Author Archives: Matt
Posted by Matt
First of all, Nick and I would both like to solemnly swear that this blog is not dead. it’s just been on graduation-related hiatus. In two weeks, we’ll be done and you’ll be bombarded with so much science you’ll be reciting the periodic table in your sleep. As we speak, I’m planning to write about my thesis work and about an initiative I’m involved in to convince Congress that disposable bags are bad.
But for now, some thoughts on a story Nick showed me. It doesn’t surprise me one bit that a third year Harvard Law student would believe that white people are smarter than black people. Racism, in all its forms and gradations, is still rampant in America. But what really hurts me on a molecular level is that she thinks there might be a genetic basis for her belief.
There is not. We tend to think there is a greater genetic difference between the social constructs we call races than there actually is, because differences in skin color and facial features appear dramatic. In reality, the genetic difference between light and dark skin is miniscule to the point of being inconsequential compared to the rest of the genome. The genes for skin color are also some of the most easily influenced by the environment. If you took a population of Swedes and put them in the middle of Africa, in 5-10,000 years they would be black.
We are one of the least genetically diverse animals on the planet, because we originated from such a small population in Africa. At some point, a small subset of that population broke off and populated the rest of the world. Because of that, Africans are actually more genetically diverse than the rest of the world combined. There is liable to be more substantial, consequential genetic difference between different regions of Africa than between Europe and Asia.
This is why it’s ludicrous to compare “white” and “black” people genetically. The Harvard student thinks that if you raised 100 white babies and 100 black babies together under utopian conditions, it would prove once and for all the differences between the races. Unfortunately, if you really wanted representative samples, the black population would be so much more diverse than the white population that the study would actually be pretty meaningless.
The state of scientific education all over the world is miserable. Maybe I’m being hopelessly optimistic, but I believe that if people really understood the science of genetics and evolution, there would be so much less controversy over these things.
I’d also like to take this time to point out this excellent blog on human intelligence by David Shenk, who just published a book called The Genius in All of Us. I intend to dig into a lot of this fascinating stuff in the near future, so watch this space.
Posted by Matt
Posted by Matt
Sorry for the nonexistent posting recently. Life has gotten real in the past few weeks and so I imagine I will write less frequently until I graduate next May. One of the reasons I asked Nick to write too was so that there would be less dead space, but of course he goes to school too and so life is just as busy for him.
But anyway, I just wanted to share this internet gem with the world. Alfred Russel Wallace was an British naturalist and contemporary of Charles Darwin. He is famous for his work in the Amazon River basin and the Malay archipelago, and developed a theory of natural selection independently of Darwin. In fact, he sent Darwin an article outlining his theory while in Malaysia, which prompted Darwin to publish both Wallace’s article and his own findings. Too often, Darwin receives sole credit (or blame, depending) for the theories of natural selection and evolution, when in reality they represent the work of countless great scientists, Wallace and Darwin included.
The frog in the header is actually an illustration from Wallace’s book The Malay Archipelago. It is Wallace’s flying frog, Rhacophorus nigropalmatus.
Posted by Matt
PEPPERED MOTHS. Why do textbooks use pictures of peppered moths camouflaged on tree trunks as evidence for natural selection — when biologists have known since the 1980s that the moths don’t normally rest on tree trunks, and all the pictures have been staged?
This was something I didn’t know much about, but before I even did any research it struck me as dishonest to cite “staged textbook photos” as evidence to invalidate scientific studies. It turns out I was right: photoillustrations of the difference between peppered moth types are often staged with dead specimens to provide the clearest illustration of the point, but they don’t pretend to be from the original studies and experiments they are meant to illustrate.
Wells is referring to the English peppered moth Biston betularia. Until 1848, only light-colored individuals had been documented, but that year the first dark-colored carbonaria variant was recorded. By 1895, the percentage of the carbonaria variant was reported at 98%. The hypothesis for this was that the industrial revolution had coated previously light-barked trees with soot, giving dark moths better camouflage protection against predators. Evidence throughout the 20th century has supported this claim, but in the past two decades Bernard Kettlewell’s classic study has come under legitimate criticism for aspects of its design which may not have fully accounted for the diversity of moths’ daytime resting places.
However, between 2001 and 2007 Michael Majerus carried out a study that included moths found all over the tree (including the trunk, despite Wells’ claim) which nevertheless supported the differential camouflage theory. Much of creationists’ ammunition against the peppered moth as an example of natural selection comes from a review by Jerry Coyne of Majerus’ 1998 book Melanism: Evolution in Action. However, Majerus and others have stated that Coyne’s review misrepresents the book’s content, and Coyne himself has even expressed dismay that people have tried to use the article to argue against natural selection.
DARWIN’S FINCHES. Why do textbooks claim that beak changes in Galapagos finches during a severe drought can explain the origin of species by natural selection — even though the changes were reversed after the drought ended, and no net evolution occurred?
I should hope that the changes were reversed when conditions were reversed. Otherwise, that wouldn’t speak very highly of natural selection, would it? The thing is that evolution never stops. Whenever conditions change, new pressures cause different traits to be selected for. This “net evolution” business is misleading, and no one is citing this study as an example of new species creation. It is, however, a vivid example of natural selection at work.
MUTANT FRUIT FLIES. Why do textbooks use fruit flies with an extra pair of wings as evidence that DNA mutations can supply raw materials for evolution — even though the extra wings have no muscles and these disabled mutants cannot survive outside the laboratory?
Whether the flies in question are viable or not is not the point. These mutant flies are a simple and striking way to show that genetic mutations can produce radical changes in body plan and structure. Wells is missing the forest for the trees. The random nature of mutation suggests that most will be nonviable or at least nonadvantageous, as is the case here. Nevertheless, these dramatic mutations are evidence against the notion that mutation cannot produce enough change to generate new species.
HUMAN ORIGINS. Why are artists’ drawings of ape-like humans used to justify materialistic claims that we are just animals and our existence is a mere accident — when fossil experts cannot even agree on who our supposed ancestors were or what they looked like?
Phrases like “just animals” and “mere accident” seem intended to make people feel insulted by the theory of evolution, but that’s just one narrow-minded way to look at things. Drawings that appear in respected literature are scientific recreations based on fossils believed from the genus Homo and current knowledge about body plans and how vertebrate animals function. While there will continue to be debate over the details, there is little debate that these fossils represent our closest genetic relatives.
EVOLUTION A FACT? Why are we told that Darwin’s theory of evolution is a scientific fact — even though many of its claims are based on misrepresentations of the facts?
Damn scientific terminology to hell. For the last time, evolution is a scientific theory. The only things that are called facts in biology are observable data points. Theories are comprehensive and mechanistic explanations for how a process works. Gravity is the current accepted theory for why objects in the atmosphere fall to earth. Evolution is the current accepted theory for how species change in response to their environment and for how new species form. Both are based on a massive amount of evidence and are the best scientific explanations available for the facts at hand. I have yet to see any compelling scientific evidence that evolution misrepresents the facts.
While I was looking around online today i found this site, a point-by-point refutation of Wells’ book Icons of Evolution that covers a lot of the same ground I have here. I’m sure there’s tons of these things all over the internet, but like I said, I wanted to address these questions for my own satisfaction and to show that, to anyone with a working knowledge of the science, these questions are nowhere near the probing criticism of evolution that Wells wants them to be.
Posted by Matt
So there’s this list of questions that’s been circulating the internet for a few years now entitled “Ten questions to ask your biology teacher about evolution”. It’s abundantly clear at this point that American adults are bitterly divided over the subject of evolution and neither side will budge. You’re tired of hearing about it. I’m tired of hearing about it. We’re all tired of hearing about it.
But this list from Jonathan Wells is targeted at teenagers still trying to make up their minds. It feeds into teens’ natural desire to stick it to the man by providing them with “Gotcha!” questions that seem like they would catch any stooge of Big Evolution off guard. The problem is that they are filled with misconceptions and false premises. Wells holds PhDs in Molecular and Cell Biology from Berkeley and Religious Studies from Yale, so he’s obviously no slouch and I do not believe he is deliberately trying to deceive people. The questions are nevertheless misleading, so, mostly for my own satisfaction, I’ll answer them here.
ORIGIN OF LIFE. Why do textbooks claim that the 1953 Miller-Urey experiment shows how life’s building blocks may have formed on the early Earth — when conditions on the early Earth were probably nothing like those used in the experiment, and the origin of life remains a mystery?
It’s true that many scientists now believe that earth’s early atmosphere was mostly nitrogen and carbon dioxide rather than the ammonia and methane used in the Miller-Urey experiment. Nitrites form under these conditions, which would prevent the stable formation of amino acids. However, Jeffrey Bada at the Scripps Institute of Oceanography has shown that when iron and carbonates, also likely abundant on primitive earth, are added to the mix, the nitrites are neutralized and amino acids do indeed form. Check out this article at Scientific American. Still, the prevailing view now is that at least some of the organic molecules essential to life arrived here on comets or meteors. All of this is pretty much educated guesswork – we’ll never definitively know until those slackers at MIT finally get a time machine up and running and —
Wait, I thought these questions were about evolution. While speculating about abiogenesis is fun, the theory of evolution works perfectly fine without it. You’re a tricky one, Wells.
DARWIN’S TREE OF LIFE. Why don’t textbooks discuss the “Cambrian explosion,” in which all major animal groups appear together in the fossil record fully formed instead of branching from a common ancestor — thus contradicting the evolutionary tree of life?
Well, I thought the book I used in freshman biology could be considered a “textbook”, but there’s the Cambrian explosion, right there in Chapter 32, so I guess it’s not a textbook after all.
When he says “all major animal groups” he can only be speaking in the broadest sense. I’m talking Porifera vs. Bilateria and protostomes vs. deuterostomes. Technically, these are the groups into which all extant animals can be classified, and they first appeared over a relatively short (“short” in this case meaning millions of years) timeframe during the Cambrian period, about 530 mil. years ago. But to say that they were “fully formed” is nonsense, unless all your friends look like this. Mammals, for one, don’t appear in the fossil record until about 190 mil. years ago, and only in most primitive form.
So I suppose his argument is that the major animal classifications arose separately and simultaneously during the Cambrian, rather than from a common ancestor. Well, we may never discover a fossil of the single organism from which all animals are descended. But current exidence suggests that these groups appeared far more gradually than was previously believed, and while we have, at best, an incomplete picture of the development of animals during these times, the rest of the fossil record overwhelmingly suggests that species develop by gradually branching off from existing evolutionary lines. I see no reason why the Cambrian should be any exception.
HOMOLOGY. Why do textbooks define homology as similarity due to common ancestry, then claim that it is evidence for common ancestry — a circular argument masquerading as scientific evidence?
This isn’t actually a circular argument. Homology was developed by studying similarities between the structures of different organisms. The textbook example is often that mammal limbs such as bat wings, whale fins, cat legs and human arms are actually composed of the same number and types of bones, shaped differently. Similarities like these suggest a greater degree of relation than analogous structures, which bear little resemblance but perform similar functions (bat wings vs. fly wings). It’s not hard to surmise that the first example suggests that the species adapted the same structure for different functions, while in the second species adapted different structures for the same function.
Today, structural homology is used mostly as anecdotal evidence to support evolutionary similarity defined by genetic homology. The genomes of many organisms have now been fully or partially sequenced, and are logged in databases accessible by nearly anyone with an internet connection. These genomes can be compared for similar sequences by powerful programs based on all current knowledge of genetic structure, transcription, and mutation. In many cases, you can trace a large number of genes among related species back to a parent gene and say with a high degree of confidence how each daughter gene mutated or changed. Through genetic knockout or amplification experiments, you can then determine the functions of these genes, and in many cases they perform a very similar role. Comparative genetics has revolutionized the study of evolution and has provided heaps of evidence that homology does indeed reflect common descent.
VERTEBRATE EMBRYOS. Why do textbooks use drawings of similarities in vertebrate embryos as evidence for their common ancestry — even though biologists have known for over a century that vertebrate embryos are not most similar in their early stages, and the drawings are faked?
Wells is referring to the embryo drawings of Ernst Haeckel (1834-1919), who infamously fudged the drawings so that vertebrates were most similar at the earliest stages of development and gradually grew apart. He did this to fabricate support for his own peculiar theory of Biogenetic Law, which holds that embryonic development sort of “replays” the evolution of that species in fast-forward. Wikipedia has a good article for background. I have seen these drawings in textbooks, but always in the context of the history of embryology and they make clear that both his drawings and theories are discredited. They also include accurate drawings or photographs showing real similarities between vertebrate embryos in order to show that embryology really does provide evidence for evolution, just not in the way Haeckel thought. I agree that books that take these drawings at face value are incorrect, but that doesn’t discredit current evolutionary theory.
ARCHAEOPTERYX. Why do textbooks portray this fossil as the missing link between dinosaurs and modern birds — even though modern birds are probably not descended from it, and its supposed ancestors do not appear until millions of years after it?
No one is suggesting that the tree should be drawn Dinosaurs -> Archaeopteryx -> Birds. It is nevertheless significant that Archaeopteryx fossils, along with fossils of many many dinosaur species, clearly show evidence of feathers remarkably similar to those of modern birds. This is one of several compelling pieces of evidence that theropod dinosaurs and birds shared a significant common ancestor. Check this article for more information.
This is getting pretty long, so I’ll post the second half of the questions tomorrow.