Some Assembly RequiredNeil ShubinPantheon, $26.95

When descendants of ancient fish firsthauled themselves onto dry land, they didnt do so with lungs evolvedspecifically for that reason. The need to breathe air ultimately led to achange in the function of an organ the fish already had. Likewise, when birdstook to the air millions of years later, they did so using feathers that may haveoriginally evolved as insulation or as a way to attract mates.

In SomeAssembly Required, Neil Shubin, a paleontologist, explores these and othergreat evolutionary innovations, as well as the invisible genetic changes thatmade them possible. The book is an impressive chronicle of what geneticresearch over the last few decades has done to complement the story ofevolution, a tale once told through fossils, anatomy and physiology alone.

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Forinstance, studies show that the genes fish need to build swim bladders theorgan that helps control buoyancy are the same ones lungfish and humans useto build lungs. Such repurposing, of both genes and anatomical features, is arecurrent theme in the tree of life, Shubin notes.

In somecases, genetic mutations trigger the production of new proteins, which caneither serve new functions or perform old tasks more efficiently and, in turn,enhance the survival of the organism. In other cases, mutations cause genes tobe switched on or off earlier or later in development and at different placesin an embryo. These changes can alter the development of skulls, fins, limbsand other anatomical features, and sometimes result in totally new features.

Many ofthese tweaks may arise when genes duplicate themselves, a process that allowsone copy of a gene to retain its original function but frees up the additionalcopy to change and gain a new purpose. For instance, research suggests that thegene NOTCH2NL, which originated via duplication of a more primitive geneand is found in humans but not monkeys, triggers the growth of brain cells wheninserted into the DNA of lab mice. The gene probably contributes to humans bigbrain, scientists have proposed.

Viralinfections have also led to evolutionary changes in the host, Shubin pointsout. Syncytin, a protein that plays a vital role in the placenta of mammals, isa viral protein that lost its ability to infect other cells. At some point inthe evolution of mammals, the protein was incorporated into its hosts geneticcode and put to work, creating intercellular pathways that enable nutrients andother substances to flow between mothers and embryos.

By taking a historical perspective and recounting the gradual accumulation of knowledge about genes and their effects, Shubin transforms a complicated topic into a smooth and fascinating read.

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A new book captures how genetics fills in the story of lifes evolution - Science News