ريتشارد دوكنز's Blog, page 703
August 28, 2015
Answer Monday
For our last Fossil Friday, we took a look at a particularly graceful little specimen rising out of the rock:
But what was it? A crinoid, as many of you probably guessed, but not just any crinoid. This particular fossil is a holotype specimen for the species Cupulocrinus crossmani, as published in the Journal of Paleontology.
While there are still plenty of crinoids around in modern oceans, back in the day they were a predominant form of life. Some fossil beds from the mid to late Paleozoic are composed almost entirely of piles and piles of crinoid parts. These organisms have and had a flower-like appearance, but they are in fact animals. The petal-like arms, which can be seen to display a huge variety of intense pigments today, serve to collect particulate food from the environment. The mouth is right at the heart of this “flower.” While the crinoids have a pretty tightly preserved body structure, in the fossil record they vary greatly in size. This week’s specimen was very small; around three centimeters. However, crinoid fossils have been found up to forty meters in length.
Worth picturing, really. An ancient seabed, covered in a forest of gigantic, brightly-colored flower-animals. Like something out of Dr. Seuss. I wonder how large a “particle” those forty-footers could eat ...
The winner this week? Once again, it's gazzang, with some nice genus level identification! Congratulations, and thanks for playing! If you have a fossil you want to share, send your pictures to me at schoerning at ncse.com. And if you need another fossil fix, check out the UIowa Palentology Repository, which we thank for this week's fossil!
Fossil Friday!
Museum of Comparative Zoology, Harvard University
I’m serving up some arty photography this week! I feel that this looks a bit M. C. Escher-esque— as if the ridges are morphing into birds. Alternatively, it could be a cool relief map showing a basin and range mountain formation. Or it could be none of those things—but it is one thing, an organism of some importance and fame. Does anyone have a guess? I’d be super-surprised if you get the genus and species on this one… but then again, you’ve been surprising me every week.
Until Monday!
Blood Test Could Predict Risk For Breast Cancer Relapse Months In Advance
Photo credit:
Africa Studio / Shutterstock
A blood test that detects tumor DNA in patients with early-stage breast cancer may predict a woman’s risk of relapse months before conventional methods. The results are published in Science Translational Medicine.
August 27, 2015
Size Matters When It Comes to Cells’ Vulnerability to Parkinson’s
Each year doctors diagnose approximately 60,000 Americans with Parkinson’s disease, an incurable neurodegenerative condition for which the number-one risk factor is age. Worldwide an estimated seven to 10 million people currently live with the malady. As U.S. and global populations grow older, it is becoming increasingly urgent to understand its causes.
So far, researchers know that Parkinson’s involves cell death in a few restricted areas of the brain including the substantia nigra (SNc), one of two big cell clusters in the midbrain that house a large population of dopamine neurons. These cells release dopamine and are involved in a variety of functions including reward processing and voluntary movement. Their death leads to the motor control and balance issues that are core symptoms of the disease.
New research shows that these brain cells, most at risk in Parkinson’s disease, require unusually high amounts of energy to carry out their tasks because of their highly branched structures. Like a massive car with an overheating engine, these neurons are susceptible to burnout and early death. This discovery emerged from a comparison of energy use in nigral dopamine neurons and in similar neurons found in the nearby ventral tegmental area (VTA), also in the midbrain. “We were trying to understand why dopamine neurons of the substantia nigra die in Parkinson’s disease patients while there are so many other brain cells that have no problem at all,” says Louis-Eric Trudeau, a neuroscientist at the University of Montreal and senior author of the study published in the August 27 Current Biology.
Although located nearly side by side, neurons in the SNc expended much larger amounts of energy than those in the VTA, and their mitochondria, the structures that create energy in cells, continuously worked at maximum capacity. On further examination, the researchers found that the huge demand of these energy-guzzling cells stemmed from the fact that they are about twice the size of their neighbors in the VTA. SNc neurons also have many more axonal extensions. Like a tree with many branches, the larger neurons require more energy to survive and carry out their functions.
When the experimenters reduced this branching by adding semaphorin, an axonal guidance protein that inhibits neural growth, it reduced mitochondrial activity, energy expenditure and vulnerability in these neurons. Unfortunately, such an approach would compromise surviving neurons, which need to increase their branching, especially in aging brains, to take over and replenish dopamine stores.
The hypothesis that extensive axonal branching contributes to the vulnerability of dopamine neurons implicated in Parkinson’s has been suggested in the past, but this is the first study that puts these claims to the test—in the lab at least. It remains to be seen if the findings also can be obtained in living animals, says André Parent, a professor at Laval University who studies neurodegenerative diseases and was not involved in the study.
All of us lose dopamine neurons as we age. This is not a problem for most people because as neurons are lost, other surviving ones take over. In some individuals, however, a “critical threshold” of neural loss is reached and the remaining cells are no longer able to compensate. “Parkinson’s is a multiple-hit disease,” Trudeau says. “To develop the disease, you need a few things: the aging process and a mutation or exposure to environmental toxins. Perhaps all of us have neurons that are at risk that will eventually die in older age. But we don’t have that second ‘hit’ that will increase the stress on these cells, leading to the development of the disease.” The large dopamine cells in the substantia nigra need extra energy to run, and this chronically elevated stress makes them more vulnerable to gene mutations, environmental effects and aging, all of which might be why they are some of the first to die off.
Trudeau and his team are now looking to use the findings from this discovery to improve rodent models of Parkinson’s disease so that they are better able to mimic what happens in the primate brain. Because such brains are bigger, dopamine neurons have more territory to cover, likely requiring them to make more connections and expend more energy. Currently, scientists are not even sure that rats or mice develop Parkinson’s at all, and it might be because their cells are too small. Future studies will hopefully reveal exactly how much size matters in brain.
Massive International Project Raises Questions about the Validity of Psychology Research
Investigators across five continents reported that they were able to replicate only about 40 percent of the results from 100 previously published studies in cognitive and social psychology, in a study described today in the influential journal Science. The massive collaboration, called the Reproducibility Project: Psychology, could serve as a model for examining reproducibility of research in other fields, and a similar effort to scrutinize studies in cancer biology is already underway.
Central to the scientific method, experiments “must be reproducible,” says Gilbert Chin, a senior editor at Science. “That is, someone other than the original experimenter should be able to obtain the same findings by following the same experimental protocol.” The more readily a study can be replicated, the more trustworthy its results. But “there has been growing concern that reproducibility may be lower than expected or desired,” says corresponding author Brian Nosek, a psychology professor at the University of Virginia.
To address the problem, scientists across many disciplines established the Center for Open Science (COS) in Charlottesville, Va. The Reproducibility Project: Psychology, their first research initiative, began recruiting volunteers in 2011. They asked teams of researchers, totaling 270 collaborating authors, to choose from a pool of studies—all reflecting basic science and not requiring specialized samples or equipment—that appeared in 2008 in one of three respected psychology journals: Psychological Science; Journal of Personality and Social Psychology; and Journal of Experimental Psychology: Learning, Memory and Cognition.
Generally evidence was weaker on replication. The stronger the evidence was to begin with, however, including a larger effect size, the more likely the results were reproduced.
Although the outcome was “somewhat disappointing,” Chin said during a teleconference to discuss the findings, he stressed that it did not necessarily speak to the validity of the theories tested or even the conclusions drawn. The scientific process involves “a continual questioning and assessment of theories and of experiments.” Even nonreproducible experiments contribute to our understanding of science by helping to rule out alternative explanations. Rather, the study suggests “we should be less confident about many of the original experimental results that were provided as empirical evidence in support of those theories.”
Speaking at the same teleconference, Alan Kraut, executive director of the Association for Psychological Science and a COS board member, made a similar point: Inevitable variations in study participants, timing, location, the skills of the research team and many other factors will always influence outcomes. “The only finding that will replicate 100 percent of the time,” Kraut noted, “is one that is likely to be trite and boring.”
The teams received set protocols and analysis plans and consulted with original study authors in order to match their study design as closely as possible. After the experiments concluded, the project coordinators aggregated the data and independently reviewed the analyses.
Study authors gaged replication success using five criteria: statistical significance and p-values—an assessment of the probability of an event within a certain predetermined likelihood (generally 95 percent, or a p-value of 0.05); the effect size, which indicates the strength of the phenomenon tested; the subjective judgment of the replication team; and a meta-analysis of the effect sizes of all 100 experiments. They also factored in various other characteristics—among them sample size, so-called “effect surprisingness” and expertise of the original team—that could potentially affect the results.
In the final analysis they found that whereas 97 percent of the original studies reported statistically significant results (obtaining a p-value of 0.05 or less) only 36 percent of replications did. A weakness of using p-values, however, is that it treats 0.05 as a “bright line” between significant and nonsignificant results. To address this, the researchers also examined effect size. The replicated experiments fared slightly better when measured this way. In total, 47 percent of the replications showed an effect that matched the original results with 95 percent confidence, although generally the strength of the effect had decreased. Subjectively, 39 percent of the research teams deemed their replication a success.
Of interest, the authors found that some types of studies were more likely to be replicated than others. Only about 25 percent of the 57 social psychology studies included in the project were successfully replicated whereas 50 percent of the 43 cognitive psychology ones were. The social psychology studies also had weaker effect sizes. In addition, the simpler the design of the original experiment, the more reliable its results. The researchers also found that “surprising” effects were less reproducible.
In this study the authors excluded research that called for advanced neuroimaging, maybe also excluding the very sorts of precision experiments that could have replicated more easily. But the authors note that the problem of reproducibility persists across all fields of science, perhaps in part due to publication bias. “Publication is the currency of science,” Nosek says. “To succeed, my collaborators and I need to publish regularly and in the most prestigious journals possible.” But academic journals routinely prioritize “novel, positive and tidy results,” he adds. Studies that fail to find a significant result rarely see the light of day. In addition, replications of previously published experiments—which are vitally important in moving science forward—are much less likely to survive peer review.
To change that, Marcia McNutt, editor in chief of Science, points out that her journal and others have recently published guidelines encouraging greater transparency and openness in their selection and review process. She adds that “authors and journal editors should be wary of publishing marginally significant results, as those are the ones that are less likely to reproduce.” If they lose sight of that fact, Nosek concludes, “then the published literature may become more beautiful than the reality.”
American Astronauts Drink Their Pee – But Russians Refuse
Photo credit:
Recycling urine into drinkable water means the ISS is its own self-contained environment. Africa Studio/Shutterstock.
The history of the Russian and American space programs has been a fraught one. But since the Space Race, when the Soviet Union and America strove to outdo each other in space-based technological prowess, relations between the two teams have improved significantly, even to the point they now cohabit the International Space Station (ISS).
But it appears one thing the two countries still can’t agree on is the necessity to drink their own urine.
This Man Has Been Shedding The Polio Virus For 28 Years
Photo credit:
Diagram of the polio virus. Petarg/Shutterstock
We’re tantalizingly close to eradicating polio. Africa has gone an entire year without a new case of wild polio and Nigeria is set to be dropped from the list of polio-endemic countries. Huge challenges still remain, however, and the international community can’t afford to be complacent. This is probably best illustrated with the announcement of a new medical oddity – a man who has been shedding the polio virus for 28 years.
Why Tropical Birds Have Fewer Chicks Than Temperate Birds
Photo credit:
Tropical species like this Whitehead's Broadbill, endemic to Borneo, commonly only raise two young, whereas temperate species generally raise more. Thomas E. Martin
Researchers have long puzzled over why tropical songbirds have fewer offspring than temperate songbirds living at higher latitudes. According to a new Science study, clutch size is a function of chick growth and parental investment strategies in response to age-related mortality risk.
Life “Not As We Know It” Could Exist On Mars, Titan And Other Worlds
Photo credit:
The Viking landers in the 1970s (image from Viking 2 shown) performed the only extensive search for life on Mars to date. But were they looking for the wrong thing? NASA.
It is looking increasing unlikely that we are alone in the universe, but our current theories for extraterrestrial life are based on one key condition: It will probably be similar to that on Earth, which is reasonable to assume, as it’s the only type of life we know to exist. But what if it can exist beyond these limitations?
Watch This Amazing Self-Healing Material That Could Instantly Repair Damaged Spacecraft
Photo credit:
This is just an artist's impression, don't worry. NikoNomad/Shutterstock.
Disaster has struck. A micrometeroid has hit the International Space Station (ISS), and the air inside has begun to rush out of the hole into the vacuum of space. But in a matter of seconds, before the station is destroyed, the hole seals itself and keeps the ISS and its crew intact.
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