Why are there so many different species on Earth?
This is an interesting question and it has to do with the tenacity and the diversity of life, both properties that we might discover out there in the cosmos. The simple answer to this question is that there are nearly an infinite number of DNA combinations possible. This incredible molecule is a marvel of chemical engineering that most people don’t really appreciate. DNA, which stands for Deoxyribonucleic acid, is responsible for the evolutionary process that led to us humans. In fact, DNA is needed for life to exist in the first place because one of the most important functions of living creatures is reproduction and DNA plays an important role in this amazing process.
How the DNA does this reproductive magic is a marvelous chemical story in itself. DNA is arranged in the biological cell in the form of long structures called chromosomes. During cell division, these chromosomes are duplicated by DNA replication.
The question you might ask is what does DNA have to do with creating another duplicate cell? That’s the job of RNA or Ribonucleic acid, which is a DNA chain spit right down the middle. The four base units on the RNA chain are used to synthesize proteins because the base units act as markers for the amino acids that make up a protein. In other words, each amino acid has an affinity for a specific base unit. The amino acid molecules line up according to the arrangement of base units on the RNA strand and then an enzyme (a biological catalyst) zips the amino acids together to make tissue proteins necessary for life. This is a very simple explanation for a much more complicated process that involves different varieties of RNA and various enzymes that are present in the nucleus of a cell.
Evolution of species occurs in one of two ways: one is random change in DNA brought about by radiation or chemical interference. The other is what Darwin called natural selection. This latter process is what causes all of the controversy because it’s based on a process that says that only the strong and the well-adapted species will survive. In other words it makes evolution random and thus not designed. I disagree with that idea because where did DNA come from? No one can answer that question. A molecule with the sophistication of DNA cannot be an accident of nature. The fact that a species adapts to a difficult environment and only the strong survive is in itself a glorious concept that couldn’t have been an accident.
This still doesn’t explain how the diversity of life came about. The only possible answer to this question is to say that life based on DNA has this property, this amazing ability to form all sorts of creatures that adapt to environmental conditions. This process is called biodiversity and it has had 3.5 billion years to work its magic. This diversity has persisted despite the Earth suffering at least three major extinctions when life was almost annihilated. Living creatures rebounded from these disasters, often reinventing their structures to adapt to the new geological era that followed these extinctions. These concepts are backed up with fossil evidence.
We modern humans are a product of this biodiversity. We evolved from a common primate that branched into apes, gorillas, chimpanzees and humans. This means that we humans did not evolve from apes, as is often incorrectly propagated since Darwin’s ‘Origin of the Species’. Apes branched off the line that led to us. Our branch was known as ‘Homo’ and it led to Homo erectus, which stood on two legs, and Neanderthals, and eventually to Homo sapiens, our species. There were several Homo species that died out. We are the end result of a torturous evolutionary trail down through geological history. Modern humans have only existed for approximately a hundred fifty thousand years, a mere drop in the bucket of time.
Thanks for reading.