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It occurred to me some time ago that I often fool myself with this hand-waving term "many generations." Maybe professionals keep a clear idea in mind about what that really means, but I'm just an amateur, and I have found myself thinking of "many generations" as meaning hundreds. I wonder if some professional scientists are also misled or, at least, have their thinking clouded by the handwaving. For my own sake, I made a table of correspondences between years and generations, and I send it now in case it might be useful to someone. Corrections/annotations are gladly accepted.

1 generation of protoHuman: 20 y

5 gen/100 y

50 gen/millennium

500 gen/10 millennia - approx. length of "written" Human history

5000 gen/100 millennia - approx. the age of modern Human

50,000 gen/1 million years - approx. Australopithecus' span

100,000 gen/2 million years - time since Erectus' appearance

160,000 gen/3.2 mya - Lucy's approx. date

220,000 gen/4.4 mya - approx time since fossil of ramidus

11,500,000 gen/~23 mya - Proconsul (already tailless)

Pleistocene era 1,640,000-10,000 yBP (82,000-500 gen)time of possible bottleneck in H. evolution 60,000 ya (3000 gen) Alan Rogers

African Climate change ~15 mya (750,000 gen)

Last African (nonhominid) fossilApe ~13 mya (650,000 gen)

Gorilla diverged 8.3-10.1 mya (415,000-505,000 gen)

Human/Chimp divergence 5.8-7. mya (290,000-350,000 gen)

Ardipithicus ramidus ~4.4 mya (220,000 gen)

A. anamensis 4.2-3.0 mya (210,000-195,000 gen)

A. afarensis 3.9, 3.5, 3.2, 3.0 mya (195,000-150,000 gen)

A. africanus ~3.0-2.5 mya (150,000-125,000 gen)

Homo habilis ~1.6 mya ( 80,000 gen)

H. erectus ~1.8 mya (90,000 gen)

archaic H. sap. ~400 ky (20,000 gen)

early H. sap. ~130-60 ky (6500-3000 gen)

modern H. sap. 20,000 ky (~1000 gen)

H. neandertal 150-30 ky (750-1500 gen)

(Note: I received this from Glenn on the HBES ListServe and posted it here with his consent -- JB)

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