Talk:Common descent
From Academic Kids
I'm studying phylogenetic trees right now, and it occured to me that our ability to produce consistant trees using parsimony analysis is good evidence of common descent. Parsimony analysis is distinct from similarity based phylogeny construction because it explicity tries to recreate the path along which the molecules evolved. As a consequence, it is capable of distinguishing between similarity by convergence and similarity by descent. So first, I object that the ability to create phylogenetic trees based upon similiarity is evidence of common ancestory. Second, I think that this article should directly mention cladistic methods of phylogeny construction, and not just reference the phylogenetics article.
A common type of ancestor, right? I mean, maybe all life evolved from the same type of single-celled organisms that, it so happens, originated in several different places in the world--not necessarily from the exact same ancestor. Or does it really mean from the exact same ancestor?
Good to see you hear, John! --LS
- As I have seen the term used, it does indeed mean that all observed life descended from the very same ancestor, which is actually quite likely given the nature of speciation and the brutal pruning of the tree of descent. I include the weasel-word there because we know so little about what might have started the process in the first place that we can barely even speculate about forms of life earlier than those we have seen. Since we have not seen any replicator sufficiently simple to have conceivably arisen spontaneously (we only assume there was one), all those we have seen are products of reproduction as we see it now, so they are almost with mathematical certainty descended from a single individual. Even if similar mutations or chance events had arisen independently early on, it is mathematically likely that only one survived (it is even more likely that none would, but obviously at least one did). -- Lee Daniel Crocker
- Yes, LUCA is presumed to be one particular organism, not a group of organisms. If you are looking for the common ancestors of humans (an obligate sexual reproducer), then you are probably going to find a group of individuals. However, if the ancestor is a single cell capable of clonal replication, as LUCA presumably is, then I would only expect to find one ancestor. Going on this model, LUCA would have had "siblings and cousins" that existed at the same time as it, but those lineages went extinct either by chance or because the LUCA lineage included some innovation that allowed it to displace the other lineages. adam
Shouldn't this article be merged with the article on LUCA (Last universal common ancestor)? They cover precisely the same topic. We should move all the text from one into the other, and then turn the empty article into a redirect. RK 16:53, 1 Sep 2003 (UTC)
- There were several theories of 'common descent' that were not theories of 'universal common descent'. I will try to fix this article accordingly but in the meantime, "Common Descent" and "LUCA" should be kept separate.Peak 04:14, 5 Dec 2003 (UTC)
