How does a species split?

[Yossi]

How does one species branch off into further species (example: humans and chimpanzees),and why?

 

New to the subject of evolution.

 

Thanks

[swansont]

Geographic separation (isolation) means the local population won't share genetic material with the outside population, so the mutations and selection pressure (or other factors like genetic drift) can make them accumulate enough of a difference that the can't or don't interbreed outside of their own group.

 

Isolation can also be temporal. There's a species of fly and some of them began laying eggs on hawthorns instead of apples. The fruits emerge at different times of the year, so even thought the flies are not geographically isolated, the populations no longer interbreed.

 

http://abacus.gene.ucl.ac.uk/jim/Sp/isolmech.html

[mistermack]

There is a lot of evidence that new species arrive more quickly on Islands.

The effect of isolation is one thing, but inbreeding can also produce fairly quick change in the island population.

And from a breeding point of view, an island doesn't have to be bounded by an ocean. It can be created by deserts that are too hard to cross, or rivers that can't be crossed as well.

 

In Africa, you have Bonobos and Chimpanzees separated by a river. (can't remember which one) And if the course of a major river changes, it can split populations and produce an "island" of population, leading to speciation. That might well have happened in the chimp/bonobo example.

[Yossi]

Great,coherent answers.

 

Thanks.