Here's what DeWitt says.
He references this paper,
Here is the abstract of the paper. It's a little heavy going, but you only need to read the first sentence, and you can skip to my observations that follow.
This is what DeWitt does not make clear, and this is how he pulls the wool over the eyes of his unjustifiably trusting readers: In all Old World primates, except chimpanzees and gorillas, there are two forms of this "C4" gene. A short one without an ERV inserted in it, and a long one with an ERV inserted in it. How come chimps and gorillas only have the short gene?
When an ERV enters the germ-line, it starts with just one individual. It may immediately die out if that individual fails to pass it on to any progeny. It may get passed on, and an increasing number of descendants might inherit it, but then again, it might wane once more and disappear from the population. On the other hand, it might eventually become "fixed" in the population - everyone has it, therefore it is impossible not to inherit it. On the third hand, it may continue to fluctuate. Some will have the ERV, and some will not. This is the case with the long C4 gene in all Old World primates, including us, except for chimps and gorillas. "Genetic drift" is a term for how gene variants can wax and wane in frequency even when there is no selection pressure to either remove them, or replicate them. ERVs, as failed retroviral integrations, are a prime example of genetic material that is typically invisible to selection. It is pure chance whether they disappear, become fixed, or linger in a subset of the members of a species
Now what could have happened in the case of chimps and gorillas? If we can't come up with a plausible scenario, the case for common descent from shared ERVs is in trouble. But we can. The common ancestors of humans, chimps and gorillas could have had "dichotomous size variation", just like the species that have it today. Then, just by chance, or genetic drift, the long C4 variant disappeared in chimps and gorillas. It did not in us.
This is sleazy deception from DeWitt, when he says,
Whoever wrote that has no right to try to use evidence to advance their case. They have already decided that evidence, whatever it is, is of no significance. And whoever they are, what sort of ego does it take to assume for themselves god-like powers of infallibility and total knowledge?
As always, do not take anything that appears in Answers in Genesis on trust. Do a bit of basic fact checking. You will soon see what a bunch of sleazy snake-oil salesmen they really are.
As Sir Winston Churchill said, "A lie gets half-way round the world before the truth gets a chance to put its trousers on."
(Return to the ERV FAQ)