If you think of the origin of life as often as I do, you perhaps have a mental image somewhere of a fish bravely crawling out of ocean water on to ground. Perhaps you imagine it desperately clawing at the sands in its attempts to move deeper inland. Perhaps in your mind, the fish survives and prospers and its equally competent descendants turn — bit by bit — into animals that are more and more suited to life as land animals.
You aren’t wrong. But what you are probably forgetting is the many, many, many fish who died after failing to do what this fish succeeded in doing. And this fish is the mere opening note of a sad song that has been playing ever since.
Earth’s evolutionary history is a tragic tale full of death and lost possibilities. Species never get mutations — especially significant mutations — exactly right the first time around. Each attempt to change is tested under nature’s merciless gaze and more often than not, rejected.
Before the fish that made it, there were many fish which came out of the water and died moments later. And before that, there were many fish that died even before they could approach shallow waters. Some fish, before this, developed mutations that might have allowed them to survive on land, but continued to live underwater and made no use of the mutations (which of course, disappeared in the course of the generations that followed).
Picture, if you will, evolution as an infinitely long corridor. Each door, on either side, opens into a whole new corridor, each full of its own evolutionary possibilities. A mutation is the equivalent of a species struggling with a door latch. If the struggle works out, the door opens and the species walks through it into a world full of more possibilities.
Here is a rather crude example to illustrate the point. Human beings never evolved to grow wings and fly like birds. But there must have been a door in the corridor somewhere which would have allowed the wing mutation to pass through. Once on the other side, we would have travelled down a corridor full of doors that will then have given shape to the flying man’s evolutionary path.
But we never opened any of those doors. As a species, we never even opened the door that led to those doors. If, at some point in the past, human beings did begin to show signs of wings, these signs must have quickly disappeared because another door — another evolutionary path — proved more suited to our continued survival than flying did. We don’t fly because nature selected us to go down another evolutionary path.
And it is not just us. For each species that lives today, there are millions that never came into being. Of all the animals that could have existed on this planet, most do not.
If you are alive, you are extremely lucky. We were “lucky” not in the sense that we were “chosen” somehow. We were lucky in the sense that we are all that remains of a great big storm — an evolutionary storm that has raged on this planet since the first self-replicating molecules caused ripples in a pool of shallow water 3.5 billion years ago.
And the storm rages on.