Biology / The Student

Aiming for imperfection

The grand design. The world is so magnificent and perfect that it must have a designer. This is the basis for the watchmaker analogy, the argument William Paley put forward in 1802; “Suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place… There must have existed, at some point, and at some place or other, an artificer or artificers, who formed [the watch] for the purpose which we find it actually to answer; who comprehended its construction, and designed its use.”

Fifty seven years later Darwin’s theory of natural selection was published, and threw the whole idea of a designer completely off kilter as it explained how the evolution of the design came through a random selection of beneficial genes. Every now and then, organisms make mistakes when copying DNA, and these mistakes can pave the way to a completely new species of organism through natural selection.

But what if this isn’t just by accident, and nature has started making these mistakes on purpose? Research has shown that some organisms are more susceptible to these DNA mutations, pushing down the accelerator to drive evolution faster in certain conditions. Dr Nick Colegrave, an evolutionary biologist at the University of Edinburgh, co-wrote a research paper that discussed the possibilities of “experimental evolution” where organisms developed mechanisms to speed up their adaptability. The paper says, “The suggestion that there are characteristics of living organisms that have evolved because they increase the rate of evolution is controversial and difficult to study.

“Are there characteristics of organisms that function not to increase their fitness, but instead to increase evolvability? That is, are there traits that are selected and maintained because they increase the ability of a population to respond to natural selection?”

The elevated mutation rate in many species of bacteria suggests that yes, there is a tendency for some organisms to deliberately make more mutations in order to advance more within their current environments. Of course, mutations by definition are random so their outcomes cannot be controlled, making this practice a gamble that only certain organisms can indulge in. These organisms have to be producing huge amounts of offspring with relatively little effort for the risk of harmful mutations to balance out with the possibility of beneficial mutations. Hence why the organisms involved in this risky business are viruses and bacteria that can reproduce incredibly fast- some bacteria can divide every twenty to thirty minutes.  Organisms like elephants invest a lot more in their offspring, with twenty two months of gestation, parents taking about seventeen years to raise their young and the young taking around ten years to reach sexual maturity. So they have to be much more careful to control the mutation rate when copying DNA so all that effort does not go into raising offspring that will not survive to reproduce.

So the organisms gambling with experimental evolution have to be producing enough offspring that the higher levels of harmful mutations will not affect their population, but this is still quite a risk to take with their survival at risk. What situations do these organisms have to be facing to develop such dangerous reproductive techniques?

Experimental evolution is quite common within pathogen populations, pathogens being microorganisms that survive by harming their host, such as the HIV virus and the tuberculosis bacterium. These organisms live in a very hostile environment that is constantly battling to kill them in the battle between the defences of the host’s immune system and the attacks from the disease. They have to be able to develop new weapons as fast as their host, and research has shown that some bacterial genes are highly mutable, suggesting that they have begun to control the levels of imperfections within their populations, only allowing mutations to prevail within areas where their effects are less likely to be hugely detrimental to the species.

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