How the giraffe got its long neck

They found that elongation of the giraffe neck occurred in stages, first in the front of the neck vertebrae and then after a few million years in the rear of the vertebrae. These stages of elongation happened in different species, but the modern giraffe is the only species that underwent both transformations, likely to get at progressively higher leaves on trees.

Evidently, though, the elongation started even before the giraffe family originated 16 million years ago. It continued with the extinct genus Samotherium, named after the Greek island of Samos where it was found, which seems to mark the beginning of the transition to modern giraffes. The front part of Samotherium’s vertebrae were elongated and it had long legs and a general slender stature. Sometime after Samotherium, the back portion of the vertebrae got longer.

While giraffes were once widespread over Africa and Eurasia only two members of the giraffe family (Giraffidae) exist today – the giraffe and the okapi. Giraffids are ruminant artiodactyls that share a common ancestor with the groups to which cows and deer belong. They evolved around 25 million years ago, which is quite late for mammal diversification.

The okapi is a part of a distinct group of giraffids, as their ancestors started off with longer necks and over time the necks became shorter. The okapi occupies an area of rainforest in central Africa. This environment is quite different than the grassland savannahs in which the giraffes live, where arid conditions produce tall trees with leaves high from the ground.

The extinct genera Bramatherium and Sivatherium, which may have lived as recently as 8,000 years ago, also seem to have gone down the okapi path. They had strange antler-like ornamentations (ossicones), large, stout bodies and shorter necks.

Lamarck really didn’t know what he was wading into more than 200 years ago. An amazing cast of characters show that giraffe neck evolution progressed in fits and starts through natural selection. Even more giraffe fossils probably lie locked in rocks around the world just waiting to add to the story.

Nick
Garland

Founder and Editor

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