Hello Carol,
Great to see you, thank you for your comment, we certainly do have much to learn!
In this case I believe the regular extinction events at around every 12,500 years (due to interactions with our Sun) have not been taken into account of the standard model!
Keep well =D
Ah, the voice of reason - thank you!!! - "regular extinction events at around every 12,500 years (due to interactions with our Sun)" - the giant sloth, woolly mammoth, saber-tooth tiger and other awesome creatures, gone, and what will arise in their place... fish and other animals keep getting smaller in size because of ecological pressure to reach adulthood (and reproduce) before becoming food. Theories do abound.