A new study tracks the human-dog relationship through DNA.
- The earliest dog, not wolf, found so far comes from over 15,000 years ago.
- A new study tracks the travel and development of dogs since the end of the Ice Age.
- Insights are derived by comparing ancient canine DNA with ancient human DNA.
DNA gets around<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDY2NDU3NC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NzkxNzkyNH0.K0JEM0y89zL-HIr_8Z_iPW-ypbebDjFBNjXAkPraqok/img.jpg?width=980" id="de25c" class="rm-shortcode" data-rm-shortcode-id="3bec27e152f342b23e248227e2697222" data-rm-shortcode-name="rebelmouse-image" data-width="1200" data-height="840" />
Assyrian dog relief
Credit: Wikimedia Commons<p>The research is the product of a collaboration between Larson and paleogenomicist <a href="https://www.crick.ac.uk/research/find-a-researcher/pontus-skoglund" target="_blank">Pontus Skoglund</a> of the UK's Francis Crick Institute. Skoglund is an expert in canine evolution, working with teams at both institutions as well as the University of Vienna.</p><p>The researchers analyzed DNA from over 2,000 sets of canine skeletal remains, some of which dated back as far as 11,000 years. Working with ancient DNA from Siberia, Europe, and the Near East, the researchers were able to add 27 newly sequenced dog genomes to the previously sequenced five.</p><p>The researchers compared the canine DNA to the genomes of 17 human individuals who lived during the same time frames in search of common influences that might further establish their connection. Indeed, correspondences were seen that reflected the impacts of humans bringing their dogs along with them as they migrated around the world.</p><p>They found that Swedish farmers and their dogs are both descended from canines of the Near East, suggesting that man and dog followed the development of agriculture together through Europe. On the other hand, German farmers 7,000 years ago came from the Near East, but their dogs didn't.</p>
Lineages intersect<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDY2NDU3OS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MjE0NDc3OH0.XLvmAchMESbLY0beM-j1NTR80JGvAWOsqzJeXjH6JGI/img.jpg?width=980" id="af19d" class="rm-shortcode" data-rm-shortcode-id="7ade8431e978b8bd5adfcecaa06697c7" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="960" />
Credit: Sabine Schönfeld/Adobe Stock<p>Based on their analysis, the scientists assert that by 11,000 years ago, just after the Ice age, there were already five distinct families (or lineages) of dogs, so the German remains were no outlier. These lineages eventually developed into later lines.</p><p>Some of this occurred through interbreeding with other dogs and also through mating with their wild wolf cousins. Comparisons between ancient dog and wolf DNA revealed a surprise: Wolves picked up DNA from dogs, but, at least judging by the remains available, there was little or no gene flow back in the other direction. Larson <a href="https://www.sciencemag.org/news/2020/10/how-dogs-tracked-their-humans-across-ancient-world" target="_blank">suggests</a> to Science that the evidence may have been tampered with, so to speak — if a dog started behaving like a wolf, its human may well have simply gotten rid of it. </p><p><a href="https://www.crick.ac.uk/research/find-a-researcher/anders-bergstrom" target="_blank">Anders Bergström</a> is the lead author of the study, and he <a href="https://www.crick.ac.uk/news/2020-10-29_study-of-ancient-dog-dna-traces-canine-diversity-to-the-ice-age" target="_blank" rel="noopener noreferrer">points out</a> a mystery it reveals: "If we look back more than four or five thousand years ago, we can see that Europe was a very diverse place when it came to dogs. Although the European dogs we see today come in such an extraordinary array of shapes and forms, genetically they derive from only a very narrow subset of the diversity that used to exist." Why — and how — one line of dogs so dominated early Europe as to wipe out other lineages remains a mystery. The researchers found no human development that mirrors, or could explain, this event.</p>
A dog's life<p>It's fun to realize that ancient dog lineages persist to this day. It turns out Chihuahuas have traces of ancient American dogs, and Huskies bear traces of their cold-weather ancestors. Skoglund tells Science that on any given day in a modern dog park, you may be looking at lineages that date back 11,000 years.</p><p>It's likely that subsequent research will reveal even more. Says co-author and University of Vienna group leader Ron Pinhasi, "Just as ancient DNA has revolutionized the study of our own ancestors, it's now starting to do the same for dogs and other domesticated animals. Studying our animal companions adds another layer to our understanding of human history."</p>
The microbes that eventually produced the planet's oxygen had to breathe something, after all.
- We owe the Earth's oxygen to ancient microbes that photosynthesized and released it into the world's oceans.
- A long-standing question has been: Before oxygen, what did they breathe?
- The discovery of microbes living in a hostile early-Earth-like environment may provide the answer.
Unassuming but remarkable microbial mats<p> Photosynthesis chiefly requires sunlight, water, and CO<sup>2</sup>. The CO<sup>2</sup> gets broken down into carbon and oxygen — the plant uses some of this oxygen and releases the rest. Without oxygen molecules, though, how did this work? </p><p> There are known microbial mats today that live in oxygen-free environments, but they're not thought to be sufficiently like their ancestors to explain ancient photosynthesis in an oxygen-free environment. </p><p> There have been a few oxygen stand-ins proposed. Photosynthesis can work with iron molecules, but fossil-record evidence doesn't support that idea. Hydrogen and sulphur have also been proposed, though evidence for them is also lacking. </p><p> The spotlight began to shift to arsenic in the first decade of the millennium when arsenic-breathing microbial mats were discovered in two hypersaline California lakes, <a href="https://science.sciencemag.org/content/308/5726/1305.abstract" target="_blank">Searles Lake</a> and <a href="https://www.discovermagazine.com/planet-earth/mono-lake-bacteria-build-their-dna-using-arsenic-and-no-this-isnt-about-aliens" target="_blank" rel="noopener noreferrer">Mono Lake</a>. In 2014, Visscher and colleagues <a href="https://www.nature.com/articles/ngeo2276" target="_blank">unearthed indications</a> of arsenic-based photosynthesis, or "arsenotrophic," microbial mats deep in the fossil record of the Tumbiana Formation of Western Australia. </p><p> Still, given the ever-shifting geology of the planets, the fractured ancient fossil record makes definitive study of ancient arsenotrophic photosynthesis difficult. The fossil record can't identify the role of the arsenic it reveals: was it involved in photosynthesis or just a toxic chemical that happened to be there? </p><p>Then, last year, arsenic-breathing microorganisms <a href="https://www.washington.edu/news/2019/05/01/arsenic-breathing-life-discovered-in-the-tropical-pacific-ocean/" target="_blank" rel="noopener noreferrer">were discovered</a> in the Pacific Ocean. A sulphur bacterium, <em>Ectothiorhodospira sp.</em> was also recently found to be metabolizing arsenic into <a href="https://en.wikipedia.org/wiki/Arsenite" target="_blank">arsenite</a> in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5064118/" target="_blank" rel="noopener noreferrer">Big Soda Lake</a> in Nevada. </p>
An ancient Earth environment, today<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQ0NzIxMC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1OTQwOTYyN30.v96ZRXpIAf4yzDwcvXzVV3Fa4qULtUMxanXguPHD2wI/img.jpg?width=980" id="9eec4" class="rm-shortcode" data-rm-shortcode-id="a23585c057ee50ed500b96125e4a6b05" data-rm-shortcode-name="rebelmouse-image" data-width="2873" data-height="1640" />
a Map of Northern Chile; b Detail of frame showing Laguna La Brava in the southern Atacama; c The channel showing the mats in purple; d Hand sample, cross-section; e Microscopic image of bacteria.
Credit: Visscher, et al./Communications Earth & Environment<p>The study reports on Visscher's discovery of a living microbial mat thriving in an arsenic environment in Laguna La Brava in the Atacama Desert in Chile. "We started working in Chile," Visscher tells <a href="https://today.uconn.edu/2020/09/without-oxygen-earths-early-microbes-relied-arsenic-sustain-life/" target="_blank"><em>UConn Today</em></a>, "where I found a blood-red river. The red sediments are made up by <a href="https://en.wikipedia.org/wiki/Anoxygenic_photosynthesis" target="_blank">anoxogenic</a> photosynthetic bacteria. The water is very high in arsenic as well. The water that flows over the mats contains hydrogen sulfide that is volcanic in origin and it flows very rapidly over these mats. There is absolutely no oxygen."</p><p>The mats had not previously been studied, and the conditions in which they live are tantalizingly similar to those of early Earth. It's a high-altitude, permanently oxygen-free state with extreme temperature swings and lots of UV exposure. </p><p>The mats that somewhat resemble Nevada's purple <em>Ectothiorhodospira sp.</em> are going about their business of making carbonate deposits, forming new stromatolites. Most excitingly, those deposits contain evidence that the mats are metabolizing arsenic. The rushing waters surrounding the mats are also rich in hydrogen sulphide and arsenic.</p><p>Says Visscher, "I have been working with microbial mats for about 35 years or so. This is the only system on Earth where I could find a microbial mat that worked absolutely in the absence of oxygen."</p><p>Not that Earth is the only place where this could happen. Visscher notes that the equipment they used for studying the Laguna La Brava mats is not unlike the system aboard the Mars Perseverance Rover. "In looking for evidence of life on Mars, they will be looking at iron, and probably they should be looking at arsenic also."</p>
A new study bases its calculations on more than the great white shark.
- Previous estimates of the megalodon's size were based solely on its teeth compared to the star of "Jaws."
- The prehistoric monster is as closely related to other sharks.
- Imagine just a dorsal fin as tall as you are.
What’s different about this analysis<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzg3MjU5OS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYxNDc2MTQyNn0.K38h9qHeCM7jtYLA2Z25W7ZC9NiekmvL6CkQy82szzU/img.png?width=980" id="24ad8" class="rm-shortcode" data-rm-shortcode-id="fbc76e6dc6f82d299c7828a80272eede" data-rm-shortcode-name="rebelmouse-image" alt="megalodon compared to a school bus" data-width="1245" data-height="701" />
The megalodon’s revised measurements<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzg0OTAwMy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNTM4MjA4M30.uArVFW_ithOZuZ1_oTKCg0y1-2Zue2VRD_C_j2KJVk4/img.jpg?width=980" id="98366" class="rm-shortcode" data-rm-shortcode-id="8caf88dda090ba04f0aac156e15b7a27" data-rm-shortcode-name="rebelmouse-image" alt="shark and diver illustration" data-width="733" data-height="462" />
Credit: Reconstruction by Oliver E. Demuth/Scientific Reports<p>The study proposes the following approximate measurements for a full-grown megalodon:</p><ul><li>Length: about 16 meters (52.5 feet). A full-size school bus is just 45 feet long</li><li>Head size: about 4.65 meters long (15.3 feet) </li><li>Dorsal fin: about 1.62 meters tall (5.3 feet). A person could stand on the back of a megalodon and be about as tall as the fin.</li><li>Tail fin: about 3.85 meters high (12.6 feet) </li></ul><p>Let's just hope this sucker is really extinct. </p>
A rare titanosaur embryo was discovered with its skull preserved in 3 dimensions.
- Researchers have uncovered what the facial features of a baby titanosaurus embryo looked like using cutting-edge imaging technology.
- This in the first-ever discovery of a 3D embryonic titanosaurian sauropod skull.
- The embryo reveals that titanosaur babies had binocularly focused vision in the front of the head rather than on each side, retracted openings on their snout, and a single horn in the front of their head.
The discovery<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzYwNDExNy9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY2OTY1MzE2M30.tM0SmjB6Mf_-7LtWFlgUWATWeWMnx7r8iXj_TKNvyls/img.png?width=1245&coordinates=42%2C0%2C42%2C0&height=700" id="4fa4f" class="rm-shortcode" data-rm-shortcode-id="ac8d1beadf2cc442bb5a9c98763e7520" data-rm-shortcode-name="rebelmouse-image" alt="3D scan of fossil" data-width="1245" data-height="700" />
Kundrát et al., Current Biology, 2020<p>About 20 years ago, a dinosaur egg was illegally smuggled into the United States from Argentina. Unbeknownst to the egg-runner, it contained one of the most exquisitely preserved skulls of a dinosaur embryo ever found. (The egg has since been returned to Argentina.)</p><p>"The preservation of embryonic dinosaurs preserved inside their eggs is extremely rare," said John Nudds, study co-author and palaeontology professor at The University of Manchester, in a statement. "Imagine the huge sauropods from 'Jurassic Park' and consider that the tiny skulls of their babies, still inside their eggs, are just a couple of centimetres long."</p><p>The embryo comes from a group of dinosaurs named titanosaurian sauropods, who are known for their long necks and tails, and tiny heads. While their species also lay claim on the largest terrestrial animal ever known to have existed, they start off small enough to fit inside an egg roughly the size of that of an ostrich. The uncovered titanosaur skull is about the size of a table grape. </p><p>Understanding the species origins may give scientists a better idea of how they grew and developed. But the task hasn't been easy. Twenty-five years ago researchers struck a bonanza when they uncovered a Cretaceous-era nesting ground of these dinosaurs in Patagonia — a site where titanosaurian sauropods once laid their eggs 80 million years ago. But unfortunately, the eggs the researchers found in the area were flattened, thus lacking key information only a 3 dimensional skull could give them. </p><p>This latest finding, detailed in a paper published last week in the journal <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(20)31150-7" target="_blank" rel="noopener noreferrer">Current Biology</a>, is 3-D enough to contain all those revealing details. Including the befuddling facial features that titanosaur babies apparently wore in their first days of life. </p>
Inside the egg<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzYwNDA5OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNDM3NTYwOH0.AfJaAsSEiTO1fy4URsrFuOrJLDrMaoyVKBzSVW9n7wI/img.jpg?width=1200&coordinates=0%2C15%2C0%2C15&height=800" id="f81d5" class="rm-shortcode" data-rm-shortcode-id="173a70baad139b140326acfb73cd297b" data-rm-shortcode-name="rebelmouse-image" data-width="1200" data-height="800" />
Kundrát et al., Current Biology, 2020<p>The research team used synchrotron microtomography, a cutting edge imaging technology, to view the embryo's bones, teeth, and soft tissues, like the calcified remains of the baby's brain case and jaw muscles.</p><p>While the prehistoric long-necked beasts have always been depicted in their adult forms, the high tech images reveal that the babies actually had some unusual physical traits. They had binocularly focused vision in the front of the head rather than on each side, retracted openings on their snout, and a single horn in the front of their head. The researchers have speculated that the horn may have helped them crack out of their shell at birth and assisted these vulnerable newborns in defending themselves. There is currently no evidence of parental care in this dinosaur species, so the baby titanosaurus would have likely been fending for itself for food and protection.</p><p>"You could call it a unicorn baby dinosaur, because it has a single horn on its head. But unlike the mythical unicorn, where the horn is on the forehead, this dinosaur has a small bumpy horn at the tip of its snout," University of Edinburgh vertebrate paleontologist Stephen Brusatte, who wasn't involved in the new study, told the New York Times. "This little embryo is one of the cutest dinosaurs I've seen, and at the same time, one of the weirdest looking."</p><p>As the dinosaur matured, its head and face would have morphed into the features we imagine them as today; their vision likely changed as their eyes shifted laterally to the sides of the head. Their snout and face may have grown faster than their braincase to get rid of the horn. This is all speculation, of course, as more examples are needed. </p><p>"We expect that the specimen will become one of the most important fossils in the study of reproduction and development of the gigantic quadrupedal dinosaurs," said Martin Kundrát in an email to CNN, study author and head of the PaleoBioImaging Lab at Pavol Jozef Šafárik University in Slovakia.</p><p>Though the researchers acknowledge that it is possible that they stumbled upon an entirely new species, the embryo is the most similar to Tapuiasaurus — a titanosaurus dinosaur that lived in Brazil between 66 million and 100.5 million years ago. </p>
"You dream about these kinds of moments when you're a kid," said lead paleontologist David Schmidt.
- The triceratops skull was first discovered in 2019, but was excavated over the summer of 2020.
- It was discovered in the South Dakota Badlands, an area where the Triceratops roamed some 66 million years ago.
- Studying dinosaurs helps scientists better understand the evolution of all life on Earth.
Credit: David Schmidt / Westminster College<p style="margin-left: 20px;">"We had to be really careful," Schmidt told St. Louis Public Radio. "We couldn't disturb anything at all, because at that point, it was under law enforcement investigation. They were telling us, 'Don't even make footprints,' and I was thinking, 'How are we supposed to do that?'"</p><p>Another difficulty was the mammoth size of the skull: about 7 feet long and more than 3,000 pounds. (For context, the largest triceratops skull ever unearthed was about <a href="https://www.tandfonline.com/doi/abs/10.1080/02724634.2010.483632" target="_blank">8.2 feet long</a>.) The skull of Schmidt's dinosaur was likely a <em>Triceratops prorsus, </em>one of two species of triceratops that roamed what's now North America about 66 million years ago.</p>
Credit: David Schmidt / Westminster College<p>The triceratops was an herbivore, but it was also a favorite meal of the T<em>yrannosaurus rex</em>. That probably explains why the Dakotas contain many scattered triceratops bone fragments, and, less commonly, complete bones and skulls. In summer 2019, for example, a separate team on a dig in North Dakota made <a href="https://www.nytimes.com/2019/07/26/science/triceratops-skull-65-million-years-old.html" target="_blank">headlines</a> after unearthing a complete triceratops skull that measured five feet in length.</p><p>Michael Kjelland, a biology professor who participated in that excavation, said digging up the dinosaur was like completing a "multi-piece, 3-D jigsaw puzzle" that required "engineering that rivaled SpaceX," he jokingly told the <a href="https://www.nytimes.com/2019/07/26/science/triceratops-skull-65-million-years-old.html" target="_blank">New York Times</a>.</p>
Morrison Formation in Colorado
James St. John via Flickr
|Credit: Nobu Tamura/Wikimedia Commons|