Fossil remains of Lucy’s braincase are fragmentary, limiting the reconstruction of her brain size. However, brain size estimates from other members of her species suggest that Lucy’s brain was probably about the size of a modern chimpanzee’s (range between 387 – 550 cc; average 446 cc)10. Although it might appear as though these australopiths had small brains, it must also be remembered that they were smaller-bodied than living humans. In fact, when her brain size compared relative to her body size, her brain would actually be considered larger than expected for a living ape of that body size11. Importantly, Lucy’s relatively small brain size (compared to humans) in combination with her bipedal adaptations of the lower limb, reveal that bipedalism evolved before large brains.
