Category Archives: evolution

Chris Smith takes on that Troublesome book

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Cain and Abel

Cain and Abel, in medieval stained glass. Photo by Fr Lawrence Lew.

Over at Nothing in Biology Makes Sense, Chris Smith has been writing a series of posts digging deep into the evolutionary claims made in Nicholas Wade’s book A Troublesome Inheritance. Last week, Chris debunked the claim that human population genetics naturally sorts into “races”—this week, he’s taking on Wade’s claim that variation at a particular gene has made some human populations more prone to violence than others:

Although some studies have found genetic variants in the MAO-A promoter region that are more common in some ethnic groups than in others (Sabol et al. 1998; Widom & Brzustowicz 2006; Reti et al. 2011) it is likely that these genetic variants are not –on their own– associated with violent or impulsive behavior (Caspi et al. 2002; Widom & Brzustowicz 2006). Instead, genetic variation in the MAO-A promoter seems to make some children less able to recover from abuse and childhood trauma, and therefore more likely to act out later in life (Caspi et al. 2002; Widom & Brzustowicz 2006). Simply carrying the ‘low expression’ allele in the MAO-A promoter does not have any effect at all on impulsivity or aggression.

Chris co-teaches a class on exactly the topics covered in A Troublesome Inheritance, so I highly recommend you read the whole thing, and follow the series to its conclusion.

My review of A Troublesome Inheritance for the Los Angeles Review of Books

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World Map - Abstract Acrylic Image by Lara Mukahirn.

I’ve written (another) review of Nicholas Wade’s “science of race” book A Troublesome Inheritance, this time for the Los Angeles Review of Books. If you’ve read the my previous review for The Molecular Ecologist, you won’t find much new here, but the LARB piece is pitched at a less technical audience, and takes a somewhat different point of entry:

CHARLES DARWIN is more usually cited for his scientific discoveries than his moral insights. In the closing pages of his travelogue The Voyage of the Beagle however, he condemns the practice of slavery — which he observed firsthand in the colonized New World — in blistering, heartfelt terms worthy of an Old Testament prophet

…

In this testimony against the great social sin of his age, Darwin makes an observation that should unsettle us even here and now: “if the misery of our poor be caused not by the laws of nature, but by our institutions, great is our sin.”

I’m extremely pleased for the chance to contribute to a great literary magazine, and I’m also quite happy to see that LARB went with my suggested, punny headline: “Cluster-struck.”◼

Nothing in Biology Makes Sense: Why evolutionary biologists are stoked about pot

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This week at Nothing in Biology Makes Sense!, guest contributor Daniela Vergara explains how CGRI, the initiative to sequence the genome-wide genetic variation of Cannabis, will answer cool evolutionary questions.

At the CGRI, we would like to understand first, how much genetic variation there is in the numerous pure C. sativa, C. indica, and C. ruderalis accessions and heirloom varieties. This will lead us to understand the relationships among the major lineages within the genus, the spread of Cannabis throughout the globe, and rates of historical hybridization between the named species.

For Daniela’s detailed run-down of important evolutionary questions in Cannabis, go read the whole thing.◼

Nothing in Biology Makes Sense: Making sense of pollination syndromes

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2010.07.15 - Eastern Tiger Swallowtail Pollinator at work. Photo by jby.

Over at Nothing in Biology Makes Sense! I’m discussing pollination syndromes—suites of traits held in common by plants that use similar pollinators.

  • Bee-pollinated flowers are usually blue or yellow, often with contrasting “guides” that point towards nectar rewards, and they usually have some sort of scent.
  • Bird-pollinated flowers tend to be red and tubular, and often open downwards. They produce lots of relatively weak nectar, and generally don’t have very strong scents …
  • Moth-pollinated flowers are usually white, opening in the evenings, and strongly scented.

To find out how evolution makes sense of these handy rules of natural historical thumb, go read the whole thing, and check out the new meta-analysis of pollination syndromes that I discuss.◼

Nothing in Biology Makes Sense: Chipmunks have no respect for species boundaries

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A yellow pine chipmunk, Tamias amoenus. Photo by Noah Reid, via Nothing in Biology Makes Sense.

At Nothing in Biology Makes Sens, Sarah Hird explains some of her own research, recently published at the journal Heredity, which documented just how “leaky” species boundaries can be in the chipmunks of western North America.

While doing a comparative phylogeography study, the Sullivan lab discovered that one particular subspecies, T. a. canicaudus, had a mitochondrial genome that was most closely related to the red-tailed chipmunk (T. ruficaudus), instead of the other yellow-pine subspecies. Additional data show that the T. a. canicaudus nuclear genome is in fact most similar to other yellow-pines – it’s just that the mitochondria is of red-tailed origin.

For all the sordid phylogenetic details, go read the whole post, and check out the original paper.◼

The Molecular Ecologist: More functions, stronger selection?

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Victorinox Swiss Army Knife Photo by James Case.

Over at The Molecular Ecologist I’m discussing a new paper in the journal Genetics, which demonstrates that selection acts more strongly on genes that affect multiple traits:

Genes that have roles in multiple traits—pleiotropic genes—have long been thought to be under stronger selection as a result of those multiple functions. The basic logic is that, when a gene produces a protein that has a lot of different functional roles, there are more functions that will be disrupted by changes to that protein. Which would be more inconvenient: if your smartphone suddenly needed a new type of power connector, or if every electrical outlet in your house suddenly accepted only plugs with four prongs?

A team at the University of Queensland tested this idea using a lot of fruit flies and some cleverly applied gene expression resources. To find out how it all worked, go read the whole post, and check out the original paper.◼

The Molecular Ecologist: Scanning the genome for local adaptation

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The collection locations for plant lines sampled in my analysis. Figure 1 from Yoder et al. (2014).

This week at The Molecular Ecologist, I’ve just posted a new discussion of the latest publication to come out of my postdoctoral research with the Medicago HapMap Project. It’s an attempt to find genome regions that might be important for adaptation to climate, by scanning through a whole lot of genetic data from plants collected in different climates.

This is what’s known as a “reverse ecology” approach—it skips over the process of identifying specific traits that are important for surviving changing climates, and instead uses population genetic patterns to infer what’s going on. One approach for such a scan is presented in my latest paper, which is in this month’s issue of Genetics. Essentially I think of this as what you can do, given a lot of genetic data for a geographically distributed sample—in this case for barrel medick, or Medicago truncatula. Medicago truncatula is a model legume species, which has been used in a great deal of laboratory and greenhouse experimentation—but in this project, I tried to treat M. truncatula as a “field model” organism.

For a run-down of what I did, and what I found, go read the whole post—or check out the paper itself [PDF].◼

The Molecular Ecologist: Charles Goodnight

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Ants and Aphids, Backlit Photo by binux.

Over at The Molecular Ecologist, John Stanton Geddes continues his interview series with quantitative geneticist Charles Goodnight, whose work covers everything from multi-level perspectives on natural selection to the the causal linkage between directly measurable trait variation and interactions between individual genes. Here’s a sample of what Goodnight has to say about the group selection versus kin selection debate (which I’ve discussed here before):

Why the controversy continues today is not so clear. It is interesting that it is mostly very one sided. Those who champion group selection tend to understand kin selection, and dismiss it because it is not useful to them. Those who tend to champion kin selection tend to not understand group selection and dismiss it because it is a priori wrong.

The interview also covers Goodnight’s thoughts about how molecular genetics has changed the field since his days in graduate school, his experience starting up the blog Evolution in Structured Populations and his estimation of the probability of extraterrestrial invasion—I recommend reading the whole thing.◼

The Molecular Ecologist: Tracing soft selective sweeps in your gut microbiota

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ποντίκι / μυς, mouse (Mus musculus) by George Shuklin Why is my poop glowing blue? Photo by George Shuklin.

Over at The Molecular Ecologist, I’m discussing a new study that traces the adaptation of bacteria moving into a mammalian gut:

João Barroso-Batista and colleagues at the Instituto Gulbenkian de Ciência and Instituto de Tecnologia Química e Biológica in Portugal first treated mice with streptomycin to clear their guts of bacteria, then fed them cultures of Escherichia coli that were genetically uniform—except that half the E. coli cells in the culture had been engineered to produce a blue fluorescent protein, and half had been engineered to produce a yellow fluorescent protein. … If a single mutation made that one cell so successful that its descendants entirely dominated the gut, the authors would be able to tell—by checking the color of the host mouse’s poop.

To find out what the study’s authors learned by sequencing the bacterial genomes in that colored mouse poop, go read the whole thing.◼

Nothing in Biology Makes Sense: Dispersal versus mutation, on the edge

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Cane Toad at Daintree Village A cane toad, living in an evolutionary “Olympic village”? Photo by tubagooba.

This week at Nothing in Biology Makes Sense!, Devin Drown explains the population dynamics that crop up near the edge of a species’s geographic range:

One famous example of this phenomenon is found among invasive cane toads (Rinella marina) in Australia. In 2006, Phillips et al found that the toads at the leading edge of the expansion had longer legs making them primary candidates for high dispersal capabilities. Later, Lindstrom et al (2013) found (via radio collar measurements) that those toads at the front of the range were more likely to disperse than those at the encamped within the population.

To find out why biologists have compared life on the range edge to living in the athletes’ dormitory at the Olympics, go the whole thing.◼