George R. McGhee, Jr. - Böcker

The invasion of land by ocean-dwelling plants and animals was one of the most revolutionary events in the evolution of life on Earth, yet the animal invasion almost failed-twice-because of the twin mass extinctions of the Late Devonian Epoch. Some 359 to 375 million years ago, these catastrophic events dealt our ancestors a blow that almost drove them back into the sea. If those extinctions had been just a bit more severe, spiders and insects-instead of vertebrates-might have become the ecologically dominant forms of animal life on land. This book examines the profound evolutionary consequences of the Late Devonian extinctions and the various theories proposed to explain their occurrence. Only one group of four-limbed vertebrates exists on Earth, while other tetrapod-like fishes are extinct. This gap is why the idea of "fish with feet" seems so peculiar to us, yet such animals were once a vital part of our world, and if the Devonian extinctions had not happened, members of these species, like the famous Acanthostega and Ichthyostega, might have continued to live in our rivers and lakes.Synthesizing decades of research and including a wealth of new discoveries, this accessible, comprehensive text explores the causes of the Devonian extinctions, the reasons vertebrates were so severely affected, and the potential evolution of the modern world if the extinctions had never taken place.

The invasion of land by ocean-dwelling plants and animals was one of the most revolutionary events in the evolution of life on Earth, yet the animal invasion almost failed-twice-because of the twin mass extinctions of the Late Devonian Epoch. Some 359 to 375 million years ago, these catastrophic events dealt our ancestors a blow that almost drove them back into the sea. If those extinctions had been just a bit more severe, spiders and insects-instead of vertebrates-might have become the ecologically dominant forms of animal life on land. This book examines the profound evolutionary consequences of the Late Devonian extinctions and the various theories proposed to explain their occurrence. Only one group of four-limbed vertebrates exists on Earth, while other tetrapod-like fishes are extinct. This gap is why the idea of "fish with feet" seems so peculiar to us, yet such animals were once a vital part of our world, and if the Devonian extinctions had not happened, members of these species, like the famous Acanthostega and Ichthyostega, might have continued to live in our rivers and lakes.Synthesizing decades of research and including a wealth of new discoveries, this accessible, comprehensive text explores the causes of the Devonian extinctions, the reasons vertebrates were so severely affected, and the potential evolution of the modern world if the extinctions had never taken place.

The metaphor of the adaptive landscape - that evolution via the process of natural selection can be visualized as a journey across adaptive hills and valleys, mountains and ravines - permeates both evolutionary biology and the philosophy of science. The focus of this 2006 book is to demonstrate to the reader that the adaptive landscape concept can be put into actual analytical practice through the usage of theoretical morphospaces - geometric spaces of both existent and non-existent biological form - and to demonstrate the power of the adaptive landscape concept in understanding the process of evolution. The adaptive landscape concept further allows us to take a spatial approach to the concepts of natural selection, evolutionary constraint and evolutionary development. For that reason, this book relies heavily on spatial graphics to convey the concepts developed within these pages, and less so on formal mathematics.