Amazing reef fishes

July 11, 2012 – 8:28 am

The Evolution meetings are over, and I’m heading home tomorrow, spending today in Ottawa to visit friends. Because of that, and other exigent tasks, posting will be light.

But thanks to pinch-blogger Matthew Cobb, who directed me to these pictures of stupendous reef fish. Those fish comprise some of the world’s most beautiful and bizarre animals.

Have a look at some of these spectacular fish from a new book, Reef Fishes of the East Indies by Gerald Allen and Mark Erdman (University of Hawaii Press); the book’s photos are excerpted in The Guardian, which adds:

A new book, Reef Fishes of the East Indies, is the culmination of a combined 60 years’ work to document the biodiversity of the hugely diverse coastal waters of the region. The three-volume publication features the 2,631 known reef fishes of the Coral Triangle, including 25 species new to science.

Non-new species: Pteroidichthys amboinensis – an unusually coloured specimen of the Ambon scorpionfish. Photograph: Roger Steene/Conservation International.

I wonder what the eyespots in the photo below are for. Could they be mimicking an octopus to ward off predators? And what about those strangely colored and shaped fins?

Some male cichlid fish have spots on their anal fins that mimic the female’s eggs. Female cichlids are often mouth-brooders, who lay eggs and then gather the unfertilized eggs into their mouths to protect them. When they see the spots on the male’s anal fin, they think they’ve lost an egg, and swim up to the male’s posterior end, opening their mouth to retrieve the supposedly stray egg. When they do that, the male squirts sperm into the female’s mouth, fertilizing her eggs. This is one example of mimicry in which members of one sex fool members of another.

Non-new species: Signigobius biocellatus. Photograph: Gerald Allen/Conservation International.

Non-new species: Synchiropus splendidus. Mandarinfish of the dragonet family mate just before sunset. The pair meets and swims slow spirals off the substrate. At the apex of their ascent they release sperm and eggs then dash back to the protection of the bottom. Photograph: Jones/Shimlock. Secret Sea Visions /Conservation International.

Non-new species: Antennarius commersoni – a frogfish spawning and then releasing a floating egg raft. Photograph: Roger Steene/Conservation International.

In contrast to many freshwater fish or open-water marine fish, reef fish are often arrayed in dazzling colors and patterns. Why is that?
Well, we don’t really know, but, as a piece by Greg Laslo emphasizes, what we see when we look at these fish may be very different from what the fish see, since their color sense may be very different from ours and they also see in the ultraviolet.

Since the fish are not sexually dimorphic in pattern and color (males and females usually look alike), it probably isn’t a result of sexual selection. I suspect, as does Laslo, that it facilitates interspecific communication.  But this is simply one of those ubiquitous phenomena that we don’t understand. Laslo gives a quote from biologist Gil Rosenthal, an acquaintance of mine and an avid diver:

“The conventional explanations for why they are colorful don’t really work,” Rosenthal says. Bright colors are useful to advertise that the species is dangerous or bad-tasting — for example, poison dart frogs in the Amazon and coral snakes or monarch butterflies in North America. So, too, in some fish — the butterflyfish has spines, and the scorpionfish will display colorful pectoral fins when they’re frightened. And while that’s all well and good, most brightly colored reef fish are actually pretty tasty. At least to humans. Bright colors could also help fish attract mates. For instance, in birds, brightly colored male peacocks are perhaps the best example, but that doesn’t work with most fish. For example, in Picasso triggerfish and Queen angelfish, the males and females are equally colorful, and you can’t tell them apart by looking at them.

“There isn’t going to be just one explanation, that’s the bottom line,” [George] Losey says. “There are going to be a lot of contributing factors.”

New species: Ptereleotris rubristigma – a blue dart fish named for the prominent red spot on the gill cover. Widespread throughout the East Indies region and found on soft bottoms exposed to currents. Photo by Gerald Allen/Conservation International.

New species: Lepidichthys akiko – a candy-striped clingfish known only from deep reefs of Cendrawasih Bay in West Papua. Photo by Gerald Allen/Conservation International.

New species: Pterapsaron longipinnis – A deep reef species (below 60m depth) discovered in Cendrawasih Bay in West Papua. The name refers to the unusually long pelvic fins which this fish uses to rest on the bottom in tripod-like fashion. Photo by Gerald Allen/Conservation International.

By whyevolutionistrue | Posted in Uncategorized | Comments (9)

Hitch arrives in Heaven

July 10, 2012 – 10:20 am

OMG! In a brand new episode of “Mr. Deity,” Hitch, contrary to all his expectations, shows up at the Pearly Gates—with a long list of demands for God.

h/t: Grania

By whyevolutionistrue | Posted in LOLz, Mr. Deity | Comments (24)

RIP Philip Tobias

July 10, 2012 – 10:01 am

If you haven’t heard of Philip Tobias—and you should if you know a bit about human evolution—you will have heard of the Sterkfontein Caves, a World Heritage Site excavated by Tobias, a paleoanthropologist who spent most of his career at the University of the Witwatersrand in Johannesburg, South Africa. Tobias died Saturday June 7 at age 86.   (I was off by a month, and hadn’t heard the news, but the man still deserves an RIP.)

Tobias was a student of Raymond Dart, who discovered the first austraolpithecine fossils in 1924, also in South Africa (I describe Dart’s dramatic find at the beginning of my chapter on human evolution in WEIT). Tobias was also mentored by the Leakeys, and worked at Olduvai on the famous hominin fossil nicknamed “Nutcracker Man” or “Dear Boy”.  As the New York Times obituary notes:

Dr. Tobias wrote a treatise that described Dear Boy in minute, almost microscopic detail.

“That monograph continues to be the benchmark on how we should chronicle these important discoveries,” said the paleoanthropologist Donald C. Johanson, co-discoverer of the famous hominin fossil Lucy and founding director of the Institute of Human Origins at Arizona State University. “It’s on every paleoanthropologist’s shelf.”

“Nutcracker Man” became the holotype specimenof Paranthropus boisei (formerly Zinjanthropus), a robust hominin (ergo the name, derived from its massive teeth) that was a sterile offshoot of the hominin tree.

The NYT adds this:

In the 1960s, Dr. Tobias became involved in excavations at South Africa’s Sterkfontein caves, which yielded a trove of hominin fossils and tools, including a specimen called Little Foot, an unusually complete hominin skeleton whose age has been estimated at 2.3 million to 4 million years. Dr. Tobias campaigned successfully to have the caves declared a World Heritage site.

“Little Foot” is an australopithecine whose affinities are still uncertain.

And an obit at tributes notes that Sterkfontein is where over a third of all known early hominin fossils have been found, including specimens of Paranthropus, Australopithecus, and Homo.

Finally, Tobias was a fierce opponent of apartheid during the years it was the law in South Africa (Witwatersrand, or “Wits,” was a center for both black and white opposition to apartheid.) The Times describes a lecture he gave in Stony Brook in 2006:

In his Stony Brook lecture, Dr. Tobias said he wanted to correct accounts in several books that said Louis Leakey had browbeaten him into agreeing that Homo habilis was a distinct species. Dr. Tobias said that he had come around gradually to agreeing with him, but that his agreement was based strictly on the evidence.

“My personality was not such as to be easily browbeaten into a certain standpoint,” Dr. Tobias said. “My individualism had stood behind me in my 40-years-long fight against apartheid and the inroads against academic freedom by the apartheid government of South Africa.”

Tobias in 2006 in Johannesburg, where he taught. Photo for the NYT by Alexander Joe/Agence France-Presse — Getty Images

By whyevolutionistrue | Posted in anthropology | Comments (5)

BBC documentary: “What Darwin Didn’t Know”

July 10, 2012 – 6:24 am

This three-year-old BBC documentary, about 1.5 hours long and hosted by developmental biologist Armand Leroi, was put on YouTube in January and is well worth watching.  Leroi travels the world pointing out the products and processes of evolution, interspersing his commentary and visits to labs and field sites with historical vignettes about the introduction of Darwinism in the nineteenth century.  The description notes:

Evolutionary biologist Professor Armand Marie Leroi charts the scientific endeavour that brought about the triumphant renaissance of Darwin’s theory. He argues that, with the new science of evolutionary developmental biology (evo devo), it may be possible to take that theory to a new level to do more than explain what has evolved in the past, and start to predict what might evolve in the future.

Well, I am a guarded fan of “evo devo”  (the field that connects developmental biology to evolution), but think that, like the human genome’s promise to cure disease, evo-devotees have sometimes been overly enthusiastic about what their field can deliver.

And as for the notion that evo devo can tell us what might evolve in the future, well, I don’t buy that.  Evo devo can give us hints about what is unlikely to evolve in the future, but that’s a different matter. And of course evolution has always been smarter than we are.  Who would have predicted that wingless insectivores could have evolved wings and given rise to bats?

Henry Gee recounts a famous anecdote about J.B.S. Haldane’s delivering a similar evo devo prediction eighty years ago:

In 1932 the British geneticist J. B. S. Haldane mused that an all-powerful genius might produce from available human genes a race with Shakespeare’s intellectual power and the stature of the giant prizefighter Primo Carnera. ”But,” he added, ”he could not produce a race of angels. For the moral character or for the wings he would have to await or produce suitable mutations.”

Yet those wing mutations did occur in the ancestors of bats, although I can’t speak for bat morality.

Still, the evo devo doesn’t dominate this video, which I recommend as a very good introduction to the tenets and evidence for evolution. Armand Leroi is an excellent presenter. I haven’t watched this in a while, but as I recall (I may be wrong) I have about five seconds as a talking head.

h/t: Al

By whyevolutionistrue | Posted in evolution, video | Comments (21)

A new “Simon’s Cat”

July 10, 2012 – 6:09 am

If you’ve followed this awesome series of animations about long-suffering Simon and his obstreperous cat, there’s a brand new one: “Window Pain”.  Have a gander:

Only one thing still this moggie’s obnoxiousness: NOMZ!

h/t: Michael

By whyevolutionistrue | Posted in felids, LOLz | Comments (10)

The chemical ghost of a 120 million year-old bird

July 9, 2012 – 2:20 pm

by Matthew Cobb

I spent Friday-Sunday last week at the Royal Society Summer Exhibition, helping out some colleagues from the Manchester University Geochemistry & Paleontology Research Group as they explained their research to the public. I had such fun, and the stuff we were talking about was so interesting. What follows is pretty much the pitch I gave to the public, as someone who wasn’t directly involved in the research. Two WEIT readers came up  who had recently graduated from Queen Mary, London – I didn’t catch their names, but hi!

The centre-piece of our display was a 120 MY old fossil of Confuciusornis sanctus, a basal bird from China – it is the earliest known bird with a beak. About the size of a pigeon, it had long twin tail-feathers strongly suggestive of sexual selection. This bird was one of a flock that was caught in a volcanic explosion one Tuesday afternoon (I made that bit up) and ended up fossilised at the bottom of a lake. The fossil itself is pretty neat, with clear impressions of feathers, bones and soft tissues (see image A below):

Fossil Confuciusornis sanctus; A: optical image B: False-colour signals from X-ray fluoroescence; Green = zinc; blue = calcium; red = copper (Wogelius et al., 2011)

As a biologist, I’d be happy with the fossil, but my colleagues Roy Wogelius and Phil Manning from Manchester Earth & Environmental Sciences, together with Uwe Bergmann from Stanford and a host of other folk, decided to use a technique they had previously employed on an Archaeopteryx fossil (Bergmann et al., 2010). They put the fossil at the sharp end of the Stanford synchotron and fired a concentrated X-ray beam at the fossil. In response to this procedure, the atoms of the different elements require different energies to fluoresce, so an ‘elemental map’ of the fossil can be built up.

Figure B above shows the signals for three elements: zinc (= green), calcium (= blue) and copper (red). The zinc is present in background levels in the matrix and shows no specific information about the fossil; calcium is present in the bones and beak, and only in the bones and beak. On the one hand, this is trivial (where else would it be?) and on the other it is amazing – it shows that the fossil is not simply a physical impression, there are also chemical traces that are trapped in the rock: atoms of calcium that were once in the bird’s bones.

The red signal of copper is the most audacious to interpret. You can see that it is on the outside of the animal, primarily in the feathers (look at the intense staining in the upper body). However, not all the feathers show this staining – look at the large wing feathers on the bottom left and bottom right of the fossil – they do not show any copper. So the distribution of copper in the feathers is non-random.

Roy and the rest of the team were able to show that this copper is definitely organic, and shows the coordination chemistry that is typical of eumelanin (I am skipping over several complicated stages of chemistry here – details in the references). This would suggest that the distribution of copper could be a biomarker for the presence/absence of melanin in the tissues of the living bird.

To test their hypothesis, they took various feathers and control samples, modern and fossil, and subjected them to the same X-ray fluoresence. The results strongly support their view (I find modern feathers D and E and their X-ray equivalents L and M particularly convincing):

A to G) optical images and (H to O) false-color images of: [(A) and (H)] Green River fossil feather; [(B), (I), and (J)] Green River fossil feather and fish; [(C) and (K)] G. yumenensis fossil feather; [(D) and (L)] eagle feather; [(E) and (M)] blue jay feather; [(F) and (N)] Hakel fossil squid; [(G) and (O)] sectioned extant squid. For H & J: red, Cu; green, Ca; and blue, Fe. For K: red, Cu; and green, Ca. For the remaining images, red, Cu. (Wogelius et al. (2011)

As a result, my colleagues interpreted the black/white distribution of colour thus:

This is cool because it shows the colour (or at least, the black and white distribution) of C. sanctus. Even more interestingly, along with the rest of their work, it clearly shows that fossils are not simply physical imprints, but also chemical traces that, with the right technology, can be interpreted in biological terms: we can work out the biochemistry of cells in an animal that died 120 million years ago. However, it isn’t straightforward: interpreting the distribution of copper was possible because they could demonstrate that it was a good biomarker for eumelanin. The distribution of other elements is not so easy to interpret – the biology is going to be as complicated as the particle physics and analytical chemistry.

There are other techniques for determining colour in fossils – in the same issue of Science that Roy and his colleagues published their findings, Ryan McKellar examined a load of late cretaceous dinosaur and bird feathers that had been trapped in amber. And in 2010 two papers on other fossils of primitive birds and dinosaurs using scanning electron microscopy suggested that the cellular structures involved in pigmentation – melanosomes – could be reliably detected in some specimens (Li et al, 2010; Zhang et al., 2010). The advantage of the technique used by my colleagues is that it relies less upon exceptional preservation, and it gives a whole-organism view. The trick, however, will be to find reliable interpretations of the elemental distribution.

To find out more about the technique, including some examples of its use on archaeological artifacts, including a ‘lost’ score by Cherubini, see Bergmann (2012).

To accompany the exhibition, Phil Manning made an e-book for the iPad, called “Chemical Ghosts”. This is available *free* from the iBook store. He also made an excellent free app, again for the iPad and called “Chemical Ghosts” (there are no Android versions I’m afraid, and they don’t work on the iPhone). At the end of the app, the camera starts up on your iPad (so it doesn’t work if, like me, you have an iPad 1 with no camera…). If you present this image to the camera (probably best to print it out), and get it in focus, you will be amazed what happens. Turn the image to one side and another – this was one of the best bits of the exhibit! People were absolutely amazed. Honest!

UPDATE: Here’s an image of what you see with an iPad with a camera – people in the comments have been asking. This was taken by Phil Manning himself. It’s a 3-D “augmented reality” rendering of the bird. You can move it in three dimensions as you move the cartoon of the bird. It’s really rather impressive (and better than this 2-d snapshot!). Note the realistic shadow!

Augmented reality Confuciusornis sanctus

Sources:

There’s a website at the Royal Society about the exhibit, and Phil Manning has his own dinosaur blog.

References (links are only to abstracts I’m afraid, unless you have personal or institutional access):

U. Bergmann, R. W. Morton, P. L. Manning, W. I. Sellers, S. Farrar, K. G. Huntley, R. A. Wogelius, and P. Larson (2010) Archaeopteryx feathers and bone chemistry fully revealed via synchrotron imaging. PNAS 107:9060-9065

Uwe Bergmann, Philip L. Manning & Roy A Wogelius (2012) Chemical mapping of paleontological and archeological artifacts with synchotron X-rays. Annual Review of Analytical Chemistry 5:361-389.

Quanguo Li, Ke-Qin Gao, Jakob Vinther, Matthew D. Shawkey, Julia A. Clarke, Liliana D’Alba, Qingjin Meng, Derek E. G. Briggs and Richard O. Prum (2010) Plumage color patterns of an extinct dinosaur. Science 327:1369-1372

Ryan C. McKellar, Brian D. E. Chatterton, Alexander P. Wolfe, Philip J. Currie (2011) A diverse assemblage of late Cretaceous dinosaur and bird reathers from Canadian amber. Science 333:1619-1622

R. A. Wogelius, P. L. Manning, H. E. Barden, N. P. Edwards, S. M. Webb, W. I. Sellers, K. G. Taylor, P. L. Larson, P. Dodson, H. You, L. Da-qing, U. Bergmann (2011) Trace metals as biomarkers for eumelanin pigment in the fossil record. Science 333:1622-1626.

Fucheng Zhang, Stuart L. Kearns, Patrick J. Orr, Michael J. Benton, Zhonghe Zhou, Diane Johnson, Xing Xu & Xiaolin Wang (2010)Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature 463:1075-1078

By whyevolutionistrue | Posted in Uncategorized | Comments (32)

RIP Ernest Borgnine

July 9, 2012 – 10:18 am

Ernest Borgnine died on Sunday in Los Angeles. He was a ripe 95 years old.

Perhaps best known for his role on the mediocre television series “McHale’s Navy,” he really shone in two movie roles. The first was “Marty” (1955), in which he played a mother-dominated Italian butcher who falls in love with a “plain” girl (Betsy Blair; I found her rather attractive, actually), abandons her when her friends make fun of him, and then realizes that what matters is love, not the opinion of his thoughtless peers. It’s a wonderful movie, and gets a rare 100% critics’ rating on Rotten Tomatoes (see link above). As the NYT notes:

Marty’s awakening, as he unexpectedly falls in love, was described by Bosley Crowther in The New York Times as “a beautiful blend of the crude and the strangely gentle and sensitive in a monosyllabic man.”

Mr. Borgnine received the Oscar for best actor for “Marty.” For the same performance he also received a Golden Globe and awards from the New York Film Critics Circle, the National Board of Review and the British Academy of Film and Television Arts.

I highly recommend “Marty”; it’s a bit of a tear-jerker but with terrific acting. And his performance is very different from the movie role that brought Borgnine to fame: the sadistic sergeant Fatso Judson in the equally watchable movie “From Here to Eternity” (1953).

When you remember Borgnine, think not of Lt. Commander Quinton McHale of the U. S. Navy but of the Everyman he played so well: the gentle butcher Marty Pilletti.

Here he is with Betsy Blair in “Marty”:

By whyevolutionistrue | Posted in movies, obituary | Comments (31)

Extinct tortoise rediscovered- sort of- and hope for Lonesome George’s clan

July 9, 2012 – 9:17 am

by Greg Mayer

The recent untimely passing of Lonesome George, the last living individual of the Galapagos tortoise subspecies from Pinta (Abingdon) Island, reminds me of a paper from earlier this year, which holds out some hope for the Pinta tortoises. In that paper, in Current Biology, Ryan Garrick and colleagues presented evidence for the continued existence of the Floreana (Charles, Santa Maria) Island tortoise. The evidence is indirect, but very interesting.

Floreana (Charles, Santa Maria) Island tortoise. Gunther 1902, plate XVI

Floreana was much visited by buccaneers and whalers, and was the first of the Galapagos islands to be colonized (in 1832). Consequently, its tortoises took it on the chin earlier than most. The last tortoises known to have been collected on the island were taken in the 1830s, and the race is supposed to have been extinct by about 1840. One of the things that made tortoises attractive to mariners was that they could survive long periods of time in the holds of ships, which sometimes led to live tortoises being brought to other islands, and, at least occasionally, their release back into the wild.

Floreana (Charles, Santa Maria) Island tortoise. Gunther 1902, plate XVII

Genetic evidence of this mixing of island tortoise populations was found by Nikos Poulalakis and colleagues. Using DNA recovered from museum specimens collected in the 19th century, Poulalakis et al. found the Floreana tortoises genetically distinctive, and that some of the Floreana genetic material was present in tortoises from the island of Isabela (Albemarle). (Michael Russello and colleagues have also found evidence of Floreana ancestry in captive tortoises.) Building on this, Garrick et al. have now shown that some of the genetically mixed tortoises on Isabela are F1 hybrids– i.e., one of their parents was a Floreana tortoise! The F1′s were also not very rare– 84 were identified– and some quite young (< 15 years), so the parents should still be around. So, a Floreana tortoise has not been found (hence the “sort of” in the title), but there’s a really good chance that they’re still out there, somewhere on Isabela. If found, they could then be bred together, and perhaps reintroduced to Floreana.

What does this mean for Lonesome George’s subspecies? Well, Michael Russello and colleagues found evidence of Pinta tortoise (that’s George’s subspecies) genetic material in Isabela tortoises, too. So, there might be a Pinta tortoise or two on Isabela as well. None of the genetically mixed tortoises have been identified as F1, though, so discovery of a living Pinta tortoise is a longer shot than finding a Floreana tortoise. But it will be very interesting to watch for the results of continued genetic surveys of Galapagos tortoises (most of the work is being carried out in the laboratory of Adalgisa Caccone at Yale), and keep our fingers crossed that Floreana and Pinta tortoises might turn up.

h/t: daveau, Dominic

______________________________________________________________

Chambers, P. 2006. A Sheltered Life: The Unexpected History of the Giant Tortoise. Oxford University Press, Oxford.

Garrick, R.C., E. Benavides, M.A. Russello, J.P. Gibbs, N. Poulakakis, K.B. Dion, C. Hyseni, B. Kajdacsi, L. Marquez, S. Bahan, C. Ciofi, W. Tapia and A. Caccone. 2012. Genetic rediscovery of an ‘extinct’ Galápagos giant tortoise species. Current Biology 22: 10-11. pdf

Gunther, A. 1902. Testudo galapagoensis Novitates Zoologicae 9:184-192. BHL

Poulakakis, N., S. Glaberman, M. Russello, L.B. Beheregaray, C. Ciofi, J.R. Powell, and A. Caccone. 2008. Historical DNA analysis reveals living descendants of an extinct species of Galapagos tortoise. Proceedings of the National Academy of Sciences 105:15464-15469. pdf (not sure if it’s open access)

Russello, M.A., L.B. Beheregaray, J.P. Gibbs, T. Fritts, N. Havill, J.R. Powell and A. Caccone. 2007. Lonesome George is not alone among Galápagos tortoises. Current Biology 17: 317-318. pdf

Russello, M.A., N. Poulakakis, J.P. Gibbs, W. Tapia, E. Benavides, J.R. Powell, and A. Caccone. 2010. DNA from the past informs ex situ conservation for the future: an “extinct” species of Galápagos tortoise identified in captivity. PLoS ONE 5(1): e8683, 7 pp. pdf

Van Denburgh, J. 1914. Expedition of the California Academy of Sciences to the Galapagos Islands, 1905-1906. X. The gigantic land tortoises of the Galapagos Archipelago. Proceedings of the California Academy of Sciences (4th Ser.) 2: 203-374. pdf

By whyevolutionistrue | Posted in animals, conservation | Tags: , | Comments (9)

Nature bejeweled

July 9, 2012 – 7:44 am

Here’s a gorgeous unmanipulated photo taken by Jens Kolk: a ladybug covered with morning dew (click to enlarge):

Biology lesson: though many of us call these “ladybugs,” they aren’t true bugs, which are members of the order Hemiptera. “Ladybugs” are beetles, in the order Coleoptera (family Coccinellidae), and probably better called “ladybird beetles.”

By whyevolutionistrue | Posted in animals, photography | Comments (31)

What would disprove evolution?

July 9, 2012 – 4:27 am

If evolution is a scientific theory worth its salt, then there must be some conceivable observations that could show it to be wrong.  I just wanted to put down, for the record, what some of those observations might be. First, let’s reprise what I see as the major components of the theory of evolution.

  1. Evolution occurs, that is, there is gene frequency change in populations over generations.
  2. Significant evolution takes time—that is, it usually (though not always) requires hundreds to thousands of generations to occur. It is not instantaneous, and it is the population and species rather than the individual that evolves.
  3. Lineages of organisms split, or speciate, so that the single lineage that gave rise to life 3.5 billion years ago has undergone numerous splitting events to produce the millions of species alive today (and also the even more millions that went extinct).
  4. The converse of #3: any pair of living species has a common ancestral species some time in the past.  That is, if you trace any pair of twigs on the tree of life, you will find a node where the line from the trunk bifurcates to produce them.
  5. The process producing the appearance of design in organisms is blind, purposeless natural selection. (There are, of course, evolutionary forces other than selection, including genetic drift, but they don’t produce the marvelous design that was once seen as the prime evidence for the hand of God.)
These parts of the theory don’t all stand together. For example, you could have evolution without branching: that would mean that only one long-evolved species would be alive today. Or you could have evolution, but not occurring by natural selection. (The complete absence of natural selection is hard to imagine, though, given that organisms replicate their genetic material, and some genes will replicate better than others in different environments. Lamarckism and teleologically-driven evolution, however, were once seen as the main drivers of adaptation.)  Finally, you could have evolution but not gradualism: every population could experience great saltational leaps in one generation.

In my general talk on the evidence for evolution, I give a list of seven observations that, if repeated and confirmed, would disprove parts of the theory of evolution described above. This shows that it is a scientific theory in the Popperian sense of being falsifiable.  Here are some of those conceivable observations:

  • Fossils in the wrong place (e.g., mammals in the Devonian). If the fossil record were all out of order like this (a single anomalous fossil might not overturn everything, of course, since it could be in the wrong place for other reasons), we’d have to seriously question the occurrence of evolution.
  • Adaptations in one species good only for a second species.  There are plenty of adaptations in species that are good for other species, but also help members of the first species: these are the basis of mutualisms. (Cleaner fish, for example, remove parasites and dead tissue from other marine fish, but thereby gain a meal.) But we don’t expect to see—and don’t see—adaptations in one species that evolved solely for the benefit of another species.
  • A general lack of genetic variation in species.  Evolution depends on genetic variation. If most species had none, they couldn’t evolve.  However, the universal efficacy of artificial selection (I’m aware of only three lab experiments that failed to show a response to such breeding experiments), shows that genetic variation is ubiquitous in nearly all species.
  • Adaptations that could not have evolved by a step-by-step process of ever-increasing fitness. This is of course the contention of advocates of Intelligent Design like Michael Behe. But adaptations like the flagellum, which Behe and other IDers cite as features that couldn’t have arisen by a step-by-step process of increasing adaptation, have been shown to plausibly arise by just that process.  We don’t need to completely reconstruct the evolution of things like flagella, but simply show that their evolution by a stepwise adaptive process was plausible.
  • The observation that most adaptations of individuals are inimical for individuals or their genes but good for populations/species.  Such adaptations aren’t expected to evolve often because they would require the inefficient process of group or species selection rather than genic, individual, or kin selection.  And indeed, we see very few features of organisms that seem inimical to organisms or their genes but useful for the population or species. One possible exception is sexual reproduction.
  • Evolved “true” altruistic behavior among non-relatives in non-social animals. What I mean by “true” altruistic behavior is the observation of an individual sacrificing its reproductive output for the benefit of individuals to which it is either unrelated or from whom it does not expect to receive return benefits.  In this “true” altruism your genes give benefits to others and get nothing back, and this shouldn’t evolve under natural selection. And, indeed, we don’t see such altruism in nature. There are reports that vampire bats regurgitate blood to other individuals in the colony to whom they’re unrelated, but those need confirmation, and there may also be reciprocal altruism, so that individuals regurgitate blood to those from whom, one day, they expect a return meal. Such cooperation can evolve by normal natural selection.
  • Complete discordance between phylogenies based on morphology/fossils and on DNA. While individual genes can show discordance by lateral transfer—rotifers, for example, have incorporated into their genome from DNA from very unrelated organisms, and this is also common for bacteria. But lateral transfer of genes, as opposed to their direct descent from parent to offspring, is relatively uncommon.  So, for example, if we sequenced the genome of a blue whale and found that on the whole the species was more closely related to fish than to mammals, we’d have a serious problem for the theory of evolution.
We don’t see any of these anomalies, and so the theory of evolution is on solid ground. As I say in my book, “Despite a million chances to be wrong, evolution always comes up right. That’s as close to a scientific truth as we can get.”

That’s my list, and I would be delighted if readers conversant with evolutionary theory and natural history would add others.

By whyevolutionistrue | Posted in evolution, WEIT | Comments (182)
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