But proponents of the so-called paleo lifestyle are taking it back a bit further—all the way to the Pleistocene.
In the Shadow of the Sabertooth: Global Warming, the Origins of the First Americans and the Terrible Beasts of the Pleistocene.
The habitat requirements of elk and their speed of migration are probably the same today as at the end of the Pleistocene.
Diprotodon, a gigantic fossil marsupial from Pleistocene beds in Australia, allied to the kangaroos.
Records of Pleistocene reptiles and amphibians from Florida.
But in the Pleistocene, at the time we are considering, the day of these modern creatures had only begun.
They are referred to the dawn of the Quaternary or Pleistocene period.
Darwin thinks that the climate of the Cordilleras has changed since the Pleistocene period.
Yet glaciation is now far less extensive than in the Pleistocene.
Now it is quite certain that the proportion of carbon-dioxide was greatly reduced in the Pleistocene.
The earlier of the two epochs of the Quaternary Period, from about 2 million to 10,000 years ago. The Pleistocene Epoch was characterized by the formation of widespread glaciers in the Northern Hemisphere and by the appearance of humans. Mammals included both small forms, such as saber-toothed tigers and horses and giant ones, such as mammoths and mastodons. Almost all the giant mammals, including woolly mammoths, giant wolves, giant ground sloths, and massive wombats disappeared at the end of the Pleistocene and the start of the Holocene. See Chart at geologic time.