Assessment 9 out of 10
This is a superb book. It describes different worlds on earth in increasingly deep time, starting with the most recent and delving into the most different and furthest away from us in time. Halliday comments on the place value of ecosystems, our expectation of what we are familiar with, noting that “fossil communities do not map neatly onto modern preconceptions.”
He writes like a poet, “Across the dusty vista, ripples dance through the grass stalks bowed, as if by an unseen brushing hand.”
“Another of the earliest Paleocene mammals has been called Earendill undomie. In Tolkein’s Arda mythology Earendil is the voyager, the morning star that heralds oncoming joy, a reference to an Anglo-Saxon poem, which uses the image to describe John the Baptist, in Christianity, the herald of Christ”. Halliday doesn’t spell it out but this seems to be a metaphor for the way burrowing mammals survived the Yucatan Mass Extinction Event 66m years ago which eradicated land based dinosaurs.
A number of significant events or patterns are referred to:
Describing the Cretaceous 125m years ago “Song birds will not arise until the Eocene” (Greek New Dawn, coming after the Paleocene pre-/old dawn, “so the dawn chorus is not yet filled with the melodious complex tunes of perching birds.”
Beringia linking Alaska & Asia was isolated from North America by the Cordilleran Ice Sheet It was relatively warm but dry, as without rain and snow ice sheets did not form. The Mammoth steppe depends on aridity giving species the ability to migrate, following their niche. The grassland was like an enclosed courtyard surrounded by ice sheets and mountains blocking the monsoon. As summers warmed up, ice thaws from below and water fails to drain away resulting in peat growth. With acidification grassland lost its fertility, bogs becoming barriers to migration.
The Zanclean Flood 5.3m years ago filled the Mediterranean
South America was an island Continent, its animals unique. Its new climate with varying drought & rainfall was perfect for the evolution of grass, Mammals became herbivores adapted to the grassland. It is suggested monkeys are descended from those which rafted across the Atlantic 2/3rds the width of what it is now.
The Great American Biotic Exchange occurred as the Isthmus of Panama rose from the Caribbean, animals moving in both directions, but generally northerners won out. The Exchange began before the final closure of the Isthmus 56m years before present.
In the early Cretaceous deposits have been found in Lake Sihetun which show the feathers, colour & vibrancy of reptiles, killed with noxious gasses associated with vulcanicity and covered with soft deposits. The preference for colours and display has persisted in birds.
Gondwanaland the Great Southern Continent broke up in the Jurassic 180 m years ago, South America and Africa splitting from India, Australia and Antarctica. There are marsupials in both South America and Australia. The Monito del Monte from Chile is the only Australian marsupial in South America. It can only there relying to survive on its relation with the quintal tree thought to have begun as much as 70m years ago.
The Triassic-Jurassic Extinction event occured 201m years ago, the result of gasses released by magma. In the Jurassic, the world was in greenhouse state, temperate into the poles. Europe was an archipelago in the Tethys Sea mostly shallow with a huge diversity of life. Glass sponges were filter feeders building the largest reefs of which there is evidence forming bioherms, which stand out as limestone landforms when surrounded by softer rocks
Halliday describes different geological epochs and creatures and plants, which either still exist, but we may not have heard, of or have long disappeared, making frequent references to the glossary or Wikipedia a necessity. So with the poetry a slow read, which I didn’t have to time to finish, but one to return to.