JoeG's Case Against Common Descent

[swamidass (S. Joshua Swamidass)]

@JoeG

The main case against Common Descent, ie the concept that life’s diversity has a common ancestor, is that we do not know what determines form/ body plan.

That is a non-sequitor on several levels. Most important, even if we grant there is ignorance (not total ignorance) about the precise determinants of form, there is independent evidence for common descent untouched by this challenge. That evidence comes, at least in part, from neutral evolution.

That is why wise ID advocates are always careful to qualify that ID is not (and should not be) an argument against common descent.

@swamidass

The DGM and common ancestry could coincide in different circumstances. For instance, if some species in the Precambrian experienced large infusions of information which led to radical new body plans, a signal could exist in the background for common ancestry, and a DG distribution of complex traits could exist in the foreground. This possibility should be studied at some point.

You are making the correct point that DGM and Common Ancestry (CA). Both can exist at the same time. There can be a signal for both CA and DGM. That is entirely correct.