Evolution Over the Next 2-3 Billion Years

Evolution has been at work since life first arose in small, warm puddles some 4 billion years ago. Evolution is the change in allele (variation of a gene) frequency in a population over time. It is the outcome of four forces (selection, genetic drift, gene flow, and mutation), the definitions of which aren’t the topic of this post, although I suspect many of you are familiar with selection. An interesting article by Jodi Brewster, Thomas Finn, Miguel Ramirez, and Wayne Patrick (I’ll refer to the authors collectively as Brewster et al going forward) raises possibilities for evolution in the future. Where we often think of evolution as bringing us to our current state, Brewster et al notes that our planet has as much as 3+ billion years before the sun expands to eradicate all life; evolution still has time to work.

It’s easy to think that evolution renders an organism to its most fit of all possible states. After all, we say colloquially that a species has evolved to its environment as a result of selection. It is true that selection will favor more fit phenotypes, often meaning more fit genotypes will become more common, but this should not be taken to mean that selection will ‘optimize’ a population. Selection, indeed all evolutionary mechanisms, only work on the genes available. Sometimes genes that would be very beneficial have never been ‘proposed’ by mutation, or getting to the ‘optional’ allele would force the population through an impassible fitness valley (more on these phenomena in future posts). 

Photo of plant cells with chloroplasts visible.
Micrograph of plant cells. Chloroplasts, where plant cells carryout photosynthesis, are visible as small green orbs. Note the cells’ rectangular shape. (Photo credit: Vierschilling)

As Brewster et al points out, many biochemical processes, those processes within a cell, have room for improvement, and synthetic biology demonstrated potential evolutionary innovations. Among those they report on, a particularly interesting case is that of carbon dioxide fixation, a fascinating process that all life depends on, directly or indirectly, but is notoriously inefficient. Biological engineering has demonstrated that carbon fixing structures within some bacteria could be transferred into hardy plants. The result: an organism that has now resistance to environmental factors but the carbon fixing efficiency of the bacteria. Could nature bring this efficiency to green plants in the future billions of years? Time will tell.

As mentioned above, stay tuned for more discussions of evolutionary mechanisms and trends.

© Peter Roehrich, 2016

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