Two scientists propose that the jump from bacteria to complex life might be much riskier than previously imagined. Even on planets with earthlike conditions, plant and animal life would therefore be incredibly rare.
All cells need power. Some cells need more than others. Bacteria are widespread, adaptable, and hardy, mainly because they don't suck down a lot of juice. Eukaryotic cells, cells with compartmentalized sections and tons of genes, need so much energy that they have mitochondria - their own little power generators. Plants, animals, and humans have eukaryotic cells, cells with nuclei which house 200,000 times the genes of bacteria. Most people consider the nucleus to be the differentiation between bacteria and more complex life.
In an paper published in Nature, two scientist think that the actual key to the switch was the mitochondria. Doctor Nick Lane of University College London explains the difference:
This overturns the traditional view that the jump to complex 'eukaryotic' cells simply required the right kinds of mutations. It actually required a kind of industrial revolution in terms of energy production. . . . This gives eukaryotes the genetic raw material that enables them to accumulate new genes, big gene families and regulatory systems on a scale that is totally unaffordable to bacteria. It's the basis of complexity, even if it's not always used.
The problem is, getting mitochondria requires more than just one cell juggling its genes. It's one cell swallowing up an entirely new cell. There are cells which do this, but they are eukaryotes, not bacteria. So in order to become a eukaryotic cell, a bacteria has to . . . do things that almost only happen in eukaryotic cells. Although it's clearly not impossible, it's one more blow to the idea of complex life evolving on alien worlds, especially those much younger than the earth. And we thought the revelation of the crop circles hoax was a disappointment.