Captioned Image Spotlight: Rising Above It in Amazonis…

Captioned Image Spotlight: Rising Above It in Amazonis Planitia

This image shows a bright, rectangular-looking landform surrounded by a dark floor. How did this feature get here if it looks so different than its surroundings?

The feature resembles a plateau. Dark streaks mark steep slopes on its sides while the top appears flat. The slope streaks are not all the same age, as we see a variation in colors from faint to dark. Craters in a variety of sizes and ages pepper the entire rectangle, but the dark, textured floor has very few noticeable craters.

The evidence suggests that this rectangular feature is a high-standing “island” of older land surrounded by one or more younger lava flows. This landmass is located in Amazonis Planitia, a smooth plains area potentially formed by large-scale lava floods between the Tharsis and Elysium volcanic regions. As lava flowed into this area, the rectangular plateau was too high to cover completely, leaving a bright spot sticking out of the dark basalt floor for us to find.

NASA/JPL/University of Arizona

Dry conditions in East Africa half a million years ago possibly shaped human evolution, study finds

Samples of ancient sediments from a lake basin in East Africa have revealed that arid conditions developed in the area around half a million years ago, an environmental change that could have played a major role in human evolution and influenced advances in stone technology, according to an international research team that includes geologists from Georgia State University.

Dry conditions in East Africa half a million years ago possibly shaped human evolution, study finds
Lake Magadi in Kenya [Credit: Georgia State University]

The team of geologists and anthropologists drilled deep cores in Lake Magadi in Kenya to obtain ancient sediment samples that date back a million years ago to the present. Georgia State researchers conducted mineral analysis on thousands of samples, and their collaborators performed other types of analyses.

Lake Magadi is one of five sites across the East African Rift that is being studied as part of the Hominin Sites and Paleolakes Drilling Project. Two additional sites are also being studied in collaboration with the Smithsonian Institution and Indiana University.

The findings, published in the Proceedings of the National Academy of Sciences, provide clues into how environmental and climate change may have played a role in human evolution and how early humans developed early stone technologies.

“The sediments that accumulated over the last million years show us that Lake Magadi used to be fresh water and gradually over the last million years has gotten more and more saline. That tells us that arid conditions developed in East Africa about half a million years ago,” said Dr. Daniel Deocampo, collaborating author of the study and professor of geosciences at Georgia State. “On top of that long-term increase in aridity in East Africa, there were also higher frequency environmental changes. There were shorter-term fluctuations where you might have some wet centuries and some dry centuries.

“The reason why this is important is that when you see these fluctuations really kicking in, that’s right about the time when the Middle Stone Age technologies were being developed by early human ancestors, about a half million years ago. These are really more meticulously made artifacts, not the crude, stone tools of a million years ago.”

While the researchers can’t directly link climate change to human evolution and advanced technology with evidence at this point, they’re using geological data to understand the details of how the environment changed.

“I think everyone in the community agrees that environmental change plays a role in evolution, including human evolution and the development of technology,” Deocampo said. “The problem that we’re trying to address is the details. In some ways, this is kind of the first step because by drilling these sediments we can better understand how the environment changed, and that’s the first step to understanding how that environmental change affected human evolution. Those are questions that will be addressed by evolutionary biologists and anthropologists. As geologists, we’re providing data on how the environment itself changed.”

Source: Georgia State University [October 17, 2018]

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Ancient Andean genomes show distinct adaptations to farming and altitude

Ancient populations in the Andes of Peru adapted to their high-altitude environment and the introduction of agriculture in ways distinct from other global populations that faced similar circumstances, according to findings presented at the American Society of Human Genetics (ASHG) 2018 Annual Meeting in San Diego, Calif.

Ancient Andean genomes show distinct adaptations to farming and altitude
Inca terrace farming [Credit: Imgur]

John Lindo, PhD, JD, assistant professor of anthropology at Emory University, and a group of international collaborators headed by Anna Di Rienzo, PhD, at the University of Chicago and Mark Aldenderfer, PhD, at the University of California, Merced, set out to use newly available samples of 7,000-year-old DNA from seven whole genomes to study how ancient people in the Andes adapted to their environment. They compared these genomes with 64 modern-day genomes from both highland Andean populations and lowland populations in Chile, in order to identify the genetic adaptations that took place before the arrival of Europeans in the 1500s.

“Contact with Europeans had a devastating impact on South American populations, such as the introduction of disease, war, and social disruption,” explained Dr. Lindo. “By focusing on the period before that, we were able to distinguish environmental adaptations from adaptations that stemmed from historical events.”

They found that Andean populations’ genomes adapted to the introduction of agriculture and resulting increase in starch consumption differently from other populations. For example, the genomes of European farming populations show an increased number of copies of the gene coding for amylase, an enzyme in saliva that helps break down starch. While Andeans also followed a high-starch diet after they started to farm, their genomes did not have additional copies of the amylase gene, prompting questions about how they may have adapted to this change.

Similarly, Tibetan genomes, which have been studied extensively for their adaptations to high altitude, show many genetic changes related to the hypoxia response — how the body responds to low levels of oxygen. The Andean genomes did not show such changes, suggesting that this group adapted to high altitude in another way.

The researchers also found that after contact with Europeans, highland Andeans experienced an effective population reduction of 27 percent, far below the estimated 96 percent experienced by lowland populations. Previous archaeological findings showed some uncertainty to this point, and the genetic results suggested that by living in a harsher environment, highland populations may have been somewhat buffered from the reach and resulting effects of European contact. The findings also showed some selection for immune-related genes after the arrival of Europeans, suggesting that Andeans who survived were better able to respond to newly introduced diseases like smallpox.

Building on these findings, Dr. Lindo and his colleagues are currently exploring a new set of ancient DNA samples from the Incan capital Cusco, as well as a nearby lowland group. They are also interested in gene flow and genetic exchange resulting from the wide-ranging trade routes of ancient Andeans.

“Our findings thus far are a great start to an interesting body of research,” said Dr. Lindo. “We would like to see future studies involving larger numbers of genomes in order to achieve a better resolution of genetic adaptations throughout history,” he said.

Source: American Society of Human Genetics [October 17, 2018]

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