassing both research and education, for not only museums, but also universities. Having been a postdoctoral fellow at the USNM twenty years ago, but not having had a chance for many years to go through the exhibits (which are a chief way in which the USNM diffuses knowledge), I wanted to see how the exhibits had changed.
The old evolution exhibit had been taken down some years ago, and a new Ocean Hall stood in its place; I was anxious to see how the newer exhibits covered evolution and the history of life, which had always been a theme throughout exhibits such as Dinosaurs and Life in the Ancient Seas, and of course are the major themes of the work of the USNM’s researchers. I didn’t think that the Smithsonian would have succumbed to any external pressures: they successfully fought off a creationist legal attack in 1980, eliciting from the DC Circuit Court of Appeals the memorable ruling that the balance between freedom of religion and learning
…was long ago struck in favor of diffusion of knowledge based on responsible scientific foundations, and against special constitutional protection of religious believers from the competition generated by such knowledge diffusion.
I’m happy to report that the presentation of evolution is even more forthright than I’d anticipated. This sign greets visitors in the Rotunda, at the feet of the USNM’s iconic elephant:
Note particularly the line “Evolution is at the heart of this museum.”
In the Ocean Hall, one of the main galleries is devoted to the origin and history of life on earth, including everything from stromatolites, to a very nice exhibit on the origin of whales (see here, too), a story highlighted in chapter 2 of WEIT. Hung from the ceiling are skeletons of the sea lion-like Maiacetus,and the fully marine, yet hind-legged, Dorudon and Basilosaurus.
There are also two temporary evolution exhibits opening next month. Darwin’s Legacy will be about Darwin and how his “theory soon found supporters at the Smithsonian, including Joseph Henry, the first Secretary of the Smithsonian Institution, and it continues to guide research at the National Museum of Natural History.” The exhibit Since Darwin: the Evolution of Evolution
focuses on the significant role that Darwin’s theories have played in explaining and unifying all the biological sciences. Specimens from the Museum’s diverse collections, along with documentation from our ongoing research, illustrate the importance of evolution as a scientific foundation, and how our knowledge of evolution has evolved over the last 150 years.
I was also interested to see how the USNM had fared with regard to two other issues facing modern museums: commercialization and exhibit design. Museums are under increasing financial pressure, and even publicly supported institutions have had to seek at least supplementary private funding. There are potential pitfalls with such funding though: private funding might distort the mission or the message of the museum. The USNM had experienced a controversy over this while I was there, when the insect extermination company Orkin sponsored, and had its name put on, the Insect Zoo. There have been other controversies concerning donors since. I found that the named-by-sponsor exhibits were still there, but had not increased substantially. The new Ocean Hall was named for Roger Sant, a member of the Smithsonian’s Board of Regents, and a major donor. And there was a temporary exhibit on forensic anthropology co-sponsored by the History Channel, but the exhibit contents largely allayed my fears that the exhibit might be made to cable TV standards of quality. Most annoying, but not at the USNM, but rather across the mall in The Castle, was a heavily hawked tie-in to the movie Night at the Museum: Battle of the Smithsonian.
In its exhibit halls, the USNM seems to have avoided the worst of corporate sponsorship, such as the garish corporate-advertising-masquerading-as-sponsorship I’ve seen in some zoos and even national parks.
As regards design, there has for many years been a tension between exhibits that are rich in the number and diversity of labeled specimens they contain, and those that are “interactive”. The modern trend in design, as Steve Gould (Natural History, January 1994; see also his “Dinomania” in the NYRB) put it, has been
…fewer specimens, more emphasis on overt pedagogy, and increasing focus on “interactive” display (meaning good and thoughtful rapport of visitor and object when done well, and glitzy, noisy, push-button-activated nonsense when done poorly)…
The former notion of what makes for a good exhibit, which Gould admired and called “cabinet museums”, still informs, if not dominates, most of the USNM’s exhibits, including the newer ones such as Ocean Hall. While not consisting of row after row of specimens in the Victorian model, the newer exhibits continue to be rich in the diversity and number of specimens exhibited, and in the excellence of their labeling. A small exhibit in The Castle harks back to the Victorian model, but the best example of this approach I know of today is the marvelous Sense of Wonder at the Milwaukee Public Museum, a deliberate recreation of the older style. The juxtaposition of specimens is a major intellectual benefit of a such a style: it practically mandates that viewers begin composing “compare and conrast” essays in their heads. Such comparisons are a source of wonder, and an inspiration for systematics, comparative anatomy, and , indeed, much of the whole of biology. As a graduate student, I spent many hours “animalizing” (as we called it) studying the skeletons in the Museum of Comparative Zoology‘s Hall of Mammals (which is also close to the Victorian model). The USNM’s Osteology Hall, with its many vertebrate skeletons, has something of the same flavor.
My major criticism of the newer exhibits, especially the Hall of Mammals, is that they have largely left out dioramas, which, to me, have always been among the most compelling components of a natural history museum. A late Victorian development of the cabinet style pioneered by Carl Akeley at the Milwaukee Public Museum, and reaching perhaps its apogee at the American Museum of Natural History, a diorama associates animals and plants that live together in a natural setting. Most suited for exhibits with a biogeographic arrangement, their richness and frequency serve as a means to distinguish the great, from the merely good, public exhibit museums.
In the mammal hall, the mammals have been removed from the environmental context provided by the diorama, and presented against stark backgrounds painted in neutral colors, with a minimal or stylized attempt to portray the environment. Glass-panel walls and overhanging girders dominate the main exhibit hall. In part, this separation of organism from environment harks back to the early Victorian cabinet museum, with its unadorned skeletons and taxidermy mounts. These early exhibits are redeemed by the richness and density of the specimens, but this only partly mitigates the present exhibit. I think there are advantages to both the diorama and the starker style evident here, but to give up the one almost entirely is a mistake. This is seen most clearly in a segment of the mammal hall entitled “Savanna Waterhole“, where a giraffe and zebra stretch to drink, but there is no waterhole, and another zebra looks back at a glass wall.
Despite this criticism, there is much to admire in the mammal hall, and much to learn in it. This hall, and the museum as a whole, is a wonder, and one of the nations, and the world’s, scientific and educational treasures. To walk through the USNM’s exhibit halls is a marvelously enjoyable, richly rewarding, and deeply edifying intellectual and aesthetic experience.
Addendum. In response to some of the comments, here are a couple more items.
I just miss hundreds of different birds in a long, long hallway.
It’s a curved hallway, and somewhat obscurely placed outside the Baird Auditorium, but the Birds of DC exhibit is hundreds of birds in a longish hallway. Here’s the cabinet that contains mostly owls, but also a passenger pigeon and a Carolina parakeet.
Is the life-size fiberglass blue whale still there??
No, but a life-size northern right whale is, right in the middle of the new Ocean Hall. It’s modeled after an actual individual whale, named Phoenix, studied by scientists from the New England Aquarium. The story of its creation is here.
I’m not sure where the blue whale is now. It was part of the Life in the Sea exhibit, which was in what is now the Hall of Mammals (I think– I’m trying to recall the hall layout from years ago, and don’t have an old floorplan). It’s story, up to 1996, is told here in Smithsonian magazine.
I have a four-year-old fan! An alert reader writes:
Dear Dr. Coyne,
I am writing to let you know how much I am enjoying reading your book ‘Why Evolution Is True.’ While I have long been interested in the sciences my eyes have been opened even farther with the evidence this book presents.
And if it wasn’t enough that I am enjoying your book, my 4 year old son keeps stealing it from me at every opportune moment. He can’t seem to get enough of all the pictures and diagrams in the book. He is particularly fond of the diagram near the beginning of the book that shows the evolutionary change from reptiles to dinosaurs to birds. Since I have explained the diagram to him he now goes around telling everyone that birds came from dinosaurs. You can never start teaching them science and critical thinking too early!
I’ve attached a picture I thought you might enjoy.
Although far from the longest chapter in WEIT, I find the chapter on biogeography the single most persuasive one for showing why evolution is true. I think Jerry finds it compelling as well. This might seem surprising since he’s a geneticist: one might think he would find some of the genetic evidence most compelling. But I don’t think it is surprising, given that it was the biogeographic evidence, that, as the great zoogeographer P.J. Darlington put it, showed Darwin evolution.
World distribution of tapirs (from Tapir Specialist Group)
The first thing you might think needs explication is the disjunct distribution. But before tackling this, a mis-impression must be corrected: although we tend to think of tapirs as typically South American, from a historical perspective, they are recent interlopers. Along with many other animals we consider typically South American (jaguars, llamas, peccaries), they entered South America from the north about 3 million years ago when the Panamanian portal became the Panamanian isthmus during the Great American Interchange.
What, then about the disjunction: how did they get from Central America to Malaya? They didn’t. Tapirs are a northern group. They and their relatives date back to the lower Eocene (ca. 50 mya). The modern genus, Tapirus, dates back to the Oligocene (ca. 30 mya), and was found in Europe, Asia, and North America. They have gone extinct in Europe, most of Asia, and most of North America. Tapirs thus have a relict distribution, being still found at two endpoints of their historical distribution. Geology, paleontology, and systematics thus combine to give a most satisfying account.
In WEIT there is a chapter on vestigial traits, defined as those traits that are evolutionary remnants of features useful in an ancestor, but now either useless or used in a different way. The paradigmatic case is, of course, the appendix, the remnant of a caecal pouch used to digest leaves and vegetation in our ancestors. But behaviors can be vestigial, too. One such behavior is the “grasping reflex” of human infants. When you put your finger into the palm of an infant, it will immediately and securely grasp it. The grasp is so tight that it’s sometimes hard to make the kid let go! It is said — though I have never seen this demonstrated — that up to a couple months of age a baby can hang suspended from a horizontal stick for several minutes.
The grasping reflex is evident in the feet, too. If you put your finger along a baby’s toes from the sole side, it will grasp with those toes. And when a baby is sitting down, its “prehensile” feet assume a curled-in posture, much like what we see in an infant or an adult chimp.
One of my friends has a four-month-old daughter, and I asked her to take a picture of the grasping reflex and the prehensile foot posture for this website. Here are both in a single picture. Although the kid is somnolent, she still holds on firmly. The sitting posture of a young chimp is given for comparison.
Why do infants show this grasping reflex, but then lose it after several months? A very plausible suggestion is that the behavior is a remnant of the grasping reflex seen in other infant primates, which they use to hold on to the hair of their mothers as they’re being carried about.
I’m not going to encourage my readers to suspend their newborns from broomsticks in the cause of evolution (they could fall, after all), but if you’re sufficiently curious and foolhardy to do this, let me know the results.
Thanks to the anonymous mom who donated her child to science.
THIS JUST IN: Photographic proof! (Thanks to commenter Wes for the link.)
A couple of reviewers of WEIT (and some of my friends and colleagues) have pointed out the book’s dearth of molecular evidence for evolution. For example, why didn’t I stress that organisms thought to be related based on morphological similarities also show similar relationships in their DNA sequences? That is, DNA phylogenies generally match morphologically-based phylogenies — doesn’t that count as evidence for evolution? To my mind, not very strongly, and for two reasons. First, at least for protein-coding genes, morphology and DNA are not independent: the genes are blueprints for the organism’s appearance, so the coincidence of trees is not independent evidence for evolution.
My strategy here was to use as evidence for evolution only those data that rule out the most widely-accepted alternative scenario, i.e., some form of creationism. Similarities of molecular and morphological trees don’t necessarily rule out the action of a celestial designer. He/She/It could have used similar genes to make similar organisms.
Well, you ask, what about those parts of the DNA that are “neutral”? (E.g., the third positions of codons, in which a mutation doesn’t necessarily change the structure of the protein made by that gene.) Well, yes, those could count provided that they really are neutral. As molecular evolutionists examine genomes more thoroughly, they often find that “neutral positions” aren’t really neutral, but could play some role in the fitness of the organism. In such cases, their phylogenetic match to appearance-based phylogenies again fails to rule out creationism.
The one type of molecular evidence that does absolutely rule out creationism, I think, involves pseudogenes: those genes that were once active in ancestors but have become inactivated. I describe several cases in chapter 3 of WEIT; they include olfactory receptor genes in humans, many of which have become inactivated in the human lineage as we gradually lost reliance on our sense of smell and became more vision-oriented. DNA changes in pseudogenes can hardly be subject to natural selection, so pseudogenes change in a purely time-dependent manner as those dead genes accumulate mutations over time. Thus, the match between phylogenetic trees based on pseudogene DNA sequences (reflecting only the passage of time) with phylogenetic trees based on organisms’ appearance are expected under an evolutionary scenario but not a creationist one. Creationists largely deny common ancestry (and don’t accept that organisms change with the passage of time). They wouldn’t, then, predict a phylogenetic match between features that simply mark the passage of time and features that independently reflect ancestry (e.g., the placenta of placental mammals that is not found in marsupials). This is why I concentrated on pseudogenes in my book. I’ve never seen a creationist explanation for why DNA trees based on pseudogenes match traditional trees based on morphology.
Similarly, people often cite Hox (“homeobox”) genes as evidence for evolution (these are the genes that demarcate different segments of animal bodies). It turns out that in organisms which are very dissimilar, such as humans and my beloved fruit flies, Hox genes nevertheless play similar roles in building bodies. Why don’t I count this as evidence for evolution? Because it doesn’t rule out the alternative of a celestial designer. Such a designer could have used the same genes in different species as His/Her/Its way of building bodies. There’s no reason why a designer couldn’t hit on certain fundamental ways of making bodies, and then use them over and over again.
This, then, was my strategy throughout the entire book: to use only that evidence that could not easily be explained by creationism or other alternatives to evolutionary theory. This, of course, is precisely the strategy that Darwin used in The Origin, since he had to convince readers that his theory was superior to the reigning creationist paradigm of the day. I guess you can say that, given prevailing opinions in the US and some other countries, I adopted the same evidence-based strategy.
Coyne methodically lays out the complete trail of evidence supporting evolution, ranging from the fossil record of dinosaur bones to sophisticated DNA analysis, and many decades of rigorous peer-reviewed scrutiny in between.
In this 200th anniversary year of Darwin’s birth, “Why Evolution Is True” ranks among the best of new titles flooding bookstores….
He makes the case for evolution in a way that is eminently understandable, colorfully articulated, and relevant to our time.
Update: Jerry and I were apparently writing posts on this review simultaneously, so I didn’t see his post till mine went up. If I knew how to delete a whole post I would, but I don’t know how!
Until Jerry settles back in there’ll be a bit of overlap in our posting, so I’m providing this Caturday’s felid. Actually it’s two felids: the lion and the tiger (both of these links come from a wonderful page maintained by Virginia Hayssen of Smith College), both photographed today at the Racine Zoo in Wisconsin.
Two young lions at the Racine Zoo
The tiger, unfortunately, sat back out of useful range of the camera I had with me, so I had to settle for this.
Tiger sign at Racine Zoo
In captivity hybrids between lions and tigers, called ligers (male lion X tigress) and tigons (male tiger X lioness), can be produced, which are healthy and vigorous. As Jerry explains in chapter 7 of WEIT, species are defined by their reproductive relationships: members of the same species will interbreed with one another, while members of different species are kept from successfully reproducing by one or more reproductive isolating barriers. Why, then, do we consider lions and tigers different species?
Historic distribution of the lion in north Africa, Europe, and Asia
Tigers were widespread in Asia, from the Caucasus to Siberia in the north and Java and Bali in the south. Until man began to decimate them, lions and tigers broadly overlapped in southern Asia, but remained distinct, without interbreeding. Thus, in nature, lions and tigers did not interbreed. And the full definition of a species, given by Ernst Mayr in 1940, is that species are groups of actually or potentially interbreeding populations in nature, reproductively isolated from other such groups.
One of the things Jerry mentioned in introducing me was that I had coauthored, with my late friend and mentor John A.W. Kirsch, a paper entitled “The platypus is not a rodent”. While there’s a certain pure amusement value in such a title (which alludes to a series of papers concerning the relationships of guinea pigs with titles such as “Is the guinea-pig a rodent?”, “The guinea-pig is not a rodent”, and “Are guinea pigs rodents?”; btw, the guinea pig is a rodent, and the platypus is an egg-laying monotreme, nowhere close to rodents), Jerry might have mentioned the paper because of its subtitle: “DNA hybridization, amniote phylogeny and the palimpsest theory”. In WEIT, Jerry likens the bodies and genomes of organisms to palimpsests. In ancient and medieval times, parchment to write on was expensive, but writing was cheap. To save parchment, the writing would be scraped off a book (for in those days, all books were written by hand), and a new book written over the old. Such reused parchments are called palimpsests. The original writing, however, can often be seen or retrieved, and thus the history of the parchment’s uses can be inferred from the existing parchment. (Here’s an example mentioned by Jerry.)
A palimpsest possesses both recently acquired features (the new writing) and remnants of old features (the old writing). So do organisms. They possess immediately adaptive characters, as well as characters from earlier in their history. This has long been recognized, and the analogy with palimpsests has been explicit. In 1910 W.K Gregory of the American Museum of Natural History made a distinction between ‘caenotelic’ and ‘paleotelic’ characters; he later called these ‘habitus and heritage’ (Gregory was the major professor of my major professor, E.E. Williams, and thus I am Gregory’s academic ‘grandson’). In 1947, Gregory christened his ideas the ‘palimpsest theory’. As John and I explained:
Habitus characters (equivalent to caenotelic features) become in time transformed into, or at least included among, those of heritage as the collected adaptive wisdom of the lineage at more general levels, by a process of sequential adaptation …. Habitus and heritage are thus ‘correlative terms’, so that ‘the remainders of the successive habitus of the remote ancestors become incorporated into the heritage of later times’ (Gregory 1947, p. 8). Heritage features are therefore of utmost importance in determining the broad affnities of a higher-category taxon, because they may be ones shared with a similarly inclusive but different group.
Thus the habitus characters are the new writing, the heritage the old. The palimpsest analogy had been published earlier by the great South African paleontologist Robert Broom (best known for his later work on australopithecines, the predecessors of our own genus, Homo) who in 1924 wrote about turtles that
Unfortunately members of the order are all extremely specialized and in some respects degenerate, so that the picking out of the ancestral [=heritage or paleotelic] characters amid the more recent specializations [=habitus or caenotelic] is somewhat like the reading of a difficult palimpsest.
Broom and Gregory were well-acquainted with one another, and Broom visited the American Museum in 1913-1914, so the use of the term palimpsest by the two of them is probably not independent.
Not all historical processes leave clear traces of their paths: if a ball rolls downhill to a resting place, we cannot infer from where on the surrounding heights it began; and one molecule of water is just like another (of the same isotopes), no matter whence it came. We are fortunate that descent with modification is a history-conserving process: bodies and genomes of organisms are documents of evolutionary history. As the many examples in WEIT show, even when a fossil record is lacking, we can learn much about an organism’s evolution.
Fig. 1. Mount Darwin, with its flat summit.
Fig. 2. Nearly at the summit.
Fig. 4. Dunbar Carpenter, too absorbed in reading to climb.
Fig. 5. Now it belongs to the ages. Inscription in the copy left at summit.
bequeathed to it by its founding benefactor, 
In the Ocean Hall, one of the main galleries is devoted to the origin and history of life on earth, including everything from 
Fig. 1. Evoutionist in statu nascendi. 
