“There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”
~ Charles Darwin
Let us sit down for a special discussion with an open mind.
Suppose you and your friend sit down to take an examination. Outside, it is raining heavily. Today is your Bengali First Paper exam, where you have to write all sorts of interpretations and elaborate analyses of different stories and poems based on the given passages. Both of you are nearing the end of your exams when, suddenly, the invigilator comes over and confiscates both of your answer scripts. What did you do wrong?
The accusation is that you left your answer script open and your friend copied everything by looking at it. But your friend is extremely stubborn. He refuses to admit that he copied. According to him, whatever similarities appear at first glance are nothing more than coincidences.
But then a rather eccentric teacher walks into the classroom. He places your two answer scripts side by side and begins examining them. That eccentric man is determined to prove that your friend is lying.
The teacher counts the characters in both answer scripts and finds that there are exactly 12,487 characters in each. There are exactly 10 answers, and all 10 answers appear in the exact same order. There are 87 identical spelling mistakes, 32 identical strike-throughs in exactly the same places, and 19 sentences that end on exactly the same lines. There are 56 commas, 10 full stops, and every single one is in exactly the same position. Even the spacing between lines, paragraph breaks, and gaps between words are identical. Apart from the handwriting, everything in the two answer scripts is 100% identical.
Now you tell me, do you really think your friend’s answers matching yours 100% is a coincidence? Would you believe him?
Anyone who has read this much of my writing and understood it has enough intellect to see through such a blatant deception from a friend. I believe you also have enough sense to understand what I am about to tell you.
Now I am going to tell you three stories. Listen patiently, and at the same time, do not forget about your friend. In the middle of these stories, you and your friend will sometimes be sent to two beaches at opposite ends of the Earth, and at other times, you will both be seated for a ball-selection experiment.
Story No. 1:
Most mammals, such as dogs, cats, and cows, can produce vitamin C inside their own bodies. Humans, chimpanzees, gorillas, and orangutans, however, cannot. If we do not consume vitamin C through food, we develop scurvy. Cows, goats, and cats have a gene called GULO, which is responsible for producing vitamin C. If we examine human DNA, we will also find the GULO gene there. But it does not work. The reason is that there is a small mutation or defect at a specific location in the gene’s code, which has rendered the gene nonfunctional. Biologists call such genes pseudogenes.
Now, the renowned Japanese researcher Mitsumitsu Nishikimi of Wakayama Medical University conducted an interesting study. He and his team examined the DNA of chimpanzees, gorillas, and macaques and found that the same gene was also nonfunctional in them. And… what is even more astonishing is that the GULO gene in these chimpanzees and gorillas had become nonfunctional due to the exact same mutation at the exact same location. The very nucleotide that is missing from the human GULO pseudogene is also missing from the chimpanzee and gorilla versions at precisely the same location.
Among the 3 billion characters, or base pairs, in DNA, the mathematical probability of humans, chimpanzees, orangutans, and gorillas independently developing the exact same defect at the exact same location in their genes purely by chance is, quite literally, almost zero. The only logical explanation is that this mutation occurred in the body of a common ancestor, and all of us inherited that broken gene from that ancestor.
Suppose humans, chimpanzees, orangutans, gorillas, and macaques did not descend from a common ancestor. In that case, the probability of the same mutation occurring at the same location in the same GULO gene across our billions of base pairs would be virtually impossible.
Scientists have calculated that the probability of such identical changes, known as parallel substitutions, occurring is approximately 1.83 × 10⁻¹²… in other words, only once in 1 trillion instances. [1]
Story No. 2: The Story of Alu Elements
Before we get into the story of Alu elements, let us bring your friend into the picture one more time. Suppose you are placed in a room somewhere in Bangladesh, while your friend is placed in a room on the other side of the world, in Brazil. You have no way of communicating with each other.
Now, in both of your rooms, there are 30,000 balls. Each ball is numbered. You are both asked to pick three balls. You pick balls numbered 4567, 278, and 8908.
Now the question is, what is the probability that your friend will also pick those exact same three numbers purely by coincidence? The mathematical probability of both of you randomly picking three balls with exactly the same numbers is 2 × 10⁻¹³, meaning at most once in several trillion attempts! In the real world, such an event would be virtually impossible. This apparent impossibility could only become possible if there were some secret form of “communication” between the two of you, or if you had already decided beforehand which balls you would pick. Simply put, the only thing capable of overcoming this mathematical impossibility is that “connection” between the two of you!
Now, let us get into the story of Alu elements…
There are some strange segments in our DNA whose function is to make copies of themselves and insert those copies into other random locations in the DNA. These are called “jumping genes,” or transposons. Among them, the most well-known are Alu elements. There are more than 1 million Alu sequences scattered throughout the human genome.
When an Alu sequence inserts itself into one of the 3 billion base pairs in our DNA, it is an entirely random event. It can potentially insert itself anywhere in our DNA. Now, suppose the theory of evolution is false. Suppose the whole idea of common ancestry is false. In that case, Alu sequences should be scattered across different locations in the genes of different species, right?
But I am sorry to disappoint you. That is not what happened.
Scientists compared human DNA with chimpanzee DNA and found that thousands of Alu elements are located at exactly the same positions in the chromosomes of humans and chimpanzees! Think about it. Out of 3 billion base pairs, thousands of Alu sequences are located at exactly the same positions in the DNA of two completely different species!
Suppose chimpanzees and humans are not connected through a common ancestor. In that case, the probability of Alu elements independently inserting themselves at exactly the same locations would be mathematically almost impossible. Once an Alu element inserts itself, it generally becomes permanent. Therefore, these insertions cannot simply occur independently in exactly the same way. [2]
Story No. 3:
When a British gentleman named Charles Darwin came forward with the theory of evolution, he had no knowledge of genetics. That is a whole story in itself. But through anatomical and embryological similarities, he was able to build a remarkably strong framework for the theory of evolution. From the nineteenth century onward, as fossils were discovered in different parts of the world, scientists gradually developed an impressive picture of common ancestry. Even before the development of genetics, the fossil record had already provided a fairly clear idea of how closely related a species was to humans and how long ago their ancestors had existed as the same species. Primates are our closest relatives, followed by other mammals, then other vertebrates, and so on.
So, the opportunity to examine and test the theory of evolution under the magnifying glass of genetics came much later. Now imagine that after studying fossils and other evidence, evolutionary theory identified orangutans as our closest relatives. But genetic analysis revealed that our closest relatives were actually goats! Just imagine the situation. The theory of evolution would have been completely undermined!
But no, that did not happen. The evolutionary picture drawn a century earlier from fossils and the fossil record was, a century later, independently confirmed by genetics in essentially the same pattern. There are countless examples of this. Let us save those examples for another day and dive straight into Story No. 3.
Cytochrome c is a protein that is essential for energy production in the cells of virtually all organisms, from plants to animals. It is made up of a chain of 104 amino acids. Even if some of the amino acids in this chain change, the protein can still continue to perform its function.
When scientists began comparing the structure of cytochrome c across different organisms, they found:
- Human cytochrome c and chimpanzee cytochrome c are 100% identical. There is no difference between them.
- Now, what about a slightly more distant relative of humans, the rhesus monkey? There is a difference of only 1 amino acid.
- Let us choose a somewhat more distant mammal. How about a dog? There is a difference of 11 amino acids.
- Let us go even farther. Suppose we choose a vertebrate that is not a mammal, such as a fish. There is a difference of 21 amino acids.
- Now let us move beyond vertebrates and look at an even more distant organism. The difference between humans and yeast is 51 amino acids.
These differences increase in exactly the same sequence as the order in which, according to the fossil record, our ancestors diverged from one another. Even without looking at fossils or bones, scientists can determine who is related to whom, and how closely, simply by comparing the structure of this protein. [3]
Now, without the concept of common ancestry, such a pattern would be virtually impossible. The number of possible amino acid sequences for a protein is enormous, approximately 10^93, which is greater than the total number of atoms in the universe.
Within such an enormous “space of possibilities,” for exactly those sequences to be selected in a way that produces a specific tree-like pattern, or nested hierarchy, across all species would be almost impossible to occur randomly.
Now you tell me, how could all of this be a coincidence?
In some future discussion, perhaps we will explore how evidence of retroviral insertions (ERVs) has been found at exactly the same locations in the DNA of humans, chimpanzees, baboons, and orangutans. The mathematical probability of this happening by coincidence is so extremely small that even dividing 1 by the total number of atoms in the universe would still be difficult to use as a comparison! We will also look at how a gene called Nanog has become disrupted in humans and chimpanzees at exactly the same location and at exactly the same nucleotide. Perhaps one day, we will read the vast history of 3.5 billion years of evolution, carefully written layer by layer throughout our DNA.
Stay hungry, stay foolish…
References:
[1] Ohta, Y., & Nishikimi, M. (1999). “Random nucleotide substitutions in primate nonfunctional gene for L-gulono-gamma-lactone oxidase, the missing enzyme in L-ascorbic acid biosynthesis.” Biochimica et Biophysica Acta (BBA) – General Subjects, 1472(1-2), 408–411. PubMed: 10572964.
[2] Salem, A. H. et al. (2003). “Alu elements and hominid phylogenetics.” Proceedings of the National Academy of Sciences (PNAS), 100(22), 12787–12791. DOI: 10.1073/pnas.2133766100
[3] Margoliash, E. (1963). “Primary structure and evolution of cytochrome c.” Proceedings of the National Academy of Sciences (PNAS)