How did animals end up with such bloated genomes?

It costs energy to maintain DNA. But not so much energy that it matters for organisms with big cells. (credit: Montelione lab, Rutgers)

Eukaryotes like us are more complex than prokaryotes. We have cells with lots of internal structures, larger genomes with more genes, and our genes are more complex. Since there seems to be no apparent evolutionary advantage to this complexity—evolutionary advantage being defined as fitness, not as things like consciousness or sex—evolutionary biologists have spent much time and energy puzzling over how it came to be.

In 2010, Nick Lane and William Martin suggested that because they don't have mitochondria, prokaryotes just can't generate enough energy to maintain large genomes. Thus it was the acquisition of mitochondria and their ability to generate cellular energy that allowed eukaryotic genomes to expand. And with the expansion came the many different types of genes that render us so complex and diverse.

Michael Lynch and Georgi Marinov are now proposing a counter offer. They analyzed the bioenergetic costs of a gene and concluded that there is in fact no energetic barrier to genetic complexity. Rather, eukaryotes can afford bigger genomes simply because they have bigger cells.

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