Evidence for evolution tends to be based on a range of research findings rather than a single wham-bam knockout factoid. For many Creationists fossils are the basis for anti-evolutionary arguments and they may not be aware of the strength of genetics in confirming evolution/common ancestry.
In my opinion, the strongest single argument for common ancestry is the existence of Endogenous Retroviruses (ERVs) in cross species DNA. Unfortunately, this can be a tedious, hard-to-follow explanation using concepts unfamiliar to most of us.
I recently came across the ‘Stated Clearly’ YouTube explanation for ERVs which does an excellent job of explaining the link between common ancestry and ERVs in plain, non-technical English with animations. I pirated the video text to put together a written version of how ERVs effectively ‘prove’ common ancestry (see below).
For those of you who prefer Talking Pictures, the YouTube version is tacked in under the text.
OB
ERVs & Common Ancestry
Several decades ago, judgements about the ancestry of species (like humans and chimpanzees) were based largely on fossil comparisons. The discovery of genes and DNA created completely new and different ways of determining these relationships through genetic comparisons.
One method involves the analysis of Endogenous Retrovirus (ERV) DNA shared between species.
A retrovirus is basically a string of RNA which penetrates a cell, converts into DNA and inserts itself, at random, directly into the cell’s DNA chain. Once inserted, the retrovirus DNA is duplicated, as part of the cell DNA, every time the cell duplicates itself.
If an infected cell happens to be a sperm or egg cell involved in fertilisation, that cell’s DNA, including the inserted ERV, will become a permanent part of every cell in the newly created offspring. Given enough time the changed DNA will spread through the entire population and all of its descendants. A retrovirus permanently implanted into a species DNA is known as an
Endogenous retrovirus. The human genome contains thousands of ERV segments from a number of different ERVs dating back millions of years.
In 2003 the chimp genome was described and found to be almost the same as human DNA. Chimp DNA also included its own ERVs. This raised immediate questions:
Do chimps and humans share the same ERVs located in the same DNA locations?
If true could this be mere coincidence?
ERV’s insert themselves into DNA at random and there are at least 10 million potential insertion locations in the human genome. The odds for the same virus, inserted in the exact same location, in both chimps and humans, being coincidental is less than 1 in 10 million.
The odds of this coincidentally happening twelve times are one in 10 million multiplied by itself twelve times – a figure bigger than the total number of atoms in the observable Universe.
To check on the possibility of common ERVs, scientists searched chimp DNA for ERVs commonly found in human DNA.
They found
205 instances of
the same ERV implanted in the same location in both chimps and humans. The odds that this is a coincidence amount to an impossible one in 5.88 x 10^
1418 (588 followed by 1416 zeros).
Odds this high amount to certainty. Beyond any reasonable doubt, chimps and humans are descended from a common ancestor.
OB
DNA Evidence That Humans & Chimps Share A Common Ancestor: Endogenous Retroviruses - YouTube
