The scientists looked at the moth genome, identifying any difference between the two coloured samples. This could be done with the current day technologies, but could not have been investigated with this precision back in the day. Machines used would be similar to ones we saw on our field museum visit.
The specific gene found to have caused the mutation is called cortex.
They used the fact that the genome, over time, gets scrambled around as
pieces switch between chromosomes in a process called
close look at the stretches right next to the cortex
mutation showed very little scrambling; this was a recent event.
And with why this mutation was favoured -- natural selection. Where the mutation turned these moths from white to black, helping them with camouflage from predators in sooted surfaces, benefiting their survival rates. Eventually, the darker coloured population increased so drastically that the lighter coloured ones were outnumbered.
This article shows the importance of technological advances in solving biological mysteries from past events, like this highly recognised peppered moth. Perhaps with these new possibilities comes the need to ask whether is is necessary to spend immense amounts of funding and time to solve unknowns from the past, even if they do not necessarily aid discoveries that help solve current problems.