It is a famous, gentle giant of the African savannah, but the giraffe’s genetics have just revealed that there is not one species, but four.
Giraffes have previously been recognised to be a single species divided into several sub-species.
But this latest study of their DNA suggests that four groups of giraffes have not cross-bred and exchanged genetic material for millions of years.
This is a clear indication that they have evolved into distinct species.
The study published in the journal Current Biology has rewritten the biology of Earth’s tallest mammal.
The scientists say their findings could inform the conservation efforts for all four species of giraffe.
Conservation was the catalyst for this genetic research; the Giraffe Conservation Foundation asked the team to carry out genetic analysis of giraffes in Namibia.
The foundation wanted to understand the genetic differences between different giraffe populations, to see how the animals might be affected if different subspecies were mixed together when animals were moved into protected areas.
What we found then, says Axel Janke, a geneticist at the Senckenberg Biodiversity and Climate Research Centre, who led the research, “was that the sub-species were genetically very different and separate.
“I’d never seen that in a population study [of a species] before.”
This initial study examined what is known as mitochondrial DNA – a packet of DNA within every cell’s “engine”. This is useful for population genetics – it can be easily isolated and contains lots of known variants that can track relatedness.
But mitochondrial DNA is not part of the code that builds an animal, so Dr Janke decided to examine and compare parts of that code – the nuclear DNA.
“It turned out, he told BBC News, that, for example, “the whole clade of northern giraffes was very different from reticulated giraffes.”