You've likely heard about being in the right place at the wrong time, but what about having the right genes in the wrong environment? In other words, could a genetic mutation (or allele) that puts populations at risk for illnesses in one environmental setting manifest itself in positive ways in a different setting?
That's the question behind a recent paper published in The FASEB Journal by several researchers including lead author Ben Trumble, an assistant professor at Arizona State University's School of Human Evolution and Social Change and ASU's Center for Evolution and Medicine.
These researchers examined how the apolipoprotein E (ApoE) gene might function differently in an infectious environment than in the urban industrialized settings where ApoE has mostly been examined. All ApoE proteins help mediate cholesterol metabolism, and assist in the crucial activity of transporting fatty acids to the brain. But in industrialized societies, ApoE4 variant carriers also face up to a four-fold higher risk for Alzheimer's disease and other age-related cognitive declines, as well as a higher risk for cardiovascular disease.
The goal of this study, Trumble explains, was to reexamine the potentially detrimental effects of the globally-present ApoE4 allele in environmental conditions more typical of those experienced throughout our species' existence -- in this case, a community of Amazonian forager-horticulturalists called the Tsimane.
"For 99% of human evolution, we lived as hunter gatherers in small bands and the last 5,000-10,000 years -- with plant and animal domestication and sedentary urban industrial life -- is completely novel," Trumble says. "I can drive to a fast-food restaurant to 'hunt and gather' 20,000 calories in a few minutes or go to the hospital if I'm sick, but this was not the case throughout most of human evolution."
Due to the tropical environment and a lack of sanitation, running water, or electricity, remote populations like the Tsimane face high exposure to parasites and pathogens, which cause their own damage to cognitive abilities when untreated.
As a result, one might expect Tsimane ApoE4 carriers who also have a high parasite burden to experience faster and more severe mental decline in the presence of both these genetic and environmental risk factors.
But when the Tsimane Health and Life History Project tested these individuals using a seven-part cognitive assessment and a medical exam, they discovered the exact opposite.
In fact, Tsimane who both carried ApoE4 and had a high parasitic burden displayed steadier or even improved cognitive function in the assessment versus non-carriers with a similar level of parasitic exposure. The researchers controlled for other potential confounders like age and schooling, but the effect still remained strong. This indicated that the allele potentially played a role in maintaining cognitive function even when exposed to environmental-based health threats.
For Tsimane ApoE4 carriers without high parasite burdens, the rates of cognitive decline were more similar to those seen in industrialized societies, where ApoE4 reduces cognitive performance.
"It seems that some of the very genetic mutations that help us succeed in more hazardous time periods and environments may actually become mismatched in our relatively safe and sterile post-industrial lifestyles," Trumble explains.
Still, the ApoE4 variant appears to be much more than an evolutionary leftover gone bad, he adds. For example, several studies have shown potential benefits of ApoE4 in early childhood development, and ApoE4 has also been shown to eliminate some infections like giardia and hepatitis.
Read more at Science Daily
Jan 2, 2017
Scientists from Florida State University (FSU) suggest, in a new study in the journal Proceedings of the National Academy of Sciences, that the answer is from 3 to 6 months, depending on the type of dinosaur.
Beyond the wow factor of the information on its own, the finding has implications for our understanding of how dinosaurs lived and why they went extinct, according to the FSU researchers.
Study lead Gregory Erickson explained in a press release that we know "virtually nothing" about dinosaurs' embryonic lives.
"Did their eggs incubate slowly like their reptilian cousins – crocodilians and lizards? Or rapidly like living dinosaurs – the birds?" he said.
Thanks to some rare embryo fossils and some high-tech equipment, Erickson and his team appear to have answered those questions.
First the scientists gathered embryo fossils from two dinosaurs: Protoceratops, whose tiny eggs weighted just 194 grams (7 ounces), and the enormous, duck-billed Hypacrosaurus, with 4 kilo (9 pound) eggs.
Then the team put the embryonic jaw of each through a CT scanner, to visualize the forming teeth, and extracted a number of individual teeth for study beneath a high-powered microscope.
Under microscopic view, Erickson and his team found growth lines on the teeth that helped the researchers establish a timeline for embryonic development.
"These are the lines that are laid down when any animal's teeth develop," Erickson said. "They're kind of like tree rings, but they're put down daily. We could literally count them to see how long each dinosaur had been developing."
In the end, the team determined that the tiny eggs from the sheep-sized dinosaur Protoceratops took about three months to hatch, while Hypacrosaurus took about 6 months.
|Researchers examined a fossilized embryo of the dinosaur Hypacrosaurus.|
First, answering Erickson's earlier questions, the discovery suggests dinosaur egg development more closely resembled that of primitive reptiles than birds. That contradicts previous theories that dinosaur incubation was bird-like in its speed, with eggs hatching in 11 days to just under two months.
Second, the team says its findings throw into doubt theories about some dinosaur migration patterns. Animals once theorized to summer in the Arctic and winter in lower Canada, for example, might not have had the time for such journeys, given the time required for long periods of egg development, maturation, and then migration.
Read more at Discovery News