Category Archives: science

dance of the tarantula and other spider myths

Right now the American Museum of Natural History is running an exhibition about arachnids called “Spiders Alive!” 

brown recluse

image via american museum of natural history

The exclamation is with good reason since the spiders really are alive. Safely ensconced behind glass but alive all the same. I’m not one of those people who gets freaked out by spiders but, even so, there’s something inherently creepy about them. Maybe it’s those wonderfully sinister names, which look like they could be splashed across the title sequence of a fifties B-movie: The Black Widow! The Brown Recluse! Tarantula!

Actually, the tarantula is a good example of how the popular imagination has demonized spiders. The vision of a hairy-legged tarantula coming in through an open window at night is a cinematic shorthand for everything that makes our skin crawl about them.

But even their name is a testament to the mythology of fear we’ve built around them. In ancient times the inhabitants of Taranto, a town in southern Italy, were terrified of a species of wolf spider which lived locally. When they were bitten by the spider the townsfolk would perform a frenetic dance in the belief that this would shake out the poison (though it turns out the spider’s venom was not fatal to humans). 

When early European colonizers of the New World were faced with the big hairy spiders of the tropics they recalled the dance of Taranto when finding a name for these creatures. The irony is that tarantulas pose virtually no threat to humans because – counter-intuitive as it might sound – bigger spiders tend to have less powerful venom.

In fact, while most spiders produce venom fewer than one percent are dangerous to humans. That’s just 200 species out of a total of over 42,000. Of course our fear of arachnids is not totally groundless. Some can give you a nasty bite, others can jolt you with a wicked dose of poison and a few of them occasionally kill.

Gooty sapphire ornamental spider

image via american museum of natural history

Many species of spider are dimorphic, which means the female is larger than the male. This means you’re much worse off getting bitten by a female black widow since she carries more poison. Most humans will survive a bite from a black widow (though you should seek medical help immediately, especially in the case of the elderly or young children). The same cannot always be said of the amorous male black widow who is frequently killed and eaten immediately after mating.

Arachnophobia, or the fear of spiders, is one of the most common phobias. According to some statistics, around 10 percent of men and 50 percent of women have an irrational fear of arachnids, which also include scorpions. If this is really true then you can’t help feeling sorry for the poor spider, who seems fated to suffer from a permanent image crisis. Fortunately for our arachnid cousins, this exhibition goes some way to redressing the balance by explaining just how amazing these creatures are.

Did you know, for example, that spiders have been on earth for 300 million years? Or that they taste with the hairs on their legs? Here’s another interesting tidbit: In the World War II the U.S. Army used black widow silk to make crosshairs for sighting devices on their weaponry. Meanwhile, in 2010 scientists identified a spider silk, from the caerostris darwini species on Madagascar, which is ten times tougher than Kevlar.

the black widow

image via american museum of natural history

Near the end of this brilliant exhibition there’s a talk by an arachnid expert who takes out a live tarantula to show the crowd. When I was there most of the audience were kids.

“How did you get to work with spiders?” One little boy asked in the Q&A, evidently eyeing the expert’s job for himself.

“It’s simple,” she answered. “You just have to really love them.”

Easier said than done for a lot of us I would imagine.

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bioluminescence

A version of this story was first published on CNN’s science blog, Light Years, June 19, 2012. 

The summer is upon us and if you live somewhere relatively hot or you’re going some place hot for your holidays, there’s a good chance you’ll see fireflies.

firefly

I live in Brooklyn, New York, and when I look out my bedroom window I can see them hovering in the yard, tiny balls of yellow light that flicker on and off in the dusk like lighters at a rock concert.

Fireflies are quite a common sight although for how long we don’t know. There have been widespread reports that fireflies numbers are dwindling. The reports are all anecdotal but they were enough of a concern for entomologists and biologists to convene a symposium in Thailand in 2008 entitled, “Diversity and Conservation of Fireflies.”

If fireflies are under threat it’s a terrible state of affairs. They are a unique and interesting creature and their loss ultimately would be our loss. They belong to a very exclusive group of land creatures that exhibit a phenomenon known as bioluminescence.

In simple terms, bioluminescence is technique certain organisms have developed to create energy, in the form of light, via a chemical reaction. This reaction often involves a chemical called luciferin.

Fireflies are unique because most bioluminescent creatures – 80 percent – live in the sea. On land only certain insects and fungi are bioluminescent.

It was in the ocean that I first found out about the phenomenon.

I grew up in England where we don’t get fireflies. We get things called glow worms, which are not worms at all but flightless insects. They’re hard to spot since they’re usually hidden away in long grass or hedgerows. Consequently most Brits will probably tell you that their only recollection of a glow worm growing up was via the pages of a cute children’s story.

It was few years ago and I was on Lombok, a tiny island next to Bali, when I first experienced the weird spectacle of nature flickering to light in the darkness. I went for a midnight swim and started to feel a strange prickling sensation and when I dipped my head underwater and ran my hand in front of me it was as if the Milky War had been miniaturized and liquified at the same time.

The trial of sparks left by your moving hand in bioluminescent waters is caused by single-cell organisms called dinoflagellates. They’re a mysterious organism scientists don’t fully understand. They’re a form of plankton and while they feed on prey and move around like animals, they can also convert the sun’s rays into food using chlorophyll in the same way plants do.

If you want to see the coolest bioluminescent creatures though, you’ve got to go into deep water.

Unless you’re James Cameron or that ridiculous (sorry, I mean romantic) couple who got wed on the deck of the wreck of the Titanic, you probably can’t afford a ride in a deep sea submersible to the ocean bottom.

Don’t despair though. If you’re lucky enough to be in the American Museum of Natural History (AMNH) anytime soon you can check out there wonderful exhibition “Creatures of Light: Nature’s Bioluminescence,” which runs till January next year.

Here, fireflies rub shoulders with the creatures of the deep. In total 80 percent of deep sea organisms are bioluminescent, and certain of them have developed fascinating and elaborate ways of illuminating the permanent night.

Anglerfish, which are frankly hideous-looking things, get their name from the modified spine which sticks out of their forehead just like a fishing rod. The rod is topped with a lure that pulses with bacterial light.

Anglerfish, like most deep sea creatures, emit blue light because it’s easier to detect at these depths. An exception is the stoplight loosejaw dragonfish which gives off red light from indents just below its eyes. The loosejaw gets its name from the fact that its jaw can dislocate from its mouth when it’s hunting prey. Consequently it looks quite a lot like the alien in Predator (which I watched as a child when I’d grown out of the cute glow worm stories).

The AMNH exhibit contains many more highlights, including a small replica of a cave in New Zealand where thousands of fly larvae have turned the ceiling into a festival of stars.

Walking around the exhibit I was reminded of the limitless capacity nature has to amaze. If you’re in New York and you have a spare afternoon, go see it. Failing that, take a look in your back yard.


what makes us better than a neanderthal?

This story was published on CNN’s science blog, Light Years, on April 6, 2012.

How did modern humans conquer the planet? It’s one of the most intriguing questions in the whole of science.

early human diorama in natural history museum

Right now, sitting pretty at the top of the food chain, it’s tempting to see our 200,000-year rise to power since the emergence of the first homo sapiens as a fait accompli: The evolutionary endpoint of a story that got started on the African savannah via the two key innovations of bigger brains and the shift to walking upright.

Yet for our ancestors things were not so clear cut. For a start they were not (as we now find ourselves) the only game in town. When Cro-Magnon (ancestors of modern humans) migrated north from Africa’s Rift Valley to settle Europe around 40,000 years ago, the continent was already populated by another breed of hominid, the Neanderthals. Within a few thousands years the Neanderthals were wiped out and the Cro-Magnon had taken over.

Why was this? What special attributes did our ancestors possess that the Neanderthals did not?

As Ian Tattersall, curator of anthropology at the American Museum of Natural History points out, the fossil record often throws up more questions than answers. Neanderthal skeletons, for example, show that they had stronger builds and the same-sized brains as Cro-Magnon. They were sophisticated tool-makers and animal remains found at Neanderthal sites reveal they were skilled hunters, expert in bringing down large prey such as woolly mammoths. Based on this evidence there is no obvious reason why we made it and they did not.

But Tattersall thinks we need to look beyond the fossil record to find the secret to our success. One place to start looking, he says, is in the Lascaux caves in southern France. Discovered accidentally in 1940 by four children, the Lascaux cave complex contains hundreds of paintings of animal figures in caverns larger than football fields.

Talking at the museum this week to promote his new book, “Masters of the Planet: The Search for Human Origins”, Tattersall describes a visit to the caves as “one of the most profound experiences of my life.” It’s more than just the beauty of the paleolithic art that moved him, however. The cave paintings, he says, prove early man’s ability to think symbolically. Horses drawn on to the cave walls are symbolic representations of real life horses.

No other species of early human left artwork behind and this, he says, is the crucial difference.

The capacity for abstract thinking is the key to our success. All our creativity stems from it. But abstract thinking is not only useful for making art. Early hunters, for example, reporting back on the movement of reindeer herds would be disadvantaged if those hearing the report could not make the mental leap of faith needed to understand that these herds existed even though they had not seen them.

“It is this capacity for ‘what if’ thinking that sets humans apart from all other creatures,” says Tattersall. He says it’s no coincidence that this advance in human cognition came along at the same time as language. “Symbolic thinking is impossible to imagine without language,” he says.

There is no evidence either way to tell us whether Cro-Magnon spoke language with each other, though Tattersall is certain they did. It’s also impossible to say if linguist ability was something early humans acquired or it was innate. Noted linguist Noam Chomsky has argued the later. He believes humans are born with an ability to learn oral language. Hence a toddlers amazing talent for stringing words together in the proper order even though they may never have heard the sentences before.

According to Tattersall, humans may have possessed the ability for language for millions of years before some, as yet unknown, cultural stimulus set it in motion. This is a common trend of evolution, says Tattersall, who has been researching our history through the fossil record since the 1960s and has written several books on the subject. “Birds had feathers for millions of years before they learned to fly. You acquire a feature and, much later on, you find a use for it.”

Of course, the capacity for symbolic thought is just one theory of how humans got to the top of the food chain, and there are many others.

It may have been, as some anthropologists have argued, that in a prehistoric age where nature was red in tooth and claw and fearsome predators such as saber-toothed tigers roamed the landscape, our ancestors were simply the most efficient at killing off the competition. Disease or drought may have played a part; so too may climate change.

That human’s unique way of seeing the world helped them on their rise to becoming the masters of the planet seems indisputable, however. Whether it was the one, big thing that made all the difference; that we may never know.