Intelligent Design and the Dunning-Kruger Effect

""Ignorance more frequently begets confidence than does knowledge" --Charles Darwin

This is a prescient summation of the "Dunning-Kruger" Effect, a phenomenon described by the authors of an infamous psychological study that showed (from the original paper's abstract):

People tend to hold overly favorable views of their abilities in many social and intellectual domains. The authors suggest that this overestimation occurs, in part, because people who are unskilled in these domains suffer a dual burden: Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it.

Few places illustrate this effect better than one of the premier websites of the Intelligent Design Movement, "Uncommon Descent". And it's not just the articles: the comments are almost textbook examples:

http://www.uncommondescent.com/

Microevolution and Macroevolution

The simplest definition of evolution is genetic change within populations. Every population undergoes change in the frequencies of gene variants known as alleles (think ‘short’ vs. “tall” pea plants from Mendel’s experiments that you studied in high school biology). The frequencies can change due to several well known, observed factors:

1. Natural Selection—if an allele enables individuals that possess it to have more offspring on average than individuals possessing other variants of the same gene, it will become more common in the population, at the expense of the other variants.

2. Mutation—mutations feed new alleles into the population all of the time.

3. Chance (also known as ‘genetic drift’)—some alleles never make it into sperm or eggs by chance. Some (actually MOST) sperm never fertilize eggs. Some individuals carrying certain alleles never find mates, or die young by accident. These chance elements can cause allele frequencies to fluctuate over time, especially in very small populations.

4. Emigration/Immigration—individuals entering or leaving a population take/bring their alleles with them, changing the total frequencies of the populations involved.

This kind of change is what most people consider “microevolution”, because it generates relatively little overall phenotypic change in the population, and is limited to the level of the species. The kinds of change reflected in differences between organisms in higher taxonomic categories such as genera (plural for “genus”), families, orders, etc., is usually referred to as “macroevolution”, or evolution above the species level. This distinction has led many to erroneously assume microevolution and macroevolution are two completely separate processes. In reality, microevolutionary processes are behind the origination of the higher taxonomic categories.

Consider a population of a species of organisms, say fruit flies. As long as the flies within that population can mate easily with any other fly, the individuals will remain more or less alike genetically. Mutations or other kinds of variation will circulate throughout the population freely. But what happens if a subgroup is prevented from mating with flies in the main group? For example, what if the subgroup was carried away by a severe storm and deposited on an island? Now if any new mutations or variations arise in the subgroup, they can no longer be shared with the main group, and vice versa. The inevitable result will be that the two populations will diverge genetically—their gene pools will become progressively more and more different. They may even become so different that they cannot interbreed, at which point the subgroup may now be considered a new species. The isolation and differentiation of subgroups from parent populations is part of an ongoing process known as speciation, or the creation of new species. As speciation continues, the two species become founders of new “lineages”, with more new species branching off of each. If one graphs out this speciation process, one sees what Darwin sketched in the only illustration in The Origin of Species: a structure resembling a tree with many branches (lineages) and twigs (species) on the branches. Branches/lineages near the top of the tree are more recent than ones on branches at the bottom. In addition (and this is important), clusters of twigs/species on a particular branch are more closely related to each other than to species on other branches—they will also tend to resemble each other more, and branches that are close together on the trunk are more closely related than those further up or down the tree.

All of the above is the result of purely microevolutionary processes, genetic change (after reproductive isolation) within the populations. However, looking at the tree after a considerable amount of time, and without pruning any branches and twigs, one can begin to see some “macroevolutionary” patterns: lineages that are far apart on the tree will look less and less alike than those closer together. Since distance represents time, one can say the longer lineages have been apart, the more different from each other they will be. The combination of reproductive isolation from other lineages and the accumulation of genetic differences over time can be expected to produce dramatic differences. But here is an interesting thing: if no branches and twigs are pruned, it can be very difficult to decide how to classify the types of organisms—there will be many gradations (‘transitionals’), a sort of fuzzy continuum. A biologist trying to classify all of the organisms would have a very hard time. A question then arises: why does life on earth today appears to have so many clear discontinuities, enabling scientists like Linnaeus to construct a classification system without going (too) insane? Does that mean microevolution cannot explain the macroevolutionary discontinuities, since we do not see all of these theoretical transitional organisms? The answer is ‘no’, because in nature the tree gets pruned by the process of natural selection and extinction. Darwin’s theory states that natural selection will eliminate species which cannot adapt to the environment. In fact, the vast majority of species which have ever existed are extinct: what Linnaeus was looking at are those lineages which are very recent, or older lineages that have proved very successful over long periods of time. As a result, we see a patchy and discontinuous array of organisms that can be classified into higher taxonomic groups because the pesky transitionals which would have made the process almost impossible are extinct. In other words, microevolutionary processes, coupled with natural selection, can explain macroevolutionary differences among organisms on Earth.

The Descent Inference

The Descent Inference:How Transitional Fossil Sequences are Evidence of Common Descent

Creationists and intelligent design advocates often argue that transitional sequences are not evidence of common descent but instead are merely assumed to be such. They frequently bring up the arguments of paleontologist Henry Gee, who has said we cannot know for sure if a fossil group is directly ancestral to another. Gee, however, is convinced that transitional sequences are evidence of common descent. So, how can this be? This essay will show that common descent is not an assumption, but an inference drawn from observed phenomena in extant organisms as well as fossil data, and will lay out the reasoning behind the inference. It will also, where possible, point out aspects of the reasoning that are understood intuitively by most people. Those confronted by students or other evolution critics can use this to effectively rebut the 'common descent is an assumption' charge.

I. Relatedness is directly proportional to genes shared in common

This is actually something most people understand intuitively. Common expressions like 'blood relative' reflect this understanding. Empirical data confirm this intuitive concept. It is the basis for DNA paternity testing, for example.

II. All organisms share at least some genes in common.

This has been confirmed by protein sequence studies. Cytochrome c is a well-known example.

III. Morphological characteristics are primarily under genic or polygenic control.

This is also something most people understand intuitively. Plant and animal breeders certainly use this concept to guide their efforts. Geneticists have also confirmed this, even to the point of identifying genes that control basic body plans (homeotic genes).

IV. Morphological similarity between organisms is directly proportional to genes shared in common.

Again, this is understood on an intuitive level, when we expect siblings to resemble each other more than they resemble distant cousins. It also follows from (I), (II) , and (III). Comparative molecular studies are consistent with this as well. For example, humans and chimpanzees, which share almost all of the genes in common, are much more alike morphologically than humans and fish, who share relatively less.

V. Populations that exchange genes are more alike genetically than those that do not.

This is confirmed via the observation that when reproductive barriers occur within a population, creating subpopulations, those isolated subpopulations will independently accumulate different mutations and will undergo different allelic frequency changes over time.

VI. Barriers to reproduction between populations lead to new species.

All observed instances of speciation involve barriers to gene exchange leading to genetic divergence. These barriers can include geographic, ecological , ethological and genetic factors, but all lead to genetic divergence. In addition, no species have ever been observed to arise spontaneously: all are descendants from pre-existing, closely-related populations.

VII. Genetic divergence between isolated populations grows over time.

Once the barriers to gene exchange are in place, divergence only grows, due to independent accumulation of more and more mutations and combinations of alleles.

VIII. Degree of ancestry is a function of time since divergence.

From V, VI and VII, it follows that recent speciation events result in descendant populations that are more genetically alike than in populations that diverged much earlier. It also follows from all of the above that:

IX. Degree of ancestry is proportional to genetic similarity.

X. Degree of ancestry is also proportional to morphological similarity.

This follows directly from IV.

Once we have reached this point, the question of fossil evidence can be addressed:

1. Fossils are the remains of ancient living organisms.

Many fossils are not completely mineralized, and show traces of organic material.

2. Fossil organisms, therefore, had ancestors and left descendants, just like extant organisms.

There is no observed evidence that fossil organisms lived and reproduced any differently than extant ones now do.

3. Common Ancestry can be inferred from morphological similarity

This follows from I-X, and 1-2. 4. Transitional morphological 'sequences' indicate chains in ancestry.

While Henry Gee's point about a transitional organism not necessarily being the direct ancestor of the next organism in the sequence is valid, from the above it can be inferred that the organism came from a population very closely related (and therefore morphologically similar) to the population that was the direct ancestor.

Great Textbook

For those interested in Molecular Ecology in general, I recommend Joanna R. Freeland's Molecular Ecology, published by Wiley. Few textbooks, in my experience, actually have the student in mind. This one does. It's at the top of my list for the following reasons:

• For such a technical subject, the language is clear and direct.
• Important concepts are defined thoroughly, with excellent worked-through examples.
• Has great practical value. For example, the chapter on Molecular Markers does an excellent job summarizing the different kinds of markers and what kinds of research questions each can answer best.
• The bibliography is comprehensive, and also includes useful websites.

Cool T-Shirt

I gotta say, this is the coolest evolution t-shirt. Ever. Courtesy of The American Museum of Natural History: http://www.amnhshop.com/25-028238.html

The classy black shirt was inspired by the museum's recently-unveiled Darwin exhibit, and sports Darwin's famous tree diagram from the Origin of Species (the only illustration in the entire book), and the caption:

Revolutionary

Modest. Understated. Honest. Kinda like the man himself.

Hello

This first post is to introduce me and this blog. I am a graduate student in Molecular Ecology, which is a branch of evolutionary biology concerned with using molecular markers to help answer ecological questions. The question I am primarily interested in is how the landscape interested in how the landscape influences the genetic structure of populations. I'll be posting on interesting papers that catch my attention, as well as textbook recommendations. In addition, I'll be commenting on evolution, the Intelligent Design movement, and various other subjects as the mood suits me.