Humans are one of the most highly evolved creatures on Earth, which we are all aware of. I am also sure that most of us would have come across the word ‘species.’ ‘Species’ is just a criterion in the classification of organisms. There are billions of organisms out there. How did they evolve? From the cell to the bone to the skin to the eye? Did all of them emerge from Noah’s Ark as we believe?
Charles Darwin
No. According to scientists like Charles Darwin, all organisms weren’t just put there – they evolved. They adapted themselves to their surroundings. What’s most interesting is that most of these adaptations were accidental.
Here’s the science behind it: When a single cell undergoes division and the others, the DNA of a cell also divides. DNA or Deoxyribonucleic acid is found in the nucleus of a cell. It is responsible for transferring hereditary genes from your parents to you (the reason you look like your parents). For the DNA to copy properly, a strict process enables certain genes to check for mistakes and repair the DNA. However, like the man, these genes are not perfect and sometimes fail to find faults.
For example, let us suppose that the Reproductive cell of a female Brown Bear in the North Pole has met with a similar situation as above. So, out of the two cubs, she gives birth to, one is brown, and the other is white. Now, who would have an advantage? The white one, as it will camouflage better in the snow. So slowly, the white bear evolved as the Arctic Bear we know today. There are no Grizzly Bears in the North Pole. In this same way, all these accidental adaptations have led to the new species we know today.
Now let’s go smaller. The Eye is one of the most complex organs in our body. Surely, it must have had its origin, too.
It has been commonly accepted that the first forms of the eye were proteins called opsins formed about 540 million years ago. Opsins detected photons(Light signals) and sent signals to the brain. As they moved on, opsins became ‘eyespots’ in unicellular organisms like Euglena, a small red area near their rear end. These eyespots were able to differentiate light from dark, but this proved useful as organisms with ‘eyespots’ could reproduce better by sensing night. Eyespots are said to have changed 40-65.
Opsins are the colored strings in between
Next, there started to be a small depression in the animal Planaria (flatworm). With a deeper depression, more photoreceptors (small molecules that detect light) immediately gave a more precise picture, and the organism was able to identify the direction of light.
Planarian Eyes
Then the depression started to fold into a pouch. As this ‘pouch’ opening started getting smaller, the depression deepened further, giving organisms a more accurate picture.
As thousands of years passed on, the eye’s overall structure began to differ. The growth of more transparent cells prevented infections. Improvements included protection from UV rays, vision in water, and differentiation of colors.
Another remarkable improvement in the eyes was the formation of Lens. The lens is a transparent covering over the eye and can alter the light to focus on the retina. The lens is made of a molecule called Crystallin, which is one of the most specialized proteins in our body. Different types of crystallin give rise to various kinds of eyes, like how our eyes are different from a cat’s or an octopus’.
The lens of the Eye
The eye is one of the smallest parts of the body. If such a small organ itself has such a vast history that is enough to cover one full Wikipedia page, what would be the history of the heart? Or the lungs? Or the brain?
Indeed, it is rightly said that there are so many secrets to life. Will man recover them all?
