In “What the Literature Says about Chromosomal Fusion and Why It Says It” (Evolution News & Views, July 24, 2012), Casey Luskin responds to the “fusion flap.”
“Fusion flap”? (Okay, Humans have 23 chromo sets and chimps 24. Some researchers provide evidence that in humans, 2 fused at some point. Luskin and others dispute that evidence on its merits. But the main issue is the implications, does human chromosome 2 provide evidence of common human-chimp ancestry?)
All the recent yelling and shouting about the evidence for (or against) chromosomal fusion has distracted from the fact that in Science and Human Origins, my main argument about chromosomal fusion isn’t to question whether it took place. …
No, his main argument is that such an event does not necessarily demonstrate common ancestry.
Quoting a previous book,
Assuming that human chromosome 2 is fused as Collins claims it is, human chromosomal fusion merely shows that at some point within our lineage, two chromosomes became fused. Logically speaking, this evidence tells us nothing about whether our human lineage leads back to a common ancestor with apes. Nor does it tell us whether the earliest humans were somehow ape-like. (Science and Human Origins, p. 92)
So my main, or “key” point on this topic is that Carl Zimmer and others can present all the evidence for human chromosomal fusion they wish, and it still doesn’t tell us whether we share a common ancestor with apes. Unfortunately, this crucial point has been lost in Zimmer’s clamor over a citation he could have found if he’d just read the book.
Given that the real, underlying issue here is common ancestry as such, perhaps Luskin’s opponent, science writer Carl Zimmer, should address it more directly.
Luskin is surely correct in saying that the existence of a fusion event is not, by itself, good evidence. It needs to be considered in relation to other evidence.
For example, the fact that a friend has a key to a murder victim’s apartment is not evidence that he is the murderer. There may be no relationship between the key and the murder. Or the friend and the murder. There must be a long, convincing chain of other evidence before the key or the friend would assume a role in the story.
Luskin and Zimmer should discuss common ancestry directly. Probably with more profit to the reader. What would either side consider good evidence?
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