Is This a Real Atavism?

[Whag]

Here's an interesting and creepy article on an atavism, but is it legit?

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3014134/

I was under the impression "ontology recapitualtes phylogeny" was invalidated when Haeckl's embryos were found to be fraudulent.

[USIncognito]

Yes. An ativism is a structure that was shared with a common ancestor - in this case a reptile like heart - manifesting in a descendant being.

And no, ontogeny recapitulates phylogeny wasn't falsified by Haeckel fudging his drawings. It wasn't actually falsified either, just not correct. Embryos don't "become" ancestral forms during development. Structures that are similar in all vertebrates develop in embryos and then become different structures as they develop. I think the authors probably should have avoided that phrase in particular and just explained what atavisms are and why our evolutionary history causes them to happen.

[NeilUnreal]

Ontogeny probably appears to recapitulate phylogeny because developmental changes are less likely to be fatal to an embryo if they are added near the end of the process. This means that developmentally earlier embryonic stages are more likely to resemble the ancestral embryonic form than are later stages.

So although ontogeny does not recapitulate phylogeny in the strict sense, the way it appears to do so during embryo development is important in understanding of the role of development in evolution. The mapping of genotype onto phenotype via a process of development is a critical part of biological evolution.

-Neil