234 posts · 316,833 views
Evolutionary Biology, Life Science, Science Education, Human Evolution, and Stuff.
Inequality in mortality is the most poignant reminder of persistent, often multi-generational differences in socioeconomic status (SES). Poor people are more likely to get sick and die than rich people. As a society develops over time, one would hope that this disparity would be reduced, but in fact, it often increases. Recent research published in PLoS Medicine heralds this bad news.
This study is fairly unique in that it examines life expectancy across counties, which are the smallest demographic unit for which the appropriate kind of data are collected. The study examines dea... Read more »
Majid Ezzati, Ari Friedman, Sandeep Kulkarni, Christopher Murray, & Thomas Novotny. (2008) The Reversal of Fortunes: Trends in County Mortality and Cross-County Mortality Disparities in the United States . PLoS Medicine, 5(4). DOI: 10.1371/journal.pmed.0050066
One of the most important evolutionary transitions in human prehistory was the rise of modern humans (Homo sapiens) from earlier hominids. A newly reported fossil from Tanzania provides an important new data point necessary to understand this transition.
Read the rest of this post... | Read the comments on this post...... Read more »
M DOMINGUEZRODRIGO, A MABULLA, L LUQUE, J THOMPSON, J RINK, P BUSHOZI, F DIEZMARTIN, & L ALCALA. (2008) A new archaic Homo sapiens fossil from Lake Eyasi, Tanzania. Journal of Human Evolution. DOI: 10.1016/j.jhevol.2008.02.002
Life is complex. The way a living system works can be described in a series of increasingly refined models, each fleshing out details of the previous model. Typically, description at one level raises questions about what is happening at the finer level. These questions induce hypotheses which drive experimental work which produces ever more detailed knowledge.
A paper about memory, just published in Cell, is an example of one incremental step in this process. In short, this research works out some of the fine detail at the molecular level for the process of forming visual mem... Read more »
S GRIFFITHS, H SCOTT, C GLOVER, A BIENEMANN, M GHORBEL, J UNEY, M BROWN, E WARBURTON, & Z BASHIR. (2008) Expression of Long-Term Depression Underlies Visual Recognition Memory. Neuron, 58(2), 186-194. DOI: 10.1016/j.neuron.2008.02.022
That elephants have an aquatic ancestry has been suspected for some time now. Moreover, the idea of elephant aquatic origins and elephant origins in general is part of a growing realization that many of the world's aquatic mammals originated in a couple of regions of Africa that were for a very long time enormous inland seas (but that is another story I won't cover here).
The earlier evidence came from observation of the ontogeny of the kidneys in elephants, during which the kidneys take on the characteristics that are found in aquatic mammals generally. That resea... Read more »
A Liu, E R Seiffert, & E L Simons. (2008) Stable isotope evidence for an amphibious phase in early proboscidean evolution. Proceedings of the National Academy of Sciences, 105(15), 5786-5791. DOI: 10.1073/pnas.0800884105
Recently published research shows that individual humans will be nicer (more altruistic) when there is the possibility that the recipient of an act can respond verbally. The paper, "Anticipated verbal feedback induces altruistic behavior" is published in Evolution and Human Behavior for March. Read the rest of this post... | Read the comments on this post...... Read more »
Developmental dyslexia is a disorder affecting as many as 17% of school children. This neurological disorder involves an impairment in reading skills, and has been found to be "associated with weak reading-related activity in left temporoparietal and occipitotemporal regions" in English speakers. However, different abnormalities in the brain are associated with dyslexic readers in the non-alphabetic Chinese language, according to research just published in the Proceedings of the National Academy of Sciences.
This is not terribly surprising. Earlier research had shown that indiv... Read more »
W Siok, Z Niu, Z Jin, C A Perfetti, & L H Tan. (2008) From the Cover: A structural-functional basis for dyslexia in the cortex of Chinese readers. Proceedings of the National Academy of Sciences, 105(14), 5561-5566. DOI: 10.1073/pnas.0801750105
Ever since 3,599 years ago humans have been asking the question "Why did our furry elephant go extinct?"
What caused the woolly mammoth's extinction? Climate warming in the Holocene might have driven the extinction of this cold-adapted species, yet the species had survived previous warming periods, suggesting that the more-plausible cause was human expansion.
The woolly mammoth went extinct less than four thousand years ago. The bones of miniaturized woolly mammoths have been found in Siberia dating to about 3,600 years ago. Indeed, woolly mammoths, the furry elephant of... Read more »
David Nogués-Bravo, Jesús Rodríguez, Joaquín Hortal, Persaram Batra, Miguel Araújo, & Anthony Barnosky. (2008) Climate Change, Humans, and the Extinction of the Woolly Mammoth. PLoS Biology, 6(4). DOI: 10.1371/journal.pbio.0060079
It is a little ironic that all nature enthusiasts know that it is "bad" to feed the animals ... they become dependent on the food, and in some cases will become a nuisance or dangerous, prying open cars or breaking into homes to get more food. Then the animal has to be put down or moved to a new habitat. But that sort of bad outcome is more common with, say, bears than it is with, say, chickadees. The irony here is that bird lovers, who are always nature enthusiasts, do not seem to balk at setting up bird feeders. In fact, approximately on half a million metric tons of seed is put out f... Read more »
Gillian Robb, Robbie A McDonald, Dan E Chamberlain, & Stuart Bearhop. (2007) Food for thought: supplementary feeding as a driver of ecological change in avian populations. Frontiers in Ecology and the Environment, preprint(2008), 1. DOI: 10.1890/060152
Gillian Robb, Robbie A McDonald, Dan E Chamberlain, S James Reynolds, Timothy JE Harrison, & Stuart Bearhop. (2008) Winter feeding of birds increases productivity in the subsequent breeding season. Biology Letters, 4(2), 220-223. DOI: 10.1098/rsbl.2007.0622
According to a study just out in PLoS, you can learn to be nice. This study, using functional MRI brain imaging, assessed brain activity while meditation experts produced a meditative state called a "loving-kindness-compassion state" (and here I was thinking that the "loving-kindness-compassion state" was Vermont... ). Read the rest of this post... | Read the comments on this post...... Read more »
Antoine Lutz, Julie Brefczynski-Lewis, Tom Johnstone, Richard Davidson, & Bernhard Baune. (2008) Regulation of the Neural Circuitry of Emotion by Compassion Meditation: Effects of Meditative Expertise. PLoS ONE, 3(3). DOI: 10.1371/journal.pone.0001897
The ape human split is a bit of a moving target. In the 1970s and early 1980s, there were geneticists who placed it at very recent (close to 4 million years ago) and palaeoanthropologists, using fossils, who placed it at much earlier. During the 1980s, the ape-human split moved back in time because of the importance of sivapithecus, then later in time when Sivapithecus slipped and fell out of the hominid/hominin (human ancestor) family tree. Meanwhile the geneticists were moving towards a more and more recent split. At one point not too long ago, all the evidence converged with the spli... Read more »
B Richmond, & W L Jungers. (2008) Orrorin tugenensis Femoral Morphology and the Evolution of Hominin Bipedalism. Science, 319(5870), 1662-1665. DOI: 10.1126/science.1154197
A "radiation" (sometimes called an "adaptive radiation") is when a single ancestral species gives rise to a number of novel species, often in a fairly short (geological) period of time. Following this radiation event, it seems often to be the case that subsequent speciation is less common. In fact, many living clades that have only a small number of extant species have such radiations in their history. It is quite possible that the radiation event occurred for reasons local in time and space, such as a recent extinction leaving various niches open, or the presence of a particular adaptat... Read more »
Significant cultural and physical differences ... the stuff of race and ethnicity ... are prominent when people move across continents or between them. Eventually, the ponderous events of history, which involve occasional foldings in the continuum of human variation, causing apparent patchiness, are offset by the frequent events of human activities, resulting in genetic and cultural admixtures. What colonialism, invasion, and migration do is undone.
A new study out in PLoS Genetics examines this phenomenon for Latin America, with a study of genetic admixture. Read the rest ... Read more »
Sijia Wang, Nicolas Ray, Winston Rojas, Maria Parra, Gabriel Bedoya, Carla Gallo, Giovanni Poletti, Guido Mazzotti, Kim Hill, Ana Hurtado.... (2008) Geographic Patterns of Genome Admixture in Latin American Mestizos. PLoS Genetics, 4(3). DOI: 10.1371/journal.pgen.1000037
A common presumption is that behavior is part of phenotype, and since phenotype arises from genotype (plus/minus Reaction Norm), that there can be a study of "behavioral genetics." This is certainly an overstatement (or oversimplification) for organisms with extensive and/or complex neural systems, such as humans and mice. Neural systems probably evolved (not initially, but eventually) to disassociate behavior with the kind of pre-determined micro-management of behavior that a simple gene-behavior link requires. However, in organisms with neural systems the size of the period at the end ... Read more »
Dietrich Gotzek, D Shoemaker, Kenneth Ross, & Stuart West. (2007) Molecular Variation at a Candidate Gene Implicated in the Regulation of Fire Ant Social Behavior. PLoS ONE, 2(11). DOI: 10.1371/journal.pone.0001088
... according to a new study published in the Proceedings of the National Academy of Sciences. The study compares skull measurements of Flores material with a wide range of other hominid data and concludes that Flores cannot be clustered with Homo sapiens. This is the first published study that takes into account how size affects shape. By correcting for size, this study makes, the authors claim, a more valid comparison between measurements taken on the Flores material and other comparative data.
Read the rest of this post... | Read the comments on this post...... Read more »
A Gordon, L Nevell, & B Wood. (2008) The Homo floresiensis cranium (LB1): Size, scaling, and early Homo affinities. Proceedings of the National Academy of Sciences, 105(12), 4650-4655. DOI: 10.1073/pnas.0710041105
Indeed, the evolutionary history of the mammalian way of providing nutrients for young is difficult to ascertain on the basis of the usual techniques: Fossils and comparative anatomy. The soft parts involved don't fossilize well, and there are not enough "intermediates" living today to develop a plausible story of the evolutionary transitions linking egg-laying to live birth and lactation.
A new study recently published in PLoS Biology brings us a long way towards understanding this set of evolutionary events. Read the rest of this post... | Read the comments on this post..... Read more »
David Brawand, Walter Wahli, & Henrik Kaessmann. (2008) Loss of Egg Yolk Genes in Mammals and the Origin of Lactation and Placentation. PLoS Biology, 6(3). DOI: 10.1371/journal.pbio.0060063
Blowflies. They are nearly impossible to swat dead, because they are so good at getting out of the way, and they are very very fast. For this reason, the blowfly, while an annoying creature, is an excelent model for research into rapid sensory information processing.
A team of scientists from Indiana University, Princeton University and the Los Alamos National Laboratory recently gained new insight into how blowflies process visual information. The findings, published in an article in the Public Library of Science Journals, show that the precise, sub-millisecond timing of "spikes"... Read more »
Ilya Nemenman, Geoffrey Lewen, William Bialek, Rob de Ruyter van Steveninck, & Karl Friston. (2008) Neural Coding of Natural Stimuli: Information at Sub-Millisecond Resolution. PLoS Computational Biology, 4(3). DOI: 10.1371/journal.pcbi.1000025
Toxoplasmosis is a disease caused by Toxoplasma gondii, a protozoan. It is very common in cats, but also known in humans. This is the disease people worry about when they have children and cats in the same house. Don't let your child eat cat poop! Pregnant women should avoid this disease, as there are especially bad outcomes for the offspring.
The good news is this: A new drug currently in testing phase for treating malaria is very effictrive against T. gondii. This new drug, a form of triazine, goes by the memorable name JPC-2067-B. Read the rest of this post... | Read... Read more »
Ernest Mui, Guy A Schiehser, Wilbur K Milhous, Honghue Hsu, Craig W Roberts, Michael Kirisits, Stephen Muench, David Rice, J P Dubey, Joseph W Fowble.... (2008) Novel Triazine JPC-2067-B Inhibits Toxoplasma gondii In Vitro and In Vivo. PLoS Neglected Tropical Diseases, 2(3). DOI: 10.1371/journal.pntd.0000190
It almost seems like there are two separate research project under way regarding the evolutionary history of Homo sapiens. One focuses on recent humans, tends to use DNA as a major source of information, and from this base projects back into the past. This approach tends to confirm the idea that humans share an African origin with a subsequent spread from Africa, with various degrees of complexity in that series of historical events. The other focuses on early human remains, sometimes including remains that would be placed by some in a separate species or sub species. This sort of appro... Read more »
M SCHILLACI. (2008) Human cranial diversity and evidence for an ancient lineage of modern humans. Journal of Human Evolution. DOI: 10.1016/j.jhevol.2007.10.010
There is a fairly new paper in PLoS on the colonization of the New World. It is the latest in a series of attempts to synthesize biogeography, climate change related paleoenvironmental reconstruction, genetics, and archaeology. Read the rest of this post... | Read the comments on this post...... Read more »
Andrew Kitchen, Michael Miyamoto, Connie Mulligan, & Henry Harpending. (2008) A Three-Stage Colonization Model for the Peopling of the Americas. PLoS ONE, 3(2). DOI: 10.1371/journal.pone.0001596
There is a new paper out suggesting that the Flores hominids, known as Hobbits, were "human endemic cretins."
From the abstract of this paper:
... We hypothesize that these individuals are myxoedematous endemic (ME) cretins, part of an inland population of (mostly unaffected) Homo sapiens. ME cretins are born without a functioning thyroid; their congenital hypothyroidism leads to severe dwarfism and reduced brain size, but less severe mental retardation and motor disability than neurological endemic cretins. We show that the fossils display many signs of congenital hypothyro... Read more »
Peter Obendorf, Charles E Oxnard, & Ben J Kefford. (2008) Are the small human-like fossils found on Flores human endemic cretins?. Proceedings of the Royal Society B: Biological Sciences, -1(-1), -1--1. DOI: 10.1098/rspb.2007.1488
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