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This week’s posts [concerning translucent sea slugs, wasps named for a crazy pop star, an elusive Indochinese cousin of the cow, and whole sunless ecoystems] have all been about finding new life-forms. There is, of course, only one place such a topic can ultimately wind up—far beyond the living jungles, azure seas, and swirling clouds of our beautiful home planet, out in the immensity of space where the greatest question of all waits like a magic golden apple spinning in darkness.
Is there life elsewhere?
Unfortunately the current answer is incomplete: all known life–in all of its ineffable variety–is Earth-based…yet the universe is vast beyond comprehension. So I’m going to mark this down as “probably.”
Many ancient societies reckoned that other worlds existed. The Norse had their nine worlds joined together by the great ash tree Yggrdasil. The Chinese had myths about Chang’e and the Jade rabbit on the moon. Even the stolid Christians believe in heaven & hell, which are places filled with intelligent beings that are not on earth (ergo, alien realms somewhere out there in the multiverse). William Herschel, great astronomer of the Enlightenment, believed that life was everwhere—particularly everywhere in the solar system.
When humankind entered space age, we used our burgeoning technology to examine the solar system for signs of Sir William’s spacefolk. Although we did not find the Venusian space hotties we were looking for (dammit), we did discover that among our neighboring planets, there are several other possible homes for earthlike living things. The cloud tops of Venus are inviting and could host bacteria-like life (although I hope not, since I want us to build a second home there). For centuries, scientists and fabulists speculated about life of Mars. We now know that the Martian magnetosphere died and the planet’s atmosphere was swept away, but perhaps there are some hardy extremophile bacteria living in the Martian rocks somewhere. It’s a sad scenario to imagine them on their dying world—like little kids left in a bathtub going cold. Certain moons of Jupiter & Saturn seem to be the real best bet for life in the solar system. The Jovian moons Europa, Ganymede, and Callisto are all believed to have extensive liquid oceans beneath their crust. Likewise the Saturn moons Titan and Enceladus are believed to have subsurface water. The discovery of life on Earth which did not directly require photosynthesis (like the cold seeps from yesterday’s post) has given scientists hope that bacterial mats—or maybe something even more advanced–exists on one of these moons.
So maybe there are some bacteria analogs or conodont-like creatures squiggling around in some cranny of the solar system. Perhaps life takes on an unknown form and we already flew over a clever, good-hearted ammonia-based life form on Enceladus (which NASA analysts then promptly dismissed as a snowbank), but I doubt it. The true answers to the questions about life lie out there among the stars. Exoplanets are being discovered at a tremendous rate and everyone hopes that some of the more earthlike examples harbor life. Unfortunately our technology is nowhere close to being able to spot the planets themselves and gauge whether life is there by means of spectrograph. We are stuck waiting for peers who are either broadcasting radio signals or screwing around with the fundamental nature of existence in such a way that would bring them to our attention. Indeed as humankind’s technological savvy grows, scientists are looking for more sophisticated signs of advanced life such as black holes of less than 3.5 solar masses or sophisticated particle radiation which could only be created (or detected) by civilizations of huge sophistication. All we can say right now is that, after a hundred years of looking, we have not found a lot of radio chatter in our neck of the galaxy—which is an answer of sorts itself.
Perhaps we are among the first sentient beings in this area of space (or anywhere, for that matter). The first generation of stars had to live and die before there were any raw materials for chemically based life. It took billions of years to get where we are, and, despite a few perilous missteps and accidents, life on Earth has been lucky. In my opinion some of those planets we are discovering are almost certainly covered with microbial life, but not many have little green scientists in many-armed lab coats firing up their radio telescopes (or forging little suits of chain mail a few hundred years behind us).
In writing about the Curiosity rover, I humorously mentioned how much it looked like the aliens from golden age science fiction. It seems we are also broadcasting retro style messages to the stars. Above is the print-out version of the Arecibo message—one of the loudest broadcasts we have sent. It’s like a macramé knitted by Dr. Zoidberg’s great aunt or a valentine from Atari’s space invaders! Imagine if you pointed your radio telescope at the heavens and received a message like that! Maybe the aliens are scared of us or maybe they don’t want to talk to a species with such homespun tastes!
So, after the whole post we are no closer to knowing if there is life in the cosmos, but what did you expect? Did you think I would tell you some secret here before you saw it blaring out of every news station on the planet? [If you did think that, then thank you so much!] I believe that extraterrestrial life is out there. I even believe that intelligent extraterrestrials are out there, but the universe really is ridiculously, ridiculously vast. It’s going to take a while to find our fellow living beings. In the mean time have faith (which is not advice I thought I would be giving) and keep looking up at the cold distant heavens.
Ferrebeekeeper has written a lot about how long trees can live. Individual yew trees can survive for thousands of years, bristlecone pines can live even longer, and clonal entities like Pando, a super-colony of quaking aspen, can potentially live for hundreds of thousands of years. Likewise colonial animals (coral, gorgonians, tubeworms, and so forth) tend to live the longest—although the constituent individuals come and go. Yet colonial animals frustrate our selfish human perception of the world. When we talk about an organism we mean an individual, and in this category, the world’s longest living animal comes as a surprise!
As you read this, somewhere, off the coast of Greenland or Virginia there is a smug little clam which was alive when Oliver Cromwell was in diapers and before Galileo discovered the moons of Jupiter. Arctica islandica, the “Ocean Quahog” or “Black Clam,” is believed to live for more than 400 years! The little bivalve laughs at nations, dynasties, and vampires as short-lived.
The venerable mollusks do not live flashy or extravagant lives. They live under a light drift of substrate on Atlantic coastal shelves at a depth of 25 to 100 meters (75 to 300 feet) although they have been found much deeper. The species is very successful and ranges from coastal Portugal up around Iceland down to the Carolinas. The little clams feed on plankton suspended in the water and they only grow to about 12 cm (5 inches) in diameter. Amazingly these Methuselah mollusks are harvested by dredge for the dinner table, so if, like me, you love spaghetti alle vongole, you might have inadvertently eaten something that lived longer than the United States has been around!
The secret behind the small bivalve’s longevity is unclear. Some scientists have speculated that antioxidant enzyme activities and the avoidance of waste accumulation are partially responsible for the clam’s age but the British Society for Research on Aging somewhat dryly remarks that, “Despite interest in this clam’s longevity and the measurement of growth increment series, little research into how this species has apparently managed to defy the onset of the ageing processes has been conducted.”
This shines a poor light on our priorities. Instead of grasping the molecular secrets of the longest living animals on Earth, the people who allocate resources to various things have decided to buy learjets and build a bunch of hokey Mcmansions for themselves. Argh! Maybe the clams’ sense of frugal austerity is what gives them such staying power.
Regular readers know how much I esteem turkeys. Unfortunately I worry that my writings are not winning additional admirers for these astonishing birds. It is time to play a trump card and reveal one of the great bizarre strengths of turkeys. They are capable of virgin birth.
Before you spring up in alarm and start shouting, allow me to present a miniature biology lesson. Parthenogenesis is a form of asexual reproduction. Some female organisms are capable of producing an ovum which develops into a new individual without being fertilized by a male gamete. In these cases, the mother contributes her genetic material to the offspring. Although natural parthenogenesis is frequently observed in rotifers, insects, mollusks, crustaceans, and flatworms, this method of reproduction is much less common among vertebrates. However a few species of fish, amphibians, and reptiles are known to reproduce via parthenogenesis (movie-goers may recall that this happened to the dinosaurs in Jurassic Park.) The turkey is very unusual in being a bird which can reproduce through this means (or at least we think it is unusual—perhaps parthenogenesis is more common among birds then we realize but we just don’t know about it except in settings like farms where it becomes obvious). Chickens can also produce self-fertilized eggs but they almost never develop beyond embryonic stages, whereas female turkeys can and frequently do produce living offspring which lack fathers.
Parthenogenesis occurs in turkeys through the doubling of haploid cells. Biologists have discovered that the rate at which this occurs can be increased by selective breeding. Poults produced by parthenogenesis are capable of growing into healthy viable toms indistinguishable from toms with more traditional parentage. You will note that I wrote “toms”—all turkeys conceived via parthenogenesis were created from doubled haploids and are are homogametic. Consequently they are all all male. (This will leave mammal enthusiasts scratching their heads–since female mammals are homogametic and have two x chromosomes. However for birds and for some reptiles, males have two Z chromosomes and thus are the homogametic sex. In such species, females have one Z and one W chromosome and are the heterogametic sex.)
Mammals do not naturally utilize parthenogenesis as a method of reproduction. Certain portions of mammalian genes consist of imprinted regions where portions of genetic data from one parent or the other are inactivated. Mammals born of parthenogenesis must therefore overcome the developmental abnormalities caused by having two sets of maternally imprinted genes. In normal circumstances this is impossible and embryos created by parthenogenesis are spontaneously rejected from the womb. Biology researchers have now found ways to surmount such obstacles and a fatherless female mouse was successfully created in Tokyo in 2004. With genetic tinkering, human parthenogenesis is also biologically feasible. Before his research was discredited and he was dismissed from his position, the South Korean (mad?) scientist Hwang Woo-Suk unknowingly created human embryos via parthenogenesis. To quote a news article by Chris Williams, “In the course of research, which culminated with false claims that stem cells had been extracted from a cloned human embryo, Hwang’s team succeeded in extracting cells from eggs that had undergone parthenogenesis… The ability to extract embryonic stem cells produced by parthenogenesis means they will be genetically identical to the egg donor. The upshot is a supply of therapeutic cells for women which won’t be rejected by their immune system, without the need for cloning.”
All of which is fascinating to biology researchers (and those who would seek greatly prolonged life via biogenetic technologies), however it seems that in nature, the turkey is the most complicated creature capable of virgin birth.