genetics
razib | August 8, 2007/. has a post with the title Humanity's Genetic Diversity on the Decline, drawing from a recent paper which found that the mtDNA haplotype diversity in England was lower than 1,000 years ago. The authors were surprised because of course one presumes England is more cosmopolitan today than in the past, and so there would be more diversity. As a resolution to their finds they suggest that demographic dynamics, such as the Black Death with resulted in the death of 1/2 of the English in 1 generation, as well as selection for mtDNA variants (i.e., a haplotype is linked toward some functional…
razib | August 7, 2007A few weeks ago the study about obesity being socially contagious was all the rage. For anyone interested in human behavior this shouldn't be surprising, we are a social creature and our peer group is an essential part of our 'extended phenotype'. The psychologist Judith Rich Harris has famously argued that the 40% of unattributed component of variation of personality is due to our peer groups (10% is parents and 50% is genes). In Harris' model the best thing that parents can do is choose a particular peer group with values which reflect their own priorities. In other words, buying a house…
purepedantry | August 6, 2007It's mad, I tell you, madddd! Mad scientists these days. Always going around saying, "Hey, you know how that animal could be better? If it had another head. Muahahaha!"
Anyway, the (possibly mad) scientists Wolfgang Jakob and Bernd Schierwater wanted to know more about the genes that determine the body plan of multicellular organisms. In mammals, these genes are called Hox genes, and in organisms that have circular symmetry like jellyfish they are called Cnox genes. We know that these genes broadly pattern the body plan of multicellular organisms because in a variety of settings if you…
razib | August 5, 2007Gene For Left-handedness Identified in ScienceDaily. The original paper is LRRTM1 on chromosome 2p12 is a maternally suppressed gene that is associated paternally with handedness and schizophrenia:
Left-right asymmetrical brain function underlies much of human cognition, behavior and emotion. Abnormalities of cerebral asymmetry are associated with schizophrenia and other neuropsychiatric disorders. The molecular, developmental and evolutionary origins of human brain asymmetry are unknown. We found significant association of a haplotype upstream of the gene LRRTM1...with a quantitative measure…
razib | August 4, 2007In many parts of the Muslim world people claim to be descendants of the Prophet. Generally these are Sayyids:
Sayyid (سÙد) (plural Saadah) is an honorific title that is given to males accepted as descendants of the Islamic prophet Muhammad through his grandsons, Hassan and Husayn, who were the sons of his daughter Fatima Zahra and son-in-law Ali ibn Abi Talib.
Are the people who claim to be Sayyids really Sayyids? If they share common descent from Ali, their Y chromosomal lineage should be the same. Or, more likely assuming a small proportion of infidelity per generation you will have one…
retrospectacle | August 4, 2007As evidenced by the Tour de France's continuing troubles with chemical and blood doping, many professional athletes (but by no means all) are willing to take drastic measures to get an "edge." Blood doping involves strengthening a person's endurance by a blood transfusion. The extra red blood cells increase the recipient's ability to transport oxygen to tissues temporarily, but also expose the athlete to serious cardiovascular risks. Doping with drugs and hormones is also widely publicized, with the some of the usual suspects being artificial testosterone, human growth hormone, modafinil, and…
razib | August 3, 2007Note: I got this article via AJHG's RSS. It doesn't seem to have gone live on the site so there might be temporary problems accessing the link.
Evidence of Still-Ongoing Convergence Evolution of the Lactase Persistence T-13910 Alleles in Humans:
A single-nucleotide variant, C/T-13910, located 14 kb upstream of the lactase gene (LCT), has been shown to be completely correlated with lactase persistence (LP) in northern Europeans. Here, we analyzed the background of the alleles carrying the critical variant in 1,611 DNA samples from 37 populations. Our data show that the T-13910 variant is found…
pharyngula | August 2, 2007Abbie of ERV has made her first guest post on the Panda's Thumb, and it's a good one. Go see how Behe was wrong and there are documented genetic and biochemical changes in the evolution of HIV, including the evolution of new molecular machinery.
razib | August 1, 2007In biological anthropology there is a Grandmother Hypothesis as an explanation for why adult human females live so long after their reproduction ceases, and, why menopause occurs in the first place (male fertility tapers off over time, while women undergo a concerted physiological change which shuts down their ability to reproduce). The basic idea is that beyond a particular age women can increase their own genetic fitness to a greater extent by investing in their daughters reproductive output.
The idea is pretty easy to illustrate. Imagine an allele, M, which induces menopause in an…
razib | August 1, 2007There has been a lot of comment on the blogosphere about eugenics. From the Right, Ross Douthat here, here & here, from the Left Ezra Klein here, here & here, Kevin Drum here & Henry Farrell here. And from the libertarian angle the Elf here. Since a few of my posts were referenced I added a bit here & here. I think I'm pretty clear about "eugenics," and biological technologies. I'm not a "bio-utopian," but I think the future is coming and we need to grapple with it. I'm not scared of the word eugenics, but accept that the new biological technologies and choices will have…
razib | July 31, 2007Gene Duplications Give Clues to Humanness:
All told, the researchers found more than 4000 genes that showed lineage-specific changes in copy number, with the numbers steadily increasing over evolutionary time. Humans, for example, only had 84 genes with increased copy numbers over those of our closet relatives. In contrast, lemurs, which have evolved for 60 million years, have 1180 genes with extra copies. "This is further evidence that genomic differences between humans and other primates is far, far more complex than we originally imagined they might be," says Ajit Varki, who studies human/…
razib | July 30, 2007Carl Zimmer has a fascinating profile of Martin Nowak, whose work I have talked about before. Carl saves the best for last:
Dr. Nowak sometimes finds his scientific colleagues astonished when he defends religion. But he believes the astonishment comes from a misunderstanding of the roles of science and religion. "Like mathematics, many theological statements do not need scientific confirmation. Once you have the proof of Fermat's Last Theorem, it's not like we have to wait for the scientists to tell us if it's right. This is it."
razib | July 30, 2007Steven Pinker explores The Genealogy Craze in America in TNR. He covers most of the angles, and expands a bit out from a laser-like focus on scientific genealogy toward the relevance of relatedness in the evolution of social behavior.
razib | July 28, 2007Ancient and continuing Darwinian selection on insulin-like growth factor II in placental fishes:
...We found that IGF2 is subject to positive Darwinian selection coincident with the evolution of placentation in fishes, with particularly strong selection among lineages that have evolved placentation recently. Positive selection is also detected along ancient lineages of placental livebearing fishes, suggesting that selection on IGF2 function is ongoing in placental species. Our observations provide a rare example of natural selection acting in synchrony at the phenotypic and molecular level.…
razib | July 27, 2007Rapid evolution in early trilobites fueled by high variation:
Webster compiled morphological data for nearly 1,000 of the 17,000 different species of trilobites, a class of marine arthropods that died out by 250 million years ago, from 49 previously published sources. By tracking different morphological features -- the number of body segments, for example -- Webster found that trilobite species exhibited more variation during the Cambrian than in later periods, he reported in Science July 27. "Once you go beyond the Cambrian, the diversity of forms within any one species drops off," he says.…
razib | July 27, 2007How bacteria evolve into superbugs:
"Bacteria that can mutate fast will quickly adapt to harsh environments containing antibiotics. Our study showed that a high rate of immigration significantly augments the regular process of genetic mutation commonly used to explain the evolution of antibiotic resistance," said co-author Dr. Andrew Gonzalez, a Canada Research Chair in Biodiversity and associate professor in the Department of Biology at McGill. Gonzalez explained that the flow of bacteria in the experiment is analogous to the immigration of bacteria-carrying individuals into a hospital, and…
razib | July 26, 2007Viral Epizootic reveals inbreeding depression in a habitually inbreeding mammal:
Inbreeding is typically detrimental to fitness. However, some animal populations are reported to inbreed without incurring inbreeding depression, ostensibly due to past "purging" of deleterious alleles. Challenging this is the position that purging can, at best, only adapt a population to a particular environment; novel selective regimes will always uncover additional inbreeding load. We consider this in a prominent test case: the eusocial naked mole-rat (Heterocephalus glaber), one of the most inbred of all free…
razib | July 25, 2007Check out a long piece on bonobos in The New Yorker. Now, I've read a fair amount of Frans de Waal's work, and I think the piece is making him out to be a little more PC than he is. Nevertheless, I am a bit disturbed by the fact that hasn't seen a Bonobo in the wild! I just happened to have missed that assumed that though most of his research was based on captive animals, there must have been some field research supplementing it. No. And de Waal's response it pretty lame:
Captivity can have a striking impact on animal behavior. As Craig Stanford, a primatologist at the University of…
evolgen | July 22, 2007Mark Liberman at Language Log has been posting on genetics recently. A couple of days ago he tried to track down the origins of the components of the gene name BTBD9. The letters and numbers in the name stand for complex-tramtrack-bric-a-brac-domain 9, which are hijacked from Drosophila nomenclature. Liberman then tries to figure out the origins of the names tramtrack and bric-a-brac using FlyNome (a cool webpage that I hadn't seen before) and FlyBase. In the end, he couldn't track down the (clever) story behind either one.
I was amused by that post, and I was further impressed by Liberman's…
razib | July 21, 2007Science makes DNA breakthrough in the tooth of a mastodon:
...after finding DNA preserved in the fossilised tooth of a beast that died up to 130,000 years ago.
...
Researchers were hoping its teeth might have preserved enough of the DNA for them to recover lengthy chunks of it, and this week they will publish research detailing how their hunch has paid off. The find has allowed them to reconstruct the entire sequence of the DNA found in the creature's mitochondria, the parts of cells concerned with energy production. It is thought to be the oldest DNA ever to have been recovered and decoded…