THE COOPERATIVE GENE

For all the talk of “selfish genes,” there’s considerable evidence that advanced life evolved from cooperation between genes.

Ridley (Zoology/Univ. of Oxford) contends that the existence of life appears to be a near-trivial chemical phenomenon. Shortly after conditions became favorable for life to exist on Earth, there were simple lifeforms growing in all available niches. Simple cells, the equivalent of our bacteria, may well have evolved on all planets capable of supporting them. But the step to complex life—the eukaryotic cell, with a nucleus and organelles—took much longer to develop, and may be rare in the universe as a whole. The eukaryotes appear to have come about in a partnership between unrelated lifeforms, one of which survived ingestion by the other and proved its value by enhancing the new cell’s ability to utilize energy sources. The ingested cells became organelles: the mitochondria, which enable the use of oxygen in metabolism, and choroplasts, the agents of photosynthesis in plants. But these adaptations (like a merger in the business world) required careful division of rights and responsibilities to avoid civil war. The most startling consequence of this primordial merger was the invention of sexual reproduction. Here, the male cell sacrifices its mitochondrial DNA, which the offspring inherit only from the maternal side. Ridley gives a detailed explanation of these processes in evolutionary terms, focusing on the exchange of genetic material and on dirty tricks certain genes play—and why, despite their selfishness, such “assassin” genes do not dominate the gene pool. Inevitably, the material is highly technical, especially in the latter chapters, but readers willing to work will get a clear view of some of the key issues in evolutionary genetics.

Worth a look for anyone with a strong interest in the biological sciences.