snip
> Another puzzling piece of this puzzle is the molecular-clock stuff.
> Last time I looked into this (admittedly a long time ago), I recall
> someone arguing rather strenuously that the pongid radiation (chimps,
> gorillas, and homo) could not have taken place more than three or
> four million years ago. Since Lucy looks pretty solidly on the Homo
> branch of that radiation (although evolution has done stranger
> things than allow a clade of afarensis to "backslide" into chimps
> and gorillas) I would guess that the estimated date for the pongid
> radiation has been pushed back to before the time of the Lucy
> fossils, but here I'm guessing. Would anyone like to elaborate on
> any of these points?
Last one I remember had the gorilla to chimp/human split at about
8 million and the human to chimp at about 6 million.
On the other hand, the east african rift dates to about 12 million,
though how long it took to really isolate breeding is a good question.
On the Aquatic angle, the start of rifting surely mucked up the river
drainages, which might well have generated a lot of lake.
Keith Henson