How many times have you heard things like “If we evolved from Chimps – why are there still chimps?” or “My ancestors were not Neanderthals”? These are common objections vomited out by creationists who believe that individual species or kinds (whatever the hell that means) where created individually by an intelligent designer. This is in direct conflict with the evolutionary principle of common descent. What both these objections demonstrate is that the person making these statements does not in fact understand what common descent is, or has not looked the evidence that actually backs it up.
I am not trying to be disparaging to creationists because when I was a JW I dismissed common descent and biological evolution because it went against my belief system. I couldn’t believe that my mother, who was a nurse and friends, many of whom were very intelligent, thoughtful and sincere people, would reject this theory if it had any credence. When I researched subject I did look outside the Watchtower publications, but focussed on creationist books and websites, falling into the trap of confirmation bias. It can be really gut-wrenching to know that along held assertion is wrong, and it is easier to read materials that support your point of view.
For a theory to be held to scrutiny the evidence supporting it needs to be falsifiable. What does that mean? It means the theory needs to have the potential for some observation to demonstrate that the theory is false. For example if in the fossil record, the clichéd fossilised rabbit being found Cambrian rocks, would completely destroy the theory as we understand today.
So what do we mean by common descent? An evolutionary biologist will describe common descent as group of organisms that have a common ancestor. But in reality it goes further than that, in that all living organisms on Earth descended from a common ancestor that lived just under 4 billion years ago. This is not a belief, it does not require blind faith, it is a theory accepted by virtually all biologists because of insurmountable, falsifiable evidence. The purpose of this thread is to show using genetic and chromosomal evidence that common descent of species is a fact beyond reasonable doubt.
I am going to start with the evidence presented by Endogenous Retroviruses (ERVs)
What is a retrovirus?
The most commonly known retrovirus is HIV. But not all such viruses are quite as good at killing their hosts as HIV. R etroviruses also know as RNA viruses have their genes encoded in RNA instead of DNA. Like all viruses once they invade a host organism they need to make copies of themselves. Retroviruses need to use the cellular machinery of the organisms they infect to do this. In order to make itself compatible with the host cell (which is encoded in DNA) the retrovirus RNA needs to be reverse-transcribed into DNA. The virus uses an enzyme called reverse-transcriptase to transform their single-stranded RNA into double-stranded DNA so that it can be integrated into the genome of the cells it has infected. Once the DNA version of the retroviral genes have been incorporated into a cell's genome, the cell copies those genes as part of its normal replication process. Thus, the cell does the work of the virus for it.
Endogenous retroviruses (ERVs) are remnant genetic sequences where a retrovirus infected the germ cells (cells that gives rise to the gametes) of an ancestor of a mammals or other vertebrate. These genetic sequences are passed on to the next generation and now remain in the genome as genetic detritus.
More to follow.........