Bill Bryson - Goodbye to All That

This chapter is mainly about life beginning on earth, extinction of certain species and the survival of other species through these extinctions. If the events that Bill Bryson describes in this chapter didn't happen, we most likely wouldn't be here.

Bill Bryson compares 4,500 million years of earth’s history to one day.

4am - simple, single-celled organisms appear

8:30pm - microbes appear

9:04pm - trilobites appear

10pm - plants begin to appear on land

11pm - dinosaurs appear

And we, humans, only come in 1 minute and 17 seconds before midnight. On this scale we can see how recent human existence is compared to all other living organisms.

Scientists have been trying to find our possible ancestors, the first land-dwelling creatures. Plants began land colonization about 450 mya. Larger animals took longer to emerge, but by about 400 mya they were out of the water. Scientists envisioned these first land dwelling creatures to look somewhat like the modern mudskipper, which can jump from puddle to puddle in a drought.

A search began for the first animals to walk the earth. A man called Erik Jarvik held up this research for almost 50 years, after finding a fossil with the help of Scandinavian scholars, thought to be a land dwelling creature old enough to be one of the first creatures on land. The problem was that he took it upon himself to examine it. Nobody knew what he had actually found because he wouldn't show his work to his fellow scholars. Only in 1998, when he died, did the other researchers see his work. It turned out to be a disappointment because the creature found clearly had 8 toes not 5 and had a weak spine which could not be strong enough for walking. Scientists are still looking for a possible ancestor of the human race.

The Ordovician, Devonian, Permian, Triassic and Cretaceous periods were the five major “extinction episodes” of Earth’s history. The Permian period (in which the dinosaurs lived), 245 mya, ended suddenly and dramatically, wiping out at least 95% of life on Earth at the time. Although scientists don’t know what exactly caused this mass extinction, they have theories of what could have happened. Some of these are solar flares, global warming, global cooling, and extreme volcanic activity. Many scientists believe that the most likely cause of this mass extinction is a solar flare, so big that it penetrated Earth’s magnetosphere and atmosphere, which literally fried the surface of the earth and most of the life on it.

Leeza :)