Long-term bottleneck effects: Europeans have more deleterious genetic variation than African populations
No time to read this now, but it looks very interesting: Proportionally more deleterious genetic variation in European than in African populations (doi). Abstract says -
Quantifying the number of deleterious mutations per diploid human genome is of crucial concern to both evolutionary and medical geneticists. Here we combine genome-wide polymorphism data from PCR-based exon resequencing, comparative genomic data across mammalian species, and protein structure predictions to estimate the number of functionally consequential single-nucleotide polymorphisms (SNPs) carried by each of 15 African American (AA) and 20 European American (EA) individuals.
We find that AAs show significantly higher levels of nucleotide heterozygosity than do EAs for all categories of functional SNPs considered, including synonymous, non-synonymous, predicted 'benign', predicted 'possibly damaging' and predicted 'probably damaging' SNPs. This result is wholly consistent with previous work showing higher overall levels of nucleotide variation in African populations than in Europeans.
EA individuals, in contrast, have significantly more genotypes homozygous for the derived allele at synonymous and non-synonymous SNPs and for the damaging allele at 'probably damaging' SNPs than AAs do. For SNPs segregating only in one population or the other, the proportion of non-synonymous SNPs is significantly higher in the EA sample (55.4%) than in the AA sample (47.0%; P < 2.3 times). We observe a similar proportional excess of SNPs that are inferred to be 'probably damaging' (15.9% in EA; 12.1% in AA; P < 3.3 times).
Using extensive simulations, we show that this excess proportion of segregating damaging alleles in Europeans is probably a consequence of a bottleneck that Europeans experienced at about the time of the migration out of Africa.
Philological Considerations on the Whence of the Maori
Conal directs me towards a wonderful paper from J.T. Thomson in 1873, Philological Considerations on the Whence of the Maori, which is particularly relevant to the recent rates of word evolution work, and manages to beat lexicostatistics and Morris Swadesh by a good 75 years:
Primary words, i.e., those that express first wants in men in their infancy—and, equally so, tribes or nations in their infancy—are the most tenacious of existence. These are common nouns, pronouns, and verbs, but more particularly the first—such as man, woman, son, daughter, food, fruit, fish, etc.; or, I, you, he, we, etc.; or, go, come, give, kill, etc. In elucidating a subject such as this, therefore, we apply our enquiries to primary terms, which we may denominate as the fossils of the languages, so that we may, from their coincidence or approximations in different and distant communities, weigh the affinities of race or blood in the communities themselves.
But while primary words are the most lasting, yet they even are subject to slow and gradual change as ages roll on.
..and even more lexicostatistics-y:
Reverting, then, to the glossarial branch of the subject, in order to fairly weigh the respective affinities of the different races under review, as read by language, I must recall your attention to the fact stated in my former paper as to the relative number of primary words retained by an European language after eight hundred years of disconnection; these amount to only about one twenty-sixth of the whole. Mr. John Crawford, by his investigations, has declared that one fifty-seventh of the Malagasi and one-fiftieth of the Maori dictionaries were Malay, thus proving a connection whose intimacy on European experience can be approximately calculated. But I may venture to remark, from my own enquiries on the same subject, that had the above ethnographer or myself had the advantage of a critical knowledge of both or all languages, instead of only one (the Malay), double the equivalents might be found, and the approaches thus drawn nearer by half. Thus, Crawford states that out of 8,000 Malagasi words he detected only 140 Malayan; while I, out of Griffiths' grammar, containing certainly not more than 500 words, detected eighty, in words that have had preservation throughout the whole region.
Papers I should Read: Culling-induced social perturbation in Eurasian badgers
I'm thoroughly intrigued by this title: "Culling-induced social perturbation in Eurasian badgers Meles meles and the management of TB in cattle: an analysis of a critical problem in applied ecology" (Abstract)
Papers I should read: The cabbage aphid, a walking mustard oil bomb
I'm completely intrigued by " The cabbage aphid: a walking mustard oil bomb" (doi:10.1098/rspb.2007.0237). The potential for self-seasoning coleslaw alone makes this worth a read.
Papers I should read: Why Barbie feels heavier than Ken
Why Barbie feels heavier than Ken: The influence of size-based expectancies and social cues on the illusory perception of weight (doi:10.1016/j.cognition.2007.05.009):
In order to examine the relative influence of size-based expectancies and social cues on the perceived weight of objects, two studies were performed, using equally weighing dolls differing in sex-related and age-related vulnerability or physical strength cues. To increase variation in perceived size, stimulus objects were viewed through optical lenses of varying reducing power. Different groups of participants were required to provide magnitude estimates of perceived size, physical strength, or weight, or of expected weight. A size–weight illusion (SWI) was demonstrated, such that smaller objects felt heavier than larger ones, that was entirely accounted for by the mediating role of expected weight. Yet, perceived physical strength exerted an additional and more reactive influence on perceived weight independently of measured expectancies. Results are used to clarify the nature of “embodied”, internal sensory–motor representations of physical and social properties.
Things I should read: Crane Music
P. A. Johnsgard (1991). Crane Music: A Natural History of American Cranes. Smithsonian Inst. Washington.
(bzzt, whir, clunk!)