Why is the KNM-ER 3733 skull important?

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Side-view illustration of a Homo erectus individual, depicted with a robust, upright body covered in hair, walking with one arm bent. A scale bar beside the figure shows measurements in inches and centimeters. — Homo erectus Artist's rendering of *Homo erectus*, which lived from approximately 1,700,000 to 200,000 years ago.

The KNM-ER 3733 skull is a significant fossil discovery from the Koobi Fora sites in Kenya because it is a remarkably complete and well-preserved cranium.1

Dated to approximately 1.75 million years ago, it is considered one of the most ancient Homo erectus fossils ever discovered in Africa. Due to its distinct characteristics, some paleontologists classify this specimen and other related finds from the region as a separate species, which they refer to as H. ergaster.1