Chemistry to the rescue!!!

Last Wednesday I decided to catch some Southern California sun during lunch time. Sitting on the concrete perimeter of the reflection pool outside Leavey Library at USC, I was enjoying my chicken pesto sandwich when I was approached by a petite Korean girl. She was in her early twenties wearing a denim mini skirt with a pink tank top.

As she sat next to me, we started talking. It was nice to have company as I was working my way through the sandwich. Imagine my surprise when she asked me if I had found Jesus in my life, after a mere five minutes of meaningless banter!

As a practicing Hindu, it was fun to discuss our religious beliefs, morals and values and our understanding of human life itself. But what struck me the most was the conviction with which she believed that our planet was about 6000 years old; even more, the fact that evolution is a conspiracy designed to undermine Christianity.

Our discussion soon turned into my fierce defense of science as I tackled the question of our planet’s age. I laid out geological measurement of time from thickness of the ice cores in the Antarctic, the slow movement of tectonic plates that have shaped the planet and then moved onto the chemistry used to determine our planet’s age.

I explained that everything is composed of unique materials called elements, the identity of the which is determined by the number of positively charged particles called protons within the nucleus, or center, of the atom, around which the same number of negatively particles called electrons revolve, just like the planets around the sun. Also residing within the nucleus are neutral particles called neutrons.

I continued explaining that each element can exist in multiple forms called isotopes. Some isotopes are stable, others are not. The unstable ones break down to give stable elements at a constant rate in a process called radioactive decay. Using this constant decay rate, the age of rocks, fossils and the earth itself can be predicted. Using the uranium-lead radioactive dating, earth’s age is calculated to be about 4.5 billion years, I concluded.

Having established to my satisfaction, but not necessarily hers, that earth is very old, I moved on perhaps the more controversial topic of evolution. Being a biologist, this was home turf for me. I took her from a prehistoric earth where life first evolved as microbes to the present day, interspersing mass extinctions, identification of missing links and finally our development as a species.

Just as Uranium-lead radioactive decay was used for measure the age of the planet, age of fossils is determined by carbon-dating. Elemental carbon exists in three major forms- C12 with 6 protons and 6 neutrons, C13 with has one extra neutron and C14 with two extra neutrons. While the first two isotopes are stable, C14 is not. It constantly decays such that its quantity is halved every 5780 years.

Measuring the relative abundance of this isotope underlies the radiocarbon dating we use to estimate the age of most fossils upto about 60,000 years back.

She respectfully listened to me. But still believed that our measurements were incorrect. I know she was not convinced, but I was hopeful that our discussion would make her give science a second chance.

As I left for my class, I remembered something from an undergrad biology lecture. Most biological molecules do not survive even a few million years. How did we ever know that life existed 2 billion years ago? I couldn’t believe I had never given a moment’s thought to this.

Seeking an answer, I spoke with Dr. Kenneth Nealson, Wrigley Chair in Environmental Studies and Professor of Earth Sciences and Biological Sciences at the University of Southern California. “We have geology to sink our claws into”, he explained.

“If you had a twelve-pound ball and a thirteen-pound ball to throw over the fence. You started to get tired and pretty soon the twelve-pound ball would be dominant”, he explained.

Similarly as carbon is processed, enzymes prefer to use the lighter C12 to the heavier C13, such that over long periods of time all or most of the carbon in these biological molecules is composed of lower atomic weight carbon. Life prefers low carbon since it requires lesser effort to process it.

If carbon were to be incorporated into molecules by random chance, then the isotopes would be in the ratio of their natural occurrence.

Thus, by comparing the ratio of isotopes in a molecule to its relative abundance, the source of the molecule can be deduced. The same holds true for other molecules significant for biological processes including oxygen, nitrogen and sulphur.

So robust and accepted is this science that this underlies NASA strategy for searching life on Mars. The Mars Science Laboratory onboard the Mars Rover Curiosity, due to the launched on 26^th November 2011 by NASA, has an atmospheric sensor called a tunable laser spectrometer, a device designed to analyze the relative abundance of elemental isotopes in the Martian atmosphere.

If the methane on Mars were an outcome of biological processes, then the results would show skewed abundance of C12 methane, thus pointing to the existence of at least microbial life at some point in history.

There is always more to learn, I told myself as I left Dr. Nealson. I am glad to have been open to talking to a complete stranger.


NOTE: This blog has been submitted to the Nescent Evolution themed Blog Post Contest 2011 for consideration for a travel award to Science Online 2012 conference in Raleigh, North Carolina. More information at http://blogcontest.nescent.org/2011/10/12/win-a-travel-award-for-best-evolution-themed-blog-post/

I am, therefore I think

Antonio Damasio takes exception to Descates’ observation, “I think, therefore I am” in his 1994 book ‘Descartes’ Error’. The overarching theme of the book is exploration of the concept of self, and identifying the physiological processes that underlie decision making of individuals.

Rather than a simple exploration of an idea, Damasio methodically takes his readers through the scientific process involved in addressing any problem. We start the book with identification of the issue at hand, introduction of the various players, development of a hypothesis, designing of experiments to test it and finally interpret the results to inform the greater community of the inferences.

The first third of the book concentrates on case studies. We are introduced to various patients and the brain lesions that have impaired their emotional and decision making capabilities.

Without lowering the level of discourse or easing up on the use of scientific jargon, Damasio provides a platform for teaching his audience about the overall anatomy of the brain, the difference between the cortical and sub-cortical structures. He then dwells into the structure, function and connectivity of the neurons, their biochemistry about the neurons, their parts, roles and finally the neurochemistry of the brain.

As we go from one patient to another, we learn about different brain structures and how lesions or injury to these parts are associated with different symptoms.

Damasio spends a decent amount of time explaining the molecular basis of behavior. Not only do we learn about the influence of the brain on the body and that of the body to the brain. Additionally, he explains how human control over our instincts as being a possible outcome the brain circuits that have evolved to learn acquired social rules.

Where Damasio shines the best in his book is the distinction that he draws between emotion and feeling. While emotion is the body state, representing the electrical and chemical make up of the body at a given time, feeling refers to the cognitive juxtaposition of the body images with context.

With these ideas in mind, we are next introduced to the concepts that underlie Somatic Marker Hypothesis, the theory of mind that analyzes the decision-making processes of our brain. Briefly, when presented with a stimulus, a thought or a future scenario, images are created in our brains, which result in somatic (body) changes manifested as something as simple as rising of the blood pressure. Presentation of any stimulus or a real life situation with social consequences thus leads to a possible physical change that can show our emotions.

He finally concludes the second portion of his book explaining how the somatic markers lead to inherent biases within the brain, which explains the different behaviors and risks that people are ready to undertake.

The third and final part of the book deals with experimentation to test the somatic marker hypothesis that was developed in the previous chapter. We learn of experiments designed to simulate real world complex decision making process. The results from these show how brain injury can lead to an impediment to sound decisions. This is used as a proxy for the bad social and economical decisions that patients of brain damage have shown in their lives.

All of this sets the stage for Damasio to explain his choice of the title. Descartes’s observation was based on his belief that the idea of self originates from the existence of a working brain and that it is the brain that distinguishes us from other animals. However, Damasio through his somatic marker hypothesis lays shows the opposite, thus correcting Descartes’ to “I am, therefore I think”. We learn of the constant feedback loop between the body and the brain that underlies our perception of self and that of others. Any breakdown within this loop leads to an altered, incomplete view of what it means to be a human being.

Sitting at the intersection of psychology, neuroscience and philosophy, I find this book highly enjoyable and recommend it book to anyone who wishes to explore what it means to be a human and if we can ascribe certain aspects of humanity to other species.

How can we save the Earth?

Millions of years of geological changes and biological evolution have endowed our planet with diverse ecological systems throughout the world. Not only do these ecosystems provide a shelter for its diverse plant and animal inhabitants, they are also responsible for providing us with the resources that enrich our lives.

However, at a time when the population of the world has reached a staggering 7 billion, not only is a greater need for space to accommodate us, but also an ever-increasing demand for food, water and other resources. 

The dilemma this poses to the citizens of the world and our governments is profound. How do we meet the requirements of the entire population without exhausting our resources for the generations to come?

While some of these resources are measurable, like the agricultural productivity of the land or the minerals extracted from the earth, others, like the carbon dioxide recycling by the trees or the protection marshes and mangroves provide against tsunamis cannot be easily assigned a monetary value.

When making projections about the number of jobs a project will create and the number of dollars it will pump into the local economy, what is usually not considered are the un-measurable services provided by our ecosystems.

What is the dollar value of the aesthetics of an ecosystem? Should we run out of space in San Francisco bay area, is extensive development of the spectacular California coastline near Big Sur warranted? Should apartment complexes prop up along the Grand Canyon or dense equatorial forests give way to the land for agriculture?

Not to forget other species we share the planet with. Is it worth the while to not encroach the Panda habitats in China? Or are the highways through the Serengti hurting the Cheetahs? 

The present laws of our governments are fragmented. Some regulate air quality, while others are concerned with water and then are the ones that deal with natural gas and endangered species. We lack is a comprehensive law that deals with the inter-relations of these.

Worse still, we do not account for the invaluable services that the ecosystems perform for us silently.

The cost-benefit analysis of any operation that we undertake needs to go beyond the immediate consequences. Rather, the long term future of our world needs to take center stage.

It is time for our generation to decide on the legacy we plan to leave for our posterity.