Event
When it Happened
on Earth
(Myrs)
How long It Took to Complete (Myrs)
Possible Minimum Time (Myrs)
Origin of life
3800-3500
<500
10
Oxygen photosynthesis
<3500
<500
Negligible
Oxygen environments
2500
1000
100
Tissue multicellularity
550
2000
Negligible
Development of animals
510
5
5
Land ecosystems
400
100
5
Animal intelligence
250
150
5
Human intelligence
3
3
3