Category Archives: Life Sciences

Editing Genes Using Molecular Scissors


In the last few years a revolutionary new technique has been developed to edit genes. In this VERITAS I will describe the technique and how it has the potential to completely transform the way we fight diseases and how it may help us come up with new disease resistant varieties of plants and animals.

Continue reading Editing Genes Using Molecular Scissors

An ugly little animal may help us beat cancer and change our perception about society


Today I will tell you about an amazing little creature. When you ask someone to name an amazing animal or a spectacular creature, they would most likely name lions or tigers or some other large creature. Indeed, most symbols that are based on animals tend to be based on a few animals- the same few animals have been used repeatedly in history and in romantic or magical tales. But today I will tell you about a little creature which does not look as spectacular as a tiger, nor does it have the strength of an elephant and it is not as beautiful as a butterfly. It is a small, ugly animal. But, I hope to convince you in this VERITAS that it is an amazing animal. So amazing that Science magazine named it “Vertebrate of the year” in 2013.

I am talking about the naked mole rat. If you search for its pictures on the internet, you will agree that it is pretty ugly and not so impressive to look at. But it has some characteristics which make it one of the most remarkable creatures that exist. But before we go into these remarkable characteristics, let’s talk about the more “commonplace” characteristics. The naked mole rat, as the name suggests, lacks hair on its body. It is 8-10 cms long and weighs about 30-35 grams. It has tiny eyes and its eyesight is very poor- so basically the eyes just help detect darkness and light. It does not need to see because it spends its entire life underground. Colonies of naked mole rats live in a complex system of subterranean tunnels in the arid and semi-arid regions of East Africa. The colonies can contain upto 300 individuals( the average size is 80 individuals) and the tunnel systems can be several kilometers long.

Now, let’s talk about the characteristics that make this an amazing creature. So amazing that it does deserve the “Vertebrate of the year” title that Science gave it in 2013. Let me first list the amazing characteristics and then explain each one of them in detail: social behavior, thermo-conformance, resistance to cancer, lack of pain and extraordinary life span.

  • Social Behaviour: Bees, Ants, Wasps and Termites live in what we call Eusocial societies- In Greek Eu means real or good. So Eusocial societies display the highest form of social behavior. Eusocial societies have a single breeding female and the rest of the females are workers/defenders. So there is a complex division of labour.  For a long time scientists believed that Bees, Ants, Wasps and Termites are the only species that display eusociality. Now, all these are insects and wasps, bees and ants belong to the same order. So scientists believed that eusocial societies are the result of certain genetic characteristics. But then they discovered the naked mole rat. Now, the naked mole rat is a mammal and is very far genetically from bees and ants but still it displays eusocial behavior. This was an amazing discovery and scientists realized that social systems in species may arise out of environment factors or evolutionary pressures. It is now understood that since living conditions for naked mole rats is very difficult so the only way they can survive is by living in large families in which some individuals do nothing else but find food, others only defend the family from predators( like snakes) and the queen only reproduces. If each individual reproduced, the family would not survive because of the competition and also because reproduction is costly in terms of time and energy and digging tunnels and finding food needs a lot of energy. So most individuals are not involved in reproduction at all and they just support the queen who has very similar genes to them- the genes are being passed on through the queen and not each individual. To give you an idea of how difficult it is for mole rats to find food consider this: naked mole rats eat tubers and sometimes the tubers are very far away from the mole rat tunnels. They do not come out of their tunnels but need to tunnel to the tuber. The tuber gives out no smell and the naked mole rats have very bad vision. So they are blindly searching for tubers by digging tunnels in all directions. No single individual can survive like this. They can succeed only if they make huge teams and dig in all directions; even then it may take them several weeks to find a tuber. Therefore the amazing fact that naked mole rats has told us is that the formation of societies and social structures is not just related to genes- there is a very strong environmental influence as well.
  • Thermo-conformance: Animals have an internal body temperature which they need to maintain in spite of the temperature of the environment outside. For example, we humans have the internal body temperature of about 37 degrees C and we need to maintain that using internal processes( like sweating, shivering etc). In other words, we humans are thermo regulators because we need to maintain a specific internal body temperature. All animals that are thermo-regulators can be divided into two kinds: warm blooded- those who can maintain temperature using internal processes and cold blooded- those that need to maintain their body temperature by moving to warm/cool areas. But naked mole rats have solved the temperature problem in a very interesting and “innovative” manner- the naked mole rat just adapts to the temperature of the environment outside! So it is not a thermo regulator, it is a thermo-conformer. Thermo conformers are very rare- the naked mole rat is the only mammalian thermo-conformer.
  • Immunity to Pain: Almost all animals experience pain when their skin comes in contract with acid or capsaicin( the stuff that gives “heat” to chili peppers). This is due to a neurotransmitter known as substance P which is present in the skin. The naked mole rat does not have substance P and is thus immune to the pain of acid or the burning sensation caused by capsaicin. P substance also causes long term inflammation in injuries and also after surgery. Thus, scientists are studying the naked mole rat to get some clues on how this pain can be managed/reduced. This is a very important field of study. There are people who live in chronic pain eveyday of their lives and we need a way to help them. The naked mole rat may offer us some clues. Note that the pain of inflammatory diseases like Arthritis is also caused because of acid buildup in tissues- so the research on naked mole rat’s pain immunity is directly applicable. Now, lets ask why the naked mole rat is immune to acid pain? It lives in deep tunnels in large groups so there is a carbon dioxide buildup inside the tunnels. We breathe air that has less than .1% C02. The naked mole rat lives in tunnels in which C02 can reach upto 10%. And C02 causes acid buildup in body tissues. So the naked mole rat evolved to be immune to the pain caused by this acid buildup.
  • Resistance to Cancer:  In all creatures Nature has mechanisms in place to control cell growth and division. A single cell moves freely and multiples without any inhibition. But when a normal cell comes in contact with another cell, it stops multiplying and tries to move away. This prevents cells crowding in a small area. The aim of nature is to stop growth when there is no space to grow and to not have cells crowd into a small area. This is called contact inhibition. But cancer cells do not have the property of growth inhibition and keep growing even when they are crowded into a small space. They keep growing even when there is no space- they grow on top of each other. Almost all animals can develop these cancer cells. But, not our amazing naked mole rat. Scientists have never found a mole rat that has cancer! And the reason is that the cells of the mole rat are hyper sensitive to contact inhibition. Or, in other words, the cells of a naked mole rat are much more likely to stop dividing when they come into contact with other cells than any other creature. In most creatures the gene p27 is responsible for contact inhibition. But in the naked mole rat there is an additional gene p16 which is even more active and prevents overcrowding at much lower population densities than p27. So even if one of the gene( p16 or 27 ) fails, the other still prevents overcrowding and cell division during crowding and thus prevents cancer. In humans we have only p27 responsible for growth inhibition and if that fails, we get cancer. Scientists are trying to understand the cancer resistance of naked mole rats and want to use that research to find a way to prevent cancer in humans.
  • Long Lifespan: A common mouse or rat lives for about 4 years. The naked mole rat can live upto 30 years. In the rodent world the naked mole rat is the longevity world champion. Ageing is caused by oxidative stress. Oxidative stress refers to the buildup of free radicals in the cells of our body. Free radicals come from metabolic processes in our body but these are harmful. Our body has ways of dealing with free radicals( basically a kind of detoxification) but over time the balance between creation of free radicals and their destruction is lost and there is a buildup of free radicals or, in other words, oxidative stress occurs. The naked mole rat has a very interesting way of dealing with this oxidative stress. Its metabolic processes become very slow when there is less food. During these times, therefore, the production of free radicals is dramatically reduced. Thus by controlling its metabolism and making it very slow for long periods the naked mole rat avoids oxidative stress for a longer period of time and lives a very long life. Oxidative stress is also responsible for diseases like Parkinson’s, Alzheimer and other age related disorders. Thus finding out why the naked mole rat lives longer may give us clues to cure these widespread and debilitating diseases.

Isn’t the naked mole rat an amazing creature? From it we may learn how to live longer, have less people suffer from Alzheimer’s disease, cure cancers( or prevent them from happening) and cure people of tremendous pain that they suffer from every day for years! Don’t underestimate the little ugly creatures. This reminds me of an urdu sher:

Hairat se yuun na dekhiye, zarra hua to kya hua!

Apni jagah pe janeman zarra bhi aaftaab hai.

( don’t look at it with disdain, though it may appear no more than a speck of dust to you!

But remember that in its place the speck of dust is no less important  or amazing than the enormous sun)


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Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun

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Original Antigenic Sin


I read a very interesting article in a recent issue of the Scientific American and I thought that I should tell you about it. The article was about a very interesting concept known as “Original Antigenic Sin” and it changed the way I look at how our immunity is formed and how it develops as we grow older. Let me also take this as a opportunity to recommend the Scientific American. It is fantastic magazine and if you have a love for science or want to inculcate the love of science in your family, you must subscribe to it.

Immunity is a fascinating concept. It is also a generally misunderstood concept. How do we become immune to something during our lifetime? What is the role of the environment in creating immunity against a certain disease or pathogen? Can we acquire immunity against a new disease when we become old? How much time after the beginning of a disease do we acquire an immunity against it? There are all very interesting questions. These are also very important questions because we are surrounded by new diseases like Ebola, swine flu and bird flu. And there are many other diseases which are on the verge of making a jump from other animals to humans by a slight change in their genetic code- a mutation. We absolutely need to know how immunity is developed if we want to save the billions of people on earth from global epidemics caused by crowded cities and the fact that millions of us travel everyday taking with us pathogens and diseases.

Before I read about the concept of Original Antigenic Sin, I thought that immunity can be built at any time during one’s life. I also assumed that if one is immune to some disease, and if a new disease strikes, the immunity can be built for the new disease without being biased by past immunities. But Original Antigenic Sin says that this is not true. The memory of earlier immunities affects the formation of immunities in the future. This effect is also known as the Hoskins’s effect.

Now let me describe Original Antigenic Sin. Let’s take two adults, Alice and Bob. Lets say that when Alice was a child she was infected with an Influenza virus of the type H7M7(I am just making up a name so as not to offend the sentiments of real diseases like H1N1 J ). Lets also assume that Bob has never had contact with H7M7 virus. When Alice was infected by the H7M7 virus her body responded by making antibodies against the antigens of the invading H7M7 virus. Lets briefly recall the terminology before proceeding further. An antigen is a substance that triggers an antibody generation. Antigens are parts of invading viruses or bacteria. For example, proteins on the surface of a bacteria are antigens. The body creates antibodies for the antigens on the germs that invade it. The antibodies have “binding sites” that allows them to bind to the antigens. The antibodies thus mark the invading germs by binding to their antigens and then the immune system unleashes its forces to kill the marked germs. Think of the antigen-antibody as a lock and key pair. The antibody that can bind to one kind of antigen cannot bind to another kind of antigen. So the body needs to make specific antibodies for the invading germ’s antigens else this system will fail because then the germs would not be marked. Now, armed with these basic concepts lets come back to our story of Alice and Bob. When Alice was infected by H7M7 in her childhood her immune system worked hard to fight the virus. It learnt to make antibodies for antigens on H7M7. After the infection was defeated the knowledge of what antibodies need to be formed for H7M7 virus was not lost. This remained with Alice’s immune system. So Alice’s immune system will always remember the H7M7 virus and antigens present on it. Alice’s immune system is always going to be prepared for H7M7 because it remembers H7M7 antigens and what antibodies to form to be able to bind to these antigens. But since Bob has never been infected by H7M7, his body does not know how to fight H7M7 ie his immune system does not know the antigens on H7M7 and what antibodies to create for these antigens.

Now lets ask: how does Alice’s immune system remember H7M7? This is done by memory B cells in her immune system. These memory B cells were formed  when H7M7 virus invaded Alice’s body and these will stay throughout her life. We all have memory B cells for every infection that has ever struck us. These cells help us to generate a fast and effective response to any infection that tries to strike us again. So Alice’s body has memory B cells for H7M7 but Bob’s body does not have memory B cells for H7M7. What will happen if H7M7 strikes Alice and Bob? You would agree that Alice’s body is prepared. Her immune system knows H7M7 antigens because of memory B cells for this virus. Her immune system immediately acts when it sees H7M7 virus and starts creating antiboidoes that bind to H7M7 antigens. The infection is soon defeated. But Bob’s body is not prepared. His immune system has to first learn about the H7M7 antigens and only then can it form antibodies. So time is spent and during this time the infection grows. Bob’s body had to fight longer to kill H7M7 and this results in Bob being sick for a much longer time as compared to Alice.

Now we come to the interesting part. Lets say that H7M7 mutates and there is now a new strain of virus known as H8M8. And lets assume that H8M8 has invaded the bodies of Alice( who has previously been exposed to H7M7) and Bob( who has never had any contact with H7M7). Who will have a better chance of effective defence against this new strain of virus? Would Alice’s previous exposure to H7M7 help her? Or would Alice’s and Bob’s immune system take the same time to understand the new virus and fight it?

The answer is neither of these. And that is because of the very interesting concept of Original Antigenic Sin. Alice’s body had been infected by H7M7 ealier and when the immune system was fighting the H7M7 virus it made a lot of memory B cells for H7M7. These memory B cells knew about the antigens on H7M7 and could quickly help in creating antiboidies to counter H7M7. So Alice’s immune system is very effective against H7M7. But this knowledge of H7M7 actually puts Alice at a disadvantage against the new strain of virus H8M8. When H8M8 enters Alice’s body, the memory B cells for H7M7 become active. The body thinks that H7M7 is the culprit, it does not realize that the virus has mutated. So when memory B cells for H7M7 become active they produce antibodies for H7M7 antigens. But the H7M7 antibodies cannot bind to H8M8 antigens because the mutation has changed the antigens on H8M8. So Alice’s immune system is completely ineffective against H8M8. Not only that, her immune’s system’s knowledge of H7M7 ( from memory B cells) causes the response to be wrong. Alice’s body wastes a lot of time in countering H8M8 with completely ineffective H7M7 antibodies. This allows H8M8 to grow and cause a lot of damage. On the other hand Bob’s immune system does not have prior knowledge of any flu virus and so can start understaning the antigens on H8M8 and then create an effective response in terms of antibodies. So Bob’s body responds better to H8M8 than Alice.

So the theory of Original Antigenic Sin refers to the ineffective response given to a new mutated virus because the immune system is trying to create antibodies of a virus that it had encountered earlier. This is similar to the adage that generals always fight the last war ie if a general has won a war he will keep using the same tactics in future wars even if those tactics are not suitable in the new situation.

The concept of Original Antigenic Sin is very important for vaccine research. If we make a vaccine for a particular strain of virus or bacteria, it may make people resistant for that specific virus or bacteria. But when that virus or bacteria mutates, the person who has been vaccinated would suffer the bad effects of the disease even more than the person who has never received the vaccine.


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Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun

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Expanding the alphabet of Life


Imagine this: you go to a strange island and find that the inhabitants have their own language. You visit their library and you find millions of books written in their language. Amazed by the size of the library and the number of books you randomly pick up a book and open it. You see something very strange: There are only 4 symbols in that book: a, t, c and g. You are also astonished to see that the letter “a” always occurs next to “t” and “c” only next to “g”. Then you pick up another book and you see the same thing. The whole library consisting of several million books has been written in a language consisting of only 4 letters and with strict restrictions of what letter can occur next to which one. You then wonder that if this amazing civilization can create so much literature out of only 4 characters, what would happen if more letters can be introduced into their alphabet. You rush out of the library to try and convince the chief of the island to include a few more letters. You are confident that the literature produced by the people of this island would be massively enriched if they expand their alphabet.

Now you may wonder why I want you to imagine such an island and you may say that it is silly to think of millions of books written using only 4 letters. But friends, the story may be fictional but its core theme is very closely related a very important true story: the story of life itself. The DNA of every living organism in the world consists of 4 nucleobases: Adenine(A), Thymine(T), Cytosine(C) and Guanine(G). So one can say that the information in a DNA is coded in terms of these 4 nucleobases. As we all know: a DNA consists of 2 strands.  You can think of these strands as sequences of nucleobases( for simplicity we will use the word bases for the rest of the article). Each base in one DNA strand is bound to a base in the other strand using chemical bonds. But the bonding between a base from one strand and that on another cannot be between any two bases: Thymine can only bind to Adenine and Cytosine can only bind to Guanine. So if one strand contains the sequence ATTCGG the second strand must contain the sequence TAAGCC.

So we see that the incredible amount of information found in the DNA of each organism that lives or ever lived on Earth is coded using only 4 letters: A, T, C and G and the letters can only occur in fixed ways: A can only occur next to T and C and only occur next to G. So the situation is very similar to the imaginary island and the incredibly interesting library that we discussed earlier. And now comes the real topic of this VERITAS: Can we increase the alphabet in the library of life and create even more complex and interesting books( organisms). Can we expand the vocabulary of life and create new “words” that benefit us? Are the bases in DNA special or can we make new ones(artificial ones)? And most importantly, if we add new letters to the alphabet of life will we be interfering with nature? There are two important properties of DNA bases/base pairs that artificial bases must have:

  • The bonds between A-T and C-G base pairs are such that the distance between the two strands of the DNA are always constant. If the A-T bond pulled the DNA strands closer than the C-G bond, the two strands could touch each other and this would be very complicated for replication.
  • A DNA must be able to replicate. DNA replication is the basis of all biological inheritance. Briefly this is how it works:  The two strands of the DNA are unwound. Each strand of the DNA now acts as the template for the creation of a new “partner” strand. So the two strands of a DNA are able to create two identical DNA double helix by first unwinding the strands and then synthesizing new strands. To give you a simplified example: Lets take the DNA strand from the earlier example that has the following base sequence: ATTCGG. The second strand would have TAAGCC. Before replication the two are connected like this :







During the replication process the two strands are first separated and so we get ATTCGG and TAAGCC as two separate unconnected strands. And then enzymes synthesize a new TAAGCC to couple with the first and a new ATTCGG to couple with the second. So we will get two DNAs which are identical to the original DNA.

So if we create new base pairs they must be able to maintain the same distance between the DNA strands as A-T and C-G. Also enzymes should be able to properly replicate them. Now replication can be challenging because the enzymes need to synthesize new bases to match the original ones. Enzymes know how to synthesize A, T, C and G. But how will we “teach” them to make the new bases that we introduce?

Scientists have been trying to create artificial bases for over 20 years now. After many years of failure scientists were able to make bases which could be placed alongside the natural bases in a DNA. Many bases and base pairs were created, some more successful than others. The best performing base pairs consisted of two mulecules called d5SICS and dNAM- Lets give them a short name: K and L ( in the original paper scientists called them X and Y but I don’t want you to confuse them with X and Y chromosomes. So I am using K and L). Now, creating a molecule that bonds with another molecule in a lab is one thing. But we want to do something far more complex- we want to add to the alphabet of inheritance and thus of life itself. So the “real” experiment needs to be done in a real cell.

And a real experiment was conducted recently. Scientists added K and L pairs to the DNA of a E. Coli bacteria. Now adding base pairs to a living cell is a challenge in itself. For this scientists relied on a “transporter” which they obtained from some algae. So the “transporter” is responsible for bringing artificial bases into the cell. Once the artificial bases were in place the DNA of the E. Coli had a mix of natural and artificial bases. So, for example, the E.Coli could have ATTKLCGG in one strand and TAALKGCC in the other( K only binds to L just like T only binds to A and C only to G). This was a major breakthrough! We had a living cell with some natural and some artificial bases in the DNA.

But the biggest success was still to come. Scientists were astonished to find that when the DNA was replicated, not only were the natural bases faithfully recreated, but the artificial bases were also replicated by the enzymes! So once you get the artificial bases into the DNA the enzymes can replicate the DNA properly and the artificial base pairs will go to future generations also. Scientists observed that the artificial bases were carried intact generation after generation of the bacteria.

So this really is a very exciting breakthrough. We can expand the alphabet of life! And we can expand it in such a way that it benefits us. When we add information to DNA we can add it in such a way that it helps us- we could create new vaccines, we could create new drugs, we could destroy certain diseases- the possibilities are endless. Of course, knowledge without wisdom can be a dangerous thing. So if we are to change the basic structures of life itself, we better do it carefully and with the intention of improving the beauty and diversity of life and not solely for profit.



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Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun

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The Good Germs

I have always loved eating out. And we go out to eat quite often. However a change has come in my restaurant “procedure” in the last few years: just after ordering, I bring out my bottle of hand sanitizer and insist that everyone’s hands are properly cleansed. I think that it is a hygienic habit, but my family thinks that one more problem has been added to my already long list of personality disorders.

Today we humans tend to think of “germs” as extremely harmful creatures. But note that our “hatred” for these microorganisms is a very recent development. Till the late 19th century it wasn’t even known that germs cause disease. Before the germ theory of disease was discovered, most people and even scientists attributed disease to “bad air”. If you were to travel to even the most advanced city in the world at any time before the 20th century you would be appalled at the lack of even the basic sanitation that is an absolute must for us today. Till the 19th century, man, rodents, garbage lived right next to each other in the bustling cities of the world. Surgeons had no idea that their hands or surgical instruments needed to be washed/sterilized before an operation!

Okay. So we all hate germs. But that is not the subject of today’s VERITAS. Today we will focus on the “good germs”. And there are a lot of them. The amount of bacteria and other microorganisms in a human body is 10 times the cells of the body. The total number of cells in a human body is about 10 trillion( 10,000,000,000,000) and the total number of germs is ( 100,000,000,000,000). And these germs constitute 1-3 % of your body weight. These germs are just about everywhere: mouth, gut, skin, eyes and at many more places. Most of these germs do not cause disease and a lot of them are in fact extremely useful for us.

The highest concentration of microorganisms in the body is in the digestive tract. These microorganisms are referred to as gut flora. These germs are so useful to us and help in digestion that the gut flora is often referred to as the “forgotten” organ. According to some estimates there are nearly 1000 different types of microbes in the human intestines. Some of these have been identified but a large number of these have not been because it is extremely difficult to grow these species in a lab.

The germs in the gut help us in a number of ways:

1) They aid digestion. There are a number of carbohydrates that we could not digest if our intestines were not full of these germs. We lack the enzymes needed to process certain starches, sugars and fibes. The germs help us digest this stuff. And as a result of this we can get more energy from the food that we eat. Experiments have shown that if we did not have gut flora we would have to eat 30% more to maintain the same body weight.
2) The microbes that constitute the gut flora help save us from diseases caused by harmful germs. The useful germs stick to the intestinal wall creating a wall or barrier that harmful germs are not able to cross. So the harmful germs are not able to infect the intestine. Also the good germs try to kill the harmful germs because they do not want any competition. If we did not have gut flora we would get illnesses of the digestive system very frequently.
3) The gut bacteria help train the immune system to be able to identify pathogens. The good germs stimulate the immune system to produce antibodies to fight pathogens. The immune system learns to fight the harmful pathogens while leaving the good germs unharmed. The gut bacteria also help train the immune system to not react to cells of its own body- allergies. So the presence of gut flora helps prevent allergies.

Okay. So we have established that gut flora is extremely useful for us. The question is : how do we acquire it? The intestines of a fetus is sterile. The acquisition of gut flora happens during or after birth. If a child is born naturally, it acquires gut flora on contact with mother’s feces during birth. However when a child is born by caesarean section, the acquisition of these good germs happens after birth – from air, kissing, or feeding. So great is the difference between the gut flora acquired from normal delivery and c-section that a c-section delivered infant takes 5-6 months more to acquire a healthy concentration of good germs in its intestines. It may sound crazy but young elephants, hippos, koalas and many other herbivores eat the feces of their mother to acquire gut flora. Without a healthy concentration of gut flora these animals would never be able to digest the vegetation that they eat.

But these useful germs also have the capability of causing harm. Remember, they are in the human gut for their own benefit. Some of these germs produce toxins that can be dangerous. Some even produce substances that can cause cancer. These bad effects happen if the numbers are not balanced ie there are too many or too few of these “good” germs.

An excellent way to increase gut flora is to consume probiotics. Many such drinks are available in the market and contain large concentrations of useful germs. For example the popular drink Yakult contains over 100 million Lactobacillus casei bacteria per ml.

Under some conditions the population of good germs is drastically reduced. One example is the usage of antibiotics. When you consume antibiotics to counter an infection, the antibiotic has the sideeffect of killing the good germs in the digestive tract causing an upset stomach. So whenever one consumes antibiotics he/she should also take tablets, drinks or sachets containing large concentrations of useful microorganisms.

Lets now briefly discuss the useful germs found on the skin. The skin has the second highest concentration of germs with over 500 species. These germs also protect us from pathogens by either creating a barrier that pathogens cannot cross or by making the surface of the skin acidic which causes pathogens to die. The acidity on the skin is because of the lactic acid produced by the useful bacteria. The lactic acid mixes with sweat to create conditions in which pathogens cannot grow. Skin flora can also cause disease if their number becomes imbalanced or if the immune system of the person is weakened. Typical skin diseases caused by good bacteria are acne and psoriasis. Also if the skin is damaged, these good germs can enter the body and cause infection. So these germs are good on the skin but not within our bodies.

Note that everything in nature has a balance which if disturbed can cause other problems. So it is okay to wash hands or use sanitizers before eating food. But too much washing hands with soap or alcohol( in sanitizers) can cause the good germs to die and will cause infection by bad germs.

Finally before I end this VERITAS, a little poem by Ogden Nash:

‘The Germ’

A mighty creature is the germ,
Though smaller than the pachyderm.
His customary dwelling place
Is deep within the human race.
His childish pride he often pleases
By giving people strange diseases.
Do you, my poppet, feel infirm?
You probably contain a germ.


Go wondrous creature, mount where science guides
go measure earth, weigh air, state the tides,
instruct the planets in what orbs to run
correct old time, regulate the sun

Why do mangoes have such huge seeds?


North Indian summers can be terribly hot and a miserable time for the residents. Every year people hope that the summer gets delayed. And when it starts people wait eagerly for the monsoons to come and provide some relief from the terribly hot days. However there is one aspect of Indian summers that somehow makes it worthwhile- mangoes. Mangoes are the most delicious fruit in the world and are rightfully given the title of the “king of fruits”. If there were a competition of deliciousness in fruits, mango would win it by a huge margin. Of course, papaya would come last- maybe it would have to pass the test of being a fruit with “grace marks”.

Have you ever wondered why mango seeds are so huge? Compare them say with the seeds of an apple. Apple seeds are so small compared to the fruit but a mango pit can be several inches long. In this VERITAS we will understand the reason for the huge pit in mangoes and will understand some interesting facts about evolution.

First, let’s understand why the seed exists. Simple. The seed exists to create the next generation. A more interesting thing to understand is why the fruit exists. The fruit exists and is sweet so that animals may eat it and disperse the seeds. This is just one of the many ways in which a plant disperses its seeds to give life to its offspring.

There are other methods too. Some plants have seeds that get entangled in the fur of animals and reach far away before falling off. Some other seeds like acorn and some nuts are foods in themselves for some animals. These seeds rely on animals like squirrels or mice trying to store them and forgetting where they were stored or not being able to eat the entire collection.

It is evolutionarily beneficial for seeds to be dispersed to great distances from the parent plant and also be dispersed in varied locations. If all seeds fall in one location and that location becomes unfavorable for the growth of the plant, then the entire next generation is gone. So plants “want” to disperse their seeds far away and in different places. However plants cannot do it by themselves. Animals provide an excellent way to do that. Other ways are to use the wind or moving water to reach distant places.

Now lets look at how fruit plants/trees use animals to disperse seeds. First they make delicious fruits and advertise the deliciousness by bright colors and delightful smells. Animals are attracted to the colour, smell and taste of the fruits. You may have noticed that most seeds have really hard coverings. Fruit trees/plants rely on animals eating the whole fruit and then passing the seeds out in their stools. The seeds have hard coverings to be able to stand the digestive juices in the stomachs of the animals and come out intact. Through this method seeds can travel huge distances- they use the digestive systems of animals as their transportation mechanisms! Now don’t be squeamish about it. This is how nature works. For an excellent discussion of how this works read Jared Diamond’s “Guns, Germs and Steel”. I have recommended this book in an earlier VERITAS article also.

The dispersal of seeds in animal feces is a hugely developed and important method for a lot of fruit plants and trees. To give you an example, there are some seeds that MUST mass through the digestive system of some animals to be able to germinate. There is a species of cucumber in Africa which is only found where an animal named  aardvark exists. It has no way to propagate  except by its fruits being eaten by aardvark and the seeds coming out of its feces. Guess what the cucumber is called. Aardvark cucumber. The fruit is so thick and the seed is so deep inside that without the aardvark’s help, the seed cannot come out. And the aardvark is equally “sincere” to the cucumber- the only fruit that the aardvark eats is this cucumber.

Another important thing is the timing. When a seed is not ready to be planted, the fruit is of a less attractive colour and does not have  good taste or smell. The fruit changes colour, smell and taste to become attractive/tasty for animals only when its seeds are ready to be planted. We call it ripe at that stage.

The interesting thing in all this is that it seems that plant evolution is acting in an intelligent fashion- using animals to disperse seeds far away. However a single plan does not even think. The “intelligence” emerges over millions on years and is caused by natural selection. Plants which succeed in dispersing their seeds far away using animals survive, the others just die. So using the animals is not a conscious intelligent choice- it just happens because other options die out.

Now, lets talk about mango. You may think that the above theory of propagation of seeds by animal’s feces would not apply to mango. You may say that the seed/pit of the mango is so huge that there is no animal that exists which can eat it whole and pass it out in its feces. You are right. There is no animal that exists TODAY which can eat a whole mango and pass out the seed in its feces. But there were animals at an earlier time in Earth’s history which could do this and mango evolved to be able to take advantage of these animals. I am talking about two extinct creatures: the giant sloth and the Gomphothere. A giant sloth could reach the height of almost 17 feet and weighed about 5 tonnes. The Gomphothere was an elephant like creature. These animals became extinct quite recently( in terms of geological time scale)- giant sloths became extinct about 5000 years ago and Gomphotheres became extinct about 10000 years ago, Mangoes used these animals for the dispersion of their seeds. These giant creatures ate mangoes whole and the seeds would come out in their feces.

Mango is not the only fruit to witness the extinction of its evolutionary “partner”. Avocado also suffered a similar fate. So mango and avocado are examples of plants who evolved to be able to take advantage of certain animals which have now become extinct. There is a scientific name for this phenomenon- evolutionary anachronism.

There are examples like this in the animal world also. The pronghorn antelope which lives in north America is built for speed. It can run at speeds of over a 100 km per hour. It is the second fastest animal in the world after the african cheetah. But why does it run so fast? There is not a single animal in America which can catch it. So how did it evolve to run so fast? There once existed a species of cheetah in North America. The pronghorn evolved to run so fast so as to save itself from the American cheetah.The American cheetah became extinct almost 11000 years back leaving the pronghorn to run superfast without a real reason!

A book that describes evolutionary anachronism in detail is: The Ghosts Of Evolution: Nonsensical Fruit, Missing Partners, And Other Ecological Anachronisms by Connie Barlow.

Let me now tell you an interesting thing about almonds. Fruits are tasty because they want to be eaten. Their seeds have a hard covering protecting them from digestive juices. However if a seed does not have a protective covering then it does not want to be tasty. It does not want to be eaten. Almonds are like that. Wild almonds are bitter and if eaten you could die from them because their bitter chemicals produce hydrogen cyanide- a deadly poison! This happened because almonds did not want to be eaten by birds. However thousands of years ago humans found a mutation of almonds which were not bitter. They started planting them and the almonds that we eat today are descended from this mutant type. So almonds evolved into their “sweet” form because of human interaction and preference.

Friends, no species in the world, animal or plant has evolved on its own. It has evolved in response to something else- living or non living. So we cannot understand any species in itself – it has to be understood as just one variable in a giant equation that involves every other creature also. And we should fear any variable of this equation becoming much bigger than others or causing other variables to vanish- the equation may become completely unbalanced and then the result may be disastrous. For all of us!





Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun


MYSTERIES OF THE BRAIN Part 23: What size is the moon?

Curious friends,

                Lets start with one of my favourite poems: “To the Moon” by Shelley

     Art thou pale for weariness

       Of climbing heaven, and gazing on the earth

       Wandering companionless

       Among the stars that have a different birth,-

       And ever-changing, like a joyless eye

       That finds no object worth its constancy?


                We have all noticed that the moon appears larger near the horizon and smaller when it is high in the sky. In this short VERITAS, I will talk about the reason for this phenomenon.

                The ancient Greeks had observed this and Aristotle had tried to explain this in terms of refraction and magnification caused by the Earth’s atmosphere. However the problem with the Greeks was that they never bothered experimenting. They would just make a theory and then assume that it is correct.

                In the 11th century the Arab/Persian scientist Ibn al-Haytham did a huge number of experiments on light and how we see. He wrote his findings in the “Book of Optics”( Kitab al-Manazir). Some scientists consider this one of the most influential books in the history of Physics along with Newton’s Principia Mathematica. This book set optics on a firm scientific foundation. The book studied reflection, refraction, visual perception, how the eye works. There is even a description of the pinhole camera! Al-Haytham even noted that the speed of light is finite and the speed changes in different mediums. He was also the first to apply geometry to the study of light forming the subject of geometrical optics. This book influenced a lot of research on light and its properties in renaissance Europe several centuries later.

                Ibn Al-Haytham also observed that the moon appears much bigger near the horizon and smaller high in the sky. He knew Aristotle’s theory also. Al-Haytham was a real scientist and experimented and immediately found that Aristotle was wrong. Using experiments and geometry Al-Haytham was able to show that if atmospheric refraction/magnification were to be taken into account, then the moon high in the sky would appear slightly larger than the moon at the horizon. However the moon at the horizon appears larger. So atmospheric refraction cannot explain this. Aristotle was wrong( as he has been on so many other occasions as well).

                Al-Haytham did many more experiments and geometrical calculations before coming to the conclusion that this phenomenon is actually an illusion! The brain is playing tricks on us. Al-Haytham was also the first to explain how or why this illusion actually occurs.

                You can yourself verify that this is an illusion by taking pictures of the moon at the horizon and high in the sky. They will have the same diameter!

                When we look at an object at a distance, it appears smaller but our brain knows that it distant and that is why it appears small. Our brain can judge the size of the object by judging its distance. That is how artists give an impression of distance on a flat canvas: as things move away, they appear smaller. This is called Linear Perspective. And in our minds the horizon is always a distant place. We see a mountain that appears so small at the horizon but our brain knows that it is much larger than it appears. Now the moon is at equal distance whether it is high in the sky or at the horizon. But our brain thinks that since it is at the horizon it is much farther away and it should be larger than it appears. So the brain compensates and makes the moon look bigger than it is.

                Note that the above is just one possible explanation of the moon illusion. There are more. Many more. There is a book on the Moon illusion in which 24 chapters are written by 24 different illusion researchers and they do not agree with each other. So this is not a closed topic!

                Another explanation is that when the moon is high in the sky there are no other objects to compare its size against. When it is at the horizon there are many things that we can compare against: the trees, the mountains, the houses and the image of the moon is bigger at the horizon than any of these objects. The human mind bases a lot of its perception on comparison. A thing placed next to larger thing appears smaller than it really is. However if the same object was placed with smaller things, it would appear bigger. The brain compares the size of the moon at the horizon with the distant and small objects at the horizon and gives us the impression that the moon is larger.

                There are more explanations as well. You can find them on the internet. Ibn Al-Haytham did a lot of experiments on illusions. In fact he was the first to show/suggest that the eye is just the place where the image is formed. The ultimate perception of seeing takes place in the brain.

                Now, you may ask, why is this still a open topic even a 1000 years after Al-Haytham first suggested that it is an illusion. Why are different theories of how this illusion works still around and there is no one explanation? The answer is simple: the illusion is not something that we can recreate outside the brain. The illusion is in the brain, caused by the brain. And what goes inside the brain is still an unsolved mystery. See the rest of the VERITAS articles on the mysteries of the brain at: VERITAS blog site(  Look at the “Mysteries of the Brain” tag).


Let me now end this VERITAS just as I started it: with a poem. This one is by Robert Frost:

I stole forth dimly in the dripping pause

Between two downpours to see what there was.

And a masked moon had spread down compass rays

To a cone mountain in the midnight haze,

As if the final estimate were hers,

And as it measured in her calipers,

The mountain stood exalted in its place.

So love will take between the hands a face….





Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun


MYSTERIES OF THE BRAIN Part 22: Classical conditioning and beyond

Veritas Readers,


                This is the 22nd part of The “Mysteries of the Brain” series.  All earlier episodes are available on the VERITAS blog site(  Look at the “Mysteries of the Brain” tag).

                Most of us have read or heard about Pavlov conditioning. However there are some lesser known experiments that he did and these experiments give some very interesting insights as to how our mind works. In this VERITAS we will study Pavlov’s experiments and their very interesting insights.

                Ivan Petrovich Pavlov was not really researching about how the brain works. He was more interested in digestion. In the 1890s he was doing experiments on digestion using dogs at the university of Saint Petersburg. He observed that the dogs started salivating whenever they saw the lab technician who usually fed them even if he arrived without any food. Pavlov wanted to understand this association and devised a series of experiments which hugely increased our understanding about our minds and our behavior.

                Pavlov started preceding the feeding of the dogs by the ringing of a bell. So first a bell rang and a few moments later the dogs were given food. After a few days of doing this Pavlov saw that the dogs started salivating as soon as they heard the bell. So the dogs had formed an association between the bell and the food. After a few days the bell was sounded without the food being given immediately afterwards. But the dogs continued to salivate at the sound of the bell. So the bell that now had nothing to do with food still triggered a salivating response in the dogs. This phenomenon is called conditioning( some people call it classical conditioning or Pavlov conditioning). Note that this is an subconscious effect.

                A few technical terms to help you understand other articles on Pavlovian conditioning using the above example

1)      Food: Unconditioned stimulus

2)      Salivation on seeing food: unconditioned response

3)      Bell: First this is a neutral object but after  the dog makes an association between the bell and the food this becomes conditioned stimulus.

4)      Salivation on hearing the bell: Conditioned response. This is not a natural response but has been learnt by association.

                A lot of our behavior is based on Pavlov conditioning. Sometimes a particular song may take you into a different time and induce a mood that you felt when you had  heard that song in the past. Let’s take the example of mathematics. We have millions of people with a fear of mathematics even in adulthood. Why? Because mathematics is associated in childhood with unpleasant feelings of fear, worry, and lowering of self esteem by “not-so-well-versed in psychology” teachers and parents. Let’s take another example: young children who suffer from cancer are sometimes given an ice cream before chemotherapy as a reward for agreeing to undergo the painful experience. Now chemotherapy induces nausea. Even when such a child grows up the association between ice cream and nausea remains causing them to feel sick even at the sight or smell of ice cream.

                Pavlov conditioning is a very powerful effect and can have a permanent effect on a person’s brain. Its proper use can be used to improve education in our schools. Of course, schools sometimes(!) end up accidently using it in a negative manner causing kids to hate studies. Pavlov conditioning has been used to cure phobias and in behavior therapy of criminals. In case of criminals, Pavlov conditioning is used to associate physical discomfort with their criminal thoughts. For example sexually deviant people are made to smell unpleasant substances when they are describing their deviant fantasies. This causes a permanent aversion to whatever they were thinking. Such methods have, in recent years come under attack from rights activists.

                Now let me describe a lesser known but very interesting experiment conducted by Pavlov. Before we proceed further I must stress once again that conditioned response comes from the subconscious. The conscious brain has no control on it. Pavlov showed some images to the dogs: whenever he showed the image of a circle it was followed by food. When the image shown was an ellipse, the dogs were given a small electric shock afterwards.  The dogs quickly learned to differentiate between the two images. When the image of the circle was shown, the dogs would start salivating and wag their tails. When the image of the ellipse was shown, the dogs would start whining and would try to run away. After a few days of doing this, Pavlov decreased the eccentricity of the ellipse( made it less longer and more circular) by a small amount. The dogs had no problem differentiating between the ellipse and the circle and the respective reactions to seeing them stayed. Pavlov continued to decrease the eccentricity of the ellipse but the dogs continued to differentiate the ellipse from the circle and their reaction of fear at seeing the ellipse and salivating when seeing the circle continued. However when the eccentricity of the ellipse was made about 9:8( nearly a circle but not exactly) the dogs were not able to differentiate- and their reactions suddenly became completely unpredictable and weird. They did not know how to react. They became very anxious and would whine and even defecate on seeing the image. And they now gave the same reaction on seeing the circles. Some of them became so disturbed to see the circle or ellipse they had a nervous breakdown. So the dogs had the nervous breakdown because they were no longer able to differentiate a happy stimulus from an unhappy one and their subconscious minds did not know how to react. Thus when the subconscious mind experiences a conflict that it cannot resolve, it causes anxiety, nervousness and at times even mental breakdown. Note that after showing the ellipses of 9:8 eccentricity, the dogs lost all differentiation of even normal circles and ellipses. The earlier conditioning was lost and a new behavior of mental disturbance set in.

                Pavlov now tried to train the dogs to differentiate the circles from the ellipses again. Once again he started using normal eccentricity ellipses and followed them with electric shocks, and he used images of circles and followed their images with food. This time the dogs had a much more difficult time learning how to differentiate between ellipses and circles compared to the first time. So he observed that once the differentiation was lost, it was difficult to create again. So in a sense the dogs had become less sensitive to external stimulus. These experiments show us that there is a difference between the first experience of something and subsequent experiences- the first experience will always make the mind condition to the stimulus much faster and better than subsequent experiences.

                Based on Pavlov’s findings, Eysenck formed his theory of extroversion and introversion. An introvert is more sensitive to external stimulus and easily conditioned. An extrovert is less sensitive and his subconscious brain is more difficult to condition. The reason for extroversion may be natural or acquired- maybe that person has been through that experience earlier and similar experiences do not cause the same conditioning and differentiation- much like Pavlov’s dogs shown the circles and ellipses after they had lost the differentiation.

                I think Pavlov’s experiments tell us a lot about how we learn things and how experience the world around us.  I don’t think we really understand how we can apply classical conditioning to enhance the learning experience of students and make studies less stressful and confusing. Also classical conditioning can give us extremely important insights into why people behave the way that they do and how socially beneficial behavior can be learnt not just by individuals but also by the whole society if we think of society as a collective conscience.

Pavlov received the Nobel Prize in 1904. But that was not for his contributions to psychology- that was for his studies on the digestive system.  

                After Pavlov’s experiments, a lot of psychologists started thinking about conditioning and its impact on behavior. They began to expand the scope of conditioning beyond classical conditioning. In general, Conditioning is an learnt association of things with each other at a subconscious level. When I say learnt I mean that this association is not natural but is acquired by a constant association which we experience in our lives. We have studied Classical conditioning. Now lets briefly look at Evaluative conditioning and social conditioning.

                Evaluative conditioning is the association of likes or dislike towards something related to something else that you may like or dislike. Lets take an example: if we strongly dislike someone say A . And a different person, B always is found with A, then we may start disliking B as well. This kind of conditioning is the basis of a lot of advertisements. You may like a celebrity and if he or she appears to like a product, you will start associating that celebrity’s characteristics with that product and will start liking it. That is why advertisers are very conscious about the brand value of celebrities. When a celebrity gets involved with a controversy( as they so often do), suddenly they start getting less advertisements.

                A very interesting experiment demonstrating evaluative conditioning was done some years back: a set of people were treated to a delicious free lunch and during the course of the lunch, a set of political slogans were shown to them. Another set of people were taken to a room filled with bad odours, and in the room they were shown the same political slogans. It was found that the free lunch subjects had a much more favourable opinion of the slogans compared to the people who saw the slogans in the bad odour filled room. This is evaluative conditioning.

                Another example which I am sure a lot of you would be familiar with. Sometimes during the naming of a new born child, parents tend to disagree with each other a lot on the choice of names. Why? Because they have associated names with characteristics of people who had those names! A husband may have had a favourite teacher named Suresh in childhood. So for him the name Suresh stands for love for knowledge, patience and kindness. However the wife may have met a uncouth, ill-mannered person named Suresh. And for her Suresh is a very bad name for a child. This is conditioning. Remember, all this is happening at a sub-conscious level!

                Now, lets talk about social conditioning. Society tends to favour certain behaviours and disapprove others. This causes a subconscious conditioning in the minds of individuals who grow up in that society. It may be related to what choice of professions are “better”,  what “kind of people” are to be liked or disliked. Even, the concept of physical beauty is related to social conditioning. The society floods us with images and messages of what is beauty and what is not. And people’s minds get conditioned to it. For example, why do Indians associate fairness with beauty? Social conditioning. Come to think of it, even patriotism is an example of social conditioning. Why should your love for humanity stop at the border? Because society wants you to think that the people on this side are our people and the people on the other side of that artificial line side are not ours- and not so nice. Social conditioning.



Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun


The Problem of Scale

Veritas Readers,


                A long time back ( 13 Feb 2000), I had written a VERITAS article “Size Does Matter” I read it again and felt that it was badly written and did not really convey what should have been conveyed. So in this article, I will try to do a better job.

Ken: What are you reading son?

Sid: “Amazing Animals”, papa. Aren’t the pictures pretty. [ He shows Ken a page which has a number of animals drawn on the page]

Ken: Isn’t it interesting that the mouse and the man seem to be of the same size. Also the whale seems to be smaller than the elephant.

Sid: Yes. It is just a drawing. But wouldn’t it be interesting if the relative sizes of animals were changed?

Ken: You mean make a mouse 10 times bigger and an elephant 10 times smaller, or something like that?

Sid: Yes. Maybe in a different world this is how it happens.

Ken: It is an interesting thought- take a picture of animal/thing from a book and scale it to whatever dimension. But do you think there would be no other problems?

Sid: Yes there will be differences. So if all our dimensions were made 10X then we will have 10 times larger houses and would eat 10 times more food. But what is the big deal. We will just get used to the new scale soon and then that scale would be our “natural” scale. In fact, I think that if magically the scale of everything around us were to be made 10X larger or smaller, we would not even be able to notice.

Ken: I think there is a flaw in your thinking. Galileo pointed this out in his book “Two New Sciences”.  Haldane had written a very interesting essay about this topic- “On being the right size”. The principle is known as the square-cube law.

Sid: Square-cube law?! What is that?

Ken: Let me explain using an example: Take a cube of side 1 cm, Now magnify each side by 10 times. What is the new side:

Sid: 10 cm.

Ken: What is the new area compared to old area:

Sid: [ thinks for a while] 100 times.

Ken: And the new volume?

Sid: 1000 times!

Ken: So if you increase the linear dimension by D  the area increases by  D squared and volume increases by D cubed.

Sid: That is correct.  But how does that relate to size of animals?

Ken: Imagine that you become 10 times larger in all dimensions. Your bones will become longer by 10 X. Your arms, legs etc – all longer by 10 X. Tell me what the cross section of the bones will be.

Sid: Thinks for a while….. umm. That is area so it will become 100X. But that is okay.

Ken: That is okay and probably expected but now tell me your new weight considering that the volume becomes 1000X.

Sid: 1000 times!

Ken: Don’t you see a problem now: a 10 times increase in size has caused 100 times area increase and a 1000 times weight increase because weight is proportional to volume.

Sid: So my 10 times thicker bones, with 100 times more area have to bear 1000 times more weight! EEKS! They will break!

Ken: Yes. That is correct. So the general principle is that if the linear dimensions increase by X the volume and thus the weight increases by X cubed. Therefore the shape cannot be scaled to any dimension. There has to be a change of shape to be able to support the many times extra weight.

Sid: And so every animal has a right  or proper size.

Ken: Yes. And that is why the very small people and very large people described in Gulliver’s travels cannot exist!

Sid: Interesting.

Ken: Let me give you some more examples: muscle strength is a factor of muscle cross section(area) and bone strength is a function of bone area and these vary as square of the dimension of the animal. However as we have seen, the weight is a function of the volume or the cube of the dimension. So the relative bone and muscle strength is much more in small animals than in large animals. You have seen cats jump from great heights and land softly. Try that with a horse! Or another example: an ant can carry 50 times its own weight, a man can carry about its own weight and an elephant can carry only a fourth of its own weight.

Sid: Wow. So you cannot just scale a shape.

Ken: Yes. Lets apply this principle to flying.  Flying is easy for small creatures. And the limit of size reaches very fast. A 2 times larger bird does not require 2 times more power – it requires much more than that.

Sid: Cool.

Ken: Now take the case of a worm. It breathes through its skin. And it has a straight gut to absorb its food. Now increase its dimension 10  times and its weight becomes 1000 times. So it will require 1000 times more food, 1000 times more oxygen and will excrete 1000 times more waste. But with 10 times increase in length how much is the increase in the area of skin and area of gut?

Sid: 100 times.

Ken: So that is not enough. So as an animal becomes larger it cannot breathe through its skin and cannot have a simple straight gut. A man has lungs because we need the 70 sq m of  surface to take in the oxygen that we need.  And our size is the reason why we have more than 25 feet of gut and all that is coiled up. Imagine a man with 70 sq metre of skin –if he has to breathe through the skin. And if our gut has to be straight- it has to be 25 feet long.

Sid: So it is because of our size that we need complex structures like lungs and long coiled intestines.

Ken: The human lung has 2400 Km of airways and 750 sq feet of surface area( equal to about a tennis court) in a small compact structure.

Sid: Wow!

Ken: Yes. As Haldane said: “The higher animals are not larger than the lower because they are more complicated. They are more complicated because they are larger.”

Sid: So it seems that larger animals have to do a lot of complex things whereas smaller animals can more easily adapt to their surroundings.

Ken: There are situations where being large is advantageous. Let’s take the case of heat dissipation from the skin. All warm blooded animals lose heat from their skins. Larger animals have less surface area with respect to their weight as compared to smaller animals. So large animals lose heat more slowly compared to small animals. So we need to eat less for our weight. A mouse has to eat about a quarter of its weight every day- most of it just to keep warm. And that is why there are no small mammals in cold countries.

Sid: Interesting.

Ken: And that is why babies of warm blooded animals are much larger compared to the adult – they have to maintain the temperature and large size gives that advantage. A cold blooded crocodile can have tiny babies less than an inch but look at our babies- much much larger. The smallest mammals like bats have babies about one fourth of the adult weight.

Sid: So size does decide a lot of stuff!

Ken: Similarly the eye becomes an efficient organ only if it is large. Read the details in Haldane’s essay. This is related to the number rods and cones and how things come to focus.

Sid: So life is very different at different sizes.

Ken: Yes. Even the forces that are important are different. Our lives are dominated by gravity. For a man, falling from even 10 feet can be “bad”. Anything more can be fatal. An ant could fall from a 50 story building and nothing happens.  However for small animals the force of surface tension becomes very important. An ant that falls into a drop of water may never be able to come out. That is why insects have a proboscis  to drink water.

Sid: Interesting.

Ken: So the next time you look at a creature, realize that it has that shape and size for a reason. And that size is most optimal for its body and its place in the natural world.

[ Just then the door bell rings. It is the pizza delivery man. Ken and Sid open the box and are delighted to see that the Pepperoni Pizza is just the right size – Large]



Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun


Extinction Events


                On 28th Nov 2011, I posted a VERITAS: Nemesis and Tyche – The myth and the hypothesis. In that VERITAS article I wrote about the theory that mass extinctions on earth occur approximately every 26 million years or so. In that article I also told you about the theories that scientists have proposed to try and explain these periodic extinction events. I told you about Nemesis and Tyche and how these disturb the OOrt cloud to cause these extinction events every 26 million years or so. You can read that article at:

                Angela Singh pointed out that the last extinction event happened 65 million years ago- the one that wiped out the dinosaurs. She asked how the 26 million year extinction period could still hold. I promised her that I would write a VERITAS to explain this. Therefore I am writing this.

                First, the periodic extinction event theory is a theory. J John Sepkoshki and David Raup, both paleontologists at the University of Chicago proposed this theory by analyzing fossil records of over 36,000 animal species from the last 600 million years. But remember, in science all knowledge is considered tentative. A better theory or new facts can always overturn a previously “accepted” theory. Einstein’s relativity replaced Newton’s theories. And some other facts may later replace Mr Einstein’s ideas. In short, the periodic extinction event theory is just another scientific theory which has certain merits but in no way anything more than any other scientific theory. Another problem is that such theories cannot be tested – one cannot create another earth complete with species. Also the timeline of the theory( 26 million years ) is so huge that it is not easily verifiable.

                Now, let’s come to the theory itself. Sepkoshki and Raup showed that the dinosaur extinction event ( 65 million years ago) was not the last extinction event. There were two after that: about 15 million years ago and about  33 million years ago. Lets now study the last the last two extinction events in a bit more detail. But first we need to understand as to what really is meant by an extinction event.

                An extinction event is a drastic reduction in the diversity and abundance of life forms on earth. Not all extinction events are of the same magnitude and same length in terms of time. Some extinction events are classified as major and others as lesser. The last major extinction event was 65 million years ago. It is commonly known as the K-T extinction event. The K stands for the German word Kreidezeit for Cretaceous. The T stands for Tertiary. It is also known as Cretaceous-Tertiary extinction event. It was a rapid extinction event- some scientists suggest that it lasted about 10 years. Some suggest a longer time frame of a few thousand. It may have been caused by an asteroid impact. This extinction event resulted in the extinction of 75% earth species in a relatively short period of time. The dinosaurs were wiped out and a new age of mammals began on earth.

                Before we go further lets understand what Cretaceous and Tertiary mean. Geologists do not like to talk in terms of years. Earth is 4.5 billion years old and talking in terms of years will make it very complicated. So the geologists have invented a geological timescale. They have divided the history of the earth into Supereons  composed of Eons which are divided into Eras. Eras are divided into Periods, Epochs and Ages. When we talk about Jurassic park we should know that Jurassic is the name of a Period which lasted from 199 Million years ago to about 145 million years ago. Similarly Cretaceous was a Period which ended 65 million years ago with the last major extinction event. What geaological time are we living in now? We are in Holocene Epoch of Quaternary period of Cenozoic era of Phanerozoic Eon. Phew, these names are complex!

                Now, let’s talk about the last two extinction events. The one that happened 33 million years ago was the Eocene-Oligocene event. Eocene and Oligocene are names of Epochs. Cretaceous and Tertiary are names of Periods. A period may contain many Epochs. So the major extinction event changed the Period but the smaller extinction event that occurred 33 million years ago changed only the  Epoch. This was caused by climate changes and lasted much longer than the C-T extinction event. Most of the species affected were marine or aquatic.

                The extinction event that took place 15 million years ago is known as the Middle Miocene disruption. Again Miocene is a epoch. This was because of major cooling in the earth’s climate. This resulted in many species dying including some crocodiles and turtles.

                And now let’s talk about something that we humans have done. Scientists have suggested that another extinction event is currently in progress- they call it the Quaternary extinction. This started during the ice age in Pleistocene about 40,000 years ago. But it has continued to the present Era: Halocene. In fact we are within this extinction event. There are two reasons for this current extinction event: Climate changes and Humans. The ice age started by killing a lot of species. But the humans soon took over most of the killing wiping out a huge number of species of animals and plants. For example, on the island of Madagascar, we humans have resulted in the extinction of almost all native animals in the last 2000 years. It is similar in most other places.

                We have to be careful, the earth’s ecosystem is a delicate balance which we do not understand completely. If we change it, we don’t know what may happen and how it may impact us humans. We humans have been on the earth for a very short time- if we were to shrink the history of the earth to 24 hours, the history of the human kind would only be the last 1.5 seconds! We homo sapiens came only 1.5 seconds ago in the 24 hour earth clock! That is how little we know the earth!

                But finally to uplift your mood, here is a little poem by Ogden Nash:

At midnight in the museum hall

The fossils gathered for a ball

There were no drums or saxophones,

But just the clatter of their bones,

A rolling, rattling, carefree circus

Of mammoth polkas and mazurkas.

Pterodactyls and brontosauruses

Sang ghostly prehistoric choruses.

Amid the mastodontic wassail

I caught the eye of one small fossil.

“Cheer up, sad world,” he said, and winked—

“It’s kind of fun to be extinct.”






Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun