by James Morris
With Halloween just around the corner, I thought it would be fun to share some of the “scarier” sides of biology. This is not for the faint of heart, so only read on if you are prepared…
We often go to the movies for a good scare. Sometimes we read horror stories. But you don’t have to look far to find all kinds of monsters lurking among us. And it turns out that they are not monsters at all. They are instead quite common and familiar.
Consider dinosaurs. You don’t need a scientist to take DNA from a mosquito entombed in amber whose last blood meal was from a dinosaur to create Jurassic Park. Instead, simply look out your window at a bird feeder.
Birds are not just related to dinosaurs or descended from dinosaurs. They are, in fact, dinosaurs. Theropod dinosaurs, to be exact.
When it is said that the dinosaurs went extinct 65 million years ago when a giant meteor struck the Earth somewhere around the Gulf of Mexico, that’s not quite accurate. Most of the dinosaurs went extinct. But one line of dinosaurs survived – the birds.
We have fantastic examples of fossils from the Jurassic period 150 million years ago showing species like Archaeopteryx (“ancient wing”) with some characteristics that resemble dinosaurs and others that resemble birds. It and many other fossils are wonderful examples of “missing links” – transitional forms between fossil organisms (feathered dinosaurs) and today’s descendants (modern birds).
We have so many examples of these missing links today that they are not really missing at all. Archaeopteryx was discovered in Germany in 1861, just two years after the publication of Darwin’s On the Origin of Species, providing one key piece of evidence for his theory.
The birds continued to diversify ever since the fateful moment when the meteor slammed into the Earth. Today, there are more than 10,000 species of birds on all continents.
Clones might also frighten us at first, bringing up images of unthinking automatons. From Blade Runner to The Boys from Brazil to Stepford Wives, clones both fascinate and terrify us. But, like dinosaurs, you likely came across a clone in the last week or so.
They are more commonly known as identical twins.
Identical twins come from a single fertilized egg that divides in two very early in embryonic development. As a result, the two individuals are genetically identical – they share exactly the same DNA – and are therefore what scientists (and science fiction writers) call clones.
Of course, that does not mean they are exactly the same. Their genetic material is the same, and it’s the genetic material that determines many traits of an organism, like eye color or hair color. But the environment plays a role too. And not just the environment like the home where they are raised. The environment inside the cell can actually change and modify DNA in ways that are stable over time. These epigenetic changes are the focus of lots of recent research.
When I gave lectures to the public at the Museum of Science in Boston, I took cuttings of jade plants and placed them in soil to make another plant. These too are clones. And, unless you forget to water them, they are not that scary.
And then there are zombies. Sometimes called the undead, zombies are corpses that come back to life with an insatiable appetite for human flesh. Today, some large urban areas host zombie walks where people actually dress up as zombies. But it turns out that you don’t need to go to Toronto or Moscow for a zombie walk, or watch World War Z. Jellyfish have some of the same bizarre characteristics.
Well, they don’t exactly die and come back to life. Nor do they eat human flesh. Instead, there is a species of jellyfish that can transform itself into an earlier stage and then grow up all over again. In this way, they provide an exception to the pattern that organisms are born, grow up, and eventually die. This immortal jellyfish, as it is commonly known, was the subject of a recent article in The New York Times Magazine by science writer Nathaniel Rich and included in The Best American Science and Nature Writing 2013.
And let’s not leave out vampires. Vampires drink blood. There are no shortages of organisms that do just that – from mosquitoes (just females, not males) to leeches to bedbugs to ticks. Lampreys that suck the blood of fish are particularly problematic in the Great Lakes and Lake Champlain, where they are decimating fish stocks. In this way, as an example of the devastating effects of invasive species, they are indeed terrifying.
Vampire bats live up to their name, but they don’t drink human blood – their meal comes from cattle and other livestock. Vampire finches from the Galápagos Islands occasionally drink the blood of other birds.
In ancient Greece, a chimera was a mixture of three animals – a lion, snake, and goat. But the term has been taken to mean any creature that is a mixture of two or more different animals. Familiar examples are the Minotaur – half bull, half human – and Medusa – with snakes in place of hair.
Today, chimeras are all around us, but they won’t turn you to stone. Many people, for example, walk around with heart valves that come from pigs to replace faulty or damaged heart valves. The field of xenotransplantation, in which animal cells, tissues, or organs are transplanted into humans, is an active area of medicine, with transplants of hearts, kidneys, skin, and even neurons from animals to treat various conditions in humans.
I can’t leave this topic without a mention of Harry Potter. To protect against death-eaters and other forms of evil and destruction, wizards and witches conjure up a Patronus using the incantation “Expecto Patronum!” Harry’s Patronum is a stag, like his father’s.
Does nature have a counterpart? It does. Squid and most other species of cephalopods can squirt dark-colored ink when threatened or attacked. What this ink does is not entirely clear. It might act as a smokescreen, allowing the squid to escape. Or, it might be an irritant. But one intriguing idea is that it acts like a decoy, called a pseudomorph, taking on the form of the squid itself. Scientists have observed predators attacking the pseudomorph, giving time for the squid to escape and protecting it like a guardian. Like a Patronus.
I suppose the lesson is that whatever Hollywood can think up or imagine may already be out there among us, so, on this Halloween, watch out!
© James Morris and Science Whys, 2014.