24 Nov 2012

Play an eco friendly game

  • Join Gaurav, host of Disney Channel’s Art Attack.
    Join Gaurav, host of Disney Channel’s Art Attack. 
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Disney Channel's Art Attack host Gaurav teaches you how to make an eco-friendly game on Children's Day.
Join Gaurav, host of Disney Channel's Art Attack and make yourself an eco friendly indoor game. You can customize and make it in whatever theme you want —Pirates, jungle etc.
You will need
1. Caps of Old Plastic Bottles – to make your Game Pieces
2. One big Cardboard Piece
3. Art Attack paste (made with one part glue and one part water)
4. Cardboard tube of an Old toilet paper roll
5. Old newspapers
6. Markers and colours
7. Scissors
8. Tape
9. Art attack paste (equal amounts of glue and water)
Step 1
Take the piece of cardboard and draw any shape you want. I have drawn the shape as shown in the image. Make a path. With the help of an adult cut the cardboard in the shape drawn as shown in the image.
Step 2
Now make trees and grass. To make the trunk of the tree, take the cardboard tube of the toilet paper roll and stick it to the centre of the board, with the help of tape.
Step 3
To increase the width of the tree take some old newspaper, fold and make strips. Stick it on the cardboard roll. Make paper balls and stick it with the tape to the top of the cardboard roll. Stick it with cellotape.
Step 4
Take pieces of newspaper and stick it on the tree with art attack paste. Cover the whole tree. To make the grass take crumbled pieces of newspaper and stick it around the tree. On the area around it, where the game has to be played, stick sheets of paper. This area should be smooth as here is where the game pieces are kept.
Step 5
Now! to do some colouring. Use dark green for the tree and brown for the trunk. For the grass use light green. Do some shading to make it look more real. With a black marker, divide the path into small parts. Make eco symbols like water taps, light bulbs etc., inside each part. Colour the individual parts wtih any two colours . Colour the start point black and white. Make sure your whole board is coloured and the newspaper can't be seen.
Tune in to Disney Channel on Sunday's at 9:30 AM to catch more of this!
Step 6
Voila! Your eco friendly game is ready! You can punish the player who reached the open tap spot and give an extra turn to the player who reached the closed tap spot.

Hills, rich in flora and fauna

Green warrior: Fighting for the hills.
Green warrior: Fighting for the hills.
             Sneha is passionate about the environment. And as a crusader for the cause, she made a presentation on the hill ranges in Andhra Pradesh.
For T. Sneha, a student of Std. IX, Sudhaha Little Citizens High School, Tirupati, biodiversity is close to her heart. She participated in the XI Conference of Parties to the Conservation of Biological Diversity, conducted in Hyderabad, under the auspices of the National Biodiversity Authority of India. She helped prepare recommendations on “Aichi targets for biodiversity conservation”. Aichi targets are the 20 Points agreed upon by signatories to the Xth convention held at Nagoya, Japan, in 2010.
Sneha, a member of National Green Corps’ (NGC) Eco-club, participated in the sub-event “Young India for biodiversity”. She was the only representative from the Rayalaseema region. She presented an overview of the Seshachalam hill ranges spread over Chittoor and Kadapa districts, which are rich in biodiversity.
Be a friend
Her presentation lasted four minutes and she spoke about the rare endemic species of fauna like golden gecko (golden lizard), civet cat, Jerdon’s Courser, Yellow-browed bulbul, Indian fox, Malabar giant squirrel, Banded peacock (butterfly), slender loris (a cat-like nocturnal animal) and flora — Cycas beddomei and Red Sanders.
The presentation highlighted the need for humans to make a difference and protect the environment.
“After the meet, we students decided to document our ‘backyard biodiversity’ i.e., the plants, creepers, insects, worms, animals, streams we see in our neighbourhood, ” said Sneha.
Strongly believing that children can make a difference, Sneha urges her peers to motivate their parents to quit practices perceived to be eco-unfriendly. She says we can make a start by ensuring segregation of waste and curb practices that could lead to the extinction of birds and animals in our neighbourhood.
Seshachalam Biosphere Reserve
This is the first biosphere reserve in Andhra Pradesh. It was notified on September 20, 2010. The total area of the Ministry of Environment and Forests-designated reserve is 4756 sq.km, which include parts of Chittoor and Kadapa districts in the Deccan peninsula. The area is divided into three — the core zone (kept free of human activity), buffer zone (where activity will have to conform to MoEF guidelines) and transition zone (comprising settlements, croplands and managed forests). Interestingly, the Tirumala hills known to be the abode of lord Venkateswara, also falls in this Reserve.
The biosphere is expected to be a part of the UNESCO network. This would facilitate exchange of information and infusion of funds through the Man And Biosphere (MAB) programme.

Arctic ice could vanish within 10 years: Scientists

The entire region could be eventually free of ice if the estimates prove accurate. This would trigger a ‘gold rush’ for oil reserves and fish stocks in the region. File Photo: AP
AP The entire region could be eventually free of ice if the estimates prove accurate. This would trigger a ‘gold rush’ for oil reserves and fish stocks in the region. File Photo: AP
Arctic sea ice could vanish within 10 years as it is melting much faster than previously believed, thanks to global warming, warn scientists, claiming that the process is 50 percent faster than the current estimates.
New satellites being operated by the European Space Agency paint a grim picture of 900 cubic km of ice already having melted over the last year.
This is 50 percent higher than the current estimates from environmentalists, they claim. It is suggested that the increase is down to global warming and rising greenhouse gas emissions, the Daily Mail reports.
The entire region could be eventually free of ice if the estimates prove accurate. This would trigger a ‘gold rush’ for oil reserves and fish stocks in the region.
“Preliminary analysis of our data indicates that the rate of loss of sea ice volume in summer in the Arctic may be far larger than we had previously suspected,” said Seymour Laxon, of the Centre for Polar Observation and Modelling at University College London (UCL), where CryoSat-2 data is being analysed.
Scientists launched the CryoSat-2 probe in 2010 specifically to study ice thickness. Until then most studies had focused on the coverage of the ice. Submarines were also sent into the water to analyse the ice. The methods are said to have given a picture of changes in the ice around the North Pole since 2004.
Data from the exploration shows that in winter 2004, the volume of sea ice in the central Arctic was approximately 17,000 cubic km. This winter it was 14,000 km, according to CryoSat.
Chris Rapley, professor at UCL added: “Before CryoSat, we could see summer ice coverage was dropping markedly in the Arctic. But we only had glimpses of what was happening to ice thickness. Obviously if it was dropping as well, the loss of summer ice was even more significant.”

Greenhouse gases at record high in 2011: UN

In this Sept. 15, 2009 file photo, a deforested area is seen near Novo Progresso, in Brazil's northern state of Para. The Brazilian Amazon is arguably the world's biggest natural defence against global warming, acting as a “sink,” or absorber, of carbon dioxide.
AP In this Sept. 15, 2009 file photo, a deforested area is seen near Novo Progresso, in Brazil's northern state of Para. The Brazilian Amazon is arguably the world's biggest natural defence against global warming, acting as a “sink,” or absorber, of carbon dioxide.
                 The UN weather agency says concentrations of the main global warming pollutant in the world’s air reached a record high in 2011.
The World Meteorological Organization says the planet averaged 390 parts per million of heat-trapping carbon dioxide in the atmosphere, up 40 per cent from before the Industrial Age when levels were about 275 parts per million.
WMO officials said on Tuesday there was a 30 per cent increase in the warming effect on the global climate between 1990 and 2011, mainly due to carbon dioxide from fossil fuel burning.
WMO Secretary-General Michel Jarraud said the 350 billion metric tons of carbon dioxide added to the atmosphere since 1750 “will remain there for centuries, causing our planet to warm further and impacting on all aspects of life on earth.”

A biological battery


                Plugging into sources of energy within our body — such as heat, internal motion or metabolites — to power implanted medical devices has long been the goal of biomedical engineers. Now researchers based in Cambridge, Massachusetts have demonstrated that a sensing device embedded in the ear can be powered by the ear’s own electrochemical battery.
Our auditory mechanism picks up external sounds and sends information to the brain in the form of neural signals. When the sound wave hits the ear, the eardrum vibrates in response. This mechanical energy must to be converted into an appropriate electrochemical impulse.
Deep inside the ear, the cochlea perceives the frequency of the vibration. It maintains a gradient of potassium and sodium ions across a delicate membrane via a system of pumps and channels. This natural battery, which makes neurotransmission of sound possible, generates a net positive voltage.
Researchers have known about the existence of this endocochlear potential (EP) for decades, but had not devised ways of using this voltage without interfering with the mammal’s hearing, says Konstantina Stankovic, otologic surgeon at Massachusetts Eye and Ear Infirmary, medical lead of the collaborative team. “What we have is both a conceptual and technological breakthrough. New electrodes and new electronics had to be developed to make safe harvesting possible,” she says.
Prof. Anantha Chandrakasan’s group at Massachusetts Institute of Technology designed the chip to extract current from the ear, keeping in mind the many physiological constraints. In the prototype, the harnessed power drives a wireless sensor that can monitor the value of the EP. A radio transmitter relays data to the clinician who uses the numbers to gauge the ear’s condition.
Though our ear functions on EP ranging from 70-100 millivolts, this voltage is not enough for electronic implants. “Since the power from the source is so small, we accumulate energy on a capacitor. Once the capacitor fills up, it can drive a higher power electronic circuit,” says Chandrakasan. “We power a 2.4 Gigahertz radio in this case.”
But transistor-based electronics need hundreds of millivolts to start. A wireless receiver on the integrated circuit gets a short burst of radio waves to kick-start the system.
The setup, implanted in the ear of a guinea pig, could transmit data for five hours without compromising normal hearing. Design optimization and more testing lie ahead.
“Thus far, we have demonstrated feasibility of sensing the EP, powered by the EP,” says Stankovic. “But we are eager to couple this energy-harvesting chip to a variety of molecular and chemical sensors to sense the inner ear and its environment and identify the most promising biomarkers relevant for the ultimate human application.”
The device cannot power multichannel cochlear implants or hearing aids as yet. But Charley C. Della Santina, professor of Otolaryngology and biomedical engineering at Johns Hopkins University, who is unconnected to the research team, points out that there is a real need for a system that can monitor the EP in animal models of Meniere’s disease — an inner ear disorder that affects balance and hearing. And, this device, he says, may just fit the bill.
Plus, the data collected in vivo could transform our understanding of how the mammalian ear works, says Stankovic. The paper that describes the findings appears in the latest issue of Nature Biotechnology.

'Death throes of a star shows how Sun may die'

Death throes

               Astronomers have discovered a dying Sun-like star briefly coming back to life after casting its gassy shells out into space, mimicking the possible fate our own Solar System faces in a few billion years.
A new picture of the planetary nebula Abell 30, located 5500 light-years from Earth, is a composite of visible images from the NASA/ESA Hubble Space Telescope and X-ray data from ESA's XMM-Newton and NASA's Chandra space telescopes.
Planetary nebula is the name given to the often-concentric shells of stellar material cast into space by dying stars. To astronomers of the 18th century, these objects looked like the colourful "blob" of a planet.
Astronomers now know that as a star with less than eight times the mass of the Sun swells into a red giant towards the end of its life, its outer layers are expelled via pulsations and winds.
The stellar wind bombarding dense clumps of material provides a chilling look at the possible fate of Earth and its fellow planets in our own Solar System in a few billion years' time, ESA said in a statement.
When our Sun emits its final gasps of life at the heart of a planetary nebula, its strong stellar wind and harsh radiation will blast and evaporate any planets that may have
survived the red giant phase of stellar evolution.
Ultraviolet radiation shining out from the stripped-down hot stellar core then lights up the ejected shells, resulting in intricate artworks that can be seen by modern telescopes.
The star at the heart of Abell 30 experienced its first brush with death 12,500 years ago - as seen from Earth - when its outer shell was stripped off by a slow and dense stellar wind.

          Optical telescopes see the remnant of this evolutionary stage as a large, near-spherical shell of glowing material expanding out into space.
About 850 years ago, the star suddenly came back to life, coughing out knots of helium and carbon-rich material in a violent event.
The star's outer envelope briefly expanded during this born-again episode, but then very rapidly contracted again within 20 years.
This had the knock-on effect of accelerating the wind from he star to its present speed of 4000 kilometres per second -over 14 million kilometres per hour.
As this fast stellar wind catches up and interacts with the slower wind and clumps of previously ejected material, complex structures are formed, including the delicate
comet-like tails seen near the central star.

13 Nov 2012

‘Thataku tapakayalu’ are here again

G. V. R. Subba Rao
The crackers lost charm after the arrival of fancy items
The ‘Thataku tapakayalu’, one of the favourite crackers of coastal Andhrites for Diwali, are on sale again at fire cracker stalls here. Also on sale are other hot favourite ‘tara juvvalu’. Juvvalu, fondly called ‘havvai suvvai’, are not available abundantly at the stalls, but they made their presence felt.
Very few stalls at the PWD Grounds where the fire crackers are on sale, have put up the thataku tapakayalu, the bombs covered with palm leaves. A bunch of 25 thataku tapakalu is available for Rs.30. “There were no ‘Lakshmi’ bombs or ‘atom’ bombs, which one saw everywhere during Diwali during one’s childhood. The ‘thataku tapakalu’ were the only source to make a loud noise during the Diwali,” recalls Chaluvadi Satyanarayana, a senior citizen.
Thataku tapakayalu lost their charm after the advent of fancy items and crackers from Sivakasi. Generally, the youth used to make thataku tapakayalu and tara juvvalu at their homes. It was a must item in the list of crackers and even children used to insist on buying a pack for them, added S. Narasimha Rao, his associate, who was at the grounds to buy crackers for his grandchildren.
Some local traders also used to make the thataku tapakaylu. But, due to cost escalation, labour problems and flooding of fancy items, the manufacturing of this item has come down. Thataku tapakayalu, also called as galaxies, were not seen during last two-three years, says Jupudi Srinivas, a stall owner. There used to be competitions between colonies and localities in lighting up tara juvvalu. The juvvalu, a primitive form of ‘rocket crackers’ used to criss-cross between two contesting groups standing at the ends of a street. The havvai suvvai were considered as big man’s cracker, and children used to look at it with awe, recalls Mr. Satyanarayana.

Why do earthen pots lose their efficiency in keeping the water cool after being used for a few years?

            Fresh earthen pots have multitudinous and crisscross narrow channels running from inside to outside of their walls like in a sponge. Or, we say that the walls of fresh earthen pot are highly porous.
When water is held in such fresh earthen pot, part of the water bleeds out through these pores by capillarity and interfacial affinity and makes the outer surface of the pot rather wet.
However, the water from inside cannot gush out though these pores like a shower because of the crisscross nature and narrowness of the channels and the fineness of the pores.
Thus, the effective exposure area for water in a fresh earthen pot, is not only the top meniscus in the pot but also the wetness on the outer surface of the pot. When water evaporates from these surfaces, the molecules leaving the pot take along heat from the pot’s walls and the water in the pot becomes cooler.
Potable water is not pure water; it contains some minerals such as potassium, sodium, magnesium and calcium salts, suspended particles, dissolved oxygen and carbon dioxide, etc among others.
During the course of usage, some of these calcium and magnesium ions in water tend to precipitate as insoluble carbonates and sulphates which gradually plug the pores and channels of the pot walls.
The suspended particles, dust collected inside and outside the pot during usage and some algal and moss growths also block these pores and discourage the development of wetness of the outer walls of the pot.
In the event of decreased net area of exposure, the rate of evaporation and the scope for loss of internal heat is drastically reduced.
That is why earthen pots lose their efficiency in keeping the water cool after being used for a few years.
Department of Chemistry
National Institute of Technology Warangal
Warangal, Andhra Pradesh

Why do we feel relief when we gargle with salt in hot water when suffering from throat pain?

Neyveli, Tamil Nadu
           Soreness in the throat can cause throat pain. Soreness of throat is generally due to the infection of the bacterium called Streptococcus. So it is called strep throat. A strep throat is usually inflamed due to bacteria making widespread damage on our soft tissues or mucosa.
These inflammations (known as edemas) are usually filled with water. When we gargle with warm salt water that is saltier than our body fluids (hypertonic solution), through osmosis the salt draws out the edema fluid.
The principle behind it is that if a porous partition separates dilute and concentrated solutions then the dilute solution permeates through the porous partition into the concentrated solution.
This process does not stop till the concentration of both the solutions is equal. Salt water is more concentrated than the water in bacteria. The membrane of the cell of inflammatory tissue acts as a porous partition. So the salt draws water from the swollen cells that are causing pain and the inability to swallow foods.
Not only that, it will also draw water from the bacteria. When the bacteria gradually lose their body fluid they cannot remain active after dehydration. So they wither and die. This phenomenon is called plasmolysis.
The other benefits are; when the salt water enters the throat, the solution helps to neutralize acids in the throat, restoring the natural pH balance that had been disrupted by the sore throat.
By doing this, the burning sensations are relieved and the mucous membranes become less irritated, which can speed healing.
In addition to neutralizing acid, the salt water gargle helps to wash away unwanted mucus and increase the blood flow to the throat. The capillaries then become dilated, which allows for faster circulation of infection-fighting cells.
Instead of table-salt-dissolved water it is better to gargle with hypertonic saline water which contains two tea spoons of table salt and one tea spoon of baking soda (sodium bicarbonate, not baking powder) dissolved in 200 ml of purified water.
The sodium bicarbonate helps to improve the mucous-solvent properties of the irrigating solution.
The warm water and salt grains bathing in our throat may feel good. But too much salt can harm our mucosa. So moderate gargling is advised.
Moreover gargling with salt water does not actually help to heal the strep throat like a medicine would, but it does provide temporary relief. If we do not experience relief as a result of the salt water gargling and if the pain persists we must consult a doctor to get proper antibiotic treatment.

12 Nov 2012

Why is a choke required in a tube light and not in a CFL?

Choke’s role

Sultanpur, Uttar Pradesh
            Both conventional fluorescent lamps (usually 4 feet long) and compact fluorescent lamps — CFLs ( much smaller both in length and diameter of the tube) used in lighting applications are low pressure mercury vapour discharge lamps.
These lamps generate light by the process of fluorescence (accomplishing conversion of invisible ultra-violet, UV to visible light) by electrical discharge-passage of electricity through gaseous-vapour medium along the column of the tube.
When electrical discharge could strike the column of the tube, lot of invisible UV radiation having wavelength dominantly at 254 nm is generated. This UV radiation when strikes the white coating inside the tube made of fluorescent material- phosphors gets converted to visible light with wavelengths in the region of 400-700 nm through the process of fluorescence.
The electrical resistance of the discharge column of the tube increases with dimensions and decreases with miniaturization of lamp dimensions.
For a conventional fluorescent lamp, the ballast used is a choke which essentially a leak transformer (made of bulk coil windings) which momentarily produces an inductive kick in the form of high voltage (approximately 1000 volts) so that the electrical discharge could be struck along the column of the tube. So in a conventional fluorescent lamp the role of the choke is to initiate the electrical discharge process.
Once the discharge is struck it can be sustained through the drop in electrical resistance of the column. But CFLs, being smaller in dimensions offering much lower electrical resistance do not require such bulky chokes. Instead the discharge in CFLs is initiated by much compact electronic circuits integrated into the CFL holder. Usually these electronic ballasts are small oscillator circuits producing high frequencies (approximately 10 kilo Hertz) facilitating flicker free quick start of lamp as electrical discharge strikes faster at such high frequencies.
Luminescence Group
Karaikudi, Tamil Nadu

4 Nov 2012

Spot your train with ease

T. Ramachandran

RailRadar helps passengers know location of 9,700 trains
Train-tracking has become easier than ever before with all trains, except those running on the Mumbai suburban network, being covered live by the web-based trainenquiry.com service of the Indian Railways. It has now taken on a new map-based dimension with the addition of railradar.trainenquiry.com.
At any point in time, information can be had online or via SMS about the location and schedule of the 9,700-odd trains that run a given week. And what is more fascinating is that the location of any train, except those in the Konkan railway belt, can now be seen on a map anytime — represented by a colour-coded arrow that indicates whether a train is running on time or late.
Though the enquiry service has been working for some years and providing information on select trains, it has become comprehensive in its new avatar launched last April. A mobile version was released in May; and just a few weeks ago came the map-based RailRadar add-on.
The site had witnessed no less than a crore visitors in the few months it was launched. And every day, on an average, more than 3.5 lakh users flocked to the trainenquiry.com and RailRadar websites, 20 per cent of whom used mobile devices to get information, said Manish Rathi, co-founder of Railyatri, which is involved in the operation of the site set up by the Centre For Railway Information Systems.
The appeal of the trainenquiry.com service lies in the ease of use. By entering some details in a search box — a train’s name or number or the names of stations — the user is presented with a list that can be narrowed down to a specific option.
By clicking on the train name displayed, the user can know where it is — whether it has halted at a station or is approaching one, the timings, the other stations en-route, the distances, and so on. Also the stations it has passed through and when, and the distance already traversed. It also tells us whether a train is running on schedule or is late at a point in time. (For getting the information via SMS, type SPOT (train number) and send the message to 139).
With RailRadar, passengers can now spot trains on a map by clicking on the blue (on time), yellow (delayed) or red (delayed by more than 15 minutes) arrows that represent individual trains, and know where it is at the moment. By clicking further, one can find out when it will arrive at different stations ahead of it and the time it passed the last few stations en route. In a nutshell, almost real-time (time lags of a few minutes are part of the system though) schedules of a train can be had by clicking on a map.
“Response to RailRadar has been tremendous — not just in India but worldwide. In the first week of its launch, RailRadar was noted as the top talked about map-based application across the world. While there are few additional countries where railways are tracked on a map, reviewers of this site have acknowledged that this has to be the biggest one just based on its sheer size and complexity,” Mr. Rathi said.

Sunita Williams embarks on seventh spacewalk to find ammonia leak

File photo shows U.S. astronaut Sunita Williams, who is scheduled to return to Earth on Nov.19, after a four-month mission.
AP File photo shows U.S. astronaut Sunita Williams, who is scheduled to return to Earth on Nov.19, after a four-month mission.
Indian-American Sunita Williams ventured out of the International Space Station (ISS) with a fellow astronaut on Thursday for a 6.5-hour sojourn, her seventh so far, to fix an ammonia leak in the radiator system.
Two spacewalking astronauts worked on the leaky radiator system outside the ISS, just hours after the vessel barely dodged a menacing piece of orbiting junk.
The U.S. space agency NASA ordered the space station to change position on Wednesday to avoid a fragment from a communication satellite that was destroyed in a high-speed collision three years ago.
Thrusters on a docked Russian supply ship were fired to move the orbiting lab out of harm’s way. But a computer error caused the thrusters to malfunction, and the space station did not reach the desired altitude.
NASA officials said the space station and its six residents were safe despite their lower-than-intended orbit.
Space station commander Sunita Williams and Japanese astronaut Akihiko Hoshide wasted no time installing jumper cables outside their home for the past four months. Their objective was to isolate a suspect radiator to help determine whether that is the source of the ammonia coolant leak and deploy a spare radiator to bypass the troublesome section.
Engineers theorize that bits of space junk may have penetrated the radiator or part of its system; another possibility is that the 12-year-old equipment simply cracked.
The radiators are needed to dissipate heat generated by electronic equipment aboard the space station. Toxic ammonia is used as the coolant, and the spacewalkers took care to avoid contamination.
In an interview with The Associated Press earlier this week, Williams said the biggest risk is the uncertainty surrounding the leak. “We have a lot of extra procedures just in case things don’t go exactly as planned,” she said. “But we’ve dealt with ammonia before.”
A small leak was detected in this area in 2007. Spacewalking astronauts added extra ammonia last year to shore up the system, but this past summer, the leakage increased fourfold. At that rate, the affected power channel could be offline by the end of the year.
That’s why Thursday’s spacewalk was ordered up, even though it comes shortly before the departure of Williams and Hoshide. The two are scheduled to return to Earth on Nov. 19, after a four-month mission.

How cooking helped us become brainier


THE DIFFERENCE: Cooking increases the nutrient content and energy intake in the consumer. Photo: M. Vedhan
THE DIFFERENCE: Cooking increases the nutrient content and energy intake in the consumer. Photo: M. Vedhan
Brain size of humans increased because they began to eat cooked food while the great apes ate everything raw
The internet is abuzz over a recent paper in the October 22 issue of Proc. Natl, Acad, Sci.US (PNAS) by Drs Fonseca-Azevedo and Herculano-Houzel of Brazil. These two ladies have claimed that the enormous increase in the brain size in humans came about because humans began to eat cooked food while our closest cousins, the great apes did not know how to use fire and ate everything raw. They claim that this sudden and large increase in brain size was an important event in human evolutions thanks to the use of fire.
Why do they claim so? We humans have the largest brains in comparison to our body size. Our brain-to-body ratio is far higher than that of the other primates. We have as many as 86 billion brain cells or neurons, compared to just 28 billion in the great apes. This is a giant step in evolution. How and why this sudden expansion came about has been a nagging question. And brain consumes a lot of energy to operate. After skeletal muscles and the liver, it is the brain that consumes most of our metabolic energy. Though it is only about 2 per cent of the total body mass, it consumes 20 per cent of the total body metabolic rate. In other primates, the number is just 9 per cent. To maintain such an energy-expensive organ, the amount of food we need to eat, or more precisely the number of calories we need, is huge indeed.
The needs
The greater the need for calories, the greater the time needed for feeding. This means more time spent on foraging for food and greater time needed for ingestion and digestion, plus of course the calorie content of the diet. And the amount of calorie intake depends on the number of hours spent on feeding and digestion. It has been estimated that gorillas spend about 10 hours a day for feeding themselves. And it is estimated that as they do so, their total body mass goes up to 120 kg or so. The metabolic cost of maintaining such a size of body is estimated by what is known as the Kleiber scale as 70 x (body mass) kilocalories per day. Since brain cells consume a lot of energy, this puts an upper limit to the brain size of an ape. Its brain can grow only if it feeds continuously the whole day.
It is here that raw versus cooked food argument comes in. Dr. Richard Wranghan of Harvard’s Peabody Museum estimated the energetic consequences of raw food and of cooked in his paper in the November 29, 2011 issue of PNAS (Incidentally both this paper and that of the Brazilian duo are downloadable free).
He and his group decided to compare the weight gain of mice fed on raw meat (lean beef) versus cooked meat, and likewise fed on raw tuber (sweet potato) versus pounded, cooked and whole, or cooked and pounded. They found that mice that ate cooked meat gained weight (this gain was not attributable to differences in food intake or activity levels); likewise with processed tuber over raw tuber. Cooked food was seen to be more digestible and also helped in killing pathogens present in the raw samples. He thus writes that adoption of cooking would have helped ancestral humans thrive.
Meat and tubers have been eaten by us for over 2 million years. And when we learnt how to make and tame fire, cooking was born. And cooking increases the nutrient content and energy intake in the consumer. Dr. Wrangham published in 2010 a book entitled: Catching Fire: How Cooking Made us Human. Here he points out that as our hominid ancestors started cooking and eating, their digestive track shrunk and brain enlarged.
Pointed out
The Brazilian ladies build on this point. They point out that the energy intake in cooked food is higher than in raw. And that it costs about 6 kilocalories per day to operate a billion neurons. In a typical daily intake of about 1800 kilocalories, 20 per cent or 360 kilocalories go to operate our brain.
Given these numbers, one can see the value of eating cooked food. In order to get 1800 kilocalories per day on raw food, a human weighing 70 kg would have to spend over 16-18 hours eating! Cooking thus not only would have let early homo erectus gain time away from foraging and eating, but also to think more using the greater brain size he would have gained! Azeredo and Herculano-Houzel thus make a logical case when they say that cooked diet may have been a major positive driving force to the rapid increase in brain size in human evolution.
Comments on the web
As expected, the internet is full of comments and criticism on the above two papers. People who prefer to eat raw food (not just plants, fruits and nuts) have written about how they are perfectly healthy, happy and brainy with raw food; others points out that even this “raw” is processed in one way or the other if it is meat or fish (marinated, fomented).
But such arguments miss the main point, namely, how evolution would have been helped by the use of fire and cooking in providing greater energy and nutritive values, at a crucial time period when several other factors would also have acted to help the emergence of homo erectus, and then on to homo sapiens like us who use our brains to think back in time on how we got our brains this big.