Ever wonder where our fear of snakes and spiders comes from?

Most of us in New Zealand and many other industrialised nations have never come across a poisonous spider in the wild - we only have two venomous species here and bites are extremely rare.

Yet the thought of any spider crawling up our arm is enough to send a shiver up our spines.

For some, this fear can even develop into anxiety which limits a person's daily life - and in developed countries, one to five per cent of the population are affected by a real phobia of creepy-crawlies.

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Now, researchers think they've put their finger on where this inherent aversion stems from - evolution.

German and Swedish scientists recently made a crucial observation: even in infants, a stress reaction was evoked when they see a spider or a snake.

And this was already at the age of six months, when they were still very immobile and have had little opportunity to learn that these animals can be dangerous.

"When we showed pictures of a snake or a spider to the babies instead of a flower or a fish of the same size and colour, they reacted with significantly bigger pupils," said study leader Stefanie Hoehl, of Germany's Max Planck Institute for Human Cognitive and Brain Sciences.

"In constant light conditions this change in size of the pupils is an important signal for the activation of the noradrenergic system in the brain, which is responsible for stress reactions.

"Accordingly, even the youngest babies seem to be stressed by these groups of animals."
"We conclude that fear of snakes and spiders is of evolutionary origin.

"Similar to primates, mechanisms in our brains enable us to identify objects as 'spider' or 'snake' and to react to them very fast."

This obviously inherited stress reaction in turn predisposes us to learn these animals as dangerous or disgusting - something that could lead to a phobia if combined with other factors.

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"A strong panicky aversion exhibited by the parents or a genetic predisposition for a hyperactive amygdala, which is important for estimating hazards, can mean that increased attention towards these creatures becomes an anxiety disorder."

Interestingly, it was known from other studies that babies do not associate pictures of rhinos, bears or other theoretically dangerous animals with fear.

"We assume that the reason for this particular reaction upon seeing spiders and snakes is due to the coexistence of these potentially dangerous animals with humans and their ancestors for more than 40 to 60 million years - and therefore much longer than with today's dangerous mammals.

"The reaction which is induced by animal groups feared from birth could have been embedded in the brain for an evolutionarily long time."

For modern risks such as knives, syringes or sockets, presumably the same is true.

From an evolutionary perspective they have only existed for a short time, and there had been no time to establish reaction mechanisms in the brain from birth.

"Parents know just how difficult it is to teach their children about everyday risks such as not poking their fingers into a socket."

Introducing... RoboBee

New, hybrid RoboBee can fly, dive into water, swim, propel itself back out of water, and safely land. Photo / Yufeng Chen/Harvard SEAS
New, hybrid RoboBee can fly, dive into water, swim, propel itself back out of water, and safely land. Photo / Yufeng Chen/Harvard SEAS

We've seen tiny robots that can fly, stick to walls, and dive into water.

Now, get ready for a hybrid "RoboBee" that can fly, dive into water, swim, propel itself back out of water, and safely land.

New floating devices allow this multipurpose air-water microrobot to stabilise on the water's surface before an internal combustion system ignites to propel it back into the air.

This latest-generation RoboBee, which is 1000 times lighter than any previous aerial-to-aquatic robot, could be used for numerous applications, from search-and-rescue operations to environmental monitoring and biological studies.

"This is the first microrobot capable of repeatedly moving in and through complex environments," said Yufeng Chen, a graduate student from Harvard University's John A Paulson School of Engineering and Applied Sciences.

"We designed new mechanisms that allow the vehicle to directly transition from water to air, something that is beyond what nature can achieve in the insect world."

Designing a millimetre-sized robot that moved in and out of water had numerous challenges.

As water was 1000 times denser than air, its wing flapping speed had to vary widely between the two mediums.

But if the flapping frequency was too low, it couldn't fly, and if too high, its wings would snap off in the water.

By combining theoretical modelling and experimental data, the researchers found the magic balance of wing size and flapping rate, scaling the design to allow the bee to operate repeatedly in both air and water.

Using this strategy, the robot was able to flap its wings at 220 to 300Hz in air and nine to 13Hz in water.

"The RoboBee represents a platform where forces are different than what we - at human scale - are used to experiencing," Harvard's Professor Robert Wood said.

"While flying the robot feels as if it is treading water; while swimming it feels like it is surrounded by molasses.

"The force from surface tension feels like an impenetrable wall. These small robots give us the opportunity to explore these non-intuitive phenomena in a very rich way."

Discovered: T.rex's cousin

Fabien Knoll, Honorary Senior Research Fellow at the University of Manchester, lies next to the new exceptionally large carnivorous dinosaur footprints found in Lesotho. Photo / Fabien Knoll
Fabien Knoll, Honorary Senior Research Fellow at the University of Manchester, lies next to the new exceptionally large carnivorous dinosaur footprints found in Lesotho. Photo / Fabien Knoll

An international team of scientists has discovered the first evidence of a huge carnivorous dinosaur that roamed southern Africa 200 million year ago.

The researchers have found several three-toed footprints measuring 57cm long and 50cm wide in an ancient land surface in Lesotho, a small country in southern Africa.

This meant the dinosaur would have an estimated body length of around nine metres and be a little less than three metres tall at the hip.

That was four times the size of a lion, currently the largest carnivore in southern Africa.

The footprints belong to a new species, named Kayentapus ambrokholohali, which was part of the group of dinosaurs called megatheropod, which include the iconic Tyrannosaurus rex.

"The latest discovery is very exciting and sheds new light on the kind of carnivore that roamed what is now southern Africa," said Dr Fabien Knoll, of the University of Manchester.

"That's because it is the first evidence of an extremely large meat-eating animal roaming a landscape otherwise dominated by a variety of herbivorous, omnivorous and much smaller carnivorous dinosaurs.

"It really would have been top of the food chain."

What made the discovery yet more important was that the footprints dated back to the Early Jurassic epoch, when it was thought the size of most theropod dinosaurs was considerably smaller.

On average they were previously thought to be around three to five metres in body length, with some records showing they may have reached seven metres at the very most.

It was only much later in the Jurassic and during the Cretaceous, which started 145 million years ago, that truly large forms of theropods, such as T. rex, appeared in body and trace fossil records.

'This discovery marks the first occurrence of very large carnivorous dinosaurs in the Early Jurassic of southern Gondwana - the prehistoric continent which would later break up and become Africa and other landmasses," said Dr Lara Sciscio, a postdoctoral research fellow at South Africa's University of Cape Town.

"This makes it a significant find. Globally, these large tracks are very rare.

"There is only one other known site similar in age and sized tracks, which is in Poland."