- Education and Science»
- Life Sciences
The Case for Evolution: DNA - 10 Amazing Facts
Theological Motivations for Rejection of Evolution
I’m often surprised by the number of people, believers of faith mainly, that still wish to deny or challenge the idea that evolution is somehow unproven, inaccurate or indefensible in its positions. Of course, there are many reasons why these people appear confident in their skepticism, the least of which is disagreement with the recorded facts. It’s usually because of a rejection of the idea that man descended from primates or that the accounts in the Bible of God creating man may be challenged as wrong. Faith does not invite debate about its own dogma. It’s a matter of devout faith – a leap of faith. Scientific study, on the other hand, demands examination, study and question.
Over the past century and a half, scientists have added volumes of evidence to support the theory of evolution. The term theory is used, rather than law, as scientific study will adapt a corroborated set of observations to a body of theory while leaving debate open for additional investigation and inclusion. Laws, such as Newton’s laws of gravity are immutable cause and effect mechanical relationships. So the term theory does not suggest an uncertainty in the concept being proposed; quite the contrary. It’s an acknowledgement that further investigation is welcome to be added to the body of accumulated evidence. And many branches of science have contributed to the evidence that supports evolution: paleontology, biogeography, comparative anatomy and genetics. Genetics, or DNA studies makes a particularly compelling case. It not only gives us a history of the evolution of man out of Africa but also the link of man to all life on Earth. How so? To understand that you have to first understand what DNA is exactly.
In simple terms, DNA, (deoxyribonucleic acid), is how biological organisms store data. It’s genetic material stored in the chromosomes of the nucleus of cells and acts as a blueprint for how to make proteins that are then turned into flesh and blood in our bodies. It’s doing this even now in every cell in your body. DNA is also a record, much like a written record, of our genealogical history, viral infections and errors in coding. DNA is made up of units called nucleotides, the name given for a polymer (molecule made up of repeating subunits) of phosphate, sugar and a nitrogen base.
Universal Common Descent
If it’s to be called science, it has to be testable, and not a single test made has ever disproved that all life on earth came from a common ancestor. There are obvious differences between plants and animals but, at the chemical level, they all contain DNA in the same shape – the famous “double helix” that looks like a twisted ladder. What’s more, all DNA molecules – in both plants and animals – are made from the same four chemical building blocks (nucleotides): Adenine (A), Thymine (T), Guanine (G) and Cytosine (C). Some of the common ingredients in biological chemistry are:
- Polynucleotides - such as deoxyribonucleic acid (DNA) and Ribonucleic Acid (RNA)
- Polypeptides - such as proteins (large biological molecules, or polymers, consisting of one or more long chains of amino acid residues)
- Polysaccharides - such as starches and glucose
- Cytochrome C - An iron-containing molecule that carries electrons during the electron transport chain in cellular respiration. The protein is found in many lineages, including those of animals, plants, and numerous single cellular species.
What tends to suggest common origin in biochemistry are the same shared chemical ingredients and processes that are identical in all living creatures even though tens, hundreds or even millions of alternate configurations would work just as well:
- DNA, RNA and proteins all have the same chemical form even though dozens of other possibilities would work.
- All life uses the same four molecules call nucleotides in the DNA ladder, even though there are more than one hundred that could be used.
- All life bases its replication on the duplication of the DNA molecule. The proteins found on all life on earth uses the same 20 amino acids in their makeup. While there are almost 400 that could have been used. 1
- All life on earth shares the same universal genetic code built into its DNA. The letters in the DNA ladder taken three at a time, form coded instructions as to which amino acids should be joined together to form a protein. Every species on Earth uses this identical code to perform this function. For example, bacteria use exactly the same codes for making proteins that humans do.
- All life on earth uses the same metabolic pathways. Glucose is metabolized in the same 10 steps in the same order using the same 10 enzymes.
- There are enough possible genetic codes using the same amino acids for every species that has ever lived to have their own unique code. If there were no common ancestor from whom all life inherited this code, it would make sense to expect a wide variety of genetic codes. This would protect each species from inter-species viral infections such as SARS that began in birds and HIV that began in monkeys and then spread to humans. The lack of this variety indicates common ancestry.
- Some proteins are found in most all life on Earth. One of these is cytochrome C found in the mitochondria of all eukaryotic (cellular) organisms. This protein can be substituted from one species to another, as from a mammal to yeast, and the cells perform as normal. The gene that codes for this protein as therefore been around for a very long time and has been subject to sequence mutations over the billions of years it has existed. What can this tell us? First, all of these mutations are silent – have no effect. But it’s this coding that can tell us the genealogy of its owners. Humans and chimps have the same amino acid sequence for this protein including all of the silent mutations. It’s hasn’t further mutated in the six or seven million years since our lines separated.
- Cytochrome C is not unique. There are billions of other possible proteins that can perform its function, yet all living things on Earth share this common protein. This means again, common ancestry.
- Gene sequences contain pseudo genes - genes that stopped working and perform no function. The only reason a species would carry a copy of this gene identical in another species is by inheritance. So it stands to reason if you see these same pseudo genes across different species, they must have been inherited at some time in the past proving common ancestry. There are many common pseudo genes shared between humans and chimpanzees. They are in the same location in the gene sequence and contain the same mutations that corrupted it.
- Retroviruses like Leukemia and HIV make a DNA copy of their genome and insert it in the host genome. If this happens to the sperm or egg cells before conception, the retroviral DNA will be inherited by the descendants of the host. These are called Endogenous retroviruses or ERV’s. In human DNA, there are over 30,000 ERV’s. There are at least 7 identical ERV’s shared between chimps and humans located in the same place in the genome for each species. One of the most powerful demonstrations of common descent is the presence of identical shared retroviral elements at identical locations in the genomes of species. As retroviruses insert randomly into the genome, the odds of the same retrovirus inserting into the same location in the genome purely by chance is unlikely.
Retro Viruses (ERV's)
Looking at the finished product of a human being and examining the billions of gene sequence codes can sometimes seem like intelligent design.
A question that often arises when discussing the genome is the mathematic impossibility of the random assembly of this massive sequence. To answer that, let’s use a simply analogy: How do we get modern art without examining how we moved artistically from the Lascaux cave paintings to Roman frescoes to mediaeval iconography to the Sistine Chapel to Monet to Picasso to Pollock to post-modernism and to Conceptualism. None of these came into existence randomly. They were built on past successes. They require the existence of their antecedents. Fitness in one generation is rewarded by having the genetic configuration that gave rise to it resulting in offspring, which carry forward the characteristics that made them fit to breed before. And when you look at the tree of life from a genetic standpoint, we see simpler life forms like bacteria, with shorter genome sequences that are also present in higher life forms along with their own additional sequences.
Given a set of preexisting conditions therefore, you can conclude that natural selection should not be described as random as much as improvement on pass successful traits.