Re: Probability and origin of life

Dr. Mainul AhsanIn response to:

http://groups.yahoo.com/group/mukto-mona/message/7163

Hello Dr. Alamgir Hussain:

I will try to shed light on one of your questions, using my very limited knowledge of science. You asked:

> * Is having a favourable entropy on the earth means that evolution must have had happened?

Apart from favourable entropy and the right energy balance, there were many other favourable factors, such as the moderate temperature on earth, presence of plenty of water, oxygen, hydrogen, carbon, etc., that contributed to the particular form of cellular life we find on earth. In other distant planets where the conditions are not so favourable (from our perspective, of course), entirely different forms of life may exist, which I cannot prove or disprove at this time. Darwin's theory of evolution is about the evolution of species; it is not about how the first proteins, DNA, RNA, and living cell was formed. Darwin's theory points to a common origin of all living things; but how that first living organism came about is still under investigation by scientists. The answer will probably come from a multidisciplinary effort, including contributions from physics, chemistry, geology, meteorology, marine science, hydrology, genetics, mathematics, computer science, etc., and last but not least, the study of evolution.

Given the favourable conditions that led to the origin of life, another question that is often asked is: what was the probability that life would originate on earth? Was it a certainty or a chance event? A scientist once claimed that the probability is of the same order as that of a "tornado blowing through a warehouse and assembling an aircraft". I'll try to analyze this statement from my own point of view. Please note that my analysis may be completely baseless!!

Extremely rare events are happening all the time. The question is how to evaluate the probability of these events. Just for the sake of explaining, I will concoct an elaborate example. Please bear with me. Let us try to solve this problem: What was the probability on January 1, 1950, that a person called Mainul Ahsan, born on an opportune day of September, 1960, would write an e-mail to a person named Alamgir Hussain, born on a ceratin day of 1970 (just an assumption, using the Internet, from a Pentium-II PC, on the 6th day of August 2002, the subject line of which would contain "Re: Negative Entropy: Evolution and the miracle of design in the cell!!"

I deliberately chose the year 1950 because my parents did not know each other until 1951, the year they got married. Let us try to approximate the probability by compounding the probabilities of the following nearly independent events:

1) My parents would meet each other out of a population of 1 million in the city where they lived: p1 = 10^(-6)

2) I would be born from the successful union of a paticular healthy sperm (out of a few millions) and a particular ovum out of a few hundreds: p2 = 10^(-6)

3) The probability that the internet would come to existence: p3 = 10^(-6)

4) The probabililty that a company called Intel would develop a computer chip called Pentium-II: p4 = 10^(-6)

5) In the mean time, a search engine named Yahoo would come to existence and a group called Mukto-Mona would be born: p5 = 10^(-6)

6) I would join the Mukto-Mona group: p6 = 10^(-3)

7) A person named Alamgir Hussain would be born in 1962, join Mukto-Mona, and start a debate on evolution theory and miracles: p7 = 10(-20).

The debate would generate sufficient interst in me to post a message in this thread: p8 = 10^(-3)

etc. etc....

If we compound just the above partial list of very conservatively estimated probabilities (by multiplying p1*p2*...*p, we will obtain an infinitesimally small number, such as 10^(-60). This is a mind- numbingly small probability and yet it just happened!! How? Because the a priori probability was very small in 1950; but probabilities also evolve with time as other events occur (in accordance with the rules of Bayesian probability calculation). The a posteriori probability of the given problem started to become larger and larger with each of the above list of events having taken place. Right now, after the event has actually happened, the a posteriori probability of the stated problem is UNITY. However, my objective was to find out the probability as it would have been calculated in the year 1950. But who in his right mind would formulate this particular problem in 1950? Stated in a different way, what was the probability that back in 1950, someone would be interested in figuring out the probability of the series of events listed above? I think that the probability that anyone would be able to construct such a question before the fact is ZERO. Therefore, the problem we tried to solve may not be a valid problem at all from the point of view of probability theory. Now may I ask: what intelligent being on the year -1 could have attempted to calculate the probability of life originating on planet earth on a certain moment in the year 0? The answer would depend on whether or not you believe that "lifeless intelligent creatures" existed prior to the creation of life. We can ponder about these improper probability problems only because life was eventually created, after all.

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