Falling in love makes men broody

 

Children on their minds? (Image: Aurelie and Morgan David de Lossy/Getty)

Falling in love really does make you broody – especially if you are a man. New lovers show greater activation of brain areas related to parental attachment when they see a baby than single people.

This was particularly pronounced in men, hinting that babies may be on their mind from the outset of a relationship. Alternatively, "men may be worried about their partner's desire for children, and their increased attention to infant stimuli is based on apprehension and the need to be more guarded", says Ruth Feldman of Bar-Ilan University in Ramat Gan, Israel, who led the research.

Feldman's team used electroencephalography to monitor the brain activity of 65 volunteers, including new parents, new lovers and singles as they viewed pictures of infants – including the parents' own babies – along with neutral pictures.

When viewing unfamiliar babies, parents and new lovers showed greater activation of brain areas associated with parenting, such as the nucleus accumbens, anterior cingulate and amygdala, than singles. The response was even greater in parents viewing their own child.

Mothers and male lovers showed slightly greater activation of these brain areas than fathers and female lovers (Biological Psychiatry, DOI: 10.1016/j.biopsycho.2011.11.008).

"This suggests that even though the lovers don't know it, they are physiologically getting ready to respond to infants," says Helen Fisher of Rutgers University in New York, author of Why We Love.

It also overturns a common assumption that men are less interested in babies than women. "It shows that we really don't understand men," says Fisher.

Personality counts

Fisher has just published the results of a survey of 6000 men and women in the US, which found that men are significantly more likely to make a long-term commitment with someone they didn't feel sexually attracted to if that person has all the other qualities they were looking for.

"Men fall in love faster than, and just as often as, women," says Fisher. "They're more likely to want to move in and start a more socially visible relationship in the first year than women, and men are 2.5 times more likely to kill themselves when a relationship ends."

In a separate study, Feldman and her colleagues found that falling in love also appears to buffer people from negative emotions. They showed 55 new lovers and 57 single people six video clips, including two selected to trigger positive emotions and two that would trigger negative emotions. Electrodes were used to monitor the volunteers for signs of stress.

While single people showed signs of stress when watching the negative films, new lovers seemed to be unaffected by them (Emotion, DOI: 10.1037/a0024090).

"There is something about this euphoria of falling in love that is like a protective buffer, so we don't really respond to negative emotions," says Feldman.

This may have evolutionary significance: by suppressing negative emotions, new couples find it easier to form a trusting bond with one another. "We need a calm state to allow ourselves to fall in love, otherwise there's no sense of safety," says Feldman.

"It shows that love is important and can reduce stress," adds Paul Zak of Claremont Graduate University in California. He suggests that high levels of the hormone oxytocin, which has calming effects, are probably responsible.

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Russian hot springs point to rocky origins for life

 

Kamchatka peninsula, a perfect place for life (Image: Anna S. Karyagina)

It's a question that strikes at the very heart of one of the deepest mysteries in the universe: how did life begin on Earth? New evidence challenges the widespread view that it all kicked off in the oceans, around deep-sea hydrothermal vents.

Instead, hot springs on land, similar to the "warm little pond" favoured by Charles Darwin, may be a better fit for the cradle of life.

The controversial new theory suggests the search for extraterrestrial life must go beyond a hunt for alien oceans (see Land ho! The search for ET, below).

Life appeared sometime before 3.8 billion years ago, towards the end of a turbulent phase in our planet's early history dubbed Hadean Earth. Exactly where and how this happened is still a mystery. The first fossils are about 3.4 billion years old, and all we know about life's very first stages comes from chemical signatures in rocks.

This hasn't stopped endless speculation. Conventional wisdom has it that hydrothermal vents on the ocean floor offered an ideal chemical environment for the earliest life. Deep, dark oceans would also have protected the delicate cells from the harmful ultraviolet light that bathed early Earth before the ozone layer formed.

Case closed? Not quite. Armen Mulkidjanian at the University of Osnabrück in Germany says there is a fundamental problem with the ocean floor hypothesis: salt. The cytoplasm found inside all cells contains much more potassium than sodium. Mulkidjanian thinks that chemistry reflects the chemistry of the water life first appeared in, yet salty seawater is sodium-rich and potassium-poor.

"The ancient sea contained the wrong balance of sodium and potassium for the origin of cells," says Mulkidjanian. Now, after extensive field studies, he claims to have found the one place on Earth where that balance is right: in the thermal springs of Kamchatka in far-east Siberia. Mulkidjanian found that puddles condensing from the hydrothermal vapour at Siberia's Mutnovsky thermal springs are potassium-rich, just like cell cytoplasm (Proceedings of the National Academy of Sciences, DOI: 10.1073.pnas.1117774109). Life first appeared in similar pools, says Mulkidjanian.

And while early life would have been damaged if over-exposed to UVs, Mulkidjanian's theory solves another puzzle. Most evolutionary biologists agree that life at this stage would have been little more than floating strands of DNA and RNA. The nucleotides that make up DNA and RNA are all surprisingly stable when exposed to UV light, suggesting they evolved in an environment where UV exposure weeded out all but the most photostable molecules. "You don't get UV light around deep-sea vents," says Mulkidjanian.

"I do not think the oceans were a favourable environment for the origin of life – freshwater ponds seem more favourable," says Nobel laureate Jack Szostak at Harvard University, a key player in the field. "Freshwater ponds have lower salt concentrations, which would allow for fatty acid based membranes to form."

While Darwin's warm little ponds appear to be coming back in vogue, this is a highly polarised field of research and many origin-of-life researchers are not convinced. Nick Lane at University College London disputes the claims that the first cells couldn't cope with life in sodium-rich water. Early cells could have actively pumped out sodium ions, he says. "This is exactly what many methanogens and acetogens do," he points out, referring to microbes that are thought to be among the earliest cellular life forms. This, says Lane, is good evidence that the earliest living cells did indeed actively pump out sodium ions.

Carrine Blank, a geologist at the University of Montana in Missoula says life was unlikely to survive on land 3.8 billion years ago, at a time when meteorites were pummelling Earth. Mulkidjanian counters that some geologists now question whether the late heavy bombardment, as it is known, really happened at that time (Elements, DOI: 10.2113/gselements.5.1.23).

Others contacted by New Scientist labelled Mulkidjanian's ideas absurd and declined to comment. Undoubtedly, most researchers still favour the sea as the cradle of life. Still, Mulkidjanian is not alone in looking for a land-based alternative.

Paul Knauth, a geologist at Arizona State University in Tempe, also thinks life may not have begun in the sea – which he says has ramifications for the search for extraterrestrial life. He has analysed the oxygen isotopes in the silica-rich rocks deposited early in Earth's history, from which you can work out temperatures at the time the rocks formed. He says that the entire planet was much hotter than anyone suspected – surface temperatures of 50 to 80 0C may have been common. The seas were also twice as salty as today, because so-called "evaporitic" deposits - which locked away vast quantities of salt - had not begun to form. "The early ocean was a deathtrap of hot salty water," he says. "I like the idea of a non-marine origin."

Then there is the fossil evidence. Although the fossil record doesn't capture events at the origin of life, it does record some slightly later chapters in life's history, which origin-of-life researchers "ignore at their peril", according to Martin Brasier at the University of Oxford. Last year Brasier unearthed the oldest fossils so far: 3.43-billion-year-old bacteria. He found them in Australia, in non-marine rocks that formed on a beach. "I am coming round to the opinion that we may be wrong about the ocean as the mother of life," says Brasier.

This doesn't mean that Mulkidjanian has all the details correct, though. Brasier agrees with Lane that early cells probably could pump out enough sodium from their cytoplasm to survive in sodium-rich environments – so life might have emerged in salty pools or shorelines rather than in Siberian-style thermal springs.

Using observations from living cells to work out what the first cells could- – and could not – do underpins most models for life's beginnings. But there will always be a degree of interpretation in how we re-construct history based on observations of living things, and that leaves room for alternative explanations.

This situation might soon change, though. Brasier's discovery last year paves the way for fossil hunting in even older non-marine rocks – something previously considered a waste of time. Studies of early rocks will take some big steps forward in the coming decade, predicts Brasier. The evidence locked inside them might help settle the debate – and say whether Darwin's hunch was correct after all. "The rock record," says Brasier, "is the only safe witness we have."

Land ho! The search for ET

"Follow the water," NASA astrobiologists like to say in conversations about the search for extraterrestrial life. "The problem," says Paul Knauth, a geologist at Arizona State University in Tempe, "is that chlorine follows the water better than any astrobiologist."
Knauth says chlorine-rich salts made the seas on early Earth far too saline for life to emerge. Only once large quantities of salt had evaporated and were locked safely away in land-based deposits could complex life take off in the oceans, suggesting rocks played a key role in life's early stages.
What's more, many of the elements life relies on probably came from the weathering of rocks, like granite, that form only on continents, says Martin Brasier at Oxford University. "If so, the prospects for life on Mars and Titan [where such rocks aren't found] seems a bit bleak."
The same rules probably apply elsewhere in the galaxy. "So, a pale blue dot would be an exciting discovery," says Knauth. "But one with brown spots would be more encouraging."

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First Neanderthal cave paintings discovered in Spain

 

Were these seals painted by Neanderthals? (Image: Nerja Cave Foundation)

Cave paintings in Malaga, Spain, could be the oldest yet found – and the first to have been created by Neanderthals.

Looking oddly akin to the DNA double helix, the images in fact depict the seals that the locals would have eaten, says José Luis Sanchidrián at the University of Cordoba, Spain. They have "no parallel in Palaeolithic art", he adds. His team say that charcoal remains found beside six of the paintings – preserved in Spain's Nerja caves – have been radiocarbon dated to between 43,500 and 42,300 years old.

That suggests the paintings may be substantially older than the 30,000-year-old Chauvet cave paintings in south-east France, thought to be the earliest example of Palaeolithic cave art.

The next step is to date the paint pigments. If they are confirmed as being of similar age, this raises the real possibility that the paintings were the handiwork of Neanderthals – an "academic bombshell", says Sanchidrián, because all other cave paintings are thought to have been produced by modern humans.

Neanderthals are in the frame for the paintings since they are thought to have remained in the south and west of the Iberian peninsula until approximately 37,000 years ago – 5000 years after they had been replaced or assimilated by modern humans elsewhere in their European heartland.

Until recently, Neanderthals were thought to have been incapable of creating artistic works. That picture is changing thanks to the discovery of a number of decorated stone and shell objects – although no permanent cave art has previously been attributed to our extinct cousins.

Neanderthals' creativity

Now some researchers think that Neanderthals had the same capabilities for symbolism, imagination and creativity as modern humans.

The finding "is potentially fascinating", says Paul Pettitt at the University of Sheffield, UK. He cautions that the dating of cave art is fraught with potential problems, though, and says that clarification of the paintings' age is vital.

"Even some sites we think we understand very well such as the Grotte Chauvet in France are very problematic in terms of how old they are," says Pettitt.

If the age is confirmed, Pettitt suggests that the cave paintings could still have been the work of modern humans. "We can't be absolutely sure that Homo sapiens were not down there in the south of Spain at this time," he says.

Sanchidrián does not rule out the possibility that the paintings were made by early Homo sapiens but says that this theory is "much more hypothetical" than the idea that Neanderthals were behind them.

Dating of the Nerja seal paintings' pigments will not take place until after 2013. Further excavations in the extensive cave system – discovered by a group of boys hunting bats in 1959 – is ongoing.

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Zoologger: Don't bite – how the zebra got its stripes

Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world

Species: Equus burchelli, E. grevyi, E. zebra

Habitat: Open grassland areas and woodlands

Zebras are quite the communists. They graze together, groom each other and stay in packs to protect themselves from predators. And while some herds reportedly contain harems, a recent study observed peaceful and equal interactions amongst the sexes.

But it's not their egalitarian habits that define them, it's their distinctive black and white stripes, which for centuries have puzzled biologists. Now Adam Egri at Eötvös University in Budapest, Hungary, and colleagues have an answer: they believe zebras evolved stripes to protect themselves from blood-sucking insects.

The zebra is completely black as an early embryo, and white stripes only appear in a later embryonic stage, when the production of dark pigmentation is blocked. Each zebra has subtly different stripes, acting like nature's own barcode.

Charles Darwin wondered what purpose they served. A popular theory, both in the 19th century and today, is that zebras evolved striped coats as camouflage in tall grass. But, as Darwin noted, the "stripes cannot afford any protection in the open plains of South Africa".
Social stripes

More recently, biologists have observed that zebras don't attempt to conceal themselves by freezing in response to predators. Zoologist Desmond Morris wrote in his Animal watching: A field guide to animal behaviour that "compared to many hoofed animals on the plains of Africa, they are remarkably mobile and noisy and never attempt to hide in cover".

Darwin suggested that zebras developed their unique stripes to recognise each other, which could be particularly important for male and female courtship. "A female zebra would not admit the addresses of a male ass until he was painted so as to resemble a zebra," Darwin wrote.

Martin How at the University of Queensland, Australia, agrees that the stripes have an obvious social function. "But it's possible they appeared for another reason and the social benefits came later."

How says he has unpublished evidence suggesting that the stripes evolved to confuse predators, giving zebras crucial time to escape. He analysed videos of zebras with a motion detection program that mimics how movement is encoded in the animal brain. Their stripe pattern generated a range of optical illusions which would baffle a predator, he says. This effect was particularly strong when the animals moved together as a herd.
Dark horse

Another suggestion is that the stripes create a visual illusion, which makes the zebra look bigger that it is. Or perhaps the stripes assist with thermoregulation. But there is little evidence to support these claims, so the evolutionary explanation for the zebras' stripes has remained murky.

Egri's team picked up on a theory first proposed in 1930 and backed up in 1981, when it was demonstrated that biting tsetse flies were least attracted to striped animal models, when compared to black or white models.

Now Egri has taken the research one step further, by showing that horseflies (tabanids) also avoid the stripes. Biting insects transmit several equine diseases, such as equine infectious anaemia, as well as leaving painful bites.

Heading to a fly-infested farm in Budapest the team painted trays with different black and white patterns, and filled them with salad oil to trap the horseflies. Trays coated with thick horizontal stripes attracted less flies than diagonal lines, or criss-crosses. Thin black stripes mimicking those of the zebra attracted fewer flies than thick lines.
Insect defence

"The stripes are messing with their heads," says Justin Marshall, a sensory neurobiologist, also at the University of Queensland. "It confuses them and provides an unattractive surface to land on."

According to experiments carried out by Egri's team, the stripes could also disrupt polarised light, making zebras less appealing to the pests. Horseflies are attracted to horizontally polarised light because they detect water through horizontal polarisation. At the watering hole, flies drink, mate and lay eggs.

Mike Archer, an evolutionary biologist at the University of New South Wales, Australia, calls this "a delightfully innovative explanation for something that's long puzzled mammalogists."

"Having been bitten myself many times by tabanids, which really hurt, this new explanation makes a great deal of sense to me," he says.

Journal Reference: The Journal of Experimental Biology, DOI: 10.1242/jeb.065540

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