A welcome new exploration of the evolution of human and animal life on Earth.
Shubin (Organismal Biology and Anatomy/Univ. of Chicago; The Universe Within: The Deep History of the Human Body, 2013, etc.), provost of the Field Museum of Natural History, begins with a venerable anti-evolution argument. Evolution is supposed to occur when a new trait gives an organism an advantage. To live on land, an animal needs lungs, but lungs took time to evolve. What is the advantage of 1% of a lung….or 10%? Case closed? The author writes that “biological innovations never come about during the great transitions they are associated with. Feathers did not arise during the evolution of flight, nor did lungs and limbs come about during the transition to land….Massive change came about by repurposing ancient structures for new uses.” Many full-time fish breathe air with rudimentary air-exchange organs. Most have air-filled sacs with other functions but lunglike possibilities. Case open, and Shubin explores it with his characteristic enthusiasm and clarity. Since well before Darwin, scientists traced life’s development through fossils, which produced material but no explanation. Darwin’s On the Origin of Species provided significant evidence for a mechanism: natural selection. This converted many—but not all—scientists, who still had no idea how it happened. Progress in genetics after 1900 led to tantalizing theories, but only during the past 50 years has DNA technology enabled scientists to understand and even tinker with evolution. Readers who assume that organisms change when their genes change are in for a jolt, as the author explains that a gene may simply multiply dozens or hundreds of times or jump wildly across the same genome. Since the beginning, viruses have broken into cells and joined cellular DNA, sometimes wreaking havoc but often remaining forever and doing good. Organisms themselves occasionally combine forces. Mitochondria inside every cell and the chlorophyll in plants were once free-living microbes that are still present in some DNA.
A fascinating wild ride through the mechanics of evolution.