Posted by Tom [Zachary] on November 26, 1999 at 11:05:09 {2lTH7z2znEMW5QGx.y.2PaEpA0ijdc}:
In Reply to: *WOW! posted by DaJahVeu on November 26, 1999 at 08:11:39:
DeJahVeu,
Show us where one species ever evolved into another.
Speciation has been directly observed. I'm not sure the examples would satisfy you though, depending on what the term "species" means to you. As I tried to explain to you below using whales as an example, it can be a slippery term.
For example, the Siberian tiger Panthera tigris altaica and the Bengal tiger Panthera tigris tigris are obviously very closely related, but not exactly the same species. The are both subspecies of Panthera tigris even as are the Sumatran tiger and the White Bengal. In captivity, they can all be interbred.
Are you using the term "species" with a rigidity that does not recognize that gradual migrations of a single species to different locales and environments produces the degree of variation recognized by the term "sub-species?" In North America there are so many eastern and western sub-species as to be hard to count.
Or are you using the term "species" a little more loosely but still with a rigidity that does not recognize the common ancestry between different species?
For example the African lion Panthera leo and the Bengal tiger Panthera tigris tigris are the same genera but not the same species at all. They are also obviously related, but not closely related like the various subspecies of tiger are to each other. However in captivity lions and tigers can still be interbred. The hybrid result is either called a "liger" (lion father/tigress mother) or a "tigon" (tiger father/lioness mother).
The obvious implication is that the lion and tiger had a common ancestry -- else they would not be able to interbreed today and the obvious question is how far the differences between species could go, given enough time.
It's impossible to know what would satisfy you as proof of speciation unless it is known exactly what the term "species" means to you and how you draw the line between what you would consider to be distinctly different species.
Tom