Like humans, ravens mirror the distress they witness in others, study suggests

Katherine J. Wu reports:

Seeing someone else suffer a big disappointment can have a pretty damaging effect on your own morale. That’s definitely the case with people—and it might be true for ravens, too.

New research suggests that, like humans and many other mammals, common ravens (Corvus corax) can read and internalize the emotional states of others. In the study, published today in the journal PNAS, ravens watch their friends grapple with a frustrating task in which they’re denied a tasty treat. Though the onlookers aren’t deprived of anything, they then seem to mirror their partners’ discontent, and start behaving pessimistically themselves.

Unlike people, ravens can’t speak freely about their emotional distress. But these results hint at the tantalizing possibility that humans aren’t alone in their interconnectedness, and could provide early evidence of something akin to empathy in birds.

“This paper is a tremendous step forward in being able to understand the evolutionary roots of empathy,” says Kaeli Swift, an animal behaviorist and corvid expert at the University of Washington who was not involved in the study. “I think it would be too far to say that [this paper shows] ravens are empathetic…but this work could be foundational in eventually arriving at that conclusion.” [Continue reading…]

I’m an evolutionary biologist – here’s why this ancient fungal fossil discovery is so revealing

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Do fungi like this Penicillium mold, which produces the the antibiotic penicillin, trace their origins to an ancestor that lived a billion years ago?
Rattiya Thongdumhyu/Shutterstock.com

By Antonis Rokas, Vanderbilt University

Biologists don’t call them “the hidden kingdom” for nothing. With an estimated 5 million species, only a mere 100,000 fungi are known to scientists. This kingdom, which includes molds, yeasts, rusts and mushrooms, receives far less attention than plants or animals. This is particularly true for fossils of fungi, most of which are discovered while hunting for more charismatic, at least to the eyes of some, plant fossils.

Fungi were key partners of plants during their colonization of land approximately 500 million years ago – an important and well-documented evolutionary transition. Therefore, it is unsurprising that the earliest fungal fossils, found in 450 million-year-old rocks, resemble modern species associated with the roots of plants. But that conflicts with DNA-based estimates, which suggest that fungi originated much earlier – a billion or more years ago. It’s a riddle in the tree of life that evolutionary biologists like me have long been puzzled about.

Fossils versus DNA

For years scientists have tried to reconcile the fungal fossil record with estimates from analyses of fungal DNA. But some of their key morphological characters – that is, the shapes they take – can only be established via microscopic and chemical analyses. That includes the complex networks of microscopic thread-like filaments and cell walls made of chitin, which are also not visible to the naked eye. The effort seemed hopeless, until now.

Corentin Loron, a graduate student at the University of Liege in Belgium and colleagues, discovered microscopic, fossilized specimens of a fungus called Ourasphaira giraldae in shale rock from the Grassy Bay Formation in the Northwest Territories of Canada. Given that Ourasphaira is found on 1,000- to 900-million-year-old rocks, the new fossil pushes back the origin of fungi by half a billion years.

[Read more…]

A jawbone shows Denisovans lived on the Tibetan Plateau long before humans

Science News reports:

Denisovans reached what’s now called “the roof of the world” at least 160,000 years ago.

Found in a Tibetan Plateau cave, a partial lower jawbone represents a Denisovan who is the oldest known hominid to reach the region’s cloud-scraping heights, researchers report online May 1 in Nature.

The fossil suggests that these perplexing, extinct members of the human lineage weathered the plateau’s frigid, thin air long before humans did. Many researchers have assumed that, as far as hominids go, only Homo sapiens settled in that high-altitude, low-oxygen environment, probably no earlier than 40,000 years ago.

“It blows my mind that Denisovans lived on the Tibetan Plateau,” paleoanthropologist and study coauthor Jean-Jacques Hublin of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, said at an April 29 news conference.

Until now, Denisovans were known only from a handful of fossils unearthed in Siberia’s Denisova Cave, and from ancient DNA extracted from one of those bones. Researchers regard Denisovans, who inhabited Denisova Cave from around 300,000 to 50,000 years ago, as close relatives of Neandertals and possibly a distinct Homo species. [Continue reading…]

How culture works with evolution to produce human cognition

Cecilia Heyes writes:

The conventional view, inside and outside academia, is that children are ‘wired’ to imitate. We are ‘Homo imitans’, animals born with a burning desire to copy the actions of others. Imitation is ‘in our genes’. Birds build nests, cats miaow, pigs are greedy, while humans possess an instinct to imitate.

The idea that humans have cognitive instincts is a cornerstone of evolutionary psychology, pioneered by Leda Cosmides, John Tooby and Steven Pinker in the 1990s. ‘[O]ur modern skulls house a Stone Age mind,’ wrote Cosmides and Tooby in 1997. On this view, the cognitive processes or ‘organs of thought’ with which we tackle contemporary life have been shaped by genetic evolution to meet the needs of small, nomadic bands of people – people who devoted most of their energy to digging up plants and hunting animals. It’s unsurprising, then, that today our Stone Age instincts often deliver clumsy or distasteful solutions, but there’s not a whole lot we can do about it. We’re simply in thrall to our thinking genes.

This all seems plausible and intuitive, doesn’t it? The trouble is, the evidence behind it is dubious. In fact, if we look closely, it’s apparent that evolutionary psychology is due for an overhaul. Rather than hard-wired cognitive instincts, our heads are much more likely to be populated by cognitive gadgets, tinkered and toyed with over successive generations. Culture is responsible not just for the grist of the mind – what we do and make – but for fabricating its mills, the very way the mind works. [Continue reading…]

New species of ancient human discovered in the Philippines

 

Science magazine reports:

A strange new species may have joined the human family. Human fossils found in a cave on Luzon, the largest island in the Philippines, include tiny molars suggesting their owners were small; curved finger and toe bones hint that they climbed trees. Homo luzonensis, as the species has been christened, lived some 50,000 to 80,000 years ago, when the world hosted multiple archaic humans, including Neanderthals and Denisovans, and when H. sapiens may have been making its first forays into Southeast Asia.

“This is a truly sensational finding,” says Adam Brumm, an archaeologist at Griffith University in Nathan, Australia. The paper, published this week in Nature, “sent shivers down my spine.”

The discovery echoes that of another unusual ancient hominin—the diminutive H. floresiensis, or “hobbit,” found on the island of Flores in Indonesia. “One is interesting. Two is a pattern,” says Jeremy DeSilva, an expert on Homo foot bones at Dartmouth College. He and others suspect the islands of Southeast Asia may have been a cradle of diversity for ancient humans, and that H. luzonensis, like H. floresiensis, may have evolved small body size in isolation on an island. [Continue reading…]

Dueling dates for Deccan Traps volcanic eruption reignite debate over dinosaurs’ death

Science News reports:

Which came first: the impact or the eruptions? That question is at the heart of two new studies in the Feb. 22 Science seeking to answer one of the most hotly debated questions in Earth’s geologic history: Whether an asteroid impact or massive volcanism that altered the global climate was mostly to blame for the demise of all nonbird dinosaurs 66 million years ago.

The dinosaur die-off is the only known mass extinction that coincides with two cataclysmic events: an asteroid impact linked to the massive Chicxulub crater in Mexico, and a gigantic volcanic eruption, evidenced by kilometers-thick layers of hardened lava at India’s Deccan Traps. The extinction marks the boundary between the Cretaceous and Paleogene periods, or the KPg boundary.

Using two different geochemical dating techniques, two separate teams dated the lava flows. The goal was to try to determine whether the bulk of the lava predates or postdates the KPg boundary. Both estimated that the eruptions lasted in total about 1 million years. But one team, using uranium-lead dating, found that some of the biggest pulses of lava erupted tens of thousands of years before the KPg boundary. The other team, using argon-argon dating, determined that three-fourths of the lava erupted afterward. [Continue reading…]

Plankton that are both plant-like and animal-like are redefining marine ecology

Knowable magazine reports:

Their color gave them away. Ecologist Diane Stoecker was looking at plankton in samples of ocean water from the dock in Woods Hole Harbor in Massachusetts some 40 years ago when she spotted something strange. Under the microscope, she recognized Laboea strobila, shaped like an ice-cream cone — “yellowish green and very beautiful,” she recalls — and the smaller, more spherical Strombidium species — also oddly greenish.

Stoecker knew that these single-celled critters, named ciliates for the hairlike cilia that they bear, got their energy by feeding on other, smaller organisms. So why were the ones she saw so green — a color that generally signifies photosynthesis? Was the pigment leftover food, ingested algae or just the algae’s chloroplasts?

After some groundbreaking experiments, Stoecker was one of the first scientists to describe how these types of plankton not only hunted their prey, but also sequestered the chloroplasts of their food sources and used them to get energy from sunlight. “I was very excited to find that they really were photosynthetic,” she says.

Traditionally, marine microplankton had been divided similarly to species on land. You had plant-like phytoplankton, such as algae, and animal-like zooplankton that ate the phytoplankton. What Stoecker found was that some of these organisms were somewhere in the middle: They could eat like animals when food was present and photosynthesize like plants in the light. “If you think about it, it can be the best of both worlds,” says marine ecologist Dave A. Caron of the University of Southern California. [Continue reading…]

How beauty is making biologists rethink evolution

Ferris Jabr writes:

A male flame bowerbird is a creature of incandescent beauty. The hue of his plumage transitions seamlessly from molten red to sunshine yellow. But that radiance is not enough to attract a mate. When males of most bowerbird species are ready to begin courting, they set about building the structure for which they are named: an assemblage of twigs shaped into a spire, corridor or hut. They decorate their bowers with scores of colorful objects, like flowers, berries, snail shells or, if they are near an urban area, bottle caps and plastic cutlery. Some bowerbirds even arrange the items in their collection from smallest to largest, forming a walkway that makes themselves and their trinkets all the more striking to a female — an optical illusion known as forced perspective that humans did not perfect until the 15th century.

Yet even this remarkable exhibition is not sufficient to satisfy a female flame bowerbird. Should a female show initial interest, the male must react immediately. Staring at the female, his pupils swelling and shrinking like a heartbeat, he begins a dance best described as psychotically sultry. He bobs, flutters, puffs his chest. He crouches low and rises slowly, brandishing one wing in front of his head like a magician’s cape. Suddenly his whole body convulses like a windup alarm clock. If the female approves, she will copulate with him for two or three seconds. They will never meet again.

The bowerbird defies traditional assumptions about animal behavior. Here is a creature that spends hours meticulously curating a cabinet of wonder, grouping his treasures by color and likeness. Here is a creature that single-beakedly builds something far more sophisticated than many celebrated examples of animal toolmaking; the stripped twigs that chimpanzees use to fish termites from their mounds pale in comparison. The bowerbird’s bower, as at least one scientist has argued, is nothing less than art. When you consider every element of his courtship — the costumes, dance and sculpture — it evokes a concept beloved by the German composer Richard Wagner: Gesamtkunstwerk, a total work of art, one that blends many different forms and stimulates all the senses.

 

This extravagance is also an affront to the rules of natural selection. Adaptations are meant to be useful — that’s the whole point — and the most successful creatures should be the ones best adapted to their particular environments. So what is the evolutionary justification for the bowerbird’s ostentatious display? Not only do the bowerbird’s colorful feathers and elaborate constructions lack obvious value outside courtship, but they also hinder his survival and general well-being, draining precious calories and making him much more noticeable to predators.

Numerous species have conspicuous, metabolically costly and physically burdensome sexual ornaments, as biologists call them. Think of the bright elastic throats of anole lizards, the Fabergé abdomens of peacock spiders and the curling, iridescent, ludicrously long feathers of birds-of-paradise. To reconcile such splendor with a utilitarian view of evolution, biologists have favored the idea that beauty in the animal kingdom is not mere decoration — it’s a code. According to this theory, ornaments evolved as indicators of a potential mate’s advantageous qualities: its overall health, intelligence and survival skills, plus the fact that it will pass down the genes underlying these traits to its children. A bowerbird with especially bright plumage might have a robust immune system, for example, while one that finds rare and distinctive trinkets might be a superb forager. Beauty, therefore, would not confound natural selection — it would be very much a part of it.

Charles Darwin himself disagreed with this theory. Although he co-discovered natural selection and devoted much of his life to demonstrating its importance, he never claimed that it could explain everything. Ornaments, Darwin proposed, evolved through a separate process he called sexual selection: Females choose the most appealing males “according to their standard of beauty” and, as a result, males evolve toward that standard, despite the costs. Darwin did not think it was necessary to link aesthetics and survival. Animals, he believed, could appreciate beauty for its own sake. Many of Darwin’s peers and successors ridiculed his proposal. To them, the idea that animals had such cognitive sophistication — and that the preferences of “capricious” females could shape entire species — was nonsense. Although never completely forgotten, Darwin’s theory of beauty was largely abandoned.

Now, nearly 150 years later, a new generation of biologists is reviving Darwin’s neglected brainchild. Beauty, they say, does not have to be a proxy for health or advantageous genes. Sometimes beauty is the glorious but meaningless flowering of arbitrary preference. [Continue reading…]

Humans: The least aggressive primate

Richard Wrangham writes:

A few years ago, I stayed in Kenya with the conservationists Karl and Kathy Ammann, who kept a rescued chimpanzee named Mzee in their home. Even as a young adult, Mzee was generally well-behaved and trustworthy. Yet he could be impulsive. At one point, over breakfast, Mzee and I reached for the jug of orange juice at the same time. He grabbed my hand as I held the jug, and he squeezed. Ouch. “You first!” I squeaked. I was still rubbing my fingers back to life once he had finished his drink.

The truth is that even when chimpanzees know the rules perfectly well, they don’t always restrain their aggression. In the wild, their lives are full of violence. A day spent with wild chimpanzees gives you a good chance of seeing chases and hitting; every month, you are likely to see bloody wounds. Compared with even an unusually violent group of humans, chimpanzees are aggressive several hundred to a thousand times more often over the course of a year.

The greater peaceability of human societies comes from our nature. We can look each other in the eye. We don’t lose our tempers easily. We normally control our aggressive urges. In primates, one of the most potent stimuli for aggression is the presence of a strange individual. By contrast, Jerome Kagan, a pioneer in developmental psychology, reports that in his hundreds of observations of two-year-olds meeting unfamiliar children, he has never seen one strike out at the other. That willingness to interact peacefully with others, even strangers, is inborn.

What accounts for this human difference? The answer lies in the evolutionary pressures that selected against aggression, particularly in men. The cultural anthropologist Christopher Boehm has found that, in hunter-gatherer societies, a man who threatens others by having too violent a temper is treated in a consistent way. If the bully can’t be contained by the cajoling effects of ridicule or ostracism, the other men reach a consensus, make a plan and execute him. Over the eons, the long-term practice of killing unrepentant aggressors must have favored genes for more peaceful behavior. [Continue reading…]

Genetic data on half a million Brits reveal ongoing evolution and Neanderthal legacy

Ann Gibbons writes:

Neanderthals are still among us, Janet Kelso realized 8 years ago. She had helped make the momentous discovery that Neanderthals repeatedly mated with the ancestors of modern humans—a finding that implies people outside of Africa still carry Neanderthal DNA today. Ever since then, Kelso has wondered exactly what modern humans got from those prehistoric liaisons—beyond babies. How do traces of the Neanderthal within shape the appearance, health, or personalities of living people?

For years, evolutionary biologists couldn’t get their rubber-gloved hands on enough people’s genomes to detect the relatively rare bits of Neanderthal DNA, much less to see whether or how our extinct cousins’ genetic legacy might influence disease or physical traits.

But a few years ago, Kelso and her colleagues at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, turned to a new tool—the UK Biobank (UKB), a large database that holds genetic and health records for half a million British volunteers. The researchers analyzed data from 112,338 of those Britons—enough that “we could actually look and say: ‘We see a Neanderthal version of the gene and we can measure its effect on phenotype in many people—how often they get sunburned, what color their hair is, and what color their eyes are,’” Kelso says. They found Neanderthal variants that boost the odds that a person smokes, is an evening person rather than a morning person, and is prone to sunburn and depression. [Continue reading…]