Why aren't our evolutionary ancestors extinct?

In a nutshell yes. It might be more helpful to think of diversity and parallel evolution. Thus, way back in time we split off from the apes. Both continued to evole but along different lines.

 

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Well sadly as my post (#19) alludes to we are talking about something virtually impossible. Guys...i dont know how to say this but...it just could not happen like that. At the very least a crucial element is missing from the equation.

 

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Evolution is like streams of water overflowing out of a larger stream or river. The larger stream does not need to dry up before the new smaller streams find the right levels from which to break out. The new streams then follow the natural contours of the earth and from them spring even more streams, as some of the older streams lose momentum and dry up and as some get even stronger; some, even join up with others creating more streams, ad infinitum.

 

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Not impossible, just improbable.

 

Good analogy. My question still remains though. If that ancestral predecessor still remains why would another species evolve? Surely other species wouldn't need to evolve from that one common species, or if it did surely the ancestors become obsolete. My understanding of evolution is species evolve to adapt to their environment more adeptly. However, if that species didn't need to adapt why would it evolve in the first place? And if it did need to evolve why would the previous species not become extinct due to its environmental ineptitude?

 

There is either a geographical, or some other separation that prevents the diverging species from jumping back into a common gene pool.

Ring species show the process of speciation in action. In ring species, the species is distributed more or less in a line, such as around the base of a mountain range. Each population is able to breed with its neighboring population, but the populations at the two ends are not able to interbreed. (In a true ring species, those two end populations are adjacent to each other, completing the ring.) Examples of ring species are


the salamander Ensatina, with seven different subspecies on the west coast of the United States. They form a ring around California's central valley. At the south end, adjacent subspecies klauberi and eschscholtzi do not interbreed (Brown n.d.; Wake 1997).​

 

Nope, doesn't answer my question though. If a species evolves the ancestor should become extinct or there would be no reason for its evolution.

 

I edited my post to include the part about ring species. The reason can be merely a variation in climate due to elevation or latitude. The ancestor stays where it is. Eventually, they evolve enough of a difference that they no longer breed with each other, thus becoming a new species.

 

EmmZ, there is no "need" to evolve anything. Either it happens or it does not. So the real question is not why it happens, but rather how.
The answer to the latter also helps to explain why ancestors to extant species (unless under very exotic circumstances) do not exist anymore.

Just to clarify the definitions. If we talk about speciation, we mean that two gene pools do not mix anymore.
Now let us envision a speciation event. We have first the ancestor species, let's call it A. Then due to some events (migration, flodding, whatever) population A splits into to two sub-populations: A1 and A2. Both diversify but do not exchange genetic material anymore (due to the separation). After sufficient generations bots subpopulation may have developed in such a way that they are unable to interbreed anymore: speciation has happened. The subpopulation A1 and A2 would now be classfied as two new speices: B and C, for example.
As you can see from this example, there is no separate ancestor population per se, as both split populations are subject to evolution themselves. However, it is quite possible that one of the two subpopulation (A1 and A2) stay genetically similar to their ancestors (the "whole" population A), nonetheless, logically they cannot be their own ancestors from a phylogenetic point of view.

 

Still, it doesn't make evolutionary sense for it to remain. Surely if a species evolves it needs to have specific requirements which would involve the eradication of the gateway species.

 

Say there are two islands. On one island, birds need a long beak to eat bugs out of holes in trees. On another, nearby island, they need short beaks to crack nuts. So one kind of bird happens to land on the first island, and after a while it evolves a long beak. Then it happens to find the second island, where the environment requires a short beak, so a short beak evolves. The first birds no longer recognize the second as their own, and as a result, they diverge into two species.

 

our direct evolutionary ancestors are dead.

 

Oh definitely CharonZ, the how is what I'm asking. The why is of no consequence here I agree. so I suppose my question might be if Species A gives rise to subspecies a1 and a2 how does species A not become extinct due to its environmental (or whatever) conditions becoming a cause for its own evolution?

 

That's besides the point draq, I'm asking about evolutionary predecessors still being around when their evolutionary offspring are. Surely if evolution is conditioned to happen there can no longer be conditions for that predecessing (pardon that bad grammar) ancestor to still co-exist in the same geological period.

 

EmmZ...the niche is not designed for anyone in particular to live in, the species just change their niche and that is their *adaptation*, our current success is yet to be tested on the long term timeframe, meanwhile in another niche some of our ancestors are still surviving quite well.

 

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Am I being a complete phylogenetic spanner here and asking inane questions?

 

The environment changes all the time, and there are variations even within one environment that can support new species.

 

Fundamental flaw here, we're not descended from apes, we share a common(oddly enough now extinct) ancestor.

 

...Who most probably fit the definition of ape.