Dinosaurs are alive! Here’s how we know, and why it matters

Feathery dinosaurs are the perfect case study of how scientific revolutions happen.

RICHARD PRUM: The origin of the birds has been a classical challenge in evolutionary biology. Traditionally, for most of the 20th century, birds were so different from other vertebrates that they were really considered to be a group apart from other vertebrates: birds and animals. And scientifically what that came to mean is that birds were a kind of reptile with no particular relation to any specific reptiles. However, in the late 20th century, scientists who were interested in explicitly reconstructing the tree of life — that is the genealogy of species— building the tree of life, discovered that birds evolved from a group of theropod dinosaurs, those are the big, bipedal meat-eaters, like Velociraptor and T-Rex, et cetera. This opinion was extremely controversial at the time and lead to a protracted debate for decades between the theropod origin — or the dinosaur origin — of birds and what came to be known as the "dino deniers", folks that rejected the dinosaur origin of birds but were unable to explicitly articulate an alternative hypothesis for the origin of birds.

This is really a case study of how scientific revolutions happen, because early on this seemed like a crackpot theory, but over basically about two decades, three decades, the evidence started to pile up until finally it was irrefutable. Of course, the final and most dramatic evidence of this was the origin of feathers. And when people found feathers on theropod dinosaurs — like close relatives of Velociraptor, the guy who chased the kids around in the kitchen in Jurassic Park — then people really realized, "Wow, birds are dinosaurs!" And in this sense they didn't just come from dinosaurs, they are dinosaurs living amongst us — 10,000 species found on all continents around the world. So the answer to how scientific revolutions happen is always "do good science". And since science is a self-repairing process, that is it improves itself with the scrutiny and new evidence, that progress has really lead to knowledge in this case.

The pattern of progress in modern science is incontrovertible. However, one of the downsides of progress is a kind of false scientific confidence. Based on previous results one can start an investigation or an inquiry with a sort of "a priori" or "from the beginning" certainty about how it should or is going to work out. This can be a real problem, in fact, because it's so congruent with what human minds have evolved to do, which is to assign agency to patterns and thereby learn about mechanisms in the world. However as a scientist, it's important to remain open minded. There are some structures in how we think about science that allow us to catch ourselves, if you will, and make sure that we're not making a mistake. One of them is to always have a null hypothesis or some simultaneous model or explanation of the data at hand, which posits that "nothing special is happening". So before we can conclude that our favorite nifty idea is actually occurring, we have to be able to reject the idea that nothing special is going on.

An example of null hypotheses include things like "cigarettes don't cause cancer". In order to confirm that cigarettes cause cancer we need to reject the null hypothesis that they don't, and so that's part of the structure of science. Now lots of people think of the null hypothesis as simple or simpler, but in fact if cigarettes don't cause lung cancer then all those cases of lung cancer are individually different and complicated, so the null hypothesis can actually be a more complicated explanation than the main hypothesis or the signal hypothesis. So in science, especially in evolutionary science, we have found that it's really important to overcome our rational desire to see meaning and direction in everyday dissent and ask the question: Do we know if anything special is really happening?

  • For most of the 20th century, figuring out the origin of birds was a great challenge of evolutionary biology — they didn't seem to fit anywhere. Then, in the late 20th century, a group of scientists discovered that birds evolved from theropod dinosaurs, which were large, bipedal meat-eaters like the Velociraptor or the T-Rex.
  • The bird-from-dinosaur theory was considered to be a crackpot idea but after three decades of research, the evidence became irrefutable. Finally, the discovery of feathers on a theropod ended the fiery 30-year debate. "[Birds] didn't just come from dinosaurs, they are dinosaurs living amongst us — 10,000 species found on all continents around the world," says Richard Prum.
  • This piece of science history is a perfect case study of how scientific revolutions happen. The scientific method is a self-repairing system that improves under scrutiny — good science, done with an open mind and not a foregone conclusion, leads to greater knowledge.

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Image source: Christian Zimmerman/USGS/Big Think
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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 .

"It could happen anytime, but the risk just goes way up as this glacier recedes," says hydrologist Anna Liljedahl of Woods Hole, one of the signatories to the letter.

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.

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