Each time I hear the rendition of Bumbleboogie, I get goosebumps.
Lets freeze that scene... Me hearing Bumbleboogie and goosebumps all over my forearm. Why do I get goosebumps? We have to search a distant past to answer that question. Because goosebumps are the vestiges of our ancient ancestors. Use the remote to reverse back a couple of scores of years. And you see, my ancient hirsute ancestors, normal mammals with hairs all over. Their hairs were raised or lowered at the behest of sensitive bodily thermostats. Too cold and the hairs were erected, thus trapping a layer of air which served as insulation from the cold. The thicker the hair layer, the more heat it retains. Warm, and the coat was flattened to allow body heat to escape more easily. Forward back to the scene where I am listening to Bumbleboogie.
There I sit, having goosebumps on my forearm. But wait, I am not cold over there. Why am I still getting goosebumps? Well, if you take a live snake to a zoo and show it to a chimp, you gonna see its hair raising up. A sudden jhatka to a cat, and its fur turns up. The reason, they say, is that when hairs stand on end, it tends to increase the body's apparent size and scare off dangerous rivals or predators. Switch back to me listening to bumblebee boogie.
But wait, what has listening to Bumbleboogie got anything to do with a sensitive bodily thermostat or fear or anger? Well, you get goosebumps not only when you are cold but when you walk the aisle to get betrothed to your loved one or when the national anthem is put on after a stunning victory by your country or when you walk through the blackness of the night and there are creepy sounds all around you. Whats common in all the above scenarios? They are all emotionally packed.
The reason for all these responses is the subconscious release of a stress hormone called adrenaline. Adrenaline, which in humans is produced in two small beanlike glands that sit atop the kidneys, not only causes the contraction of skin muscles but also influences many other body reactions. In animals, this hormone is released when the animal is cold or facing a stressful situation, preparing the animal for flight-or-fight reaction. In humans, adrenaline is often released when we feel cold or afraid, but also if we are under stress and feel strong emotions, such as anger or excitement. Other signs of adrenaline release include tears, sweaty palms, trembling hands, an increase in blood pressure, a racing heart or the feeling of 'butterflies' in the stomach.
The hair-erection machinery is a vestige, a non-functional relic of something that did a useful job in our long-dead ancestors. Vestigial hairs are among the many instances of history written all over us.
Wednesday, June 30, 2010
Sunday, June 27, 2010
Birds
There are some sunning films available on YouTube of balletic maneuvers of the flocking behavior of starlings. These were taken by Dylan Winter over Otmoor near Oxford. What is remarkable about the starlings behavior is that, despite all appearances, there is no choreographer and as far as we know, no leader. Each individual bird is just following local rules.
THE BOIDS
The numbers of individual birds in these flocks can run into thousands, yet they almost literally never collide. Which is just as well for, given the speed at which they fly, any such impact would severely injure them. Often the whole flock seems to behave as a single individual, wheeling and turning as one.
The whole performance would make a more than usually elegant screensaver on a computer. And this is neatly possible in an almost analogical way to how embryology works. Here's how to program flocking behavior in starlings. Devote almost all your effort to programming the behavior of a single individual bird. Build into your robo-starling detailed rules for how to fly, and how to react to the presence of the neighbouring starlings depending on their distance and relative position. Build in rules for how much weight to give individual initiative in changing direction. These model rules would be informed by careful measurements of real birds in action. Endow your cyberbird with a certain tendency to vary its rules at random. Having written a complicated program to specify the behavioural rules of a single starling, now clone the single bird to make a thousand copied, all same as each other (or maybe with some slight random variation among them in their rules) and release them to freely interact with each other.
Craig Reynolds called it boids and wrote a program along these lines in 1986. The basic flocking model in his program consisted of 3 elements:
1. Separation (steer to avoid crowding local flockmates)
2. Alignment (steer to the average heading of local flockmates)
3. Cohesion (steer to move towards the average position of local flockmates)
Each boid has direct access to the whole scene's geometric description, but flocking requires that it only interacts with flockmates within a certain small neighbourhood around itself. The neighbourhood is characterized by distance (measured from center of the boid) and an angled (measured from the direction of boid's flight). Flockmates outside this neighbourhood are ignored.
The key point is that there is no choreographer and no leader. Order, organization, structure - these all emerge as by-products of rules which are obeyed locally and many times over, not globally. And that is how embryology works. It is all done by local rules, at various levels but especially the level of the single cell. In the field of development, or manufacture, the equivalent of this kind of programming is self-assembly.
THE BOIDS
- the story of regularity in chaos in nature
The numbers of individual birds in these flocks can run into thousands, yet they almost literally never collide. Which is just as well for, given the speed at which they fly, any such impact would severely injure them. Often the whole flock seems to behave as a single individual, wheeling and turning as one.
The whole performance would make a more than usually elegant screensaver on a computer. And this is neatly possible in an almost analogical way to how embryology works. Here's how to program flocking behavior in starlings. Devote almost all your effort to programming the behavior of a single individual bird. Build into your robo-starling detailed rules for how to fly, and how to react to the presence of the neighbouring starlings depending on their distance and relative position. Build in rules for how much weight to give individual initiative in changing direction. These model rules would be informed by careful measurements of real birds in action. Endow your cyberbird with a certain tendency to vary its rules at random. Having written a complicated program to specify the behavioural rules of a single starling, now clone the single bird to make a thousand copied, all same as each other (or maybe with some slight random variation among them in their rules) and release them to freely interact with each other.
Craig Reynolds called it boids and wrote a program along these lines in 1986. The basic flocking model in his program consisted of 3 elements:
1. Separation (steer to avoid crowding local flockmates)
2. Alignment (steer to the average heading of local flockmates)
3. Cohesion (steer to move towards the average position of local flockmates)
Each boid has direct access to the whole scene's geometric description, but flocking requires that it only interacts with flockmates within a certain small neighbourhood around itself. The neighbourhood is characterized by distance (measured from center of the boid) and an angled (measured from the direction of boid's flight). Flockmates outside this neighbourhood are ignored.
The key point is that there is no choreographer and no leader. Order, organization, structure - these all emerge as by-products of rules which are obeyed locally and many times over, not globally. And that is how embryology works. It is all done by local rules, at various levels but especially the level of the single cell. In the field of development, or manufacture, the equivalent of this kind of programming is self-assembly.Monday, June 21, 2010
Dogs
The origin of Dogs is regarded a controversial subject. Where did they come from? Overwhelming evidence from behavior, vocalizations, morphology, and molecular biology led to the contemporary scientific understanding that a single species, the gray wolf, is the common ancestor for all breeds of domestic dogs. However, the time-frame and mechanisms by which the divergence actually happened is controversial.
Raymond Coppinger points out that when domestic animals break free and go feral for many generations, they usually revert to something close to their wild ancestor. We might expect feral dogs, therefore to become rather wolf-like. But this doesn't happen. Instead, dogs left to go feral (wild) seem to become the ubiquitous 'village dogs' - 'pyre dogs' - that hang around human settlements all over the third world. Coppinger believes that the dogs on which which human breeders finally went to work were wolves no longer. They had already changed themselves into dogs: village dogs, pye-dogs, perhaps dingos.
The current consensus among biologists and archaeologists is that the dating of first domestication is indeterminate. There is conclusive evidence that dogs genetically diverged from their wolf ancestors at least 15,000 years ago, but some believe domestication to have occurred earlier. It is not known whether humans domesticated the wolf as such to initiate dog's divergence from its ancestors, or whether dog's evolutionary path had already taken a different course prior to domestication. Here is the story of an experiment that happened in Novosibirsk, Siberia that tries to prove the latter.
Raymond Coppinger points out that when domestic animals break free and go feral for many generations, they usually revert to something close to their wild ancestor. We might expect feral dogs, therefore to become rather wolf-like. But this doesn't happen. Instead, dogs left to go feral (wild) seem to become the ubiquitous 'village dogs' - 'pyre dogs' - that hang around human settlements all over the third world. Coppinger believes that the dogs on which which human breeders finally went to work were wolves no longer. They had already changed themselves into dogs: village dogs, pye-dogs, perhaps dingos.
The current consensus among biologists and archaeologists is that the dating of first domestication is indeterminate. There is conclusive evidence that dogs genetically diverged from their wolf ancestors at least 15,000 years ago, but some believe domestication to have occurred earlier. It is not known whether humans domesticated the wolf as such to initiate dog's divergence from its ancestors, or whether dog's evolutionary path had already taken a different course prior to domestication. Here is the story of an experiment that happened in Novosibirsk, Siberia that tries to prove the latter.
THE SILVER FOX EXPERIMENT
- a real life study in domestication
The silver fox is a melanistic colour variant of the familiar red fox, Vulpes vulpes. The Russian geneticist Dimitri Belyaev was employed to run a fox fur farm in the 1950s.
Domesticated Silver Fox
Wild foxes are tricky to handle, and Belyaev set out deliberately to breed for tameness. Like any other animal or plant breeder of his time, his method was to exploit natural variation (no genetic engineering in those days) and choose, for breeding, those males and females that came closest to the ideal he was seeking. In selecting for tameness, Belyaev could have chosen, for breeding, those dogs and bitches that most appealed to him, or looked at him with the cutest facial expressions. That might well have had the desired effect on the tameness of future generations. More systematically than that, however, he used a measure that was pretty close to the flight distance.
One of the main difference between wolf and dog behaviour is the flight distance. Real wolves are pack hunters. Village dogs are scavengers that frequent middens and rubbish dumps. Wolves scavenge too, but they are not temeperamentally suited to scavenging human rubbish because of their long flight distance. If you see an animal feeding, you can measure its flight distance by seeing how close it will let you approach before fleeing. For any given species in any given situation, there will be an optimal flight distance, somewhere between too risky or foolhardy and too flighty or risk averse. Individuals that take off too late when danger threatens are more likely to be killed by that danger. Individuals that are too flighty never get a square meal, because they run away at the first hint of danger on the horizon.
Belyaev and his colleagues (and successors, for the experimental program continued after his death) subjected fox cubs to standardized tests in which an experimenter would offer a cub food by hand, while trying to stroke or fondle it. The cubs were classified into three classes. Class III cubs were those that fled from or bit the person. Class II cubs would allow themselves to be handled, but showed no positive responsiveness to the experimenters. Class I cubs, the tamest of all, positively approached the handlers, wagging their tails and whining. When the cubs grew up, the experimenters systematically bred only from this tamest class.
After a mere six generations of this selective breeding for tameness, the foxes had changed so much that the experimenters felt obliged to name a new category, the domesticated elite class, which were eager to establish human contact, whimpering to attract attention and sniffing and licking experimenters like dogs. At the beginning of the experiment, none of the foxes were in the elite class. After 10 generations of breeding for tameness, 18 percent were elite. After 20 generations, 35 percent and after 30-35 generations, domesticated elite individuals constituted between 70 - 80 percent of the experimental population.
Such results are perhaps not too surprising, except for the astonishing magnitude and speed of the effect. 35 generations would pass unnoticed on the geological timescale. Even more interesting, however, were the unexpected side-effects of the selective breeding for tameness. The tame foxes not only behaved like domestic dogs, they looked like them. They lost their foxy pelage and became piebald black and white, like Welsh collies. Their foxy prick ears were replaced by doggy down like a fox's brush. The females came on heat every six months like a bitch, instead of every year like a vixen. According to Belyaev, they even sounded like dogs.
In fact, when USSR collapsed the fur farm was forced to find funds by selling 600 of their 700 silver foxes as pets. At last report, "Most of the project expenses are covered by selling the foxes as pets, but the project remains in a difficult situation, looking for new sources of revenue from outside funding."
These dog-like features were side-effects. Belyaev and his team did not deliberately breed for them, only for tameness. Those other dog-like characteristics seemingly rode on the evolutionary coat-tails of the genes for tameness. To geneticists, this is not surprising. They recognize a widespread phenomenon called pleiotropy. Presumably genes for floppy ears and piebald coats are pleiotropically linked to genes for tameness, in foxes as well as in dogs. This illustrates a generally important point of evolution. When you notice a characterstic of an animal and ask what its Darwinian survival value is, you maybe asking the wrong question. It could be that the characteristic you have picked out is not the one that matters. It may have come along for the ride dragged along in evolution by some other characteristic to which it is pleiotropically linked.
The evolution of the dog then, if Coppinger is right, was not just a matter of artificial selection, but a complicated mixture of natural selection (which predominated in the early stages of domestication) and artificial selection (which came to the fore more recently).
In answer to the more controversial question, when did wolves suddenly evolve to dogs, this laboratory experiment gives a lower bound on how long it took. The true answer is somewhat still argued upon.
A couple of other findings with the Silver Fox experiments: The experimenters also breeded the most aggressive of silver foxes for comparison with domestic ones trying to find which genes controlled the aggressive behavior. The answer is not one particular set of genes but a lot of changes that controls the behavior. To the nurture v/s nature argument, they tried interchanging cubs of the tamer species with the aggressive ones and vice versa. But it doesnt matter what genes your surrogate mother has. The essential gene that controlled the aggressiveness and tameness still controlled the nature of the cub.
The silver fox is a melanistic colour variant of the familiar red fox, Vulpes vulpes. The Russian geneticist Dimitri Belyaev was employed to run a fox fur farm in the 1950s.
Domesticated Silver FoxWild foxes are tricky to handle, and Belyaev set out deliberately to breed for tameness. Like any other animal or plant breeder of his time, his method was to exploit natural variation (no genetic engineering in those days) and choose, for breeding, those males and females that came closest to the ideal he was seeking. In selecting for tameness, Belyaev could have chosen, for breeding, those dogs and bitches that most appealed to him, or looked at him with the cutest facial expressions. That might well have had the desired effect on the tameness of future generations. More systematically than that, however, he used a measure that was pretty close to the flight distance.
One of the main difference between wolf and dog behaviour is the flight distance. Real wolves are pack hunters. Village dogs are scavengers that frequent middens and rubbish dumps. Wolves scavenge too, but they are not temeperamentally suited to scavenging human rubbish because of their long flight distance. If you see an animal feeding, you can measure its flight distance by seeing how close it will let you approach before fleeing. For any given species in any given situation, there will be an optimal flight distance, somewhere between too risky or foolhardy and too flighty or risk averse. Individuals that take off too late when danger threatens are more likely to be killed by that danger. Individuals that are too flighty never get a square meal, because they run away at the first hint of danger on the horizon.
Belyaev and his colleagues (and successors, for the experimental program continued after his death) subjected fox cubs to standardized tests in which an experimenter would offer a cub food by hand, while trying to stroke or fondle it. The cubs were classified into three classes. Class III cubs were those that fled from or bit the person. Class II cubs would allow themselves to be handled, but showed no positive responsiveness to the experimenters. Class I cubs, the tamest of all, positively approached the handlers, wagging their tails and whining. When the cubs grew up, the experimenters systematically bred only from this tamest class.
After a mere six generations of this selective breeding for tameness, the foxes had changed so much that the experimenters felt obliged to name a new category, the domesticated elite class, which were eager to establish human contact, whimpering to attract attention and sniffing and licking experimenters like dogs. At the beginning of the experiment, none of the foxes were in the elite class. After 10 generations of breeding for tameness, 18 percent were elite. After 20 generations, 35 percent and after 30-35 generations, domesticated elite individuals constituted between 70 - 80 percent of the experimental population.
Such results are perhaps not too surprising, except for the astonishing magnitude and speed of the effect. 35 generations would pass unnoticed on the geological timescale. Even more interesting, however, were the unexpected side-effects of the selective breeding for tameness. The tame foxes not only behaved like domestic dogs, they looked like them. They lost their foxy pelage and became piebald black and white, like Welsh collies. Their foxy prick ears were replaced by doggy down like a fox's brush. The females came on heat every six months like a bitch, instead of every year like a vixen. According to Belyaev, they even sounded like dogs.
In fact, when USSR collapsed the fur farm was forced to find funds by selling 600 of their 700 silver foxes as pets. At last report, "Most of the project expenses are covered by selling the foxes as pets, but the project remains in a difficult situation, looking for new sources of revenue from outside funding."
These dog-like features were side-effects. Belyaev and his team did not deliberately breed for them, only for tameness. Those other dog-like characteristics seemingly rode on the evolutionary coat-tails of the genes for tameness. To geneticists, this is not surprising. They recognize a widespread phenomenon called pleiotropy. Presumably genes for floppy ears and piebald coats are pleiotropically linked to genes for tameness, in foxes as well as in dogs. This illustrates a generally important point of evolution. When you notice a characterstic of an animal and ask what its Darwinian survival value is, you maybe asking the wrong question. It could be that the characteristic you have picked out is not the one that matters. It may have come along for the ride dragged along in evolution by some other characteristic to which it is pleiotropically linked.
The evolution of the dog then, if Coppinger is right, was not just a matter of artificial selection, but a complicated mixture of natural selection (which predominated in the early stages of domestication) and artificial selection (which came to the fore more recently).
In answer to the more controversial question, when did wolves suddenly evolve to dogs, this laboratory experiment gives a lower bound on how long it took. The true answer is somewhat still argued upon.
A couple of other findings with the Silver Fox experiments: The experimenters also breeded the most aggressive of silver foxes for comparison with domestic ones trying to find which genes controlled the aggressive behavior. The answer is not one particular set of genes but a lot of changes that controls the behavior. To the nurture v/s nature argument, they tried interchanging cubs of the tamer species with the aggressive ones and vice versa. But it doesnt matter what genes your surrogate mother has. The essential gene that controlled the aggressiveness and tameness still controlled the nature of the cub.
Saturday, June 19, 2010
Lizards
In 1971, biologists moved 5 adult pairs of Italian Wall lizards from their home island of Pod Kopiste, in the South Adriatic sea to the neighboring island of Pod Mrcaru. Podarcis Sicula which mainly eats insects, was present on Pod Kopiste but there were none on Pod Mrcaru. Largely insect eaters, the half foot long reptiles would find themselves in a terrain that had insects in short supply.
Because of political upheaval in the region (the adriatic sea borders croatia), it was not until 2004 that Duncan J. Irkshik, a professor of biology at University of Massachusetts and a team of international biologists could return to find out what had happened to the lizards.
THE LIZARDS OF POD MRCARU
- a real life study of Evolution
Duncan says:
"As a scientist, it was a once in a lifetime opportunity. Historical circumstances prevented people from going back to the island for a very long time. So when we first went out there in 2004, we didnt know what we would find. We chartered a boat out to the island, and it was amazing. The island was swarming with lizards."
Pod Mrcaru Lizards
Duncan:
"Pod Mrcaru is a tiny rock in the middle of the water. You could walk from one end of the rock to the other in 5 minutes. It has a Mediterranean climate - hot and very dry. Its mainly rock with little shrubby plants sticking up out here and there. It looks very inhospitable."
Researches returned to the island twice a year for 3 years, in the spring and summer of 2004, 2005 and 2006. Captured lizards were transported to a field laboratory where their snout-vent length, head dimensions and body mass were measured. Tail clips taken for DNA analysis confirmed that the Pod Mrcaru lizards were genetically identical to the source population on Pod Kopiste.
Two of the most striking changes that were observed in the lizards were increase in head size and change in head shape. Observed differences in head morphology were caused by adaptation to a different food source. Lizards on Pod Kopiste were well suited to catching mobile prey, feasting mainly on insects. Life on Pod Mrcaru offered them an abundant supply of plant foods including the leaves and stems of native shrubs.
Italian Wall Lizard - Source populant of Pod Kopiste
Analysis of the stomach content of the lizards of Pod Mrcaru showed that their diet included two-third plants, depending on the season, a large increase over the population of lizards on Pod Kopiste.
Graphs illustrating difference in diet between population in spring (A) and summer (B). Differences in the proportion of plants (black bars), invertebrate prey (white), and the rest fraction (gray) are highly significant between populations. Seasonal differences in diet that were highly significant on Pod Mrcaru but not on Pod Kopiste. Error bars depict 1 standard deviation.
Duncan:
"Individuals on Pod Mrcaru have heads that are longer, wider and taller than those on Pod Kopiste, which translates into a big increase in bite force. Because plants are tough and fibrous, high bite force allows the lizard to crop smaller pieces from plants, which can help them break down indigestible cell walls."
Examination of the lizard's digestive tracts revealed something even more surprising. Eating more plants caused the development of new structures called cecal valves, designed to slow the passage of food by creating fermentation chambers in the gut, where microbes can break down the difficult to digest portion of plants. Cecal valves, which were found in hatchlings, juveniles and adults on Pod Mrcaru has never been reported for this species including the source population on Pod Kopiste.
Photographs illustrating the cecal valves in a male (A), a female (B), and a hatchling (C) P. sicula from Pod Mrcaru. Note the thick cecal wall and pronounced ridges. The arrow in C indicates the position of the cecal valve in a hatchling as seen from the outside
Duncan:
"These structures occur less than 1% of all known species of scaled reptiles. Our data shows that evolution of novel structures can occur in extremely short time scales. Cecal valve evolution went hand in hand with a novel association between the lizards on Pod Mrcaru and microorganisms called nematodes that break down cellulose which were found in their hindguts."
Change in diet also affected the population density and social structure of the Pod Mrcaru population. Because plants offer a larger and more predictable food supply, there were more lizards in a given area in Pod Mrcaru. Food was obtained through browsing than active pursuit prey and the lizard has given up defending territories.
Oddly, Pod Mrcaru's original lizard residents, Podarcis Melisellensis were nowhere to be found. There used to thrive a healthy population of lizards which were less agressive than the new implants. The new species apparently wiped out the indigenous lizard populations, although how it happened is not known.
Crabs
In Japan, the mythology of Heike-gani and why this animal has a human face on its back is taught even in classrooms at public schools throughout the nation of Japan. The back of the Heike-gani has the face of an angry Japanese samurai warrior - face of the Tiara clan.
The human-faced crabs in Japan from Fauna Japonica. Crustacea. (detail of the Heike-gani in the right)
From the top: Heike-gani, Samehada-heike-gani (Shark-skin Taira-clan’s crab), Kimen-gani (Devil’s mask crab)
Kyoto University Library in Japan
The species of the crab known as Heikea Japonica is found in Japanese waters. The generic name, Heikea, comes from a japanese clan called the Heike, who were defeated at sea in the battle of Danno-Ura (1185) by a river clan called Genji. Legend tells that the ghosts of drowned Heike warriors now inhabit the bottom of the sea, in the bodies of crabs - Heikea Japonica. The myth is encouraged by the pattern on the back of the this crab, which resembles the fiercely grimacing face of a samurai warrior
Heikea Japonica
Orchids
Angraecum Sesquipedale is an orchid from Madagascar that made rounds in botanical circle when it proved a prediction that Darwin and his co-discoverer of natural selection, Wallace. This flower is also known as Darwin's Orchid, Christmas Orchid, Star of Bethelhem Orchid, King of Angraecums.
Angraecum Sesquipedale
This orchid has tubular nectaries that reach down more than 11 inches Darwin's own ruler. That's nearly 30 centimeters. A related Angarecum Longicalcar has nectar bearing spurs that are even longer upto 40 centimeter (more than 15 inches). Darwin, purely on the strength of A. sesquipedale's existence in Madagascar, predicted in his orchid book of 1862 that there must be moths capable of extension to a length of between 10 - 11 inches.
In 1903, after Darwin's death but well within Wallace's long lifetime, a hitherto unknown moth was discovered which turned out to fulfill the Darwin/Wallace prediction and was duly honoured with the sub-specific name praedicta. But even Xanthopan morgani praedicta, Darwin's hawk moth is not sufficiently well endowed to pollinate A. longicalcar and the existence of this flower encourages us to suspect the existence of an even longer-tongued moth.
Angraecum Longicalcar
Thursday, June 17, 2010
Sunflowers
Helianthus Annuuss is a North American plant whose wild form looks like an aster or large daisy. Cultivated Sunflowers today have been domesticated to the point where their flowers are the size of a dinner plate.
Mammoth sunflowers, originally bred in Russian, are 12 to 17 feet high, the head diameter is close to one foot which is more than ten times the size of a wild sunflower's disc, and there is normally only one head per plant, instead of the many, much smaller, flowers of the wild plant. The Russians started breeding this American flower for religious reasons. During Lent and Advent, the use of oil in cooking was banned by the Orthodox Church. But sunflower seed oil was deemed to be exempt from this prohibition. This provided one of the economic pressures that drove the recent selective breeding of the sunflower.
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