In On the Origin of Species, Charles Darwin posited that animal lineages with more species should also have more sub-species, or "varieties" in Darwin's terminology. Now, nearly 140 years after Darwin's death, Laura van Holstein, a PhD student in Biological Anthropology at the University of Cambridge, and her colleagues have proven Darwin right. According to a University of Cambridge report
, "her research could now be used to predict which species conservationists should focus on protecting to stop them becoming endangered or extinct":
A species is a group of animals that can interbreed freely amongst themselves. Some species contain subspecies – populations within a species that differ from each other by having different physical traits and their own breeding ranges. Northern giraffes have three subspecies that usually live in different locations to each other and red foxes have the most subspecies – 45 known varieties – spread all over the world. Humans have no subspecies.
van Holstein said: “We are standing on the shoulders of giants... My research investigating the relationship between species and the variety of subspecies proves that sub-species play a critical role in long-term evolutionary dynamics and in future evolution of species. And they always have, which is what Darwin suspected when he was defining what a species actually was.”
van Holstein’s research also proved that evolution happens differently in land mammals (terrestrial) and sea mammals and bats (non-terrestrial) because of differences in their habitats and differences in their ability to roam freely.
Here is the scientific paper: "Terrestrial habitats decouple the relationship between species and subspecies diversification in mammals" (The Royal Society)
image credit: Nordin Ćatić, University of Cambridge news release
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A team of researchers at Cornell University recently published a new paper titled "Evolutionary dynamics of recent selection on cognitive abilities." But that's a mouthful that kind of buries the lede, which is the fact that Northern paper wasps are apparently much smarter than we had previously realized. From the abstract (emphasis added):
Cognitive abilities can vary dramatically among species. […] Here, we investigate recent selection related to cognition in the paper wasp Polistes fuscatus—a wasp that has uniquely evolved visual individual recognition abilities. We generate high quality de novo genome assemblies and population genomic resources for multiple species of paper wasps and use a population genomic framework to interrogate the probable mode and tempo of cognitive evolution. Recent, strong, hard selective sweeps in P. fuscatus contain loci annotated with functions in long-term memory formation, mushroom body development, and visual processing, traits which have recently evolved in association with individual recognition. […] These data provide unprecedented insight into some of the processes by which cognition evolves.
On the surface, this might sound terrifying. But according to the researchers, these wasps have only thus far evolved to recognize each other, rather than That Human Kid Who Keeps Coming Back And Messing With Their Nest. As Michael Sheehan, professor of neurobiology and behavior at Cornell, and senior author on the paper, told Phys.org, "The really surprising conclusion here is that the most intense selection pressures in the recent history of these wasps has not been dealing with climate, catching food or parasites but getting better at dealing with each other. Read the rest
Some species of sharks have evolved to literally walk along the ocean floor (no, not on land) using their fins as feet. New research Conservation International’s Mark Erdmann and colleagues determined that walking sharks only evolved their unique capability 9 million years ago, "making them the 'youngest' sharks on our planet." Of course, a distinct species usually forms when some members of a species are physically separated from others. So how did that speciation occur in the case of the walking sharks? From an interview with Erdmann at Conservation International:
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For most of the walking shark species, our findings support the idea that speciation occurred because the populations slowly expanded their range by walking or swimming, then some individuals eventually became isolated by environmental factors such as sea level rise or the formation of large river systems that broke up their habitats.
For the four walking shark species found at the Bird’s Head Seascape, we suspect that they actually hitched a ride — on a drifting island...
Q: Is there another mystery about walking sharks you hope to solve?
From a scientific perspective, there is still so much to learn from walking sharks. We know that the world’s species that exist today are basically the existing “genetic reservoir” (raw genetic material) we have to adapt to global changes. We also know that walking sharks are very resilient to warm water and that they have a tolerance for oxygen deprivation. Any time you have an animal or plant that can survive in these extreme conditions, there is typically something unique about their genes — a “special sauce”.
When I was little, my big brother would take me fossil-hunting on a quest for trilobites, marine arthropods that have been extinct for around 250 million years. Occasionally we'd find lone specimens but never a bunch of them in a conga line as seen above. Paleontologists at France's Université Claude Bernard Lyon 1 studied lines of nearly two dozen trilobytes from Moroccan fossil beds to gain insight into the origins of collective social behavior. From the New York Times:
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These trilobites lived during the Great Ordovician Biodiversification Event, a period defined by a dramatic increase in the variety and complexity of marine life. It was the evolutionary sequel to the first major diversification event, the so-called Cambrian explosion, which established most animal groups in the fossil record some 541 million years ago.
Before the Cambrian, there is “no evidence for group behavior” in animals, (paleontologist Jean) Vannier said, because Precambrian life-forms lacked sophisticated nervous systems.
Ampyx trilobites, in contrast, had an anatomy that could have enabled chemical communication and sensory stimulation. Though they were visually blind, the trilobites had long spikes protruding from their rear ends. These appendages clearly overlap and link individuals in the fossilized chains, and perhaps allowed tactile or pheromone signals to be exchanged.
Evolutionary psychologist Katja Liebal literally wrote the book on Primate Communication. A professor of developmental psychology at the Freie Universität Berlin, Liebal's research focuses "on the cognitive and communicative skills that might be uniquely human and those shared with other primate species." According to BBC Earth, Liebal observes chimps in "hopes to compile the world's first chimpanzee dictionary."
I think learning chimpanzee should be an educational requirement beginning in elementary school to prepare our children for when, y'know, they take over.
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New, high-res 3D images of human embryos show a variety of muscles that were "present in our ancestors but normally absent from the adult human." For example, there are hand muscles that temporarily appear in human embryos but usually disappear before birth. According to the researchers, our human ancestors lost those "muscles from the back of the hand about 250 million years ago as mammals and reptiles split on the evolutionary tree." From Science News:
These appearing and disappearing, or atavistic, muscles are remnants of evolution, says biologist Rui Diogo of Howard University in Washington, D.C. Such atavistic muscles are built as a base from which to start paring down to the final set of muscles that people are born with, he says. “Losing and specializing, that’s what happens in human evolution.”
Other animals have kept some of those muscles. Adult chimpanzees and human embryos have epitrochleoanconeus muscles in their forearms, but most adult humans don’t. Human’s mammalian ancestors also lost dorsometacarpales muscles from the back of the hand about 250 million years ago as mammals and reptiles split on the evolutionary tree. Lizards still have those muscles, and they appear in human embryos, but then are lost or fuse with other muscles during development and aren’t found in most adults.
"Development of human limb muscles based on whole-mount immunostaining and the links between ontogeny and evolution" (Development)
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Why do humans have so little hair, at least compared to all other primates? At Smithsonian, Jason Daley shares the latest genetic research on the biological factors that result in humans' minimal body hair and its unusual distribution. Daley also surveys the fascinating current theories about why we evolved into the only naked apes. From Smithsonian:
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One popular idea that has gone in and out of favor since it was proposed is called the aquatic ape theory. The hypothesis suggests that human ancestors lived on the savannahs of Africa, gathering and hunting prey. But during the dry season, they would move to oases and lakesides and wade into shallow waters to collect aquatic tubers, shellfish or other food sources. The hypothesis suggests that, since hair is not a very good insulator in water, our species traded in most of our fur for a layer of fat. The hypothesis even suggests we might have developed bipedalism to become more effective waders. But this idea, which has been around for decades, hasn’t received much support from the fossil record and isn’t taken seriously by most researchers.
A more widely accepted theory is that, when human ancestors moved from the cool shady forests into the savannah, they needed better thermoregulation. Losing all that fur made it possible for hominins to hunt during the day in the hot grasslands without overheating. An increase in sweat glands, many more than other primates, also kept early humans on the cool side. The development of fire and clothing meant that humans could keep cool during the day and cozy up at night.
Tyrannosaurus rex is known for being huge and threatening. What's with those tiny arms though? Don't call them useless.
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YouTuber Retic over at Prehistoric Pets TV has a huge collection of pythons and other ancient creatures. Here he shows how and why a clutch of python eggs can be lifted up in giant sticky clumps. Read the rest
Yeast has brought a lot of joy into the world, but its evolutionary origins were unclear until scientists did a worldwide genomic survey of the humble organism. Based on the genetic diversity of strains found in China, they concluded that its origin is almost certainly in that part of the world. Read the rest
Squid ancestors were happy creatures with shells until about 400 million years ago, when the emergence of fish with jaws set off an evolutionary arms race between fish and cephalopods. Read the rest
Matt Baker from UsefulCharts.com made a detailed poster and video of how the English alphabet evolved over the last 4,000 years, but his elegant and colorful topline is the simplest iteration of the process: Read the rest
It's long been known that birds possess magnetoreception, or ability to sense earth's magnetic fields. Now researchers are narrowing down a specific eye protein called Cry4 that appears to allow birds to sense magnetic waves in the presence of blue light. Read the rest
Turtles were at the center of a hundred-year evolutionary controversy since the 1887 discovery of a Proganochelys fossil in Germany. AS PBS Eons explains, the question of how turtles got their shells led scientists "to rethink the entire history of reptile evolution." Read the rest
Fun fact: trilobites were able to see thanks to eyes made of calcite instead of soft tissue. YouTuber Thunderf00t shows off a cool fossil and explains the phenomenon. Read the rest
The EVO evolution webshop offers this fantastic flipbook of human evolution. It's €7.50.
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In many, animal species are domesticated when humans bring them into their homes whether they want to be there or not. For example, it's mostly accepted that humans domesticated wolves, breeding them in captivity until they became the modern dogs we love today. Now, a new study of cat genetics reveals that cats just kind of hung around humans for thousands of years before they were domesticated. From Casey Smith's article in National Geographic:
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The earlier ancestors of today’s domestic cats spread from southwest Asia and into Europe as early as 4400 B.C. The cats likely started hanging around farming communities in the Fertile Crescent about 8,000 years ago, where they settled into a mutually beneficial relationship as humans’ rodent patrol.
Mice and rats were attracted to crops and other agricultural byproducts being produced by human civilizations. Cats likely followed the rodent populations and, in turn, frequently approached the human settlements.
“This is probably how the first encounter between humans and cats occurred,” says study coauthor Claudio Ottoni of the University of Leuven. “It’s not that humans took some cats and put them inside cages,” he says. Instead, people more or less allowed cats to domesticate themselves.
A second lineage, consisting of African cats that dominated Egypt, spread into the Mediterranean and most of the Old World beginning around 1500 B.C. This Egyptian cat probably had behaviors that made it attractive to humans, such as sociability and tameness.
The results suggest that prehistoric human populations probably began carrying their cats along ancient land and sea trade routes to control rodents.