A 45-year study found that red deer in the highlands developed due to climate change, the birth pattern of deer on the island of Rum.
Warmer temperatures not only encourage deer to give birth earlier in the year, but they have also meant that the gene for the former rearing of deer has become more common.
Researchers said it was "rare" to observe evolution over such a short period of time.
Why did it happen?
Previous studies have shown that the deer have been born earlier since the 1
This is partly due to the effects of warmer temperatures on deer behavior and physiology.
Now researchers say that the deer that give birth earlier have more calves in their lifetime – that is, they have more reproductive success.
The gene that causes an earlier birth is therefore much more abundant in the ruminant population over time.
This is an example of natural selection, the theory of evolution, developed by Charles Darwin.
Evolution in action.
A team that included scientists from the University of Edinburgh made the discovery using field records and genetic data collected over a period of 45 years since 1972 on rum.
Researchers also involved scientists from the Australian National University and the University of Edinburgh Universities St. Andrews and Cambridge.
Dr. Timothée Bonnet of the Australian National University, who led the study, said they documented "evolution in action".
- Hot deer is cooling in the highland hole.
- Opposition to nocturnal red deer shots.  He added that research has shown that natural selection can "help people adjust to global warming".
Robin Parker of WWF Scotland, however, said that urgent action to mitigate climate change was needed.
He said: "Climate change is here and this report highlights the impact our changing climate already has on animals.
In order to tackle the common natural and climate emergencies, it is important that we take action
"In this way we can protect our precious wildlife and at the same time create a healthier, fairer and more prosperous Scotland for all of us."