The blue whale is not only the largest animal alive today, it is the largest one in history.
But how it got to be so large has remained somewhat of a mystery ... Until now, that is.
In 2006, a farmer near the southern Italian town of Matera discovered several large vertebrae protruding from the clay on the shore of a lake he uses to irrigate his crops.
Over the course of three autumn seasons, when it was possible to lower the water level without ruining the harvest, Italian palaeontologist Giovanni Bianucci of the University of Pisa and his team dug out the remains.
Studies later confirmed the fossil is that of a blue whale.
The fossil skull of the whale has helped scientists from Italy, Australia, and Belgium to produce a reconstruction of the full skull for an anatomical analysis.
The researchers reported in the journal Biology Letters that the whale would have been around 85 feet long, making it the largest known in fossil records.
Dating shows that the fossil is approximately 1.5 million years old.
When the researchers combined data from the blue whale with data from other baleen fossils, they determined a new time scale: it seems the large size of the baleen whales occurred around 3.6 million years ago, and maybe even as far back as 6 million years ago.
The report also suggests that the change in size likely occurred gradually.
Discovering how blue whales came to be so big has previously proved a challenge, as large whale fossils from the past 2.5 million years are scarce.
This is probably because the planet experienced a series of ice ages during this period, when masses of water froze into ice and sea levels dropped dramatically.
The remains of whales that died in that period are likely many dozens of feet below sea level now.
In 2017, a study analysing the body size of all known baleen whale species suggested an increase in body size may have happened quite suddenly, likely around 300,000 years ago but possibly as far as back as 4.5 million years.
Researchers who favour this theory suggest that at some point in time, the climate changed in a way that very strongly impacted krill, the main food source of baleen whales.
In order to survive, the whales would have had to eat enormous amounts of the tiny sea creatures before swimming a very long way to find another meal, hence their rapid growth.
But now, this theory is being challenged by the analysis of the Matera whale.
That said, researchers acknowledged that they have considerable work to do to give their theory credibility, which will involve the study of other whale fossils.
