Language dialect is something that we often pick up unconsciously, so I find it an interesting if narcissistic project to query my own dialect affinities. The above was generated using a 140 question test (warning: server often slow). In case you were curious, my most ‘similar’ city (to my dialect) is Sunnyvale, California. Though most of my life has been spent on the West coast of the United States, I did spend my elementary age years in upstate New York. You can see evidence of that in the heat-map. There are particular words I use and pronunciations that I have which I know are probably relics of my formative years, but it was a little surprising that this survey picked up on that, as I thought most of them had disappeared.

How do people manage to keep track of the scientific literature in their area?

A little editorializing by me….

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First, you should probably read Sabine and Chad. Second, I’ll be up front and admit that I don’t give much thought in the details to this sort of thing (though I follow with interest the opinions of others, such as Bora Zivkovic, on this topic). I really only have one qualification: I’ve been doing this for a long time. Since spring of 2002. To my knowledge only Derek Lowe has been blogging continually and without interruption about science longer than I have (Chad Orzel of Uncertain Principles also started in the spring of 2002).

So in no special order, my “advice”….

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In my post below where I take a stand against the tired, but inevitable, assumption that a post demographic transition society necessarily entails a cessation of biology evolution, a reader brings up a trite but specious observation:

But you’re missing the point really. We’ve slowed (not stopped because it can’t be stopped) because we now control our environment. Evolution is moving from individual biological expression to cultural and technological evolution.

This isn’t novel or exceptional in its wrongheadedness. The same idea comes up when I engage in discussion with the types of intellectuals in sociology or anthropology unencumbered by the constraints of “Western linear thinking.” The presumption is that natural selection operates through exogenous environmental pressures, and as we attenuate those pressures we diminish the rate of evolutionary change. The stylized model being:

Rate of evolution ∝ natural selection ∝ 1/(control of environment)

As the magnitude of human control of the environment increases, the magnitude of natural selection decreases, and so does the rate of evolutionary change. This impression was already cursorily dispatched in my prior post. But as there hasn’t been strong selection in the human past for reading and comprehending something before commenting on it, this issue might require a little teasing out, as the stylized model above is so ubiquitous as to be a background assumption of many.

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Unless you are under a rock you are aware of the controversy around the sound that the fox makes. But did you know about Stonehenge?

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The trait of lactase persistence (lactose tolerance) is probably one of the better schoolbook examples of natural selection in human populations. The reasons for this are probably two-fold. There is a very strong signature of selection within a specific gene known to associate with the trait in question in many populations. And, there is a very compelling historical narrative which explains rather neatly how this particular functional change could have undergone such strong selection within the past ~5,000 years across these populations. But the elucidation of the origin and spread of this genetic adaptation is also interesting because it looks as if it was not a singular event. Populations as disparate as Arabians, Danes, and Masai seem to carry different alleles around the locus of interest which confer the ability to digest milk. This illustrates the fact when selection pressures have a viable target, there is a rapid response on the genomic level. At some point during the maturation of a mammal the regulatory pathway which produces lactase enzyme shuts down. Yet within numerous human populations this gradual shutdown process has been short-circuited.

The variety of response in relation to this adaptation was brought home to me as I read Diversity of Lactase Persistence Alleles in Ethiopia – Signature of a Soft Selective Sweep, in the latest issue of The American Journal of Human Genetics:

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Today Dienekes points to a PLoS ONE paper, mtDNA from the Early Bronze Age to the Roman Period Suggests a Genetic Link between the Indian Subcontinent and Mesopotamian Cradle of Civilization. The title is pretty self-explanatory, though above I’ve posted a figure which shows the mtDNA haplogroup affiliations of the four individuals dated to between 2500 BC and 500 AD. If you are a even moderately familiar with the human mtDNA phylogeographic literature then you know that haplogroup M is not West Eurasian, and these lineages are often South Asian. The existence of people of South Asian origin in West Asia during the Roman period is rather unsurprising, the Persian (and Hellenistic) polities spanned West and South Asia (albeit, in a liminal sense in the latter case). But what about extremely ancient finds? This too has an explanation. From Brotherhood of Kings: How International Relations Shaped the Ancient Near East:

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Sir David Attenborough is the latest public intellectual who should know better than to opine that evolution has ended for human beings. Here are the quotes from The Telgraph: “Because if natural selection, as proposed by Darwin, is the main mechanism of evolution – there may be other things, but it does look as though that’s the case – then we’ve stopped natural selection. We stopped natural selection as soon as we started being able to rear 95–99 per cent of our babies that are born.“

John Hawks does a good job hitting back the balls hanging just over the plate. There are still many parts of the world where 95-99 percent of babies being born do not reach adult. Second, there is still a great deal of variation in fertility. Some people choose not to have any children, while others are quite prolific. For adaptation by natural selection to occur what you need is heritable variation of some sort to correlate with this fertility variation. It seems highly plausible that indeed heritable variation does correlate with fertility variation. As John notes the advancement of genome sequencing over the population will probably answer these questions definitively within the next 10 years (e.g., I am willing to bet that siblings who score higher on impulsiveness and lower on IQ tests will be more reproductively fit than their less impulsive and more intelligent brothers and sisters).

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The two phylogenies above represent Mycobacterium tuberculosis, to the left, and human mitochondrial DNA (passed from mother to daughter) on the right. It was pulled from the paper, Out-of-Africa migration and Neolithic coexpansion of Mycobacterium tuberculosis with modern humans, which just came out recently, and has naturally been making a splash. As the title implies the paper concludes that humans and tuberculosis have been each other’s “partners,” after a fashion, for the whole existence of modern humanity. The main method here is somewhat brute force and straightforward, by sequencing 259 tuberculosis strains from all across the world they managed to make relatively robust phylogeographic inferences. Throwing data at a question usually resolves something. The correspondence between human and pathogen strains is qualitatively uncanny, and there is plenty enough statistical footwork to confirm it more rigorously within the body of the text.

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