Over at The Molecular Ecologist I’ve done an in-depth review of the population genetics data cited by Nicholas Wade in his book A Troublesome Inheritance, which argues that social, cultural, and economic differences between human populations are all in our genes. Digging into the book’s endnotes, it didn’t take me long to find discrepancies between Wade’s description of basic population genetic results and the actual, um, results.
First and foremost, Wade claims that when population geneticists apply a class of statistical methods called clustering algorithms to datasets containing hundreds or thousands of genetic markers, they objectively identify five geographic groups that he calls “continental races”—differentiating African, European/Middle Eastern/South Asian, East Asian, Oceanian, and American people. What he does not make particularly clear is that while clustering methods do group genetic samples without direct instructions, the algorithms do not decide how many clusters there are. The geneticists using them do.
To make me feel somewhat better for having paid actual money to read this book, go read my whole review.◼
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.◼
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.◼
Produced with genetic engineering.
Contents derived from organisms produced by millennia of only occasionally deliberate selective breeding, and which may be so freakishly modified from their ancestral state that they would not survive five days without constant care and attention.
Product may make your tongue appear to be purple in color, but this effect is not permanent.
Useful for, at most, temporary relief of emotional distress resulting from a breakup, firing, or other traumatic life experience.
Will not taste anything like what your mother used to make.
Processed in a facility that also sells to Republicans.
Can be habit-forming if consumed periodically in a regular place, at a set time of day, or in conjunction with routine activities.
Contains no material that is truly describable using the word “marshmallow.”
May produce sensory stimuli with strong associations to formative childhood experiences, which can trigger periods of abstraction, rumination, nostalgia, regret, and panic attacks.
Made in desperation.◼
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.◼
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.◼