Is there a Tree of life
Is there a tree of life? Most people have the impression that all the life on this planet originated from a single event. The idea being that all biology has DNA, so it all had to come from a single source. Other evidence for this idea comes from the fact that the difference between a human and say a reptile isn't all that much in terms of DNA. Small variations in the code make vast differences in species.
Certainly humans all have common ancestry; and we are obviously related to much of the life on the planet. So we can assume a tree of life of some sort. But there are a lot of questions as to how speciation works and how far back common ancestry goes.
It is assumed by most people that humans and primates had a common ancestor a few million years ago. But who is to say where we actually split?
There is an interesting fact that has recently been discovered. Life started on this planet very early on. As it happens, much earlier than anyone had thought. From what we now understand, life started on this planet less than a billion years after the earth was formed. The earth being 4.5 billion years old, we found bacteria that seems to have appeared as early as a billion years after the earth formed.
A bacteria is a complex system. For it to exist DNA has had to have time to develop. Cells have had to have time to form. So it seems that life formed as soon as the earth was solid or stable enough to sustain it.
But is DNA the beginning of life? Apparently not. Recent work by Sidney Altman, professor of Molecular Biology at Yale University has discovered that RNA can act like DNA even though it no longer does. This is because RNA can have “enzymatic function”. There is good evidence that suggests that the first life forms had single strand RNA instead of double strand DNA. It is being called: RNA world. Even now some viruses store all their genes in RNA and have no DNA at all.
Some scientists are even wondering if life could form without DNA or RNA, but with some other type of code or mechanism. This is being talked about at NASA. Scientists are even looking for other types of life right here on earth. For example, in a few inches of soil there might be millions of microbes. It came as a bit of a surprise to me that not nearly all have been studied extensively or even cataloged In the sea there are millions more we know nothing about. Seems that for obvious reasons we only pay attention to the ones that can harm us. They all look pretty much alike. Could there be life that did not come from our family tree right here in our own back yard?
There is no real concrete definition of life. Chris McKay, a scientist at NASA and Seti, is quoted as saying it doesn't matter that there is no good definition for life. “We will know it when we see it.” But will we? I did another essay on my own opinion of life so I won’t go into that in this one.
The interesting thing here is that if life began here very early on; really as soon as it could, basic life must be abundant out there. Recently we have found many new planets; some of which are probably very much like earth as far as size and position go. It would be very surprising to find no other life out there. But only time will tell whether life is special, or the default. I’d bet on it being inevitable.
Besides which, even here life springs up in places we never thought possible. There may be many life forms on planets where we couldn't survive. Perhaps even some in our solar system. It doesn't have to be intelligent life to prove the point. But again, we will have wait and see.
So there may not be one tree of life on this earth, or at least there may have been others that died out or even that co-exist with ours. In other words: life may not have been a single event on this planet at all. It may be that the formation of DNA/RNA is inevitable or the natural byproduct of the formation of certain types of planets and the electro-chemical interactions that take place just because they are there; as it were.
And though we know all of life on this planet is related, who is to say it all came from the same event and the same primordial sea or pool? We may have common ancestors with the primates, but it is also possible that those ancestors were not mammals or even reptiles. They may have been single celled animals. We may have developed parallel to them for millions of years rather than having split relatively recently. There is so much still to learn, and we have barely scratched the surface of it all.
Craig Venter and his institute have created the first artificial DNA and consequently a new species. Yes, he has almost created life from scratch, and soon will have. He is also the man responsible for sequencing the human genome. The only reason we can’t say he already has created life is because he used a bacterial cell to do it and replaced its DNA with his own code. Next he’ll have to build his own cell from scratch. I have little doubt he will do that in the very near future if he hasn't already.
These scientists like Venter and Altman are poised to change the world as we know it. What they have discovered so far has already altered the way we understand evolution. That is to say how it all happened.
It amazing to think that what makes us who and what we are comes down to acids, carbon sugars, phosphates, and four bases: thymine, cytosine, guanine, and adenine. That’s what our DNA is made of. The proteins that are manufactured by this code give us our traits and characteristics.
But so what if there is not one tree of life? Nothing really changes. In a sense all life is related because all life is made of molecules which in the end are all made of atoms; and they are the same all over the universe, as are the laws of physics which are responsible for how they all interact.
Life is amazing. And the more we discover the more amazing it gets.
More by this Author
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