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Ornamental dinosaur frills seem to have evolved thanks to sexual selection
While other factors exist, sexual prowess appears to have helped determine the role of Protoceratops frills.
- New research seeks to explain why dinosaurs featured an elaborate diversity of ornamentation in their frills and crests.
- A team at the Natural History Museum in London investigated a sheep-size Gobi Desert dweller known as Protoceratops.
- While sex alone does not explain the design, "socio-sexual selection" seems to have played an essential role.
Fewer than 1 percent of all animals that ever lived have been fossilized. Yet fossils are essential for understanding the nature, notes Paige Williams in "The Dinosaur Artist." They provide an evolutionary glimpse into an ancient world. As she writes,
"Without fossils, an understanding of the earth's formation and history would not be possible… We would not know that the climate has warmed and cooled and is changing still… Without fossils, we would not know that birds evolved from dinosaurs; or that Earth was already billions of years old before flowering plants appeared; or that sea creatures transitioned to life on land and primates to creatures that crafted tools, grew crops, and started wars."
Dinosaurs occupy a particularly special place in our collective imagination. Williams states that natural history museums would likely not exist without fossils as well. Now a new study, conducted by researchers at the Natural History Museum in London and published in the journal Proceedings of the Royal Society B, might have answered an age-old question: Why did dinosaurs feature such an elaborate diversity of ornamentation in their frills and crests?
The answer probably won't surprise you, however: sex.
The New Face of Protoceratops?
While there is no way to definitively answer an evolutionary question about Triassic reptiles, postdoctoral researcher Dr. Andrew Knapp has been closely analyzing Protoceratops frills. He was investigating if sexual selection played a role in this sheep-size Gobi Desert dweller.
"In many fossil animals, we have unusual structures and traits which aren't really seen in living animals today. Protoceratops didn't have any horns but they still had a huge frill."
The researchers highlight the importance of "socio-sexual selection" throughout history: traits that serve a variety of purposes, including ornamentation and weaponry, as well as behaviors that helped to establish dominance hierarchies in societies. Humans are not the only species in which the loudest and/or flashiest alphas rise to the top; that information long predates our own genes.
Common examples of sexual selection include the famous tail feathers of peacocks or the elaborate mating rituals of bowerbirds. As Knapp says, however, such rituals are "quite often more complicated than just males being big and flashy and females being dull." He continues,
"While there are quite a few examples in living animals where usually females select males based on the size of their tail feathers or calls, it is quite often overlooked that males do the same thing with females as well."
The case of Protoceratops frills is complex. Knapp and his team made four predictions about the shape of their skulls as possibly playing socio-sexual signaling roles at the outset of their study. Three were supported by the research:
- low integration with the rest of the skull
- significantly higher rate of change in size and shape during ontogeny
- higher morphological variance than other skull regions
The fourth prediction, sexual dimorphism (two different forms existing in the same population), is notoriously difficult to determine given that large sample sizes are needed to understand the impact of each form.
The group looked at 3D scans of 30 Protoceratops skulls and found positive allometry—distinct patterns of growth that could have been sexually selected. Yet without including other factors, such as selecting for coloration of these reptilian ornaments, the team couldn't conclude with certainty that frills were due to mating alone.
Knapp concludes that it's only sex that determined the impact of these frills—but it certainly seems to have played a role.
"The boundaries between sexual and social selection are quite blurred, and social selection will quite often be an important factor too."
Stay in touch with Derek on Twitter and Facebook. His most recent book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."
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An open letter predicts that a massive wall of rock is about to plunge into Barry Arm Fjord in Alaska.
- A remote area visited by tourists and cruises, and home to fishing villages, is about to be visited by a devastating tsunami.
- A wall of rock exposed by a receding glacier is about crash into the waters below.
- Glaciers hold such areas together — and when they're gone, bad stuff can be left behind.
The Barry Glacier gives its name to Alaska's Barry Arm Fjord, and a new open letter forecasts trouble ahead.
Thanks to global warming, the glacier has been retreating, so far removing two-thirds of its support for a steep mile-long slope, or scarp, containing perhaps 500 million cubic meters of material. (Think the Hoover Dam times several hundred.) The slope has been moving slowly since 1957, but scientists say it's become an avalanche waiting to happen, maybe within the next year, and likely within 20. When it does come crashing down into the fjord, it could set in motion a frightening tsunami overwhelming the fjord's normally peaceful waters .
The Barry Arm Fjord
Camping on the fjord's Black Sand Beach
Image source: Matt Zimmerman
The Barry Arm Fjord is a stretch of water between the Harriman Fjord and the Port Wills Fjord, located at the northwest corner of the well-known Prince William Sound. It's a beautiful area, home to a few hundred people supporting the local fishing industry, and it's also a popular destination for tourists — its Black Sand Beach is one of Alaska's most scenic — and cruise ships.
Not Alaska’s first watery rodeo, but likely the biggest
Image source: whrc.org
There have been at least two similar events in the state's recent history, though not on such a massive scale. On July 9, 1958, an earthquake nearby caused 40 million cubic yards of rock to suddenly slide 2,000 feet down into Lituya Bay, producing a tsunami whose peak waves reportedly reached 1,720 feet in height. By the time the wall of water reached the mouth of the bay, it was still 75 feet high. At Taan Fjord in 2015, a landslide caused a tsunami that crested at 600 feet. Both of these events thankfully occurred in sparsely populated areas, so few fatalities occurred.
The Barry Arm event will be larger than either of these by far.
"This is an enormous slope — the mass that could fail weighs over a billion tonnes," said geologist Dave Petley, speaking to Earther. "The internal structure of that rock mass, which will determine whether it collapses, is very complex. At the moment we don't know enough about it to be able to forecast its future behavior."
Outside of Alaska, on the west coast of Greenland, a landslide-produced tsunami towered 300 feet high, obliterating a fishing village in its path.
What the letter predicts for Barry Arm Fjord
Moving slowly at first...
Image source: whrc.org
"The effects would be especially severe near where the landslide enters the water at the head of Barry Arm. Additionally, areas of shallow water, or low-lying land near the shore, would be in danger even further from the source. A minor failure may not produce significant impacts beyond the inner parts of the fiord, while a complete failure could be destructive throughout Barry Arm, Harriman Fiord, and parts of Port Wells. Our initial results show complex impacts further from the landslide than Barry Arm, with over 30 foot waves in some distant bays, including Whittier."
The discovery of the impeding landslide began with an observation by the sister of geologist Hig Higman of Ground Truth, an organization in Seldovia, Alaska. Artist Valisa Higman was vacationing in the area and sent her brother some photos of worrying fractures she noticed in the slope, taken while she was on a boat cruising the fjord.
Higman confirmed his sister's hunch via available satellite imagery and, digging deeper, found that between 2009 and 2015 the slope had moved 600 feet downhill, leaving a prominent scar.
Ohio State's Chunli Dai unearthed a connection between the movement and the receding of the Barry Glacier. Comparison of the Barry Arm slope with other similar areas, combined with computer modeling of the possible resulting tsunamis, led to the publication of the group's letter.
While the full group of signatories from 14 organizations and institutions has only been working on the situation for a month, the implications were immediately clear. The signers include experts from Ohio State University, the University of Southern California, and the Anchorage and Fairbanks campuses of the University of Alaska.
Once informed of the open letter's contents, the Alaska's Department of Natural Resources immediately released a warning that "an increasingly likely landslide could generate a wave with devastating effects on fishermen and recreationalists."
How do you prepare for something like this?
Image source: whrc.org
The obvious question is what can be done to prepare for the landslide and tsunami? For one thing, there's more to understand about the upcoming event, and the researchers lay out their plan in the letter:
"To inform and refine hazard mitigation efforts, we would like to pursue several lines of investigation: Detect changes in the slope that might forewarn of a landslide, better understand what could trigger a landslide, and refine tsunami model projections. By mapping the landslide and nearby terrain, both above and below sea level, we can more accurately determine the basic physical dimensions of the landslide. This can be paired with GPS and seismic measurements made over time to see how the slope responds to changes in the glacier and to events like rainstorms and earthquakes. Field and satellite data can support near-real time hazard monitoring, while computer models of landslide and tsunami scenarios can help identify specific places that are most at risk."
In the letter, the authors reached out to those living in and visiting the area, asking, "What specific questions are most important to you?" and "What could be done to reduce the danger to people who want to visit or work in Barry Arm?" They also invited locals to let them know about any changes, including even small rock-falls and landslides.
What makes some people more likely to shiver than others?
Some people just aren't bothered by the cold, no matter how low the temperature dips. And the reason for this may be in a person's genes.
Eating veggies is good for you. Now we can stop debating how much we should eat.
- A massive new study confirms that five servings of fruit and veggies a day can lower the risk of death.
- The maximum benefit is found at two servings of fruit and three of veggies—anything more offers no extra benefit according to the researchers.
- Not all fruits and veggies are equal. Leafy greens are better for you than starchy corn and potatoes.