Group selection, which was once widely rejected as a significant evolutionary force, is now accepted by all who seriously study the subject. There is still widespread confusion about group selection, however, not only among students and the general public, but among professional evolutionists who do not directly study the subject. We list eight criticisms that are frequently invoked against group selection, which can be permanently laid to rest based upon current knowledge. Experts will always find something to critique about group selection, as for any important subject, but these eight criticisms are not among them. Laying them to rest will enable authors to openly use the term group selection without being handicapped during the review process. [HTML],
[PDF]
posted by Blasdelb
on Jan 15, 2013 -
41 comments
The Norovirus: A Study in Puked Perfection, "Each norovirus carries just nine protein-coding genes (you have about 20,000). Even with that skimpy genetic toolkit, noroviruses can break the locks on our cells, slip in, and hack our own DNA to make new noroviruses. The details of this invasion are sketchy, alas, because scientists haven’t figured out a good way to rear noroviruses in human cells in their labs. It’s not even clear exactly which type of cell they invade once they reach the gut. Regardless of the type, they clearly know how to exploit their hosts. Noroviruses come roaring out of the infected cells in vast numbers. And then they come roaring out of the body. Within a day of infection, noroviruses have rewired our digestive system so that stuff comes flying out from both ends."
[more inside]
posted by Blasdelb
on Jan 3, 2013 -
120 comments
One of the many problems farmers of various kinds of legumes need to deal with is the
pea aphid. They reproduce incredibly fast and live by sucking the sap out of the plants,
an electron micrograph of one in action. However, while they are terrifying parasites of legumes, they have their own yet more horrific parasites, a
parasitoid wasp.
Here is a really nice close up picture of one doing its thing,
a video of the act, and
here is a brain meltingly horrific video of a dissection of the mummified aftermath 8 days later. Essentially,
these wasps deposit their eggs in a pea aphid and the growing larva feeds on it, developing there for about a week, and then consuming the host from the inside out like a
Xenomorph. When it’s done, the wasp larva dries the aphid’s cuticle into a papery brittle shell and an adult wasp emerges from the aphid mummy. Legume farmers love them,
and you can even order their mummies online these days. However, farmers noticed that the wasps didn't work as effectively on all of the aphids, and so researchers went to work figuring out why. It turns out that all aphids have a
primary bacterial endosymbiont living inside their cells, in addition to and just like a mitochondria, and that many have some combination of five other secondary endosymbionts. Interestingly, two of those other five,
Hamiltonella defensa and
Serratia symbiotica have been shown to confer varying levels of resistance to the parasitoid wasp, allowing the aphid to survive infection. However, it turns out that there is yet one more layer to this story,
[more inside]
posted by Blasdelb
on Oct 22, 2012 -
50 comments
In this sprightly talk (transcript and video) Daniel Lieberman describes why our bodies are so good at running long distances, how our social intelligence developed and how modernity and capitalism require us to learn (or relearn) how to use our bodies. (May inspire tolerance for people who wear five-fingered shoes.) Prof. Lieberman studies human evolution at Harvard where he focuses on
heads and feet. (via
Tyler Cowen)
posted by noway
on Oct 20, 2012 -
40 comments
Mitigating Mutational Meltdown in Mammalian Mitochondria PLoS Biol 6(2): e35. [The PDF, where you can read the paper in its much prettier intended format.]Mitochondria are remarkable microorganisms. About two billion years ago, their distant free-living ancestors hooked up with a truly foreign lineage of archaebacteria and started a genomic merger that led to the most successful coevolved mutualism on the planet: the eukaryotic cell. Along the way, evolving mitochondria lost a lot of genomic baggage, entrusted their emerging hosts with their own replication, sorted out genomic conflicts by following maternal inheritance, and have mostly abstained from sex and recombination. What mitochondria did retain was a subset of genes that encode critical components of the electron transport chain and ATP synthesis enzymes that carry out oxidative phosphorylation. Because mitochondria house the biochemical machinery that requires us to breathe oxygen, it was first assumed that mitochondrial genes would show very slow rates of molecular evolution. So it was big news almost 30 years ago when mitochondrial DNA (mtDNA) evolution was observed to be quite rapid [1]. How could the genes for a highly conserved and critical function sustain the consequences of high mutation pressure and permit rapid rates of nucleotide substitution between species? Without the benefits of recombination, where offspring can carry fewer mutations than either parent, mutations should accumulate in mitochondrial genomes through the random loss of less-mutated genomes, a process referred to as Muller's ratchet [2,3]. How have mitochondria avoided a mutational meltdown, or at least significant declines in fitness?
Here is a jaw droppingly beautiful 3D animation of what Mitochindria look like in action.
[more inside]
posted by Blasdelb
on Oct 19, 2012 -
37 comments
Provirophages and transpovirons as the diverse mobilome of giant viruses Abstract: A distinct class of infectious agents, the virophages1 that infect giant viruses of the Mimiviridae family, has been recently described. Here we report the simultaneous discovery of a giant virus of Acanthamoeba polyphaga (Lentille virus) that contains an integrated genome2 of a virophage (Sputnik 2), and a member of a previously unknown class of mobile genetic elements3, the transpovirons4. The transpovirons are linear DNA elements of ∼7 kb [kilobases]5 that encompass six to eight protein-coding genes, two of which are homologous6 to virophage genes. Fluorescence7 in situ hybridization8 showed that the free form of the transpoviron replicates within the giant virus factory and accumulates in high copy numbers inside giant virus particles, Sputnik 2 particles, and amoeba cytoplasm. Analysis of deep-sequencing data showed that the virophage and the transpoviron can integrate9 in nearly any place in the chromosome of the giant virus host and that, although less frequently, the transpoviron can also be linked to the virophage chromosome. In addition, integrated fragments of transpoviron DNA were detected in several giant virus and Sputnik genomes. Analysis of 19 Mimivirus strains revealed three distinct transpovirons associated with three subgroups of Mimiviruses. The virophage, the transpoviron, and the previously identified self-splicing introns10 and inteins11 constitute the complex, interconnected mobilome12 of the giant viruses and are likely to substantially contribute to interviral gene transfer.
[
Full Text PDF] and
two explanations in English [more inside]
posted by Blasdelb
on Oct 16, 2012 -
28 comments
"In an effort to outwit raccoons, are we pushing their brain development and perhaps even sending them down a new evolutionary path? Using high-definition, infrared cameras that turn pitch dark into daylight ...
Raccoon Nation [
alt link] achieves something that has never been done before: it intimately follows a family of urban raccoons over the course of six months as the young – under the watchful eye of their mother – grow, develop, and begin to find their way in the complex world of a big city." "Raccoon populations have grown twenty-fold in North American cities over the last seventy years. And as this documentary will show, city life is changing raccoons in remarkable ways." (45:08 min. video)
posted by Jasper Friendly Bear
on Oct 13, 2012 -
42 comments
Trees of Life: A Visual History of Evolution Trees of Life: A Visual History of Evolution catalogs 230 tree-like branching diagrams, culled from 450 years of mankind’s visual curiosity about the living world and our quest to understand the complex ecosystem we share with other organisms, from bacteria to birds, microbes to mammals. (More trees are visible at the
Google Books site.)
posted by OmieWise
on May 31, 2012 -
4 comments
Larry Gonick is a veteran American cartoonist best known for his delightful comic-book guides to science and history, many of which have previews online. Chief among them is his long-running
Cartoon History of the Universe (later
The Cartoon History of the Modern World), a sprawling multi-volume opus documenting everything from the Big Bang to the Bush administration. Published over the course of three decades, it takes a truly global view -- its time-traveling Professor thoroughly explores not only familiar topics like Rome and World War II but the oft-neglected stories of Asia and Africa, blending caricature and myth with careful scholarship (cited by
fun illustrated bibliographies) and tackling even the most obscure events
with intelligence and wit. This savvy satire carried over to Gonick's
Zinn-by-way-of-
Pogo chronicle
The Cartoon History of the United States, along with a bevy of
Cartoon Guides to other topics, including
Genetics, Computer Science, Chemistry, Physics, Statistics, The Environment, and (yes!)
Sex. Gonick has also maintained a few sideprojects, such as
a webcomic look at Chinese invention,
assorted math comics (
previously), the
Muse magazine mainstay
Kokopelli & Co. (featuring the shenanigans of his
"New Muses"), and
more. See also
these lengthy interview snippets, linked
previously. Want more? Amazon links to the complete oeuvre inside!
[more inside]
posted by Rhaomi
on Jun 6, 2011 -
29 comments
Swimming around in a mixture of language and matter, humans occupy a particular evolutionary niche mediated by something we call 'consciousness'. To Professor Nicholas Humphrey we're made up of "
soul dust": "a kind of theatre... an entertainment which we put on for ourselves inside our own heads." But just as that theatre is directed by the relationship between language and matter,
it is also undermined by it. It all depends how you think it.
posted by 0bvious
on Feb 4, 2011 -
17 comments
Our minds boggle at how the wolf could become the chihuahua, the Saint Bernard, the poodle and the
Komondor. Artificial selection was likewise responsible for transforming the humble wild mustard plant
Brassica oleracea into cabbage, broccoli, Brussels sprouts and the breathtaking fractal
Romanesco, all in the span of a few centuries.
[more inside]
posted by overeducated_alligator
on Aug 23, 2010 -
54 comments
