It is another important evidence for the theory of evolution.
Endogenous retroviruses are essentially, viruses that have their genetic makeup inserted into our DNA. When living things are attacked by these viruses, the genes that contain the DNA of the viruses, depending on what cells they attack within living things, can be passed on to our children. and our children pass it to their children etc etc, just like all DNA is passed on to our progeny. Ok so, now, if you think about, a family tree. That of a kin of people. distant cousins and second cousins and third cousins and second aunts and uncles etc etc, all will be on small distant branches of a family tree. Whereas parents, first brothers and sisters, will be on primary branches.
With that understanding, lets say i am attacked by an ERV. ok so now, my children will have the retroviral signature within them. Now lets say one of my children are attacked by a second ERV. now my grandchildren will have the ERV signature of me, and my children's ERV within them (2 ERV traces total). so my grandchildren will have 2 signatures (1 from me, and 1 from my children), and my children will have 1 signature (from me). With multiple attacks occuring over time, the later generations of an organism will have more and more Retroviral traces within their DNA.
So in the picture above, we can see a family tree. The parents being on the left while the progeny being on the right. You have your viruses indicated by an orange color inserting themselves (attacking the grandparent) and all the predecessors containing that marker from the attack. And then again later in time (the children) get attacked again, leaving the grand children (gorilla, chimp, bonobo, and human) with both sets of viruses at current times.
Now, with this said, we can determine the relatedness of living things based on the number of ERV signatures they have within them. For example, i can tell my grandchildren are closer related to my children than they are to me, because they have more ERVs traces in common. And likewise i can tell that Chimps, bonobos, humans and gorillas are closer related to eachother than tarsiers or gibbons. And we can make a tree out of this.
Now, some people may say, well maybe the ERVs just happen to match up like our DNA does. Well, first off there are roughly 30 thousand ERV traces within our DNA. Thats 30 thousand, that have insterted into very specific base pairs of our genome which number in the millions. So it would be essentially like throwing 30 thousand darts at a dart board with billions of holes at random. And then our children identically threw 30 thousand darts and hit the exact same holes in the dart board of billions of holes by pure chance. The chances of this not demonstrating common descent are essentially non existent.
But heres the kicker, The phylogenetic tree of life that we create based on ERV traces, matches the trees that we create in other fields of science like paleontology. So, the order and sequence that i find bones in the earth, matches the order and sequence that i find ERVs in living mammals such as ourselves.
It essentially proves common descent between us and the animal kingdom and it proves our relatedness by family and ancestor.
Edited by iSilurian, 18 December 2011 - 08:30 PM.