Sandstone Reveals Ostrich Family Tree

Is the Namib truly the oldest desert on Earth? And did the ostrich originate in Africa or Eurasia?

The breathtaking dune landscapes of the Gondwana Namib Park hold the clues to answer these questions.

The first piece of evidence is easy to spot: the fossilised dunes, visible across the landscape, formed roughly 20 million years ago. Over time, the sand transformed into sandstone during more humid periods between eight and 16 million years ago. Yet, even during these wetter phases, desert conditions persisted in many parts of today’s Namib, solidifying its reputation as the world’s oldest desert.

Visitors to Gondwana’s Namib Desert Lodge rest at the base of these ancient dunes, sleeping beside a living history.

Unveiling the origins of the ostrich, however, requires a closer look. The Tsondab Sandstone, the rock type of these fossilised dunes, is rich in plant and animal fossils (note: fossil collecting is prohibited!).

Traces of roots, tunnels made by ants, termites, beetles and spiders, and even preserved spider webs – a rare find – have been discovered. The fossils of small mammals and reptiles, as well as species reminiscent of today’s aardvark, giraffe and elephant, paint a vivid picture of a landscape much like what we see today.

Among the most intriguing fossils embedded in the Tsondab Sandstone are fragments of large eggshells, strikingly similar to modern ostrich eggs. These shells vary in thickness and pore structure, indicating that several ostrich-like species once roamed the area.

Since similar eggshells are found in layers from different time periods, scientists believe that these species did not coexist, but evolved in succession over time.

The oldest eggshells, dating back approximately 16 million years, were much thicker – around 4mm – compared to today’s ostrich eggshells, which are about 2.5 to 3mm in thickness.

These ancient eggs were also larger, weighing over 2kg, with a volume of up to 1.7 litres, compared to modern ostrich eggs, which weigh about 1.5kg and hold 1 litre.

In 2005, paleontologist Fritz Curschmann discovered fossil shells that differ from any known type. They are currently being studied by experts.

The Tsondab Sandstone layers contain the evolutionary history of today’s ostrich. By examining the eggshells, scientists have traced the lineage of the modern ostrich back to an early ancestor that lived 16 million years ago. This ancestor may have resembled the giant bird that once inhabited Madagascar, suggesting that the ostrich likely originated in Africa and only later spread to Eurasia.

Source: ‘Passage through Time: The Fossils of Namibia’, written by geologist Gabi Schneider and illustrated by artist Christine Marais (Gamsberg Macmillan, Windhoek, 2004, ISBN 99916-0515-0).