Tags

, , ,

After bees, the first ants appeared 0.08 bya. Ants, descended from wasps, took chemical and biological sociality to its extreme. There are solitary bee species, but there are no solitary ants. The 14,000 species of ant now occupy more of the world than we do.

It was in the late Jurassic (0.08 bya) that dinosaur diversity reached its peak. The most elaborate forms of dinosaurs, such as Tyranosaurs, Triceratops, Raptors and Diplodocus., This was still their world. The last tiny ancestor of Mice and Men scurried among the cracks of this dinosaur word 0.075 bya according to genomic evidence.

Everything changed in the second-worst documented mega-extinction in the history of life, (0.066 bya). A meteorite 7 miles across hit the earth near the Yucatan Peninsula, ejecting a cloud of dust from the Chicxulub Crater and debris to keep conditions in winter for years*. The outline of the crater is near the Yucatan peninsula, in southern Mexico. The cold-blooded dinosaurs, who depended on warm ambient heat to keep moving, were not able to withstand years of starvation, and the ratlike mammals feasted.   About half of the species on Earth disappeared after this event.

As with every mega-extinction, life blossomed to fill suddenly unoccupied niches. Through evolution of the ecological marketplace, life bloomed by discovering new niches. By 0.065 bya, the common ancestor of primates, bats, and shrews had evolved. By 0.062 bya), Miacids, the ancestors of carnivores, had evolved. By (0.055 bya) proto-rodents had evolved. By 0.054 bya, the first ancestors of cows and deer had evolved.   By 0.052 bya, bats had begun flying in the night skies. And by 0.05 bya, the first proto-horse first appeared in the fossil record. The fossil lineage of the horse in the 50 million years since is remarkably detailed and well documented.

The diversification of mammals 50 to 60 million years ago challenged even the “multis”, an early marsupial form that began to decline after 0.056 bya. They were the longest lived mammalian order ever, lasting over 100 million years.


Ptilodus, a Multituberculate survivor of the Cretaceous meteor impact.

Most important to our story as people, however, is the lineage of the primates. The dry nosed and wet nosed primates diverged about 0.56 bya, with the wet nosed primates enduring today as Lemurs, Lorises, and the Aye-Aye. By 0.055 bya, proto-simians had evolved opposing digits, allowing us to pick things up for the first time.

The Cretaceous-Paelogene extinction event was a brief interlude in a very hot period in the Earth’s history. One of the hottest periods in the earth history was 10 million years, and the hot period did not truly end until the Azolla Event (0.049 bya). Azolla was an abundant fern species at the warm arctic that sequestered a great deal of carbon, then sunk to the bottom of the ocean to be buried in sediment**, removing large amounts of carbon from the atmosphere. The Azolla Event was the largest carbon sequestration in the history of Earth, and changed our climate from a hot earth to a cooler Earth.

Now a little over 63/64 the way through the history of life.

* It is unknown exactly how many years, or if the meteoric impact was the sole extinction event then.

Advertisements