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Evolution is such a core part of biological studies that it is almost guaranteed to come up in an interview setting. If you think about it, there is almost no part of biology which cannot be discussed in the light of evolution and natural selection. First and foremost, what is evolution? Can you reply in one sentence? My favourite summary is:

‘Evolution is the change in frequency of a gene over time’.

This is an apt description as it shows an immediate understanding of how natural selection and evolution differ – a pair of terms that students frequently confuse and use (incorrectly) interchangeably. Natural selection describes a process where a ‘selective pressure’ (such as a predator or increasing temperatures) leads to the increase in frequency of a particular gene allele versus another.  Of course, there is another factor driving evolution called ‘drift’ which can also be thought of as luck! Let’s imagine a species of monkeys lives on a tropical island and these monkeys can have either black or white fur, a genetically determined trait. The frequency of white to black monkeys was 50:50. Now imagine that one day nearly all the white fur monkeys happened to be foraging on the beach while the black fur monkeys were foraging in the mountains. A surprise tidal wave occurs and washes away all the white monkeys on the beach. As a result, the ratio of white to black furred monkeys is now 10:90 – there has been a change in gene frequency, and hence evolution, but it was driven by genetic ‘drift’ rather than any process of natural selection!

In today’s blog, I wanted to draw your attention to a phenomenal piece of research that I think is essential to understand for any biologist interested in evolution. Throughout your studies you will likely have been taught some examples of ‘evolution in action’, most commonly the example of the emergence of antibiotic resistance, or perhaps the example of the UK’s peppered moth during the industrial revolution. Critics of these examples point to the fact that it is nearly impossible to find an example that is ‘natural’ and isn’t, in some manner, human influenced or driven. Well, now you have one! This amazing study looks at the change in frequency of alleles driving field mice’s coat color in Nebraska’s Sand Hills. In this example, the driving natural selection force is entirely natural in the form of predation (including eagles, foxes, etc.) and not from a human source (such as antibiotics driving resistance or industrial pollution driving wing colour with the peppered moths). Do read the article linked above and remember this excellent example when a question related to evolution next comes up in conversation, or indeed in your Oxbridge interview!

By Dr. Adrian Charbin

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