A beautiful woman
The conditions our ancestors had to struggle with during the Ice Age were pretty uncomfortable. A female fossil found in China reveals the anatomical adaptations of humans to the harsh climate: The lady was not only exceptionally tall, but also showed a remarkable head.
The temperatures in his African homeland were pleasantly warm. But some Homo erectus did not last long here: Shortly after their first appearance, approximately 1.8 million years ago, some of the "upright people" set off north towards Asia and Europe.
Times got tougher here - not just because it's generally a bit cooler in more northern regions than in the African savannahs. The emergence of Homo erectus coincides with an epoch of geological history known as the Pleistocene with multiple ice ages. How did the human species meet this challenge anatomically?
Because the German anatomist and physiologist Carl Bergmann (1814-1865) already noticed that the body structure of animals adapts to colder climates: The representatives of northern populations of a species are usually somewhat larger than their southern counterparts. Bergmann explained this with the relatively small surface area of large bodies in relation to volume. Larger animals therefore lose a lower percentage of heat across their surface than their smaller conspecifics.
The American zoologist Joel Asaph Allen (1838–1921) made a similar observation: In cold regions, related mammal species tend to have shorter appendages in order to minimize heat loss there as well. It is reasonable to assume that these ecogeographical climate rules also apply to humans.
However, direct proof is not easy. Because mostly only a few bones remain from our ancestors, which different individuals from different times left behind - this makes a direct comparison difficult.
The human fossil from Jinnuishan, which was unearthed in 1984 near the northeast Chinese city of Yinkou, presented itself as a rare stroke of luck. The paleontologists were able to salvage an almost complete skull, a hip bone, six vertebrae, two ribs, an ulna, a kneecap and several hand and foot bones.
Since no piece of bone was repeated and the individual parts fit together well, it quickly became clear that it must have been a single individual. The dating gave an age of 260,000 years; the creature had thus lived during the Middle Pleistocene.
Karen Rosenberg from the University of Delaware and her colleagues have now taken a closer look at the fossil. Due to the wide pelvis, the researchers are certain when determining the sex: female. From the length of the ulnar bone, a height of 169 centimeters could be calculated - making the Lady of Jinnuishan one of the tallest known women of the Pleistocene.
It was more difficult to estimate body weight, which the researchers deduced from the width of the hips and the size of the thigh joint: with an estimated 78.6 kilograms, this revealed a weighty personality.
If the fossil was typical of their time and region, then Bergmann's rule seems to hold true for the genus Homo as well: the Ice Age climate apparently made humans shoot up. And the relatively clumsy shape of the fossil reflects Allen's rule of proportion.
The researchers were particularly interested in the Ice Age woman's brain volume: at 1.33 liters and an estimated brain weight of 1.28 kilograms, her brain hardly differed from the mass of today's human thought organs, which weigh between 1.2 and 1, 5 kg varies.
The so-called encephalization quotient, which could be calculated from brain and body mass and was only slightly lower than in anatomically modern humans, shows how far the development of the brain had progressed in the middle Pleistocene.
Rosenberg and her colleagues conclude that the harsh Ice Age must have been extremely good for the Homo genus: in adapting to the climate, body and mind grew to unimagined sizes.
