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We can tell about when the split occured (about 150,000 years ago) by diffrentiating the degree of difference in the mitochondrial dna of the woman of today with fossils before that time.
I took an evolutionary biology course a couple of years ago (as a refresher) and the professor was actively involved in this research.
Extracting mtDNA from fossils to calibrate molecular clocks? Where has this been published?
BTW, the Eve hypothesis doesn't postulate extinctions of populations based on natural disaster, but rather purely on outbreeding the competition. Of course natural disasters happened too, but even w/o them, outbreeding accounts for our common maternal anscestor.
I didn't realize that the hypothesis explicitely postulated either. I thought that the original studies done in Wilson's lab out at UC Berkeley (Cann et al., Vigilante et al., etc...) simply calculated that the gene tree that includes chimps (the outgroup used to "calibrate" the molecular clock) and humans coalesced whenever it did (I don't remember how long ago they said it coaslesced. Note also that they did not compare human mtDNA with fossil human mtDNA to calibrate their clock. They did it by comparing to present day chimp mtDNA.).
Coalescence theory doesn't really involve WHY certain copies of a given gene aren't passed on to the next generation.
Also, although there are many definitions of species, don't they all require that the organisms in question be able to interbreed? After speciation for example, the 2 species can no longer produce viable offspring. (They may be able to physically have sex, but not produce viable kids)
Close, and generally true, but it doesn't always work this way.
There are certainly examples of distinct species that produce fertile offspring. Take for example, members of the genus Anas (ducks). Mallards can interbreed with pintails (less common) and with black ducks (more common) - I think to the point that someone at Cornell (those wacky bird people) was telling me that black ducks are endangered because they're intrebreeding so much with the ubiquitous mallard duck. There are many other examples like this.
Or take for example, a "ring species" hybridization can occur between populations that are adjacent to each other, but the populations that aren't adjascent, can't. (i.e. say populations occur from east to west in a line, A-B-C-D. A&B can breed, B&C can breed and C&D can breed. But A&D can't.) It's a bit of a gray area.
The most widely accepted definition (or the most popular? whatever) of a species was Mayr's biological species concept, which defines a species as a groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups (I think that's almost if not exactly verbatim - I guess I did learn something when I was studying for prelims last year!!) (under this definition, I guess all those ducks aren't in fact distinct species? I don't know...)
The problem with that is that it defines species in terms of animals TODAY.
There are also the evolutionary species concept (single ancestor-descendant lineage), phylogenetic species concept (smallest monophyletic group of common ancestry), recognition species concept (sharing a common fertilization system), cohesion species concept (most inclusive population with potential for phenotypic cohesion), ecological species concept (lineage that occupies its own adaptive zone and evolves on its own), and the internodal species concept (organisms are conspecific because they are members of a genealogical network between two permanent splitting events ) (thank you Doug Futuyma! I didn't remember some of these so I looked them up in my notes from his class)
You'll note that most of these do not explicitely require species to be able to produce viable offspring exclusively with conspecifics, per se. That's just sort of the outcome of it.
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