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" />
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" />
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>
"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|
Our family tree is complicated, and some of the branches are still unlabeled.
- A new study of the genomes of Modern Humans, Neanderthals, and Denisovans suggests the three were interbreeding quite often.
- The study also found DNA from an unidentified, archaic human ancestor which we inherited from the Denisovans.
- Homo Erectus is the most likely source of this DNA.
Some of our evolutionary relatives never really left, genetically speaking.<p>The paper titled "<a href="https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1008895" target="_blank">Mapping gene flow between ancient hominins through demography-aware inference of the ancestral recombination graph</a><em>" </em>was published in PLOS Genetics. It's authors used a new statistical method to analyze the genomes of two Neanderthals, a Denisovan, and two modern humans.</p><p>The new method allowed the researchers to determine when segments of one individual's DNA are worked into the chromosomes of another. These occurrences are called "recombination events" and can be used to determine when specific genes entered our genome and provide evidence of where it came from. As an example of how this can be <a href="https://www.livescience.com/mystery-ancestor-mated-with-humans.html" target="_blank">used</a>, if Neanderthal DNA contained genes from another pre-human ancestor that they then passed to us, this method would identify it. </p><p>The analysis confirmed previous studies that showed that Modern Humans interbred with Neanderthals and Denisovans. However, this analysis suggests that some of this mixing took place between 200,000 and 300,000 years ago, long before what previous studies had suggested. It also indicates that more instances of interbreeding occurred than previously suspected.</p><p>Most interestingly, the researchers noticed that one percent of the DNA in the Denisovans from an even more ancient human ancestor. Fifteen percent of the genes that this ancestor passed onto the Denisovans still exist in the Modern Human <a href="https://phys.org/news/2020-08-dna-ancient-unidentified-ancestor-humans.html" target="_blank">genome</a>. </p><p>Exactly who this ancestor was remains unknown, but there are some clues. The fact that this ancestor separated from the linage that would lead to modern humans about 1,000,000 years ago is the most useful one we currently have. This led the researchers to suggest Homo Erectus as the most likely candidate. </p>
Who was Homo Erectus?<div class="rm-shortcode" data-media_id="oZzgXq4d" data-player_id="FvQKszTI" data-rm-shortcode-id="0007d6c597f8cc6c95d9d3b5fae7c1ad"> <div id="botr_oZzgXq4d_FvQKszTI_div" class="jwplayer-media" data-jwplayer-video-src="https://content.jwplatform.com/players/oZzgXq4d-FvQKszTI.js"> <img src="https://cdn.jwplayer.com/thumbs/oZzgXq4d-1920.jpg" class="jwplayer-media-preview" /> </div> <script src="https://content.jwplatform.com/players/oZzgXq4d-FvQKszTI.js"></script> </div> <p>The bane of all school teachers focusing on human evolution and the original "missing link," <a href="https://en.wikipedia.org/wiki/Homo_erectus" target="_blank">Homo Erectus</a> was the first human ancestor to leave Africa. They spread widely throughout the old world, with their remains found from Spain to Java. They resembled modern humans, though they were a tad shorter. They were the first to control fire, made tools, created artwork, and likely had rudimentary language.</p><p>It should be repeated that while Homo Erectus is the probable source of this ancient DNA, the jury is still out. Scientists would have to sequence its genome to know for sure. </p><p>Studying human evolution leads us down some very strange roads. It is increasingly clear to us that wherever there was an overlap of human species, there was interbreeding and that a considerable amount of the genetic remnants of this endure to this day. While this might get in the way of the old view of evolution as a slow climb to the humanity, the pinnacle of biological achievement, it does provide us a richer view of who we are, where we come form, and where we might be going. </p>
Big brains come at a big cost, however.
- A recent study examined the relationship between brain size and the development of motor skills across 36 primate species.
- The researchers observed more than 120 captive primates in 13 zoos for over seven years.
- The results suggest that primates follow rigid patterns in terms of which manipulative skills they learn first, and that the ultimate complexity of these skills depends on brain size.
Fig. 1 Eight food manipulation categories and their order of emergence during ontogeny. Ninety-seven percent of all observed species (N = 36) and 82% of all observed individuals (N = 128) strictly followed this ontogenetic sequence.
Heldstab et al.<p style="margin-left: 20px;">"Our results show that the neural development follows extremely rigid patterns -- even in primate species that differ greatly in other respects," Sandra Heldstab, an evolutionary biologist in the Department of Anthropology at the University of Zurich, said in a <a href="https://www.media.uzh.ch/en/Press-Releases/2020/Dexterity.html" target="_blank">press release</a>.<br></p><p>For the study, the researchers observed 128 primates in 13 European zoos over seven years, recording more than 10,000 observations from the time the animals were born until they reached adult-level dexterity. The team found that smaller-brained primates, like lemurs, start learning simple motor skills at an earlier age than larger-brained primates, like chimpanzees.</p>
Heldstab et al.<p>But the wait pays off for larger-brained primates: They're eventually able to perform more complex tasks with their hands, like using tools, or moving both hands simultaneously to move multiple objects.</p><p style="margin-left: 20px;">"It is no coincidence that we humans are so good at using our hands and using tools, our large brains made it possible," Heldstab said. "A big brain equals great dexterity."</p><p>It seems inefficient that primates, like chimps and humans, undergo such a long period of learning and dependency. But the researchers suggest this represents a fitness tradeoff: primate parents and children spend more time on development, but it leads to complex skills that help them get more food, and survive longer. In other words, animals don't evolve to perform complex manipulative tasks unless it significantly prolongs lifespan.</p>
William Vanderson / Stringer<p>So, what does this mean for the evolution of other animals? The researchers say their findings imply that if a species is going to make and use tools, it needs to have "reached a sufficiently slow life history pace to permit such a change in their foraging niche." In other words, the baby giraffe that hits the ground running might be good at escaping predators, but don't expect it to do something like <a href="https://www.youtube.com/watch?v=qEk_sNYAyCo" target="_blank">build a primitive fishing rod to "fish" for algae</a>.</p><p style="margin-left: 20px;">"Our study shows once again that in the course of evolution, only mammals that live a long time and have enough time to learn were able to develop a large brain and complex fine motor skills including the ability to use tools," Heldstab said. "This makes it clear why so few species could follow our path and why humans could become the most technologically accomplished organism on this planet."</p>
In one of the ocean's most lifeless places, scientists discover and resuscitate ancient organisms.
- Seemingly dead microbes from 100 million years ago spring back to life.
- The microbes were buried deep beneath the Pacific's "Point Nemo."
- There's crushing pressure beneath the seabed, but these microbes apparently survived anyway.
There is a place in the South Pacific that's as far as you can get from land. This "oceanic pole of inaccessibility" lies beneath the South Pacific Gyre that covers 10 percent of Earth's ocean surface. It's so remote that spacecraft are regularly guided down into its waters at the end of their missions. Says NASA, "It's in the Pacific Ocean and is pretty much the farthest place from any human civilization you can find."
There's another reason, though, that this so-called "Point Nemo" isn't like anywhere else. It's an oceanic desert, about as devoid of standard marine life as any stretch of water can be. Nutrients from land can't reach it, and currents keep its waters isolated from the rest of the ocean. There's also an excess of ultraviolet light out there.
While there is some microbial life floating in the area, a team of scientists from Japan and the U.S. wanted to know if anything could possibly be living in the area's desolate seabed. What they found and retrieved were seemingly lifeless microbes trapped down there for 100 million years. It turns out that the tiny organisms are still alive after all this time —all they needed was food and oxygen.
"Our main question was whether life could exist in such a nutrient-limited environment, or if this was a lifeless zone," says study leader microbiologist Yuki Morono of the Japan Agency for Marine-Earth Science and Technology. "And we wanted to know how long the microbes could sustain their life in a near-absence of food." Apparently hundred of millions of years. Take that, tardigrades.
The research in published in the journal Nature Communications.
It's hardly a hospitable environment down there, and the weight of all that water above presses down hard on anything beneath it. Organisms trapped under this kind of pressure typically die and fossilize, given a million years or so. Still, for some reason, these microbes evaded that fate.
Co-author Steven D'Hondt, a geomicrobiologist from University of Rhode Island, says, "We knew that there was life in deep sediment near the continents where there's a lot of buried organic matter. But what we found was that life extends in the deep ocean from the seafloor all the way to the underlying rocky basement."
Morono (left) and D'Hondt (right) examining cores aboard JODIES Resolution.
Image source: IODP JRSO/University of Rhode Island
The microbes were brought up through 3.7 miles of water from the ocean bottom during the JOIDES Resolution drill ship's 2010 expedition to the Gyre. The researchers extracted samples from an array of sites and depths, including pelagic clay sediments as deep as 75 meters (246 feet) beneath the sea floor.
Examining the sediment cores on the ship, the researchers found small numbers of oxygen-consuming microbes in every sample from every depth. The samples were removed from the cores to see if their occupants could be resuscitated. They were given oxygen and their presumed food of choice, substrates of carbon and nitrogen, by syringe. The samples were then sealed in glass vials and incubated.
Growth of microbes after being fed carbon (top) and nitrogen (bottom)
Image source: Morono, et al
Vials were opened after 21 days, 6 weeks, and 18 months. Stunningly, up to 99 percent of the microbes were revived, even those from the deepest — and thus oldest — cores. Some had increased 10,000 times their number, consuming all of the carbon and nitrogen they'd been given.
The scientists could hardly believe what they were seeing. "At first I was skeptical, but we found that up to 99.1 % of the microbes in sediment deposited 101.5 million years ago were still alive and were ready to eat," recalls Morono.
A bottomless research opportunity
"It shows that there are no limits to life in the old sediment of the world's ocean," says D-Hondt. "In the oldest sediment we've drilled, with the least amount of food, there are still living organisms, and they can wake up, grow and multiply."
Some have suggested that the microbe may be more recent descendants of their 100-million-year-old ancestors, but D'Hondt says there isn't enough in the way of nutrients or energy down there to support cell division. That is, unless there's some other form of energy that has been overlooked, say, some form of radiation. "If they are not dividing at all, they are living for 100 million years, but that seems insane," he says.