Recently in Evolution Category

Felis catus

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Photograph by Andrey Pavlov.

Photography contest, Finalist.

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Felis catus – domesticated cat. Mr. Pavlov tells us, “The photo of the cat is my cat Rosie, short for Rosen of Einstein-Podolsky-Rosen (her sister is named Electron, not pictured). She is a daughter of a feral cat, rescued from a swamp in central Louisiana.”

Eumorpha achemon

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Photograph by Gabrielle Hovinen.

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Eumorpha achemon – achemon sphinx moth.

Noncircular pupils explained

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Several years ago, I reviewed the book Evolution’s Witness: How Eyes Evolved, by Ivan Schwab. The book is downright encyclopedic, and I could not praise it highly enough. But in my review I wondered about elongated pupils, such as those of a cat, which are barely discussed the book. I remember reading somewhere that the elongated pupil could be stopped down farther than a circular pupil, but that explanation does not account for the problem that horizontal structures will be more clearly resolved than vertical structures (presuming that the pupil is elongated vertically and the eye is nearly diffraction limited).

A team from Berkeley and Durham University now proposes a better explanation. Without going into detail, they find that predators that ambush their prey, like cats, typically have vertically elongated pupils. From the abstract:

Vertically elongated pupils create astigmatic depth of field such that images of vertical contours nearer or farther than the distance to which the eye is focused are sharp, whereas images of horizontal contours at different distances are blurred. This is advantageous for ambush predators to use stereopsis to estimate distances of vertical contours and defocus blur to estimate distances of horizontal contours.

One way to put it: All the blur due to defocus is in the vertical direction, so horizontal contours are blurred when defocused, whereas vertical contours are not, because the blur is parallel to the contour; see their Figure 2(A). I do not want to go into detail, but they demonstrate that ambush predators, like the cat, that prowl close to the ground benefit from having good stereo vision for vertical contours. Prey animals, like the goat, often have horizontal pupils, which supposedly facilitate wide-angle views. Curiously, their pupils remain horizontal regardless of the orientation of their heads.

This paper goes a long way toward explaining why different animals have differently oriented pupils. You may see a video and a short article here and an NPR report here.

The paper does not explain how, when I was an elongating pupil in fourth grade, my teacher, an ambush predator if ever there was one, managed to see through 360°.

Who? The Chevalier de Lamarck, that’s who. Born 1 August 1744, he was the first evolutionary biologist who gave a mechanism that could, in principle, explain adaptation. Even though his mechanism was wrong, he was a true pioneer and a great biologist. (I’ll leave this post short, so as not to push Matt’s photo contest off the page).

Actias luna

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Photograph by Tom Gillespie.

Photography Contest, Second Place.

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Actias luna – Luna moth, Duluth, Georgia. Shot from underneath, as it was resting upside-down in my azalea bush.

Domesticated: Book review

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A number of years ago, I found a family of raccoons living in my chimney.1 I got them out by dropping a trouble light down the flue and turning it on for a few days. According to Richard C. Francis, in his splendid book, Domesticated, animals such as raccoons living in urbanized areas represent the first step toward domesticating those animals.

The full title of the book is Domesticated: Evolution in a Man-Made World, and Francis shows in considerable detail how various animals became domesticated: dogs, cats, pigs, sheep and goats, reindeer, camels, horses, rodents, and perhaps humans, as well as other predators such as raccoons and ferrets. Each scenario is slightly different, each seems well documented, and each has just a little bit of just-so story in it.

Melting of polar ice

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Photograph by Dan Moore.

Photography Contest VII: Winner.

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Melting of polar ice. Mr. Moore writes, “Our ship got caught in the ice and had to be freed by a Canadian ice breaker. Global warming – what?? Actually, yes – we could not get through because so much ice broke free further north near the polar ice cap and was blown south into the shipping channels.” Mr. Moore will receive a signed copy of Why Evolution Works (and Creationism Fails), which has been donated by one of the authors.

Here are the finalists of the 2015 photography contest. We received 16 photographs from 7 photographers, somewhat fewer than in previous years. This year we decided to choose 1 picture from each entrant and enlisted our wife to help with the choices. The text was written by the photographers and lightly edited for consistency.

The finalists are given below the proverbial fold, in alphabetical order of last name. Please look through their photographs before voting for your favorite. You will have to be logged in to vote on the poll. We know it is possible to game these polls. Please be responsible and vote only once. If we think that the results are invalid, we will cancel the contest.

Polling will close Friday, July 17, at approximately 12:00 CST.

Reed Cartwright contributed to this post.

Zenaida macroura

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Zenaida macroura – mourning dove, Walden Ponds Wildlife Habitat, Boulder, Colorado, spring, 2015. I have not seen nor heard a mourning dove within the city limits since the collared doves took over.

Photography contest finalists next week, July 6, noon, CST.

Unidentified fossil

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David MacMillan, who wrote an 8-part series on creationism for us, sent us these 4 photographs, along with the following request:

“I recently moved back to central Kentucky. One of the things I came across while visiting my family was this fossilized object I discovered near my home here when I was about 9 or 10 years old.

“Back in the late 90s, we were living in a new development and there was a lot of excavation going on near our house. I believe I found this half-buried in the bottom of a rain-fed creek just after a particularly heavy period of excavation followed by some heavy rainstorms.

“It appears to be a vertebra, due to the shape and orientation of the various spurs, and what seems to be a very large nerve opening going in the side. The exterior is dotted with what appear to be marine fossil concretions, including scallops and similar creatures.

“This region of Kentucky comprises primarily Ordovician limestone and shales, which is puzzling because this would have to be a pretty large marine vertebrate, and there were virtually no large bony vertebrates in the Ordovician. Perhaps this is actually not a vertebra at all and is rather some sort of oddly-shaped shell?

“The largest human lumbar vertebrae are around 13 mm thick, while this measures over 5 cm thick. If it is a vertebra, it would have to come from an animal with a spinal column at least five times the length of a human spine.

“Basically, I’m stumped. Any idea whether any of the readers of Panda’s Thumb might be able to identify it?”

Ondatra zibethicus

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Ondatra zibethicus – muskrat, Elmer’s Two-Mile Creek, Boulder, Colorado, May, 2015. The muskrat shown here disappeared after the 2013 flood, and I did not see any muskrats again till this spring.

Don’t forget to enter the photography contest – 1 week remaining!

Photography Contest VII

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Polish your lenses, oil your tripods, search your archives – the seventh Panda’s Thumb photography contest, begins – now!

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Polaroid Land Camera, Model 160, 1962-1965. Apologies for the moiré pattern on the face of camera!

We will accept entries from 12:00 CST, June 8, through 12:00 CST, June 22. We encourage pictures of just about anything of scientific interest. If we get enough entries, consistently with Rules 11 and 12, we may assign entries to different categories and award additional prizes, presuming, of course, that we can find more prizes.

The first-place winner will receive a signed copy of Why Evolution Works (and Creationism Fails), which has been donated by one of the authors. The second-place winner will receive a copy of The Devil in Dover, which has been generously donated by the National Center for Science Education.

Selasphorus platycercus

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Photograph by David Young.

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Selasphorus platycercus – broad-tailed hummingbird, Boulder, Colorado, May, 2015.

… June 8. That is, we will accept entries from noon, June 8, to noon, June 22, where noon is defined by the Panda’s Thumb server, which thinks it is still in Central Standard Time, or UTC(GMT) – 5 h. The rules will be essentially the same as previous years’. We have not chosen categories yet, but please be assured that they (or it) will be all-inclusive. So wipe your lenses, grease your shutters, and be ready!

Chrysemys picta

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Chrysemys picta – painted turtle, Walden Ponds Wildlife Habitat, Boulder, yesterday. See also here.

The majority of U.S. medical schools do not require evolutionary biology as a prerequisite for acceptance and do not offer courses dedicated to the subject. But as we talked about last time, adopting an evolutionary perspective on medical issues can potentially give new insights into disease treatment, prevention, and diagnosis. Where do we and should we begin to teach this kind of thinking? What resources are available to teachers and students to learn about evolution and its application to modern day problems?

Evolutionary training can help doctors look at diseases in a different light (Nesse et al, 2006). Take, for instance, sickle cell anemia: carriers of the sickle cell trait, a disease which is highly prevalent in tropical regions, are resistant to malaria, likely as a result of natural selection. This knowledge is helpful in developing ways to prevent malaria and perhaps similar evolutionary links between other diseases or infections and protective traits exist, but examining this hypothesis requires a thorough understanding of evolution and population genetics. Based on examples like this proponents of evolutionary medicine believe evolutionary biology should be considered a core subject for medical students, side by side with anatomy, physiology, biochemistry, and embryology, and that medical license exams should include questions about evolutionary biology.

People with sickle-cell anemia, whose bodies produce abnormal, crescent-shaped red blood cells, also carry genes that protect against malaria. This is most likely the reason sickle cell anemia is so common in areas where malaria is highly prevalent.

Image source: National Health Service

But while most medical schools do not offer much in the way of evolutionary education, there are some resources available for K-12 students and teachers as well as college undergraduates and graduates. One example is the BEACON Center for the Study of Evolution in Action at Michigan State, an interdisciplinary research team working on applying evolutionary principles to a wide range of problems in fields such as medicine, computer science, ecology, and engineering. Along with research, BEACON is focused on evolution outreach and education: researchers are conducting studies to see if integrating undergraduate cellular and molecular biology courses with evolution improves evolutionary understanding. The center also organizes K-12 summer programs, activities for K-12 teachers, and undergraduate and graduate-level courses.

While BEACON is enjoying great success, the NESCent (National Evolutionary Synthesis) Center, a center in North Carolina promoting multidisciplinary evolutionary research, will be closing this year after a decade of operation. Like BEACON, NEScent was also active in public outreach and education, organizing events like Darwin Day for K-12 students and training workshops for graduate students and teachers. But a new center is opening in the wake of NESCent: the Triangle Center for Evolutionary Medicine (TriCEM), which will focus on the partnership of evolutionary biology with human and veterinary medicine.

We’ve made the case for why an evolutionary understanding can improve research in medicine. But if we want to shift the paradigm of medical thought to one that emphasizes evolutionary biology, we need to reevaluate how we teach evolution from the earliest levels of education through medical school.

This series is supported by NSF Grant #DBI-1356548 to RA Cartwright.

Colaptes auratus

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Photograph by Louis Shackleton.

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Colaptes auratus – female yellow-shafted northern flicker, University of North Carolina at Wilmington campus. Mr. Shackleton writes, “She is gaping, that is, thermoregulating by opening her beak and just breathing, because birds do not sweat.”

Cereopsis novaehollandiae

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Cereopsis novaehollandiae – Cape Barren Goose, Flinders Chase National Park, Kangaroo Island, Australia.

Eudyptula Minor

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Eudyptula Minor – little penguin, Kangaroo Island, Australia. These penguins are nocturnal, but are apparently blind to the red light. Unfortunately, according to Kangaroo Island Penguin Center, “Our nocturnal Penguin Tours ceased in November 2013 due to the very low numbers of Penguins in the Kingscote colony. Predation by the increasing numbers of New Zealand Fur Seals from 2010 onwards has decimated the Penguin Colony, because the seals kill the adult penguins as they swim ashore at night to feed their chicks and therefore the chicks also die. We apologise for this, but the situation has been beyond our control.”

This post is by Joe Felsenstein and Tom English

Back in October, one of us (JF) commented at Panda’s Thumb on William Dembski’s seminar presentation at the University of Chicago, Conservation of Information in Evolutionary Search. In his reply at the Discovery Institute’s Evolution News and Views blog, Dembski pointed out that he had referred to three of his own papers, and that Joe had mentioned only two. He generously characterized Joe’s post as an “argument by misdirection”, the sort of thing magicians do when they are deliberately trying to fool you. (Thanks, how kind).

Dembski is right that Joe did not cite his most recent paper, and that he should have. The paper, “A General Theory of Information Cost Incurred by Successful Search”, by Dembski, Winston Ewert, and Robert J. Marks II (henceforth DEM), defines search differently than do the other papers. However, it does not jibe with the “Seven Components of Search” slide of the presentation (details here). One of us (TE) asked Dembski for technical clarification. He responded only that he simplified for the talk, and stands by the approach of DEM.

Whatever our skills at prestidigitation, we will not try to untangle the differences between the talk and the DEM paper. Rather than guess how Dembski simplified, we will regard the DEM paper as his authoritative source. Studying that paper, we found that:

  1. They address “search” in a space of points. To make this less abstract, and to have an example for discussing evolution, we assume a space of possible genotypes. For example, we may have a stretch of 1000 bases of DNA in a haploid organism, so that the points in the space are all 41000 possible sequences.

  2. A “search” generates a sequence of genotypes, and then chooses one of them as the final result. The process is random to some degree, so each genotype has a probability of being the outcome. DEM ultimately describe the search in terms of its results, as a probability distribution on the space of genotypes.

  3. A set of genotypes is designated the “target”. A “search” is said to succeed when its outcome is in the target. Because the outcome is random, the search has some probability of success.

  4. DEM assume that there is a baseline “search” that does not favor any particular “target”. For our space of genotypes, the baseline search generates all outcomes with equal probability. DEM in fact note that on average over all possible searches, the probability of success is the same as if we simply drew randomly (uniformly) from the space of genotypes.

  5. They calculate the “active information” of a “search” by taking the ratio of its probability of success to that of the baseline search, and then taking the logarithm of the ratio. The logarithm is not essential to their argument.

  6. Contrary to what Joe said in his previous post, DEM do not explicitly consider all possible fitness surfaces. He was certainly wrong about that. But as we will show, the situation is even worse than he thought. There are “searches” that go downhill on the fitness surface, ones that go sideways, and ones that pay no attention at all to fitnesses.

  7. If we make a simplified model of a “greedy” uphill-climbing algorithm that looks at the neighboring genotypes in the space, and which prefers to move to a nearby genotype if that genotype has higher fitness than the current one, its search will do a lot better than the baseline search, and thus a lot better than the average over all possible searches. Such processes will be in an extremely small fraction of all of DEM’s possible searches, the small fraction that does a lot better than picking a genotype at random.

  8. So just by having genotypes that have different fitnesses, evolutionary processes will do considerably better than random choice, and will be considered by DEM to use substantial values of Active Information. That is simply a result of having fitnesses, and does not require that a Designer choose the fitness surface. This shows that even a search which is evolution on a white-noise fitness surface is very special by DEM’s standards.

  9. Searches that are like real evolutionary processes do have fitness surfaces. Furthermore, these fitness surfaces are smoother than white-noise surfaces “because physics”. That too increases the probability of success, and by a large amount.

  10. Arguing whether a Designer has acted by setting up the laws of physics themselves is an argument one should have with cosmologists, not with biologists. Evolutionary biologists are concerned with how an evolving system will behave in our present universe, with the laws of physics that we have now. These predispose to fitness surfaces substantially smoother than white-noise surfaces.

  11. Although moving uphill on a fitness surface is helpful to the organism, evolution is not actually a search for a particular small set of target genotypes; it is not only successful when it finds the absolutely most-fit genotypes in the space. We almost certainly do not reach optimal genotypes or phenotypes, and that’s OK. Evolution may not have made us optimal, but it has at least made us fit enough to survive and flourish, and smart enough to be capable of evaluating DEM’s arguments, and seeing that they do not make a case that evolution is a search actively chosen by a Designer.

This is the essence of our argument. It is a lot to consider, so let’s explain this in more detail below:

As usual I will pa-troll the comments, and send off-topic stuff by our usual trolls and replies to their off-topic stuff to the Bathroom Wall

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This page is an archive of recent entries in the Evolution category.

Eugenics is the previous category.

Evolution Education is the next category.

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