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…]

Cells talk in a language that looks like viruses

Carrie Arnold writes:

For cells, communication is a matter of life and death. The ability to tell other members of your species — or other parts of the body — that food supplies are running low or that an invading pathogen is near can be the difference between survival and extinction. Scientists have known for decades that cells can secrete chemicals into their surroundings, releasing a free-floating message for all to read. More recently, however, scientists discovered that cells could package their molecular information in what are known as extracellular vesicles. Like notes passed by children in class, the information packaged in an extracellular vesicle is folded and delivered to the recipient.

The past five years have seen an explosion of research into extracellular vesicles. As scientists uncovered the secrets about how the vesicles are made, how they package their information and how they’re released, it became clear that there are powerful similarities between vesicles and viruses.

A small group of researchers, led by Leonid Margolis, a Russian-born virologist at the National Institute of Child Health and Human Development (NICHD), and Robert Gallo, the HIV pioneer at the University of Maryland School of Medicine, has proposed that this similarity is more than mere coincidence. It’s not just that viruses appear to hijack the cellular pathways used to make extracellular vesicles for their own production — or that cells have also taken on some viral components to use in their vesicles. Extracellular vesicles and viruses, Margolis argues, are part of a continuum of membranous particles produced by cells. Between these two extremes are lipid-lined sacs filled with a variety of genetic material and proteins — some from hosts, some from viruses — that cells can use to send messages to one another.

“There are fundamental differences between viruses and vesicles: Viruses can replicate and vesicles cannot,” Margolis said. “But there are many variants in between. Where do viruses start, and where do extracellular vesicles start?”

Whether cells started using vesicles for communication first and viruses copied them, or cells stole the idea from viruses, or both evolved the strategy in tandem is currently impossible to determine: Sending information in extracellular vesicles must have first appeared billions of years ago because even bacteria do it. “This idea of using a membrane-bound sac of information to transport between cells has been around a long time,” said David Meckes, Jr., a virologist at Florida State University. [Continue reading…]

The sugar that makes up DNA could be made in space

Science News reports:

Parts of DNA can form in space.

For the first time, scientists have made 2-deoxyribose, the sugar that makes up the backbone of DNA, under cosmic conditions in the lab by blasting ice with radiation. The result, reported December 18 in Nature Communications, suggests that there are several ways for prebiotic chemistry to take place in space, and supports the idea that the stuff of life could have been delivered to Earth from elsewhere.

“It tells us that this process happens everywhere, at least in our galaxy,” says astrochemist Michel Nuevo of NASA’s Ames Research Center in Moffett Field, Calif.

Nuevo and his colleagues cooled ices of frozen water and methanol to about –260° Celsius inside a vacuum chamber and blasted the ice with ultraviolet light, mimicking the conditions found in interstellar clouds. Warming the irradiated ices simulated what happens when a young star is born. After analyzing the ice’s contents, the team identified 2-deoxyribose, as well as several other kinds of sugars made in similar experiments in the past (SN: 4/30/16, p. 18). [Continue reading…]

The discovery of vast populations of subsurface microbial beings is shaking up what we think we know about life

JoAnna Klein writes:

At the surface, boiling water kills off most life. But Geogemma barossii is a living thing from another world, deep within our very own. Boiling water — 212 degrees Fahrenheit — would be practically freezing for this creature, which thrives at temperatures around 250 degrees Fahrenheit.

No other organism on the planet is known to be able to live at such extreme heat.

But it’s just one of many mysterious microbes living in a massive subterranean habitat that until recently has been practically invisible. Over the past decade, scientists from around the world have banded together under the Deep Carbon Observatory to make sense of these hidden habitats. The observatory’s researchers presented some of their recent discoveries last week.

With high-tech drills, ROVs and submersibles, pressurized collection tubes, the latest DNA technology and computer modeling, the researchers have explored volcanoes, diamond mines, deep-sea hot springs, underwater mud volcanoes and other extreme sites beneath our oceans and continents. What they’ve found turns what we know about the world literally upside down.

So science fiction fans, rejoice. The real journey to the center of the Earth has begun.

These Altiarchaeales belong to a domain of nucleus-lacking single-celled microbes called Archaea. Archaea and bacteria make up the majority of life in the deep subsurface, and it’s estimated that there are more of these kinds of microbes below ground than above.

Some 200 to 600 octillion microbes live beneath our continents, suggests an analysis of data from sites all over the world, and even more live beneath the seafloor. Together they weigh the equivalent of up to 200 million blue whales — and far more than all 7.5 billion humans. Subterranean diversity rivals that of the surface, with most underground organisms yet to be discovered or characterized. [Continue reading…]

Our world and our brains have been profoundly shaped by bees

Tim Flannery writes:

According to Thor Hanson’s Buzz, the relationship between bees and the human lineage goes back three million years, to a time when our ancestors shared the African savannah with a small, brownish, robin-sized bird—the first honeyguide. Honeyguides are very good at locating beehives, but they are unable to break into them to feed on the bee larvae and beeswax they eat. So they recruit humans to help, attracting them with a call and leading them to the hive. In return for the service, Africans leave a small gift of honey and wax: not enough that the bird is uninterested in locating another hive, but sufficient to make it feel that its efforts have been worthwhile. Honeyguides may have been critical to our evolution: today, honey contributes about 15 percent of the calories consumed by the Hadza people—Africa’s last hunter-gatherers—and because brains run on glucose, honey located by honeyguides may have helped increase our brain size, and thus intelligence.

Bees evolved from wasp ancestors around 100 million years ago. Most wasps are sleek carnivores, but bees are flower-loving, long-haired, and often social vegetarians (the branched hairs that cover their bodies trap pollen, which, along with nectar, is their principal source of food). Their shift to a vegetarian diet had a profound effect on the evolution of flowering plants. If we want to know what a world without bees looks like, Hanson writes, we should visit the bee-less island of Juan Fernández off the coast of Chile, where, despite varied vegetation, almost all flowers are small, white, and inconspicuous. But it is not just gloriously colored flowers that we owe to bees, for many of our crops rely on them for pollination. Both our world and our brains, it seems, have been profoundly shaped by bees.

There are around 20,000 bee species, classified into seven families. The most familiar are the apids, including bumblebees, carpenter bees, and honeybees. The most primitive bees, largely restricted to Australia, are classified into two families that only experts would recognize. Mining bees, which dig nest tunnels nearly ten feet deep and inhabit arid regions, represent another family; oil-collecting bees and a family including leafcutter bees and mason bees make up two more. Sweat bees comprise the final group. In addition to collecting pollen and nectar from flowers, they drink mammals’ sweat for its moisture and salts: as thousands of tiny bee tongues lick deep inside a person’s ears, nose, and other sensitive parts, they can inflict maddening torture; if brushed away they deliver a sting like an electric shock. [Continue reading…]

What a newfound kingdom means for the tree of life

Jonathan Lambert writes:

The tree of life just got another major branch. Researchers recently found a certain rare and mysterious microbe called a hemimastigote in a clump of Nova Scotian soil. Their subsequent analysis of its DNA revealed that it was neither animal, plant, fungus nor any recognized type of protozoan — that it in fact fell far outside any of the known large categories for classifying complex forms of life (eukaryotes). Instead, this flagella-waving oddball stands as the first member of its own “supra-kingdom” group, which probably peeled away from the other big branches of life at least a billion years ago.

“It’s the sort of result you hope to see once in a career,” said Alastair Simpson, a microbiologist at Dalhousie University who led the study.

Impressive as this finding about hemimastigotes is on its own, what matters more is that it’s just the latest (and most profound) of a quietly and steadily growing number of major taxonomic additions. Researchers keep uncovering not just new species or classes but entirely new kingdoms of life — raising questions about how they have stayed hidden for so long and how close we are to finding them all. [Continue reading…]

An ant colony has memories that its individual members don’t have

By Deborah M Gordon

Like a brain, an ant colony operates without central control. Each is a set of interacting individuals, either neurons or ants, using simple chemical interactions that in the aggregate generate their behaviour. People use their brains to remember. Can ant colonies do that? This question leads to another question: what is memory? For people, memory is the capacity to recall something that happened in the past. We also ask computers to reproduce past actions – the blending of the idea of the computer as brain and brain as computer has lead us to take ‘memory’ to mean something like the information stored on a hard drive. We know that our memory relies on changes in how much a set of linked neurons stimulate each other; that it is reinforced somehow during sleep; and that recent and long-term memory involve different circuits of connected neurons. But there is much we still don’t know about how those neural events come together, whether there are stored representations that we use to talk about something that happened in the past, or how we can keep performing a previously learned task such as reading or riding a bicycle. 

Any living being can exhibit the simplest form of memory, a change due to past events. Look at a tree that has lost a branch. It remembers by how it grows around the wound, leaving traces in the pattern of the bark and the shape of the tree. You might be able to describe the last time you had the flu, or you might not. Either way, in some sense your body ‘remembers’, because some of your cells now have different antibodies, molecular receptors, which fit that particular virus.

Past events can alter the behaviour of both individual ants and ant colonies. Individual carpenter ants offered a sugar treat remembered its location for a few minutes; they were likely to return to where the food had been. Another species, the Sahara Desert ant, meanders around the barren desert, searching for food. It appears that an ant of this species can remember how far it walked, or how many steps it took, since the last time it was at the nest.

[Read more…]

Should evolution treat our microbes as part of us?

Jonathan Lambert writes:

Twilight falls on the Tanzanian plain. As the sky turns a deeper purple, a solitary spotted hyena awakens. She trots along the border of her clan’s territory, marking the boundary with a sour paste from under her tail. She sniffs a passing breeze for hints of itinerant males interested in mating, giving little attention to her stomach’s rumbling over the remnants of the previous night’s hunt or the itch on her flank. The lone hyena chooses what she will do next to make her living.

Except she is not alone. That paste she secretes is produced not by her own cells but by billions of bacteria housed within her scent glands. The scents on the breeze from potential mates also come from unique microbial concoctions. A diverse array of bacteria that line her gut are helping to break down her meal. Others assist her immune system in fending off the hordes of parasites and pathogens trying to invade her skin and other tissues.

Who precisely is it, then, trying to survive on the Tanzanian plain? Can we consider the fates of the hyena and the microbes within her independently? Or does their interaction form something new, greater than each part alone?

“We’ve underestimated the potential contribution of microbes to traits we’ve been studying for decades or centuries,” said Kevin Theis, a microbiologist at Wayne State University who studies the paste-making microbes of the hyena. “If the genes for these important traits are actually in the microbiome and not the animal itself, then we need to take a systems-level approach and look at the host-microbe system as a whole.” [Continue reading…]