The characteristic neck of the modern giraffe, the tallest land animal and largest ruminant on Earth, has long been considered a classic example of adaptive evolution and natural selection since Charles Darwin first developed the concepts.
The neck of a giraffe is a marvellous thing. Comprised of only seven vertebrae* – no more than in your neck – the towering feat of natural engineering is at once stunning and ridiculous. How could such a structure have evolved?
It is commonly believed that competition for food drove neck elongation and allowed giraffes to browse for treetop leaves in the African Savannah woodlands.
However, a Chinese research team says that their long necks grew so they could compete for mates, rather than reach for food. Long necks are a distinct advantage when you want to headbutt love rivals in mating battles. Any boxer will tell you that long arms are an advantage, even when not fighting a love rival.
An analysis of an early giraffe ancestor’s unique head and neck fossils – disc-shaped helmet-like headgear and highly complex head-neck joints – suggests sexual selection, driven by competition among males, may have also contributed to neck evolution.
As observation of giraffe behaviour increased, scientists began to realise that the long neck of giraffes actually serves as a weapon in male courtship competition and that may be the key to the giraffe evolutionary mystery.
The longer the neck, the greater the damage to the opponent. And, as luck would then have it, give giraffes the extra benefit of being able to reach leaves that other ruminants can't.
* There is an ongoing anatomical debate about whether giraffes have only seven neck vertebrae or eight, the extra one being a modified part of the back.
