Are ERVs (Endogenous Retroviruses) evidence for evolution that humans and chimpanzees are related and have a common ancestor? Consider the facts and you decide.
Summary of Facts:
1. Some viruses (we'll call them ERVs) insert their genetic material into the genomes of organisms in random places and this genetic material can be inherited. [Analogy: Imagine an ERV is like a food stain on a random page of a book]
2. In humans, there are >100,000 such places in our genome where genetic material from these ERVs has been randomly inserted. [Analogy: Imagine you get a book that has over 100,000 random stains of different shapes and sizes on different pages]
3. Over 99.9% of these >100,000 ERVs are also found in the chimpanzee genome in the same, corresponding locations. [Analogy: Imagine a friend gets a copy of the book and when you compare you discover that it, too, has >100,000 random stains, and 99.9% of these stains are in the same, corresponding places as your book]
What Would You Conclude? (What is the best explanation of the facts?)
A. Independent Ancestry: The human and chimpanzees genomes independently acquired >100,000 bits of viral genetic material in the same corresponding locations by luck. [Analogy: The two books independently acquired almost all of these >100,000 stains in the same places by luck]
B. Common Ancestry: 99.9% of these >100,000 ERVs are found in the same, corresponding places in the human genome and chimpanzee genome because humans and chimpanzees are related and have a common ancestor that already had 99.9% of these >100,000 ERVs in the places where they're found. [Analogy: The two books have >100,000 food stains nearly all in the same place because they are photocopies of a third book that already had 99.9% of these stains in the locations where they're found]