It is true. It's genetic fact.
, that could be because people were infected by the same viruses at the same time
There are, give or take, some 3000 different such viruses.
There are about 3 billion potential insertion spots.
The probability of 1 identical ERV to form in 2 different species through 2 distinct independent infections, is thus 1 in 3000*3 billion.
For 2 such identical ERV's to form in 2 different species through distinct independent infections, is thus 1 in (3000 * 3 billion)^2
For 3 such identical ERV's to form in 2 different species through distinct independent infections, is thus 1 in (3000 * 3 billion)^3
We share HUNDREDS. And they map out in the same nested hierarchy as other genetic markers, matching the same phylogenetic tree (aka, family tree).
We obtain this same tree from various multiple independent lines of evidence.
Even including geographic distribution of species and even fossils. Comparative anatomy, DNA sequencing, full genomes, ERV's, other genetic markers,...
All independent lines of evidence that all converge on the same family tree.
Doesn't necessary mean any relationship, except maybe that they lived in same area.
It means exactly that.
When 2 individuals share the same ERV, it means a common ancestor had the initial infection which inserted itself into its DNA which was then past on to off spring.
That's literally what and ERV
is.