Fig. 9. Skull of an adult Homo ergaster (KNM-ER 3733), from Koobi Fora, East 
Turkana, Kenya. Scale is 1 cm. 
And it seems that once emancipation from the forest had thus been 
achieved, the way was open for ancient humans to indulge their 
wanderlust. New dates suggest that humans had not only exited 
Africa but had reached all the way to eastern Asia almost immedi- 
ately after achieving modern body form (see review in Tattersall, 
1997). 
Still, while the Boy and his relatives had larger brains than any 
of their predecessors, these were not a lot more than half the size 
of ours today. What’s more, while the face of Homo ergaster is 
substantially reduced compared to those of australopiths, it still juts 
out in front of the braincase and is equipped with modestly large 
teeth (fig. 9). There are incipient signs of the flexion of the cranial 
base that signals the presence of a vocal tract capable of producing 
the sounds associated with articulate speech; but speech and hence 
language are belied by the narrowness of the thoracic vertebral canal 
that carries the innervation of the thoracic musculature. The Boy 
apparently lacked the fine control of the musculature which produces 
the moving air column that we modulate to generate speech 
(McLarnon, 1993). 
For all the innovations borne by Homo ergaster, we have to wait 
over a quarter of a million years after its first appearance before we 
encounter the next technological innovation. The Boy and his kin 
made stone tools that were for the most part indistinguishable from 
is) 
