(May 30, 2014 at 9:46 pm)Heywood Wrote:(May 30, 2014 at 9:44 pm)Rhythm Wrote: Isn't every branch just some other branch past the starting gate? If "plants" or a monolithic sub-lineage why are so many infertile?
Every branch belongs to the lineage of life that all traces back to a Universal Common Ancestor.
Sure, it seems very likely given that everything seems to share immense amounts of DNA. But I wouldn't say there is any in-principle reason to rule out an alternative to the assumption of a common ancestor. It could well be that the conditions which give rise to life in similar but separate regions would develop along a narrow range of possibilities. I don't see how we can rule that out.
If abiogenesis no longer occurs it could be because the presence of more evolved models suppresses initial states of life. Or perhaps the necessary conditions no longer exist. Never under estimate just how much we don't know.